Purpose: To analyze the outer retinal layers using spectral domain optical coherence tomography (SD-OCT) in patients with cone-rod dystrophy.
Methods: The diagnosis of cone-rod dystrophy 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 24 eyes of 12 patients with cone-rod dystrophy. From the innermost to the outermost, the four studied hyperreflective outer retinal bands were labeled Band 1, the external limiting membrane; Band 2, the ellipsoid zone; Band 3, the interdigitation zone between the cone outer segments and the apical processes of the retinal pigment epithelium; and Band 4, the retinal pigment epithelium 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 interdigitation zone in the entire length of SD-OCT scan, including the foveal area, in all 24 study eyes. Outside the foveal area, the external limiting membrane and ellipsoid zone were intact in all study eyes. The intensity of the ellipsoid zone was decreased in the entire length of SD-OCT scan in all study eyes. Within the foveal area, there was loss of the external limiting membrane and ellipsoid zone in 20 (83%) and 22 eyes (92%), respectively. The retinal pigment epithelium complex was identified in all study eyes. None of the study eyes revealed cystoid macular edema.
Conclusion: SD-OCT scans demonstrated complete absence of the interdigitation zone in patients with cone-rod dystrophy. Consistent with the 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 retinal pigment epithelium with the cone outer segments.
Spectral domain optical coherence tomography showed lack of the third hyperreflective outer retinal band in a series of cone-rod dystrophy patients. Loss of the third band may be caused by the loss of the cone outer segments or by an abnormal or absent investment of the outer segments by the apical processes of the retinal pigment epithelium.
*The Vitreous, Retina, Macula Consultants of New York and the LuEsther T. Mertz Retina Research Center, Manhattan Eye, Ear, and Throat Hospital, New York, New York; and
†Department of Ophthalmology, Federal University of Sao Paulo (UNIFESP), Sao Paulo, Brazil.
Reprint requests: Richard F. Spaide, MD, The Vitreous-Retina-Macula Consultants of New York, 460 Park Avenue, 5th Floor, New York, NY 10022; e-mail: firstname.lastname@example.org
Supported by the LuEsther T. Mertz Retinal Research Center, Manhattan Eye, Ear, and Throat Hospital, and the Macula Foundation, Inc.
None of the authors have any conflicting interests to disclose. Richard F. Spaide is a consultant to Bausch and Lomb, Topcon, and Thrombogenics. He receives royalties from Topcon.