Participants will receive a single high dose of BIIB112 by sub-retinal injection.

Participants will receive a single low dose of BIIB112 by sub-retinal injection.

Participants will receive no intervention to allow for a controlled comparison.

An AE is any untoward medical occurrence in a participant or clinical investigation participant administered a pharmaceutical product and that does not necessarily have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product. TEAEs are defined as AEs starting on or after the day of the first surgery.

MAIA microperimetry assessment was measured in dB using a 10-2 grid of 68 points. Each point was labelled as '< 0', '0' or a positive integer. The point labelled as '< 0' was assigned a value of '-1' by MAIA in the calculation. Improvement in Retinal Sensitivity in whole grid was defined as an increase from baseline of 7 or more dBs in any 5 or more points of the grid as a whole (68 points).

MAIA microperimetry assessment was measured in dB using a 10-2 grid of 68 points. Each point was labelled as '< 0', '0' or a positive integer. The point labelled as '< 0' is assigned a value of '-1' by MAIA in the calculation. Improvement in mean sensitivity in center grid was defined as an increase from baseline of 7 or more dBs in any 5 or more points out of the 16 central points. Here negative values indicate a decline in retinal sensitivity.

MAIA microperimetry assessment was measured in dB using a 10-2 grid of 68 points. Each point was labelled as '< 0', '0' or a positive integer. The point labelled as '< 0' is assigned a value of '-1' by MAIA in the calculation. Improvement in mean sensitivity in whole grid was defined as an increase from baseline of 7 or more dBs in any 5 or more points of the grid as a whole (68 points). Here negative values indicate a decline in retinal sensitivity.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. BCVA was reported as number of letters read correctly by the participants using the ETDRS Scale (ranging from 0 to 100 letters). The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). An increase in the number of letters read correctly means that vision has improved. Here negative values indicate decline in BCVA.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. LLVA was reported as number of letters read correctly by the participant using the ETDRS Scale (ranging from 0 to 100 letters). The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). An increase in the number of letters read correctly means that vision has improved. Here negative values indicate decline in LLVA.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥15 letters increase from baseline for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥15 letters increase from baseline for LLVA were reported for study and non-study eyes.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥10 letters increase from baseline for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥10 letters increase from baseline for LLVA were reported for study and non-study eyes.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters increase from baseline for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters increase from baseline for LLVA were reported for study and non-study eyes.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥15 letters loss from baseline for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥15 letters loss from baseline for LLVA were reported for study and non-study eyes.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥10 letters loss from baseline for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥10 letters loss from baseline for LLVA were reported for study and non-study eyes.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters loss from baseline for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters loss from baseline for LLVA were reported for study and non-study eyes.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). An increase in the number of letters read correctly means that vision has improved. Percentage of eyes with a change from baseline of ≥ -5 letters for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). An increase in the number of letters read correctly means that vision has improved. Percentage of eyes with a change from baseline of ≥ -5 letters for LLVA were reported for study and non-study eyes.

Spectral Domain Optical Coherence Tomography (SD-OCT) was used to assess change in central ellipsoid area. The measurements were taken after dilation of the participant's pupil. A negative change from baseline indicates a decline in central ellipsoid area.

SD-OCT was used to assess change in central horizontal ellipsoid width. The measurements were taken after dilation of the participant's pupil. A negative change from baseline indicates a decline in central horizontal ellipsoid width.

Fundus Autofluoroscence was used to assess the total area of preserved autofluoroscence. Areas of preserved AF were identified as well-demarcated regions of relative hyper autofluorescence (hyper AF) compared with the background areas of surrounding atrophy. A negative change from baseline indicates a decline in total area of preserved autofluoroscence.

Fundus Autofluoroscence was used to assess the distance from FC to nearest border of preserved autofluoroscence. A negative change from baseline indicates a decline in the total area of preserved autofluoroscence.

