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Kazushige Tsunoda, Tetsuhisa Hatase, Tomoaki Usui, Kaoru Fujinami, Yozo Miyake; Optical Coherent Tomography (OCT) Findings In Occult Macular Dystrophy (OMD) With RP1L1 Mutation. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2211.
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Occult Macular Dystrophy (OMD) is an inherited macular dystrophy characterized by progressive loss of macular function. Typical OMD is characterized by a central cone dysfunction despite normal ophthalmoscopic appearance, normal fluorescein angiography, and normal full-field electroretinogram (ERG) but the amplitudes of the focal macular ERGs and multifocal ERGs are significantly reduced at the central retina. Mutations in RP1L1 gene were determined to be responsible for dominantly inherited OMD (Akahori M et al., Am. J. Hum. Genet. 2010). Previous studies using OCT have revealed structural changes in the photoreceptor layer in OMD, however, most of the cases were sporadic and the results may represent different disease entities with similar retinal dysfunctions. In order to investigate the etiology of this disease, we have obtained OCT images from patients with the same mutation, and classified the stages of OMD based on the OCT findings.
OCT images were obtained with a Fourier-domain OCT (HD-OCT; Carl Zeiss and 3D-OCT-1000, Mark II; Topcon) on 24 eyes of 12 patients with RP1L1 mutation (p.Arg45Trp). The OCT findings were compared with the results of other ophthalmological examinations including multifocal ERG.
Patients with normal macular ERG showed normal photoreceptor structures in OCT (Stage 0). Patients with decreased macular ERG without subjective visual disturbances showed absence of cone outer segment tip (COST) line only in the macula (Stage I). Patients with both decreased macular ERG and subjective visual disturbances showed blurring of photoreceptor inner / outer segment (IS/OS) junction line together with the absence of COST line (Stage II). Patients with longer durations over 40 years showed both disruption of IS/OS junction line and thinning of retinal thickness at the fovea (Stage III).
Our results demonstrated that disappearance of the COST line at the fovea is the earliest abnormality in OCT in patients with RP1L1 mutation. The OCT abnormality in the photoreceptor layer without subjective visual disturbances may be attributed to the important role of RP1L1 in maintaining the photoreceptor structures.
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