Abstract
Purpose: :
To study cone photoreceptor structure and function in patients with mutations in the peripherin/RDS gene.
Methods: :
High-resolution images of the macula were obtained with Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) and spectral domain optical coherence tomography (SDOCT) in 2 patients with bilateral maculopathy and compared with data from normal subjects. Measures of retinal structure and fundus autofluorescence (FAF) were correlated with visual function including visual acuity (VA), color vision, kinetic and static perimetry, fundus-guided microperimetry and full-field (ffERG) and multifocal electroretinography (mfERG). Mutation analysis of the peripherin/RDS gene was carried out by sequencing the coding regions in each patient.
Results: :
Molecular analysis revealed heterozygous mutations in peripherin/RDS in each patient (Patient 1, R172W; Patient 2, G208D). VA was correctable to 20/40 or better in both eyes of each patient and foveal sensitivity was moderately reduced between 26-37 dB. Fundus exam in both subjects revealed extrafoveal areas of macular retinal pigment epithelium (RPE) atrophy (inferotemporal in Patient 1; bull’s eye maculopathy in Patient 2). Dense pericentral scotomas were present in each patient extending from 5-15 degrees eccentricity. While ffERG amplitudes and timing were normal, mfERG amplitudes were reduced and timing was delayed in the affected areas of each patient. The macula of each patient showed large areas of speckled FAF, with an extrafoveal area of virtually absent FAF corresponding to chorioretinal atrophy in Patient 1. SDOCT revealed normal foveal contours; however, thickness and reflectivity were increased between the junction of the photoreceptor inner and outer segments and the RPE at the fovea of each patient. Cone spacing was significantly increased between 2.7-6.7 standard deviations from normal throughout much of the central 4 degrees of the macula in each patient, although regions with normal cone spacing were present 2 degrees temporal to fixation in Patient 2.
Conclusions: :
Mutations in peripherin/RDS affect macular FAF and photoreceptor structure. SDOCT shows disruption of the photoreceptor/RPE junction with increased reflectivity of the foveal cone outer segments, surrounded by photoreceptor atrophy. AOSLO shows increased cone spacing consistent with cone loss in regions where photoreceptors are preserved.
Keywords: retinal degenerations: hereditary • imaging/image analysis: clinical • macula/fovea