Abstract
Purpose::
To show the genetic, Electroretinogram (ERG) and Optical Coherence Tomography (OCT) findings in a family with Enhanced S-Cone Syndrome and hearing loss.
Methods::
Two of ten siblings, Forty-five years old man with visual acuity of 2/20 in both eyes and his forty-one years old brother with visual acuity of 0.5/20 in both eyes had reduced central vision, photophobia and hearing loss. The parents were first order cousin of Arab origin. ERG was performed (LKC, UTAS-3000) according to the ISCEV protocol. Stratus OCT 3 (version 4.0.1) scans and Auditory Brainstem Evoked Response (ABR) were performed. Mutation analysis of the NRE2E3 gene was performed by direct sequencing of PCR amplified exons.
Results::
The photopic ERG results showed non-detectable wavelength amplitude for the 30Hz flicker and long wavelength single flash stimuli, while the white and the short wavelength single flash stimuli were remarkably higher (b wave: 50-60 microvolt). Scotopic responses were within the normal limits. The OCT results showed in the macular area loss of normal neuroretinal contour and loss of normal neuroretinal architecture with severe thinning of the photoreceptor layer and absence of the outer and inner segments of the photorecepter layer. ABR of wave III and V showed delayed latencies in both ears. No pathogenic mutation was identified in the coding region or in the exon-intron boundaries of the NRE2E3 gene. However the possibility of a mutation in the non-coding regions, a large deletion, or a rearrangement has not been ruled out.
Conclusions::
Enhanced S-Cone Syndrome was diagnosed based on the ERG results with preserved s-cone response and non-detectable L-cone response. The OCT showed thinning of the photorecepter layer which rationalized with the ERG results. The ABR demonstrated a nero-sensory defect which had not been described in previous reports. However, no pathogenic mutation was identified.
Keywords: photoreceptors • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • gene screening