Background: Cysteine beta-synthase (CBS) deficiency, often known as classic homocystinuria (HCU), is an uncommon inborn mistake in methionine metabolism. Developmental delay, intellectual incapacity, skeletal and vascular symptoms, and ocular abnormalities are possible main clinical characteristics.

Objective: This study sought to describe the ocular anomalies that King Fahad Armed Forces Hospital, Jeddah, Saudi Arabia, HCU patients presented with between 2018 and 2022.

This retrospective research included 6 HCU patients. Demographic and clinical characteristics of patients as age, gender, comorbidities were collected. Relevant clinical and ophthalmic assessments, like visual acuity, fundus examination findings, complications and type of surgery were also reported

Inclusion Criteria:

• All patients from all age groups who were diagnosed with homocystinuria between 2018 and 2022 were included, regardless of whether the diagnosis was made biochemically (by exhibiting hyperhomocysteinaemia and hypermethioninaemia) or genetically (by discovering biallelic pathogenic mutations in the CBS gene)

Exclusion Criteria:

• Patients with incomplete investigations for various reasons

The patient's records gathered from outpatient internal medicine and pediatric encounters. Six patients met study inclusion criteria. Demographic and clinical characteristics of patients were collected. Relevant clinical and ophthalmic assessments, as visual acuity, fundus examination, complications and surgery type were also obtained. Visual acuity, in-clinic dilated fundus examination, optical coherence tomography (OCT) angiography, macular OCT scan, and fundus photography were components of ophthalmic examinations. Fundus examination involved retinal inspection, visual acuity measured using tumbling E chart.

The data available with principal investigator when needed