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

To study the influence of photodynamic therapy (PDT) on retinal function in patients with a predominantly classic choroidal neovascular membrane. Comparative observational study. Sixteen eyes with a choroidal neovascular membrane eligible for PDT were included. 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. 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. 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° was reduced below the normal level. Although it improved slightly after PDT, it remained below the normal range. In the central 7.5°, retinal sensitivity increased by up to 80 dB and within the paracentral 7.5° to 15°, it increased by up to 183 dB in 13 eyes. 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.