A Case Presentation Emphasizing the Value of Full-field ERG in Retinal Dystrophies

ABSTRACT: Purpose: A case presentation is used to discuss the value of full-field ERG in the diagnosis of cone-rod dystrophy. Case report: A 49 year old female patient known with amblyopia and myopic astigmatism since childhood, visited us complaining of decreased visual acuity and photophobia. Her BCVA was 0.6 in the RE and 0.4 in the LE. The fundus examination revealed normal colored and sharply limited papilla, normal macula and narrower vascularization. The Ishihara test was 10/15 in both eyes. The fundus autofluorescence and optical coherence tomography were normal. The DA 3 ERG was decreased and slightly delayed as well as the DA 0.01 ERG. Regarding the cone response, the LA 3.0 and 30 Hz flicker ERG were markedly reduced and delayed. The ERG findings indicated cone-rod dystrophy. At the 8 years follow-up examination, the BCVA decreased to 0.4 and 0.2 in the right and left eye, respectively, the Ishihara test was 1/15 in both eyes and the fundus examination showed a macula with no reflex, otherwise no changes compared to the first examination. The fundus autofluorescence and OCT were still normal. The ERG showed a much decreased and delayed rod response compared to the first examination, while the cone response was undetectable. Conclusion: Our case demonstrates the importance of standard full-field ERG in diagnosing CRD. The Full-field ERG responses were decreased and delayed, or even undetectable, while morphological examinations were still unchanged.