A Case of Occult Macular Dystrophy with Foveal Detachment by Vitreomacular Traction

Abstract

 

Purpose

 

Occult macular dystrophy (OMD) is a macular dystrophy characterized by normal fundus but progressively decreased visual acuity due to macular dysfunction. The RP1L1 gene mutations have been reported to be responsible for the OMD, and the RP1L1 protein was thought to play important roles in the morphogenesis of the photoreceptors. We herein describe the characteristic changes of foveal structure in association with vitreomacular traction in a case with OMD harboring RP1L1 mutation.

 

Methods

 

A sixty-seven-year-old female with diabetes mellitus was diagnosed as OMD, and serial fundus imaging has been performed for four years. A single missense RP1L1 mutation was identified by targeted next-generation sequencing. The decimal visual acuity was 0.3 and 0.2 in the right and left eye, and the funduscopic appearance was normal. At the age of 67, optical coherence tomography (OCT) demonstrated disappeared cone outer segment tip (COST) line and blurred photoreceptor inner segment elipsoid (ISe) line at the macula bilaterally, which was compatible to typical OMD with RP1L1 mutations (Tsunoda et al., Retina 2012).

 

Results

 

The photoreceptor layer gradually detached from retinal pigment epithelium (RPE) bilaterally at the fovea, as the vitreomacular traction became apparent at the age of 69. The subretinal space has been enlarged with the increased foveal traction; forming an dome-shaped ISe line. Within the subretinal space, granular regions with high refractivity were observed below the ISe. Neither thickening of outer nuclear layer nor inner retinal cysts were observed. Despite the occurrence of foveal detachment, the subjective complaint, visual acuity and the foveal sensitivity threshold of the Humphry field analyzer had not been remarkably changed. Fluorescein angiography did not show any leakage associated with diabetic maculopathy. We have reviewed the OCT findings of 9 other cases with RP1L1 mutations; the granular regions of high refractivity below the ISe were observed in all cases, with no cases showing the similar foveal detachment or vitreomacular traction.

 

Conclusions

 

Similar structural findings of the fovea have not been observed in vitreomacular traction syndrome or other macular dystrophies. Weakened adhesion between photoreceptor and RPE due to the dysfunctional RP1L1 protein may explain these characteristic changes.

 

 

Keywords: 696 retinal degenerations: hereditary • 585 macula/fovea • 692 retinal adhesion