Follow up in open angle glaucoma. A comparison of static perimetry and the fast stimulation mfERG

PURPOSE: To compare changes in the mfERG to visual field changes observed in OAG. METHODS: Twenty-nine eyes with OAG were included. Visual fields (Octopus d32) and mfERGs (VERIS) were obtained at a mean interval of 9 months (SD 6 months). MfERG recording parameters were as follows: 103 hexagons stimulated the central 50 degrees. M-sequence 2--5, stimulus base interval 13.33 ms, Lmax 200 cd/m2, contrast 99%. First (KI) and second (KII) order response components were analyzed for the individual quadrants of the visual field and compared to the corresponding mean deviation (MD) of the static perimetry. RESULTS: Changes in visual field parameters and changes in the mfERG did not differ significantly. Overall, as mean deviation increased there was a tendency for implicit times to increase and for amplitudes to decrease. However, over the follow up interval of 9 months only minor changes were observed. The second order response component correlated best with changes in MD (p < 0.05). These were the correlation between MD and KII N1 (r: 0.36) in the upper temporal field, between MD and KII N2 (r: 0.40) in the upper nasal field and between MD and KII P1 (r: 0.38) in the lower temporal field. When a subgroup of 10 eyes that had been tested at least 3 times over 16.8 months (SD 5.5) was examined there were still only minor changes observed in either parameter. CONCLUSION: While the changes over time in the mfERG and the visual field showed a reasonable correlation, changes observed in either parameter were extremely small over the time period observed, thus requiring a longer follow up and/or a more sensitive stimulation technique.