Abstract:

Objective To investigate the characteristics of outer retinal structure and retinal function in patients with cone dystrophy (COD). Design Retrospective case series. Participants 12 (24 eyes) COD and 20 (40 eyes) normal controls were retrospectively analyzed. Methods Full-field flash electroretinogram (ERG) was used to examine the function of retinal cone and rod system. Outer retinal structure was examined by optical coherence tomography(OCT). COD was divided into two categories based on the results of ERG. Category 1: The function of cone responses decreased remarkably while the function of rod system was normal. Category 2: The function of cone responses decreased remarkably and the function of rod system decreased slightly. Main Outcome Measures Morphological changes of the outer retinal structure, central macular thickness (CMT), The amplitude of rod b-wave under dark adaptation, cone response a-wave and 30 Hz flicker response under light adaptation. Results Category 1: there was no obvious difference compared to normal controls in the appearance of fundus images and the outer retinal structure. Category 2: macular reflex diffused or disappeared on color fundus images. The outer limited membrane, ellipsoid zone and interdigitation zone blurred or disappeared, but the RPE/Bruch`s complex was intact. The CMT of Category 2 COD (213.42±12.10 μm) was significantly thinner than that of normal (253.56±3.98 μm) and category 1 COD (248.25±8.79 μm) (P<0.0001, P=0.03 respectively). Conclusion Clinical diagnosis of Category 1 COD relies on ERG, since the outer retinal structure shows almost normal. On the contrary, Category 2 COD not only shows abnormal function of cones, but also shows abnormal outer retinal structure. （Ophthalmol CHN， 2019， 28： 359-363）

Key words: cone dystrophy, optical coherence tomography, electroretinogram