Abstract
Purpose:
To analyze the outer retinal layers with spectral-domain optical coherence tomography (SD-OCT) in patients with cone-rod dystrophy (CRD)
Methods:
The diagnosis of CRD was determined by primary cone involvement or concomitant loss of both cones and rods. Electroretinography showed implicit time shift at 30-Hz flicker response and prevalent decrease of photopic over scotopic responses. Using SD-OCT, the outer retina was retrospectively evaluated in twenty-four eyes of twelve CRD patients. From the innermost to the outermost, the 4 studied hyperreflective outer retinal bands were labeled Band 1, the external limiting membrane (ELM), Band 2, the ellipsoid zone (EZ), Band 3, the interdigitation zone (IZ) between the cone outer segments and the apical processes of the retinal pigment epithelium (RPE) and Band 4, the retinal pigment epithelium (RPE complex
Results:
The mean age of study patients was 30 years and the median visual acuity was 20/30. A ring maculopathy appearance involving the fovea area was observed in all study eyes. There was an absence of IZ in the entire length of SD-OCT scan, including the foveal area, in all 24 study eyes. Outside the foveal area, the ELM and EZ were intact in all study eyes. The intensity of the EZ was decreased in the entire length of SD-OCT scan in all study eyes. Within the foveal area, there was loss of the ELM and EZ in twenty (83%) and twenty-two eyes (92%), respectively. The RPE complex was identified in all study eyes. None of the study eyes revealed cystoid macular edema
Conclusions:
SD-OCT scans demonstrated complete absence of the IZ in CRD patients. Consistent with known histology of animal models of cone dystrophy, this finding may represent abnormal outer retinal morphology, including an absence of the outer segments themselves or a defective or absent interdigitation between the apical processes of the RPE with the cone outer segments
Keywords: 688 retina •
550 imaging/image analysis: clinical •
494 degenerations/dystrophies