Natural History Study of CEP290-Related Retinal Degeneration

The purpose of the study is to describe the natural history of CEP290-related retinal
degeneration caused by a compound heterozygous or homozygous intron 26 c.2991+1655A>G
mutation and to better understand the best assessments for evaluation of patients with this
condition in a future interventional trial. Patients meeting the entry criteria will be
enrolled in the study. Visits will occur at Screening, Baseline, and Months 3, 6, and 12, for
a total duration of 1 year.

Inclusion Criteria:

- Patient and/or parent/legal guardian must complete/sign an informed consent form
(ICF). If required on a per patient basis, provisions can be made for alternative
forms of consent (eg, witnessed consent). Where required by the IRB/IEC, minors must
also verbalize or sign a confirmation of assent. Refer to Section 11.3.

- Is at least 3 years of age at screening.

- Has abnormally decreased vision, defined as having light perception to 20/60 visual
acuity in each eye, with examination and test results consistent with an inherited
retinal degeneration due to mutations in the CEP290 gene.

- Has CEP290-related retinal degeneration caused by a compound heterozygous or
homozygous intron 26 c.2991+1655A>G mutation (ie, 1 or 2 copies of the intron 26
c.2991+1655A>G mutation) confirmed by deoxyribonucleic acid sequencing.

- Has ability to cooperate with assessments relative to age.

- Has clear ocular media and adequate pupil dilation in at least 1 eye, to permit good
quality fundus examination and optical coherence tomography (OCT) imaging.

- Must be able to successfully navigate the mobility courses at a level of difficulty
that is below the maximum performance level (ie, below a passing score at 1) with each
eye independently and both eyes together in the order specified by Investigator.

Exclusion Criteria

- Has history or current evidence of a medical condition (systemic or ophthalmic
disease, metabolic dysfunction, physical examination finding, or clinical laboratory
finding) that may, in the opinion of the Investigator, preclude adherence to the
scheduled study visits, safe participation in the study, or affect the results of the
study (eg, uncontrolled systemic hypertension, autoimmune disease, advanced coronary
artery disease, or cerebral vascular disease, other unstable or progressive
cardiovascular, pulmonary, Parkinson's, liver or renal disease, cancer, or dementia).

- Has history or current evidence of ocular disease in either eye that, in the opinion
of the Investigator, may confound assessment of this inherited retinal disease or the
assessments utilized herein (eg, glaucoma, age-related macular degeneration, diabetic
retinopathy, uveitis, or the presence of any condition that precludes adequate
visualization of the fundus such as dense cataracts or corneal scarring).

- Is currently receiving gene therapy and/or has received gene therapy.

- Is currently enrolled in an investigational or interventional drug or device study
and/or has participated in such a study within 30 days of Screening.