Abstract

FR.18.01

Cone dystrophies – is multifocal ERG or quantified OCT better for diagnosis?

Fleischhauer J.¹, Barthelmes D.¹, Sutter F.², Niemeyer G.², Wildberger H.², Helbig H.^3
1Department of Ophthalmology, University Hospital Bern, Switzerland; ²Department of Ophthalmology, University Hospital Zürich, Switzerland; ³Department of Ophthalmology, University Hospital Regensburg, Germany

Objective: Evaluation of sensitivity of quantified OCT (qOCT) images and multifocal (mf)ERG compared to full field (ff)ERG as additional test for diagnosis of cone-dystrophy (CD).
Methods: 43 patients with CD, 53 healthy controls were compared. ERG (ISCEV protocol), best corrected visual acuity test and slit lamp examination were performed in all participants. 3 groups were established within the CD patients based on ffERG cone recordings (slightly subnormal, severely impaired, nearly extinguished). Quantification of OCT images (Zeiss Stratus OCT 3) was performed, calculating density profiles of the light reflection (from pigment epithelium side to vitreous). In each patient, these longitudinal reflectivity profiles (LRP), passing through the fovea, were calculated from 20 scans. LRPs were averaged and analyzed quantitatively (intensity peaks) for retinal thickness and distances between different retinal layers. 61 hexagon mfERGs were recorded binocularly (Veris). mfERG signals were analyzed for P1 amplitude and latency in the central hexagon and adjacent Ring 2. Abnormal values (qOCT and mfERG) were defined as differing more than twice the standard deviation from the average of controls. Sensitivity of mfERG and qOCT for pathological values was compared to Ganzfeld ERG.
Results: qOCT showed significant and characteristic changes of LRPs (photoreceptor inner/outer segment layer, ELM) in all CD patients. Retinal thickness was not reduced in patients with mild disease, but was reduced significantly for both other groups. mfERG showed pathologies in 72% (31/43) of patients with CD. All patients showing false negative mfERGs had mild CD.
Conclusions: Quantitative OCT analysis is helpful in diagnosing patients suffering from a mild form of CD, while mfERG is not as sensitive. In mild forms of CD qOCT should be preferred as additional test.

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