ABSTRACT
Among a series of patients with age-related macular degeneration (ARMD), a few individuals could be identified showing larger amplitudes of pattern reversal visual evoked potentials (prVEP) after stimulation of a central 3 degrees field compared to stimulation of a 13 degrees field although in the majority of ARMD patients and in normals, VEP amplitudes increased with increasing field size. An analysis of prVEPs recorded after stimulation of different macular zones showed that the 3 degrees central area and the perifoveal zone contributed differently to the 13 degrees response or macular response. Perifoveal activity in this subgroup of ARMD patients seemed to mask the foveal contribution to the macular prVEP. The cortical magnification factor in ARMD may be higher than in normal controls. Small-field stimulation techniques are therefore also recommended in patients with central retinal pathology.
Subject(s)
Evoked Potentials, Visual , Fovea Centralis/physiopathology , Macular Degeneration/physiopathology , Visual Cortex/physiopathology , Adult , Aged , Evoked Potentials, Visual/physiology , Female , Humans , Male , Photic Stimulation , Reproducibility of Results , Signal Processing, Computer-AssistedABSTRACT
BACKGROUND: Results from psychophysical tests indicate that in age related macular degeneration (ARMD) retinal function is globally impaired. Observations in single ARMD cases showing abnormalities of the electrooculogram (EOG) and electroretinogram (ERG) encouraged us to systematically examine ARMD patients by means of electrophysiological tests to confirm a global retinal dysfunction in ARMD. METHODS: Sixty-six patients with ARMD were examined clinically and by means of EOG, ERG, triple scotopic ERG, and fluorescein angiography (FA). RESULTS: EOG data were considerably reduced in ARMD. Scotopic a- and b-waves of the ERG were mildly affected. The bright flash response showed reduced b-waves with normal implicit times. The amplitude of the oscillatory potential OP2 was significantly reduced and photopic responses were also pathologic compared with an age-matched control group. Geographic atrophy and pigment epithelium detachment showed specific abnormalities in the ERG, whereas in soft drusen EOG changes were more conspicuous. CONCLUSIONS: In addition to data from psychophysical tests the results from electrophysiological examinations indicated a global reduction of retinal function in ARMD which seemed to be present not only in the macula but also elsewhere in the retina.
