Purpose: To describe the functional phenotypic features of East Asian patients with RP1L1-associated occult macular dystrophy (ie, Miyake disease). Design: An international multicenter retrospective cohort study. Methods: Twenty-eight participants (53 eyes) with Miyake disease were enrolled at 3 centers (in Japan, China, and South Korea). Ophthalmologic examinations including spectral-domain optical coherence tomography (SDOCT) and multifocal electroretinogram (mfERG) were performed. Patients were classified into 3 functional groups based on mfERG: Group 1, paracentral dysfunction with relatively preserved central/peripheral function; Group 2, homogeneous central dysfunction with preserved peripheral function; and Group 3, widespread dysfunction over the recorded area. Three functional phenotypes were compared in clinical parameters and SDOCT morphologic classification (severe phenotype, blurred/flat ellipsoid zone and absence of the interdigitation zone; mild phenotype, preserved ellipsoid zone). Results: There were 8 eyes in Group 1, 40 eyes in Group 2, and 5 eyes in Group 3. The patients in Group 1 showed significantly later onset (P =.005) and shorter disease duration (P =.002), compared with those in Group 2. All 8 eyes in Group 1 showed the mild morphologic phenotype, while 43 of 45 eyes in Groups 2 and 3 presented the severe phenotype, which identified a significant association between the functional grouping and the morphologic classification (P <.001). Conclusions: A spectrum of functional phenotypes of Miyake disease was first documented with identification of 3 functional subtypes. Patients with paracentral dysfunction had the mildest phenotype, and those with homogeneous central or widespread dysfunction showed overlapping clinical findings with severe photoreceptor changes, suggesting various extents of visual impairment.
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