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

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.

Influence of cataract on the multifocal ERG recording--a pre- and postoperative comparison.

To study the influence of cataract on the multifocal electroretinogram (mfERG), 18 patients underwent mfERG recordings prior to and following cataract surgery. The central 50 degrees of the retina were stimulated by 103 hexagons alternating independently between white and black according to a binary m-sequence. The frame rate was 75 Hz. The maximum luminance was 200 cd/m2, the minimum luminance < 1 cd/m2 with a mean luminance of 100 cd/m2. For each retinal location, the latencies of the first negative peak (N1), the first positive peak (P1) and the second negative peak (N2) as well as the amplitude from N1 to P1 and the amplitude from P1 to N2 of the first order response were obtained. Concentric ring averages around the foveal response were analyzed. Following cataract surgery, the mean amplitude of the response in the central four degrees increased from 37.83 to 42.37 for N1P1 (p = 0.019) and from 39.44 to 47.20 for P1N2 (p = 0.001). To reduce the influence of retest variability, each response average was divided by the recording's overall amplitude. For the central 4 degrees this ratio increased by 0.18 (p = 0.002) for N1P1 and by 0.27 (p < 0.001) for P1N2. Clouding of the optic media such as produced by cataracts has a slight but significant influence on the multifocal ERG.

Detection of retinal dysfunction in vitelliform macular dystrophy using the multifocal ERG (MF-ERG).

Vitelliform macular dystrophy (VMD) is widely known for an abnormal EOG in the presence of a normal ERG. In this study the multifocal electroretinogram (MF-ERG) is described as an additional tool to detect retinal dysfunction in VMD. Three patients aged 30, 37 and 59 years with VMD and a visual acuity of OD: 0.4; OS 0.05 (patient 1), 1.25 OU (patient 2) and OU: 0.6 (patient 3) underwent additional electrophysiological testing with the MF-ERG. A multifocal-ERG of the central 50 degrees of the retina was obtained using the VERIS-system. During recording 103 hexagons flickered according to a binary m-sequence of 2(15). Mean luminance was 100 cd/m2, contrast was set at 99%. The MF-ERG recordings were compared to age matched control groups. In all three patients the MF-ERG of the central 6 degrees showed reduced amplitudes for N1P1 (first negative peak to first positive peak) and for P1N2 (P1 to the second negative peak). Implicit times were not affected. Therefore the MF-ERG can detect focal retinal dysfunction in VMD which would not be apparent in the summed retinal response recorded with the ganzfeld ERG. In contrast to other diseases, amplitudes rather than implicit times seem to be affected in the MF-ERG of vitelliform macular dystrophy.

Multifocal stimulation techniques in ophthalmology -- Current knowledge and perspectives.

The purpose of this paper is to give a brief overview on the application of multifocal stimulation techniques in ophthalmology. The use of m-sequences as a stimulus sequence allows a high-resolution topographic mapping of sensory function. Outer retinal dysfunction can readily be detected with the multifocal ERG (mfERG). When the inner retinal contribution to the mfERG response is enhanced through adapting the stimulation sequence, the sensitivity of the mfERG to detect retinal dysfunction in glaucoma can be increased. Testing of the entire visual pathway with multifocal cortical evoked visual potentials is also possible and recent studies have focused on reducing interindividual variability. The use of m-sequence stimulation in magnetic encephalography offers new ways to study visual processing without the need to apply electrodes.

Influence of photodynamic therapy in choroidal neovascularization on focal retinal function assessed with the multifocal electroretinogram and perimetry.

PURPOSE: To study the influence of photodynamic therapy (PDT) on retinal function in patients with a predominantly classic choroidal neovascular membrane. DESIGN: Comparative observational study. PARTICIPANTS: Sixteen eyes with a choroidal neovascular membrane eligible for PDT were included. METHODS: Visual acuity, multifocal electroretinogram (MF-ERG, Electrodiagnostic Imaging, San Mateo, CA) recordings and visual fields (Octopus d32) were obtained before PDT with Visudyne, Novartis AG, Basel, Switzerland, and at follow-up 2 weeks to 3 months later. MAIN OUTCOME MEASURES: Visual acuity as well as peak-to-peak amplitudes, peak latencies, and focal differences in the scalar product of the two MF-ERG recordings were analyzed. Mean deviation, loss variance, and the absolute difference in sensitivity in the fields obtained were also analyzed. RESULTS: After PDT, mean visual acuity stabilized or improved in 13 eyes. Except for two eyes with a predominantly parafoveolar choroidal neovascular membrane, the MF-ERG contribution from the central 4 degrees was reduced below the normal level. Although it improved slightly after PDT, it remained below the normal range. In the central 7.5 degrees, retinal sensitivity increased by up to 80 dB and within the paracentral 7.5 degrees to 15 degrees, it increased by up to 183 dB in 13 eyes. CONCLUSIONS: Consistent with the results of the treatment of age-related macular degeneration with photodynamic therapy (TAP) study, PDT can lead to stabilization of visual acuity. Improvement in parafoveal function can be demonstrated in the central visual field, as well as in MF-ERG recordings, even in patients whose visual acuity remains stable. Therefore, the MF-ERG and central perimetry may aid the assessment of retinal function in treatment trials of patients with age-related macular degeneration.