PURPOSE: To report the ocular complications of cobalamin-C type methylmalonic aciduria with homocystinuria (cblC) in a large consecutive series of patients. METHODS: Medical records of patients with genetically diagnosed cblC disease from Mount Sinai Medical Center, New York, and Hôpital Necker, Paris, France, were reviewed. All patients with the diagnosis of cblC seen after January 2008 at Mount Sinai and January 1998 at Hôpital Necker were included. RESULTS: A total of 9 cases are reported. Age at initial ocular examination ranged from 3.5 months to 10 years of age. All 9 patients had early-onset disease, with manifestation of disease presenting prior to 1 year of age. Two patients had definitive optic nerve pallor. All patients had retinal findings ranging from peripheral pigmentary retinal changes to central macular atrophy with Bull's eye lesions. Optical coherence tomography was performed on one child and showed retinal thinning in the area of the bull's eye lesions. Electroretinography was performed in 6 of the 9 patients, three of whom showed decreased scotopic and photopic responses. The other three patients had normal responses on electroretinography. CONCLUSIONS: Ocular findings in patients with cblC are variable. All patients in the study exhibited early-onset disease and had noteworthy ophthalmic findings. To the best of our knowledge, this is the first study in the literature correlating optical coherence tomography findings with fundus findings in cblC.