To investigate ophthalmic features in a large group of patients with primary hyperoxaluria type 1 (PH1) and to determine the relation between ocular involvement and systemic disease severity.

Retrospective, cross-sectional, multicenter study of the OxalEurope Registry Network.

Sixty-eight patients with PH1 were included. Infantile PH1 was diagnosed in 12 patients, and non-infantile PH1 was diagnosed in 56 patients (17 with end-stage renal disease). Ophthalmic examination included best corrected visual acuity (BCVA) testing and multimodal retinal imaging, including fundus photography and optical coherence tomography (OCT). In selected cases, fundus autofluorescence imaging was performed.

All eyes (n = 24) of infantile PH1 patients revealed severe retinal alterations and oxalate deposits, including macular crystals and hyperpigmentations (n = 9, 38%), and subretinal fibrosis (n = 15, 63%) with (n = 7, 47%) or without (n = 8; 53%) associated chronic retinal edema. In 9 eyes (38%, all with subretinal fibrosis), BCVA was significantly reduced (<20/50 Snellen equivalent). In contrast, all eyes (n = 112) of patients with non-infantile PH1 had a BCVA in the normal range (median, 20/20). Only 6 patients with non-infantile disease (11%, all with end-stage renal disease) showed mild, likely PH1-related retinal features. These deposits appeared as focal hyperreflective subretinal lesions on OCT imaging and were hyperautofluorescent on autofluorescence images.

Severe ocular alterations occur in infantile cases, whereas mild or no ocular alterations are typical in non-infantile PH1 patients. The natural history of (sub)retinal oxalate deposits, the pathogenesis of subretinal fibrosis, and exact factors influencing the overall severity of ocular disease manifestation remain to be determined.