Outer Retinal Changes Associated with the RPGR Carrier Phenotype: Insights from high-resolution imaging

Abstract

Purpose: Retinal structure and function in carriers of X-linked retinitis pigmentosa (XLRP) have been investigated previously, with an inconsistent correlation between the tapetal-like reflex seen on clinical examination and various imaging modalities. In this study we assessed the cone and rod photoreceptor mosaic in a cohort of unrelated carriers of RPGR-associated XLRP and examined retinal reflectivity using a multimodal imaging approach.

Methods: Obligate carriers of XLRP were identified and underwent full ophthalmic examination including visual acuity, color fundus photography, fundus autofluorescence (AF) imaging, spectral domain optical coherence tomography (SDOCT), and adaptive optics scanning light ophthalmoscopy (AOSLO).

Results: Five subjects with an age range of 28 to 62 years were examined. All had 20/20 visual acuity in both eyes, except for one patient who had unilateral amblyopia. Two patients described difficulties with night vision. In four patients a tapetal-like reflex (TLR) was clinically detectable bilaterally. The fifth subject had sparse bone-spicule retinal pigmentation. Fundus AF imaging ranged from normal to peri-macular areas of increased AF, with no definite co-localization with the TLR. SDOCT showed normal retinal lamination in all patients. AOSLO showed multiple small areas of variable rod loss and rod hyper-reflectivity, with normal appearing cones, in the 4 subjects with a TLR. The fifth subject with bone-spicule pigmentation had no evidence of rod loss or abnormality in rod reflectivity.

Conclusions: We speculate that the rod hyper-reflectivity may underlie the TLR seen clinically. It is of note that no abnormality in rod reflectance was seen in the single obligate carrier without a TLR. It remains to be established via serial assessments over time whether the degree of rod loss and photoreceptor reflectance disturbance have prognostic implications.

Keywords: 550 imaging/image analysis: clinical • 648 photoreceptors • 696 retinal degenerations: hereditary