Progressive expansion of the hyperautofluorescent ring in cone-rod dystrophy patients

Purpose: To evaluate the expansion of the hyperautofluorescent ring and the retinal structure changes over time in cone-rod dystrophy (CRD) patients, using fundus autofluorescence (FAF) and spectral-domain optical coherence tomography (SD-OCT).

Methods: Retrospective case series study. Six eyes of three CRD patients with a parafoveal hyperautofluorescent ring were studied. The diagnosis of CRD was established by the presence of the implicit time shift at 30-Hz flicker and prevalent decrease of photopic over scotopic responses on electroretinography. External and internal ring expansion was evaluated by measurements of its area at baseline and at 24-month follow-up using FAF. SD-OCT analyzed the retinal structure of the ring and the length of devoid ellipsoid zone (EZ) was measured over time.

Results: The mean age of study patients was 21 years old and the mean baseline visual acuity was 20/200. The external and internal FAF rings involving the fovea were identified in all study eyes. SD-OCT showed a normal retinal structure outside the ring. At the transitional zone of the ring, disorganization of both EZ and external limiting membrane (ELM) was observed. Inside the hyperautofluorescent ring, EZ and ELM were not identified. At 24-month follow-up examination, the mean % area increase of external and internal rings were 18.32% and 20.42%, respectively, and was concordant with the EZ band defect length enlargement.

Conclusion: Progressive expansion of hyperautofluorescent macular ring with a correspondent EZ band defect enlargement was observed over time in CRD patients.