Pathologic Changes of Cone Photoreceptors in Eyes With Occult Macular Dystrophy

Purpose: Occult macular dystrophy (OMD) is an inherited retinal disease characterized by a progressive decrease of vision and appearance of normal fundus. To determine the pathologic features of OMD, we investigated the alternation of the photoreceptors using quantitative image analysis.

Methods: We studied 22 eyes of 11 OMD patients. Three of them had a mutation (R45W) in RP1L1. The relative intensities of the ellipsoid zone in the spectral-domain optical coherence tomography (SD-OCT) images and the density of the cone photoreceptors in the adaptive optics (AO) fundus images of the OMD patients were compared to those of normal controls.

Results: The relative intensities of the ellipsoid zone in the SD-OCT images of patients with OMD were significantly lower (P < 0.001) by an average of 16% compared to that of the normal controls. Normal cone mosaics were not observed in the AO images of the macula in the eyes with OMD. The mean ± SD of cone density of the 9 OMD patients was 1970 ± 884 cells/mm2 at 2°, 1124 ± 483 cells/mm2 at 3°, and 1288 ± 715 cells/mm2 at 4° nasal to the fovea. The cone densities at 2°, 3°, and 4° nasal to the fovea of OMD were significantly lower than those of the normal controls (P < 0.001).

Conclusions: A sparse array of cone photoreceptors with significantly reduced density of the macula is one of the morphologic features of OMD.