Visual field testing was performed to assess the volume of 30-degree hill vision, reported as dBs. Reliability Factor (RF)=number of false positive responses + number of false negative responses/number of false positive presentations + number of false negative presentations*100. If there are 0 responses, then RF value=0. RFpositive=number of false positive responses/number of false positive presentations*100. If RF≤ 20% measurement is considered reliable. If 20% < RF ≤ 25% and RFpositive ≤ 10% measurement is also considered reliable. Otherwise if 20% < RF ≤ 25% and RFpositive > 10%, or RF > 25%, measurement is not reliable. Only reliable measurements were included for analysis of this outcome measure. Here negative values indicate decline in volume of 30-degree hill vision.

Visual field testing was performed to assess the volume of full field of hill vision, reported as dBs. RF =number of false positive responses + number of false negative responses/number of false positive presentations + number of false negative presentations*100. If there are 0 responses, then RF value=0. RFpositive=number of false positive responses/number of false positive presentations*100. If RF≤ 20% measurement is considered reliable. If 20% < RF ≤ 25% and RFpositive ≤ 10% measurement is also considered reliable. Otherwise if 20% < RF ≤ 25% and RFpositive > 10%, or RF > 25%, measurement is not reliable. Only reliable measurements were included for analysis of this outcome measure. Here negative values indicate decline in volume of 30-degree hill vision.

Change in CS was assessed by Pelli-Robson chart which uses a single large letter size (20/60 optotype), with contrast varying across groups of letters. Chart uses letters (6 per line), arranged in groups whose contrast varies from high to low. Participants read the letters, starting with the highest contrast, until they were unable to read two or three letters in a single group. Each group had three letters of the same contrast level, so there were three trials per contrast level. Participant is assigned a score based on the contrast of the last group in which two or three letters were correctly read. Score is a measure of the participant's log contrast sensitivity ranging from 0-2.25, with 0 being no letters read, and 2.25 being all letters read. Total CS score = [(total letters correct - 3) x 0.05].

MAIA microperimetry assessment was measured in dBs using a 10-2 grid of 68 points. Each point was labelled as '< 0', '0' or a positive integer. The point labelled as '< 0' is assigned a value of '-1' by MAIA in the calculation. Improvement in mean sensitivity in center grid was defined as an increase from baseline of 7 or more dBs in any 5 or more points out of the 16 central points.

MAIA microperimetry assessment was measured in dBs using a 10-2 grid of 68 points. Each point was labelled as '< 0', '0' or a positive integer. The point labelled as '< 0' was assigned a value of '-1' by MAIA in the calculation. Improvement in mean sensitivity in whole grid was defined as an increase from baseline of 7 or more dBs in any 5 or more points of the grid as a whole (68 points).

MAIA microperimetry assessment was measured in dB using a 10-2 grid of 68 points. Each point was labelled as '< 0', '0' or a positive integer. The point labelled as '< 0' was assigned a value of '-1' by MAIA in the calculation. Mean Sensitivity in center grid was defined as the mean in dB of the 16 points located in the center of the grid. Here negative values indicate a decline in retinal sensitivity.

MAIA microperimetry assessment was measured in dB using a 10-2 grid of 68 points. Each point was labelled as '< 0', '0' or a positive integer. The point labelled as '< 0' was assigned a value of '-1' by MAIA in the calculation. Improvement in mean ensitivity in whole grid was defined as an increase from baseline of 7 or more dBs in any 5 or more points of the grid as a whole (68 points). Here negative values indicate a decline in retinal sensitivity.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. BCVA was reported as number of letters read correctly by the participant, using the ETDRS Scale (ranging from 0 to 100 letters). The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). An increase in the number of letters read correctly means that vision has improved. Here negative values indicate a decline in BCVA.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. LLVA was reported as number of letters read correctly by the participant, using the ETDRS Scale (ranging from 0 to 100 letters). The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). An increase in the number of letters read correctly means that vision has improved. Here negative values indicate a decline in LLVA.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥15 letters increase from baseline for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥15 letters increase from baseline for LLVA were reported for study and non-study eyes.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). An increase in the number of letters read correctly means that vision has improved. Percentage of eyes with a ≥10 letters increase from baseline for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥10 letters increase from baseline for LLVA were reported for study and non-study eyes.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters increase from baseline for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters increase from baseline for LLVA were reported for study and non-study eyes.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters loss from baseline for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥15 letters loss from baseline for LLVA were reported for study and non-study eyes.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥10 letters loss from baseline for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥10 letters loss from baseline for LLVA were reported for study and non-study eyes.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters loss from baseline for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters loss from baseline for LLVA were reported for study and non-study eyes.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a change from baseline of ≥ -5 letters for BCVA were reported for study and non-study eyes.

