Variability in Photoreceptor Inner Segment Morphology in Best Vitelliform Macular Dystrophy

Abstract

 

Purpose

 

Best Vitelliform Macular Dystrophy (BVMD) is an autosomal dominant macular degeneration characterized by macular vitelliform lesions. Previous adaptive optics scanning light ophthalmoscope (AOSLO) imaging revealed patchy photoreceptor mosaic disruption with areas of no waveguiding photoreceptors where vitelliform lesions are/had been present. However, it was unclear if these variations in photoreceptor reflectivity were due to loss of structure, change in orientation, or the inability to waveguide light. Here we apply a new imaging technique, split-detector AOSLO, to further characterize photoreceptor morphology in BVMD.

 

Methods

 

Three affected family members with BVMD and known heterozygous BEST1 gene mutation (p.Arg218Cys) underwent comprehensive ophthalmic exams and high resolution retinal imaging. Outer retinal structure was assessed using spectral domain optical coherence tomography (SD-OCT), and photoreceptor mosaic was imaged with confocal and split-detector AOSLO.

 

Results

 

SD-OCT confirmed patchy areas of outer retinal structure loss with focal areas of subretinal fluid and debris in areas with or with previous vitelliform lesions. Split-detector AOSLO revealed photoreceptor structure in areas where no waveguiding cones were visualized by confocal AOSLO (Figure 1), allowing for a more precise assessment of photoreceptor structure. Inner segment morphology varied significantly, ranging from a near-normal to enlarged, anomalously shaped inner segments with some having a long, tapering process extending from a more circular head (Figure 1B - arrow).

 

Conclusions

 

When compared to SD-OCT or even confocal AOSLO, split-detector AOSLO allows for a more precise assessment of photoreceptor structure, highlighting the significant variability in inner segment morphology within areas of vitelliform lesions in BVMD. This demonstrates the potential utility of split-detector AOSLO for assessment of photoreceptor structure alterations in retinal degenerative processes such as BVMD.

 

 

Foveal photoreceptor mosaic in a patient with BVMD. (A) Confocal AOSLO image in log scale showing significant mosaic disruption with patchy areas of waveguiding photoreceptors surrounded by areas with no waveguiding (dark) cones. (B) Split-detector AOSLO image at the same location, revealing significant variability of photoreceptor inner segment morphology. (Arrow) -Anomalous photoreceptor inner segment. Scale bar-50 microns.

 

Keywords: 550 imaging/image analysis: clinical • 696 retinal degenerations: hereditary • 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)