High resolution cone photoreceptor imaging analysis of an occult macular dystrophy patient with RP1L1 mutation

Abstract

Purpose: To analyze cone photoreceptor degeneration by adaptive optics (AO) fundus camera in a Japanese occult macular dystrophy (OMD) patient with mutation in the RP1-like protein 1 (RP1L1) gene.

Methods: An OMD patient with RP1L1 mutation (S1199C) and 20 normal volunteer underwent high resolution imaging analysis. High-resolution en face images were obtained using a flood-illumination AO fundus camera (Imagine Eyes, Orsay, France). We have statistically analyzed biomarker metrics (cone density, inter-cell spacing) computed from the images. These metrics are analyzed from the images obtained at 600 μm and 1200 μm from the fovea.

Results: The mean age of volunteers is 36.0±10.5 (range 20-57 years). The mean cone density of volunteers was 2.11±0.37 x 10⁴ cones/mm² at 600 μm from the fovea and 1.70±0.31 x 10⁴ cones/mm² at 1200 μm from the fovea. The mean inter-cell spacing of volunteers was 7.73±0.81 μm at 600 μm from the fovea and 8.56±0.93 μm at 1200 μm from the fovea. The cone density of the right eye of the patient was 4.72 x 10³ cones/mm² at 600 μm from the fovea and 3.04 x 10³ cones/mm² at 1200 μm from the fovea. The inter-cell spacing of the right eye of the patient was 13.0 μm at 600 μm from the fovea and 16.9 μm at 1200 μm from the fovea. The cone density and inter-cell spacing of the patient were outside the range of the both standard deviation and 95% confidence intervals of normal volunteer.

Conclusions: We have analyzed high resolution images of a Japanese OMD patient with RP1L1 mutation. An OMD patient showed decreased cone density and increased inter-cell spacing at both 600 μm and 1200 μm from the fovea. AO fundus camera and its computed metrics analysis were useful to detect the changes in the cone photoreceptors in OMD.

Keywords: 507 electrophysiology: clinical • 550 imaging/image analysis: clinical • 585 macula/fovea