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a change from baseline of ≥ -5 letters for LLVA were reported for study and non-study eyes.

Visual field testing was performed to assess the volume of 30-degree hill vision, reported as dBs. RF=number of false positive responses + number of false negative responses/number of false positive presentations + number of false negative presentations*100. If there are 0 responses, then RF value=0. RFpositive=number of false positive responses/number of false positive presentations*100. If RF≤ 20% measurement is considered reliable. If 20% < RF ≤ 25% and RFpositive ≤ 10% measurement is also considered reliable. Otherwise if 20% < RF ≤ 25% and RFpositive > 10%, or RF > 25%, measurement is not reliable. Only reliable measurements were included for analysis of this outcome measure. Here negative values indicate decline in the volume of 30-degree hill vision.

Visual field testing was performed to assess the volume of full field of hill vision, reported as dBs. RF=number of false positive responses + number of false negative responses/number of false positive presentations + number of false negative presentations*100. If there are 0 responses, then RF value=0. RFpositive=number of false positive responses/number of false positive presentations*100. If RF≤ 20% measurement is considered reliable. If 20% < RF ≤ 25% and RFpositive ≤ 10% measurement is also considered reliable. Otherwise if 20% < RF ≤ 25% and RFpositive > 10%, or RF > 25%, measurement is not reliable. Only reliable measurements were included for analysis of this outcome measure. Here negative values indicate decline in volume of full field hill vision.

Followed by vitrectomy and retinal detachment in the study eye, participants received a single dose 3 (5 × 10^10 vg) of BIIB112 by sub-retinal injection on Day 0 (surgery day).

Followed by vitrectomy and retinal detachment in the study eye, participants received a single dose 4 (1 × 10^11 vg) of BIIB112 by sub-retinal injection on Day 0 (surgery day).

Followed by vitrectomy and retinal detachment in the study eye, participants received a single dose 5 (2.5 × 10^11 vg) of BIIB112 by sub-retinal injection on Day 0 (surgery day).

Followed by vitrectomy and retinal detachment in the study eye, participants received a single dose 6 (5 × 10^11 vg) of BIIB112 by sub-retinal injection on Day 0 (surgery day).

Participants received no intervention to allow for a controlled comparison.

Followed by vitrectomy and retinal detachment in study eye, participants received a single low dose (5 × 10^10 vg) of BIIB112 by sub-retinal injection on Day 0 (surgery day).

Followed by vitrectomy and retinal detachment in study eye, participants received a single high dose (2.5 × 10^11 vg) of BIIB112 by sub-retinal injection on Day 0 (surgery day).

Total of all reporting groups

An AE is any untoward medical occurrence in a participant or clinical investigation participant administered a pharmaceutical product and that does not necessarily have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product. TEAEs are defined as the AEs starting or worsening on or after the day of the first surgery.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112).

MAIA microperimetry assessment was measured in dB using a 10-2 grid of 68 points. Each point was labelled as '< 0', '0', or a positive integer. The point labelled as '< 0' was assigned a value of '-1' by MAIA in the calculation. Improvement in Retinal Sensitivity in center grid was defined as an increase from baseline of 7 or more dBs in any 5 or more points out of the 16 central points.

