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Correlation of Multifokal-ERG (MF-ERG) and Heidelberg Retina Tomograph (HRT) in the follow up of Open Angle Glaucoma (OAG).
B. Heinemann-Vernaleken, A. M. Palmowski, R. Allgayer, U. Müller-Richter
Purpose: To study the correlation between changes in retinal function using the MF-ERG and alterations in optic disc parameters using the HRT in the follow-up of patients with OAG.
Methods: 11 eyes were included in the study. MF-ERG recordings and HRT were obtained on the same day and at follow-up ~3 months later. During an 8-minute MF-ERG recording (M-sequence 215, Lmax: 200 cd/m2, 100% contrast) 103 Hexacons stimulated the central 50 deg.of the retina. The first order response component was analyzed. The ratio of the peripheral response average (P) and of the responses grouped around the optic disc (O) to the central response average (C)was obtained for each recording. The percentage of difference between these 2 MF-ERG recordings and those of the individual HRT measurements were correlated.
Results: Changes in the MF-ERG of glaucoma patients compare to changes in the optic nerve head morphology observed in the HRT. Interestingly, in the MF-ERG this correlation is especially apparent in regard to changes in the ratio of the peripheral response average versus the response averages around the optic disc. The best correlation was seen between the latency of the first negative peak and the cup area as well as the cup/disc area ratio (r>0.9 for P/O). The mean cup depth correlated well (r>0.7 for P/C) with the latency of the first positive peak.
Discussion: These results are in agreement with the notion that retinal function in glaucoma is affected differently in the area around the optic nerve head as is also seen in form of Bjerrum scotomata in conventional visual fields (eg. Octopus G32).
Conclusion: This pilot study shows a good correlation between MF-ERG measures and HRT measurements. Therefore it seems worthwhile to further assess the clinical utility of this finding using a larger patient group and a longer follow up.
Supported by DFG Pa 609/2
Universitätsaugenklinik, Kirrbergerstr. 1, D-66421 Homburg, Germany