This study is investigating whether eye exercises for abducens palsy and internuclear ophthalmoplegia increase ocular range of motion in the paretic direction when performed in virtual reality under head-cancelled compared to head-active conditions.

Participants with abducens palsy or internuclear ophthalmoplegia, two common types of ocular cranial nerve palsies, will perform 3 different tasks in virtual reality under head-cancelled and head-active conditions. Head active is the normal state, where gaze can be shifted by moving the head, the eyes, or a combination of the two. Head-cancelled refers to the condition where the scene moves with the head, rendering head movement ineffective to shift gaze. In this condition, the eyes must move in order to shift gaze. The hypothesis is that this requirement for eye movement will result in larger eye movements, which could be therapeutic. The tasks performed under the two conditions will include horizontal transposition of coins, repetitive horizontal saccades, and game play. The primary analysis will be a within subject's comparison of eye movement amplitude in head-cancelled (experimental) versus head-active (control) conditions. Additionally, as a control comparison for secondary analysis, a group with normal vision will also perform the tasks under both conditions.

OCNP Group Inclusion Criteria:

• Presence of OCNP in one eye with 50% range-of-motion limitation or worse
• Able to provide informed consent and will be able to fluently read and understand spoken English

OCNP Group Exclusion Criteria:

• Presence of bilateral OCNP
• Range of motion better than 50%
• Visual acuity worse than 20/100 in either eye
• Greater than 4-line difference in visual acuity between the eyes,
• Structural anomalies or sensory sensitivities (e.g. visual motion sensitivity) that would prevent them from wearing or tolerating a VR headset

Participants will be excluded if they are unable to participate if inclusion criteria are not met.

Normal Group Inclusion Criteria:

• Absence of OCNP or other neurological or neuro-ophthalmic diseases
• No strabismus
• Have normal or near-normal vision with glasses or contact lenses.
• Be able to provide informed consent and will be able to fluently read and understand spoken English

Normal Group Exclusion Criteria:

• Visual acuity worse than 20/100 in either eye
• Greater than 4-line difference in visual acuity between the eyes
• Structural anomalies or sensory sensitivities (e.g. visual motion sensitivity) that would prevent them from wearing or tolerating a VR headset
• Known inability to tolerate visual testing of at least 20 minutes continuously.