Abstract
Abstract: :
Purpose: Choroideremia is a rare X–linked retinal degeneration caused by mutations in REP–1. Due to lyonization the fundus appearance of carriers is variable. Histopathologic studies disclosed patchy degenerations, but the photoreceptor and retinal pigment epithelium (RPE) loss were considered to be independent (Syed et al. 2001). The goal of this presentation is to make these changes visible and to characterize corresponding retinal function. Methods: In five independent carriers for choroideremia a complete ophthalmologic examination, full–field ERG (according to the ISCEV standard) and two–color threshold perimetry (2 CT perimetry, modified Humphrey–Field–Analyzer, HFA) were performed. In addition four carriers were tested with mfERG (stimulus resolution: 103 elements, stimulus size: visual angle of 25 degrees). Fundus autofluorescence (AF) was recorded using a HRA (Heidelberg Retina Angiograph).To date, three families have verified mutations in REP1 as detected by SSCP and direct sequencing. Results: All five carriers had good visual acuity, but complained about photophobia and impaired vision in dim light. Full– field ERGs showed minor asymmetric findings with otherwise normal amplitudes and latencies in four carriers. On ophthalmoscopy, comparable RPE changes were seen in all carriers. AF revealed a characteristic speckled pattern. This pattern was clearly different from the pattern seen in carriers for RP3 (Wegscheider et al., 2004). All carriers showed reduced AF around the optic nerve head to a variable extend, corresponding to peripapillary atrophy. The entire macular region revealed small areas of reduced AF. Adjacent spots of enhanced AF were present in two carriers. The perifoveal area covering 3° to 4° appeared relatively more homogenous. 2 CT perimetry revealed localized areas of sensitivity losses with rods more affected than cones. Those markedly affected areas were partly congruent with localized reduction in AF. MfERG detected corresponding areas of functional disturbances in cones. Conclusions: All five carriers showed a similar specific AF pattern that was markedly different from the pattern seen in carriers for RP3. In hemizygotes, early stages of both diseases may have a relatively similar fundus appearance. AF may therefore help to differentiate the two disease entities and initiate gene–directed mutational analysis.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • degenerations/dystrophies • retinal pigment epithelium