Ophthalmic Findings in the KIF1A-Associated Neurologic Disorder (KAND)

To define the ophthalmic manifestations in KIF1A-associated neurologic disorder (KAND), a rare, progressive neurodegenerative disorder caused by pathogenic variants in the KIFA1 gene.

Cross-sectional study.

Clinical ophthalmic examination and multimodal imaging were performed for 24 participants enrolled in the KIF1AOutcome measures, Assessments, Longitudinal And endpoints (KOALA) Study. Visual evoked potentials (VEPs) were performed on select participants.

The average central visual acuity in pediatric participants was 20/43 (logMAR 0.329, range 0.0-1.0) and 20/119 (logMAR 0.773, range 0.471-1.351) in adults. Ninety-five percent of participants examined had some degree of optic nerve atrophy detected by clinical examination and/or optical coherence tomography (OCT). Almost 40% had strabismus. Color vision, visual fields, and stereopsis were impaired in most participants who were able to participate in testing. VEP showed varying degrees of signal slowing and diffuseness.

Optic nerve atrophy is the primary ocular finding in individuals with KAND and is present at higher prevalence than previously reported. The degree of the atrophy is likely dependent on the severity of the pathogenic variant and possibly the age of the patient. Adults had worse vision on average than children, suggesting possible decline in vision with age. Strabismus in this cohort was common. VEPs showed findings consistent with optic neuropathy and visual dysfunction even in the absence of obvious structural changes on OCT. Families should be counseled regarding visual impairment in KAND patients, so as to obtain appropriate support and assistance to maximize safety, functionality, and learning.