Abstract
Abstract: :
Purpose: This study examined the effect of age on the multifocal flash electroretinogram (mFERG). Methods: mFERGs were recorded with a VERIS system (Electro-diagnostic Imaging, CA) using DTL fiber electrodes from 60 normal phakic subjects (21-80 yrs) and 10 pseudophakes (60-80 yrs). Their pupils were fully dilated, refractive errors corrected and accommodation of the phakic subjects blocked. Visual stimuli consisted of 103-scaled hexagons with a mean luminance 100cd/m 2 and 50% contrast. The entire stimulus array subtended 31 deg vertically and 37 deg horizontally at a viewing distance of 48 cms. The monitor frame rate was 75Hz, M-sequence exponent 15 with 1 frame/M-step and amplifier cut off frequencies 1 and 100Hz. In each quadrant the responses were analyzed in 3 groups (12 groups altogether). Only the first order kernel was analyzed. Results: Under the above recording conditions the mFERG responses of phakics consisted of an early negative potential N1, followed by two positive potentials P1 and P2. The implicit times of N1 showed statistically significant increase with age at various locations in both nasal and temporal fields, however N1 amplitudes did not change with age. The implicit times of P1 and P2 increased with age. For each individual, the amplitude of P1 measured from the N1 trough was larger in the nasal field and decreased in size at locations equidistant from fixation in the temporal field. On the other hand, P2 amplitude measured from N1 trough did not show significant differences between nasal and temporal field locations. At each retinal location P1 amplitude showed a tendency to decrease with age, which was strongest for extreme locations in the nasal field. P2 amplitudes did not change appreciably with age. Consequently for each subject, the P2/P1 amplitude ratio was lower in the nasal field compared to ratios at comparable eccentricities in the temporal field. Further, within each retinal location the ratio increased with age, again the effect being stronger for nasal field locations. Implicit times and amplitudes of N1, P1 and P2 for pseudophakics were comparable to those of age-matched phakic subjects indicating that the effects of age observed under the above recording conditions are not due to age-related changes in the optical quality of the lens. Conclusions: mFERG responses obtained with the above recording paradigm demonstrate age-related alterations. Age-related lenticular changes cannot satisfactorily account for these effects. Neural factors are likely to make significant contributions.
Keywords: electroretinography: clinical • visual fields • aging