[Foveal electroretinogram: its application in the diagnosis of macular diseases. Preliminary report]

To present difficult method of recording and analysis of the Foveal Cone Electroretinogram (FCERG, a type of focal ERG) for evaluation of foveal cone function in healthy subjects and patients with different macular diseases. The FCERG signal is of great importance in diagnosis of these diseases because the full-field ERG is dominated by the extrafoveal cones activity.

In this study FCERGs were obtained in 90 healthy subjects (90 normal eyes), several with known macular diseases and subjects with optic neuritis and suspected maculopathy. The fovea was stimulated with a 5-degree flickering light spot surrounded by a 20-degree annulus of steady retinal illuminace. The stimulus was applied to the eye with the use of a hand-held stimulator-ophthalmoscope. FCERG signals were analysed by means of Fast Fourier Transformation method.

Mean FCERG amplitudes, phase and standard deviation (SD) values were established in 3 control groups of different age. There was in decrease in amplitude of FCERGs with age, which is a agreement with literature data. In this study significant abnormalities of the FCERG recordings are illustrated in some cases of known macular diseases.

Our preliminary clinical investigations manifest the value of the FCERGs in objective evaluations of macular diseases undetectable with conventional electroretinography.