Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Participants (Par) with a Baseline strabismus angle (BSA) >=10 prism dioptre (PD) and <20 PD received no treatment at the start of the First Treatment Period (FTP). Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 1.25 Units (U) or 2.5 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the Second Treatment Period (STP) to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 1.25 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 1.25 U or 2.5 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=10 PD and <20 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received no treatment at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received the injection of GSK1358820, either 2.5 U or 5.0 U, at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 2 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 2.5 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 2.5 U or 5.0, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.

Par with a BSA >=20 PD and <50 PD received the first injection of GSK1358820 5.0 U at one site of the medial rectus muscle or the lateral rectus muscle of the affected eye at the start of the FTP. Par who met the additional injection criteria at 4 weeks after the start of the FTP received an additional injection of GSK1358820, either 5.0 U or 10.0 U, at the same site and in the same eye as the previous injection, then were observed for 12-24 weeks. Par who met the re-injection criteria at 12-24 weeks after the last injection (of the FTP) entered the STP to receive the re-injection at an appropriate dose level selected by the investigator from the prior dose level, then were observed for 24 weeks. Par who did not meet the re-injection criteria were observed for 24 more weeks. Par received a maximum of 3 injections.