Fundus albipunctatus photoreceptor microstructure revealed using adaptive optics scanning light ophthalmoscopy

Fundus albipunctatus is an inherited cause of congenital stationary night blindness. The objective of this report is to describe structural changes occurring in a macular phenotype of a novel RDH5 mutation producing fundus albipunctatus using high-resolution in vivo imaging. A 62-year-old male with longstanding night blindness underwent imaging and genetic evaluation. High-resolution images of the photoreceptor mosaic were compared to those of a healthy subject. Results of a comprehensive ophthalmic evaluation and genetic testing with imaging including fundus photography, spectral-domain optical coherence tomography (OCT), fluorescein angiography (FA), OCT angiography (OCT-A), and adaptive optics scanning light ophthalmoscopy (AOSLO) are described.

The patient presented with visual acuity of 20/25 in both eyes and longstanding poor dark adaptation. Anterior segment examination was unremarkable. Fundoscopy revealed well circumscribed bilateral perifoveal mottling and atrophy in both eyes. Discrete white-yellow flecks were present beyond the vascular arcades extending to the far periphery. Genetic testing revealed a novel compound heterozygous RDH5 mutation (c.388C > T, p.Gln130*; c.665T > C, p.Leu222Pro). OCT demonstrated perifoveal photoreceptor and outer retinal irregularities, which corresponded to a window defect with late staining on FA. OCT-A demonstrated normal retinal vasculature with patchy areas of non-perfusion in the choriocapillaris. Macular abnormalities in both eyes were imaged using AOSLO to assess cone and rod photoreceptor architecture. While clinical features are consistent with a primary rod disorder, confocal AOSLO showed a paucity of normal cones with a small spared central island in both eyes. Rods appeared larger and more irregular throughout the macula. Non-confocal split detection AOSLO imaging revealed the presence of cone inner segments in dark regions of confocal imaging, indicating some degree of photoreceptor preservation.

The AOSLO imaging of this particular macular phenotype of fundus albipunctatus demonstrates some of the structural photoreceptor abnormalities that occur in this condition, adding insight to the variable presentation of RDH5 retinopathy. The presence of preserved inner segment architecture suggests the possibility that gene therapy could play a future role in treating this condition.