Functional evaluation using multifocal electroretinogram after selective retina therapy with a microsecond-pulsed laser

PURPOSE. To evaluate the changes of retinal function with multifocal electroretinogram (mfERG), and estimate the association between functional and structural changes after selective retina therapy (SRT) with microsecond-pulsed laser in comparison to continuous wave laser photocoagulation (cwPC).

METHODS. Selective retina therapy and cwPC were applied with 10 × 10 shots and 1/2 lesionwidth on the retina in the right and left eyes of 20 healthy Chinchilla Bastard rabbits, respectively. Optical coherence tomography (OCT), fundus fluorescein angiography (FFA), and mfERG were performed before, and on days 1, 7, and 30 after both laser treatments. The mean ratios of amplitudes and implicit times of N1 and P1 from eight hexagons covering lasertreated retinal lesions/total retina were measured. Histology was obtained after killing three rabbits at each time period to observe the anatomic changes after both laser treatments.

RESULTS. The mean ratios of amplitudes of N1 and P1 in SRT lesions did not change significantly for 30 days after laser treatment. Only subtle reductions of the mean ratios of N1 and P1 amplitudes on day 1, thereafter the amplitudes showed the trend to recover toward baseline values. Histology and OCT revealed temporary and reversible morphologic changes after SRT, which restored to normal within 1 month. However, the mean ratios of N1 amplitudes on days 7 and 30 (P = 0.010, P < 0.001, respectively), and P1 amplitudes on days 7 and 30 (P < 0.001, P < 0.001, respectively) declined significantly in cwPC lesions compared with baseline. Disorganization and atrophic changes were identified on histology and OCT after cwPC.

CONCLUSIONS. The results suggest that SRT preserved retinal function as well as anatomical structure after treatment.