Focal electroretinograms and fundus appearance in nonexudative age-relatedmacular degeneration - Quantitative relationship between retinal morphology and function

Background: The aim of this study was to evaluate the focal electroretinogr am (FERG), an objective indicator of outer retinal function, in nonexudativ e age-related macular degeneration (NE-AMD), and to compare FERG results wi th morphological lesions assessed by stereoscopic fundus photographs and fl uorescein angiograms. Methods: Twenty-five patients (25 eyes) with bilateral NE-AMD (visual acuit y of the study eyes greater than or equal to 0.4) as well as 10 age- and se x-matched control subjects (10 eyes) were evaluated. FERGs were recorded fr om the macular region (9 degrees) in response to sinusoidal stimuli flicker ed at 32 Hz. Amplitude and phase angle of the Fourier-analyzed FERG fundame ntal component were measured. Fundus lesions were graded from color slides according to the Wisconsin age-related maculopathy grading system [15]. Flu orescein angiograms were evaluated by an image analysis technique to comput e the area with pathological hyperfluorescence (associated with drusen and/ or retinal pigment epithelial atrophy) within the macular (approximately 9 degrees x9 degrees) region. Results: Compared to control eyes, NE-AMD eyes had a reduction in the mean FERG amplitude (57% loss, P<0.001) with no phase changes. Amplitudes of ind ividual affected eyes were negatively correlated with either the Wisconsin grading score (r=-0.63, P<0.001) or the percentage area of pathological hyp erfluorescence (r=-0.70, P<0.01). Eyes with minimal NE-AMD lesions (Wiscons in score less than or equal to 6) and normal acuity had a lower mean amplit ude (47% loss, P<0.05) than that of control eyes. Conclusions: The results indicate that, in NE-AMD, the FERG is altered in p arallel with the extent and severity of fundus lesions. However, a function al impairment of outer macular layers, which is detected by FERG losses, co uld precede morphological changes typical of more advanced disease.