Intent-to-treat (ITT) analysis set included all participants that were randomized under the 3-arm randomization schedules. "Overall number of participants analyzed" signifies the number of participants with data available for analysis of this outcome measure.

An AE is any untoward medical occurrence in a participant or clinical investigation participant administered a pharmaceutical product and that does not necessarily have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product. TEAEs are defined as AEs starting on or after the day of the first surgery.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112).

MAIA microperimetry assessment was measured in dB using a 10-2 grid of 68 points. Each point was labelled as '< 0', '0' or a positive integer. The point labelled as '< 0' was assigned a value of '-1' by MAIA in the calculation. Improvement in Retinal Sensitivity in center grid was defined as an increase from baseline of 7 or more dBs in any 5 or more points out of the 16 central points.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure. 'Number of participants analyzed' signifies the number of participants with data available for analysis at specified timepoint.

MAIA microperimetry assessment was measured in dB using a 10-2 grid of 68 points. Each point was labelled as '< 0', '0' or a positive integer. The point labelled as '< 0' was assigned a value of '-1' by MAIA in the calculation. Improvement in Retinal Sensitivity in whole grid was defined as an increase from baseline of 7 or more dBs in any 5 or more points of the grid as a whole (68 points).

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure. 'Number of participants analyzed' signifies the number of participants with data available for analysis at specified timepoint.

MAIA microperimetry assessment was measured in dB using a 10-2 grid of 68 points. Each point was labelled as '< 0', '0' or a positive integer. The point labelled as '< 0' is assigned a value of '-1' by MAIA in the calculation. Improvement in mean sensitivity in center grid was defined as an increase from baseline of 7 or more dBs in any 5 or more points out of the 16 central points. Here negative values indicate a decline in retinal sensitivity.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure. 'Number of participants analyzed' signifies the number of participants with data available for analysis at specified timepoint.

MAIA microperimetry assessment was measured in dB using a 10-2 grid of 68 points. Each point was labelled as '< 0', '0' or a positive integer. The point labelled as '< 0' is assigned a value of '-1' by MAIA in the calculation. Improvement in mean sensitivity in whole grid was defined as an increase from baseline of 7 or more dBs in any 5 or more points of the grid as a whole (68 points). Here negative values indicate a decline in retinal sensitivity.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure. 'Number of participants analyzed' signifies the number of participants with data available for analysis at specified timepoint.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. BCVA was reported as number of letters read correctly by the participants using the ETDRS Scale (ranging from 0 to 100 letters). The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). An increase in the number of letters read correctly means that vision has improved. Here negative values indicate decline in BCVA.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112).

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. LLVA was reported as number of letters read correctly by the participant using the ETDRS Scale (ranging from 0 to 100 letters). The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). An increase in the number of letters read correctly means that vision has improved. Here negative values indicate decline in LLVA.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥15 letters increase from baseline for BCVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112).

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥15 letters increase from baseline for LLVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥10 letters increase from baseline for BCVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112).

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥10 letters increase from baseline for LLVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters increase from baseline for BCVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112).

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters increase from baseline for LLVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥15 letters loss from baseline for BCVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112).

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥15 letters loss from baseline for LLVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥10 letters loss from baseline for BCVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112).

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥10 letters loss from baseline for LLVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters loss from baseline for BCVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112).

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). Percentage of eyes with a ≥5 letters loss from baseline for LLVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure.

BCVA was assessed for both eyes using the ETDRS VA chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). An increase in the number of letters read correctly means that vision has improved. Percentage of eyes with a change from baseline of ≥ -5 letters for BCVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112).

