HELICOIDAL PERIPAPILLARY CHORIORETINAL DEGENERATION - ELECTROPHYSIOLOGY AND PSYCHOPHYSICS IN 17 PATIENTS

Aims-To characterise retinal function using electrophysiological and p sychophysical tests in 17 patients with helicoidal peripapillary chori oretinal degeneration. Methods-The electroretinogram (ERG) was recorde d using gold foil corneal electrodes. The electro-oculogram (EGG) was recorded using a standard protocol. Dark adaptometry was recorded with an SST-1 dark adaptometer and colour vision assessed with Ishihara pl ates and Farnsworth D-15. Results-All subjects had a recordable ERG. T he amplitudes and implicit times of the a-and b-waves were within norm al limits at all luminances in five subjects (age 21-70 years, mean 40 years). The ERG of six (age 26-55 years, mean 40.7 years) had subnorm al amplitudes at all luminances, but normal implicit times, and six (a ge 38-81 years, mean 60.7 years) had abnormal ERGs with marked reducti on of a-and b-waves, and delayed implicit times of the b-wave. The imp licit times of the a-wave were normal in all subjects. A reduction in the bla wave ratios was not found, nor was there selective loss of sco topic, mixed rod/cone, or cone responses. The light/dark ratio of the EOG was subnormal (150-185%) or abnormal (below 150%) in all but three subjects. Two patients with normal EOG showed normal ERGs in both eye s, but one had subnormal ERGs in both eyes. The scotopic sensitivity w as normal in all subjects and dark adaptation showed a normal time cou rse. Colour vision was normal in all patients. Conclusion-The results suggest that in most cases the function of the retinal pigment epithel ium is affected by this disease before any changes in the function of the sensory retina are detectable by our methods, and that retinal dys function is fetal rather than diffuse.