The goal of this observational study is to define the course of the retinal degeneration in a ZSD patient cohort.

The objective of this study is to gather information so the investigators can:

1. define the course of the retinal degeneration in a ZSD patient cohort with retinal degeneration
2. define what tests best monitor the progression of the retinal degeneration
3. generate prognostic information about vision loss in ZSD.

At each yearly visit, the participants will answer a functional vision questionnaire, have a physical evaluation, blood test, and participate in a variety of vision tests. The investigators will also collect pertinent medical history.

Participants will travel to study site. The study will provide financial support for board and travel.

Participants/guardians will have a 1-hour virtual interview before the first visit to review the tests and determine which tests the participant is able to perform.

Below is a list of the vision tests used for this study:

Prior to each visit, the participant will complete the PedEyeQ or VFQ-25 questionnaire about functional vision.

At each clinic visit :

• Refraction and glasses test: this is a general vision test, as commonly conducted by an optometrist, before and after pupil dilation
• Best corrected visual acuity: the participant's vision will be tested using cards or a chart.
• Contrast sensitivity: the participant's ability to detect contrast will be tested using a chart.
• Visual field: the participant's field of vision will be tested by asking them to indicate when they see a stimulus.
• Reading test: the participant's ability to see written text will be tested using the International Reading Speed Test
• Color vision test: the participant's ability to see color will be tested using cards
• Eye exam: the participant's eyes will be examined with a lamp
• Pupil dilation: to allow the completion of some tests, the participant's pupils will be dilated using medicated eye drops
• Microperimetry: the participant's macula (central retina) will be visualized.
• Fundus photography: the participant's fundus (central retina) will be photographed in light and dark conditions
• Full field stimulus threshold test: the participant's ability to perceive light in different parts of their visual field will be tested
• Optical coherence tomography (OCT): detailed images of the participant's retina will be taken
• Fundus autofluorescence: the participant's retinal health will be assessed by imaging the natural fluorescent properties of their retinal pigment epithelium
• Chromatic pupillometry: the function of different cells in the participant's retina will be determined by measuring their response to light
• Multi-luminance mobility test (MLMT): the participant will walk through an obstacle course at varying light levels to test their functional vision in different light conditions.
• Blood collection: a blood sample will be collected and banked to measure peroxisome functions.

Inclusion Criteria:

• confirmed ZSD with deleterious variants in PEX genes identified
• confirmed or expected retinal involvement

Exclusion Criteria:

• unable to perform a minimum of one vision test
• severe ZSD disease

any age, with appropriate diagnosis