LLVA was measured by placing a 2.0-log-unit neutral density filter over the front of each eye and having the participant read the normally illuminated ETDRS chart. Initially, letters were read at a distance of 4 meters from the chart. If <20 letters were read at 4 meters, testing at 1 meter was performed. The lower the number of letters read correctly on the eye chart, the worse the vision (or VA). An increase in the number of letters read correctly means that vision has improved. Percentage of eyes with a change from baseline of ≥ -5 letters for LLVA were reported for study and non-study eyes.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure.

Spectral Domain Optical Coherence Tomography (SD-OCT) was used to assess change in central ellipsoid area. The measurements were taken after dilation of the participant's pupil. A negative change from baseline indicates a decline in central ellipsoid area.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Number analyzed' signifies the number of participants with data available for analysis at specified timepoint.

SD-OCT was used to assess change in central horizontal ellipsoid width. The measurements were taken after dilation of the participant's pupil. A negative change from baseline indicates a decline in central horizontal ellipsoid width.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Number analyzed' signifies the number of participants with data available for analysis at specified timepoint.

Fundus Autofluoroscence was used to assess the total area of preserved autofluoroscence. Areas of preserved AF were identified as well-demarcated regions of relative hyper autofluorescence (hyper AF) compared with the background areas of surrounding atrophy. A negative change from baseline indicates a decline in total area of preserved autofluoroscence.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure. 'Number analyzed' signifies the number of participants with data available for analysis at specified timepoint.

Fundus Autofluoroscence was used to assess the distance from FC to nearest border of preserved autofluoroscence. A negative change from baseline indicates a decline in the total area of preserved autofluoroscence.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure. 'Number analyzed' signifies the number of participants with data available for analysis at specified timepoint.

Visual field testing was performed to assess the volume of 30-degree hill vision, reported as dBs. Reliability Factor (RF)=number of false positive responses + number of false negative responses/number of false positive presentations + number of false negative presentations*100. If there are 0 responses, then RF value=0. RFpositive=number of false positive responses/number of false positive presentations*100. If RF≤ 20% measurement is considered reliable. If 20% < RF ≤ 25% and RFpositive ≤ 10% measurement is also considered reliable. Otherwise if 20% < RF ≤ 25% and RFpositive > 10%, or RF > 25%, measurement is not reliable. Only reliable measurements were included for analysis of this outcome measure. Here negative values indicate decline in volume of 30-degree hill vision.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure. 'Number analyzed' signifies the number of participants with data available for analysis at specified timepoint.

Visual field testing was performed to assess the volume of full field of hill vision, reported as dBs. RF =number of false positive responses + number of false negative responses/number of false positive presentations + number of false negative presentations*100. If there are 0 responses, then RF value=0. RFpositive=number of false positive responses/number of false positive presentations*100. If RF≤ 20% measurement is considered reliable. If 20% < RF ≤ 25% and RFpositive ≤ 10% measurement is also considered reliable. Otherwise if 20% < RF ≤ 25% and RFpositive > 10%, or RF > 25%, measurement is not reliable. Only reliable measurements were included for analysis of this outcome measure. Here negative values indicate decline in volume of 30-degree hill vision.

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Overall number of participants analyzed' signifies the number of participants with data available for analysis of outcome measure. 'Number analyzed' signifies the number of participants with data available for analysis at specified timepoint.

Change in CS was assessed by Pelli-Robson chart which uses a single large letter size (20/60 optotype), with contrast varying across groups of letters. Chart uses letters (6 per line), arranged in groups whose contrast varies from high to low. Participants read the letters, starting with the highest contrast, until they were unable to read two or three letters in a single group. Each group had three letters of the same contrast level, so there were three trials per contrast level. Participant is assigned a score based on the contrast of the last group in which two or three letters were correctly read. Score is a measure of the participant's log contrast sensitivity ranging from 0-2.25, with 0 being no letters read, and 2.25 being all letters read. Total CS score = [(total letters correct - 3) x 0.05].

Safety analysis set included all participants who received study treatment (vitrectomy/BIIB112). 'Number analyzed' signifies the number of participants with data available for analysis at specified timepoint.