Long-term Safety and Efficacy Follow-up of BIIB111 for the Treatment of Choroideremia and BIIB112 for the Treatment of X-Linked Retinitis Pigmentosa

Change from Baseline in Best-Corrected Visual Acuity (BCVA)

BCVA will be assessed for both eyes using the Early Treatment of Diabetic Retinopathy Study (ETDRS) visual acuity (VA) chart. BCVA test should be performed prior to pupil dilation, and distance refraction should be carried out before BCVA is measured. Initially, letters are read at a distance of 4 meters from the chart. If \<20 letters are read at 4 meters, testing at 1 meter should be performed. BCVA is to be reported as number of letters read correctly by the participant using the ETDRS Scale (ranging from 0 to 100 letters) in the study eye. The lower the number of letters read correctly on the eye chart, the worse the vision (or visual acuity). An increase in the number of letters read correctly means that vision has improved.

Time frame: Up to 5 years

Percentage of Participants with no Decrease from Baseline in BCVA or a Decrease from Baseline in BCVA of <5 ETDRS Letters in Choroideremia (CHM) Participants

BCVA will be assessed for both eyes using the Early Treatment of Diabetic Retinopathy Study (ETDRS) visual acuity (VA) chart. BCVA test should be performed prior to pupil dilation, and distance refraction should be carried out before BCVA is measured. Initially, letters are read at a distance of 4 meters from the chart. If \<20 letters are read at 4 meters, testing at 1 meter should be performed. BCVA is to be reported as number of letters read correctly by the participant using the ETDRS Scale (ranging from 0 to 100 letters) in the study eye. The lower the number of letters read correctly on the eye chart, the worse the vision (or visual acuity). An increase in the number of letters read correctly means that vision has improved.

Time frame: Up to 5 years

Percentage of Participants with an Increase from Baseline in BCVA of ≥10 ETDRS Letters in CHM Participants

BCVA will be assessed for both eyes using the Early Treatment of Diabetic Retinopathy Study (ETDRS) visual acuity (VA) chart. BCVA test should be performed prior to pupil dilation, and distance refraction should be carried out before BCVA is measured. Initially, letters are read at a distance of 4 meters from the chart. If \<20 letters are read at 4 meters, testing at 1 meter should be performed. BCVA is to be reported as number of letters read correctly by the participant using the ETDRS Scale (ranging from 0 to 100 letters) in the study eye. The lower the number of letters read correctly on the eye chart, the worse the vision (or visual acuity). An increase in the number of letters read correctly means that vision has improved.

Time frame: Up to 5 years

Percentage of Participants with an Increase from Baseline in BCVA of ≥15 ETDRS Letters in CHM Participants

BCVA will be assessed for both eyes using the Early Treatment of Diabetic Retinopathy Study (ETDRS) visual acuity (VA) chart. BCVA test should be performed prior to pupil dilation, and distance refraction should be carried out before BCVA is measured. Initially, letters are read at a distance of 4 meters from the chart. If \<20 letters are read at 4 meters, testing at 1 meter should be performed. BCVA is to be reported as number of letters read correctly by the participant using the ETDRS Scale (ranging from 0 to 100 letters) in the study eye. The lower the number of letters read correctly on the eye chart, the worse the vision (or visual acuity). An increase in the number of letters read correctly means that vision has improved.

Time frame: Up to 5 years

Assessment of Fundus Autofluorescence (AF) at Each Visit

Fundus Autofluoroscence will be performed on both eyes to assess the change in the area of viable retinal tissue. It will be reported in square millimetres (mm\^2).

Time frame: Up to 5 years

Assessment of Fundus Photography at Each Visit

Fundus photography will be performed on both eyes following the dilation of the participant's pupils.

Time frame: Up to 5 years

Assessment of Spectral Domain Optical Coherence Tomography (SD-OCT) at Each Visit

SD-OCT will be performed on both eyes to assess the foveal changes and other potential anatomic changes. The measurements were taken after dilation of the participant's pupil and would be reported in micrometres (µm).

Time frame: Up to 5 years

Assessment of Microperimetry at Each Visit

Microperimetry will be performed on both eyes to assess changes in retinal sensitivity within the macula. It will be reported in decibels (dB).

Time frame: Up to 5 years

Change from Baseline in 25-Item Visual Function Questionnaire (VFQ-25)

VFQ-25 questionnaire measures dimensions of self-reported vision-targeted health status that are most important to persons with eye disease. Total score ranges from 0-100, where a score of 0 represents the worst outcome and 100 represents the best outcome.

Time frame: Up to 5 years

Change from Baseline in Visual Field

The outcome measure will be assessed in BIIB112-treated participants.

Time frame: Up to 5 years

Percentage of Participants with an Increase from Baseline in Luminance Visual Acuity (LLVA) of ≥10 ETDRS Letters in BIIB112-treated Participants

The LLVA was measured by placing a 2.0-log-unit neutral density filter over the best correction for that eye and having the participant read the normally illuminated ETDRS chart. The assessment was performed prior to dilating the eyes. Initially, letters are read at a distance of 4 metres from the chart. If \<20 letters are read at 4 metres, testing at 1 metre should be performed. BCVA is to be reported as number of letters read correctly by the participant.

Time frame: 18 Months to 60 Months, Post-Day 0 Visits

Percentage of Participants with an Increase from Baseline in Luminance Visual Acuity (LLVA) of ≥15 ETDRS Letters in BIIB112-treated Participants

The LLVA was measured by placing a 2.0-log-unit neutral density filter over the best correction for that eye and having the participant read the normally illuminated ETDRS chart. The assessment was performed prior to dilating the eyes. Initially, letters are read at a distance of 4 metres from the chart. If \<20 letters are read at 4 metres, testing at 1 metre should be performed. BCVA is to be reported as number of letters read correctly by the participant.

Time frame: 18 Months to 60 Months, Post-Day 0 Visits