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A Comparison of the Fast Stimulation Multifocal-ERG in Patients with an IOL and Control Groups of Different Age
Purpose: It has been shown that a cataract significantly reduces mfERG responses in the central 4-14°. Removing the cataract, leads to a significant increase in the response of the central 4°. In this study we compare the mfERG of Woerdehoff etal.'s patients' [Doc Ophthalmol 2004; 108(1): 67-75] following cataract surgery to a healthy control group in order to assess whether, in the elderly, further influences of age need to be considered in addition to optical effects. Methods: Eighteen patients with an IOL following cataract surgery and 29 healthy volunteers (without clouding of the media or retinal changes) underwent testing of the mfERG (103 hexagons stimulating the central 50°, M-sequence 215, Lmax: 200cd/m2, Lmin <1cd/m2). For the first order response component we compared the latencies of N1,P1 and N2 as well as the natural logarithm (ln) of the amplitudes N1P1 and P1N2 for four group averages: I. the central 4°, II. 4-7°, III. 7-10° and IV. 10-15°. Results: Mean age was 67years (SD 10.1) for the IOL patients, 28.5years (SD 5.6) for a young group of controls (n=15) and 60.2years (SD 9.2) for the older control group (n=14). Patients with an IOL did not differ in latency from either control group (ANOVA, Tukey). Interestingly, at 10-15° eccentricity, the latency of N2 differed significantly between the younger (41.4ms, SD 1.4) and the older (43.0ms, SD 1.9) control group. In the central 4° LnN1P1 amplitudes were significantly lower in the IOL group (mean: 3.7, SD 0.2) than either the younger (mean: 3.9, SD 3.3) or the older (mean: 4.0, SD 0.3) control group. In all other amplitude measures, the older control group had slightly larger mean amplitudes than the younger control group and significantly larger amplitudes than the patients with an IOL, whose amplitudes were lowest. Discussion: Both, primarily optical but also neural phenomena have been described to affect the mfERG changes observed with age. Our results, are in support of this, as the improvement of the mfERG response following cataract surgery does not seem to reach the level of a healthy control group of equal age. Thus, our results suggest, that a control group with an IOL should be used when retinal function is tested in subjects with an IO