Multifocal electroretinograms in age-related macular degeneration before and after photodynamic therapy

To evaluate multifocal electroretinograms (mfERG) and macular retinal thickness before and after photodynamic therapy (PDT) for predominantly classic choroidal neovascularization (CNV) (classic type) and occult with no classic CNV (occult type).

Recording of mfERG and measurement of macular retinal thickness were performed before and after PDT in 19 patients (19 eyes) with the classic type and 24 (26 eyes) with the occult type. The evaluation items were the amplitude of the first negative wave (N1), the amplitude from the peak of the negative wave to that of the following positive wave (P1), and the peak latencies of the negative and positive waves.

Compared with mfERG before PDT, that after PDT showed a significant decrease in the P1 latency in the central area (31.1 ± 1.9 ms before and 29.6 ± 1.6 ms after PDT) for the classic type and significant decreases in both the central (32.0 ± 2.0 ms before and 30.5 ± 2.4 ms after PDT) and peripheral (30.2 ± 2.0 ms before and 29.5 ± 2.0 ms after PDT) areas for the occult type. Optical coherence tomography showed significant decreases in macular retinal thickness in both groups (464 and 314 µm before and after PDT, respectively, for the classic type and 516 and 340 µm for the occult type).

After PDT, retinal function evaluated by mfERG improved for both the classic and occult types, and the recovery of P1 latency may be due to improvement in retinal edema.