Purpose: To determine the course of occult macular dystrophy (OMD, Miyake's disease) and to propose stages of OMD based on the optical coherence tomographic (OCT) findings.
Methods: Sixty-one patients from 33 families with OMD who carried one of the proven variants of the RP1L1 gene were studied at seven centers in Japan. Ophthalmological examinations including the best-corrected visual acuity (BVCA) and OCT were performed.
Results: The median age at the last visit was 50 years with a range of 10 to 88 years, and the median age at the symptom onset was 30 years with a range of 3 to 60 years. There were significant negative correlations between the duration of OMD and BCVA, the central retinal thickness (CRT) and the thickness between external limiting membrane and retinal pigment epithelium (ERT). The BCVA gradually decreased for 10 years after symptom onset and was stable thereafter. Kaplan-Meier survival curves of the BCVA and retinal thickness showed that all of the patients had retained a vision of 1.0 logMAR, and over 80% of the patients had retained 50% thickness of the normal CRT and ERT for at least 60 years after symptom onset. The stages of OMD based on the visual symptoms and OCT findings are proposed.
Conclusions: The photoreceptors do not become completely atrophic even at the late stage, which may account for the good retinal pigment epithelium (RPE) structure and normal-appearing fundus. The proposed stages facilitate the investigation of the pathogenicity of OMD and provide information to determine the effectiveness of therapeutic procedures.