Dynamics of retinal function after multiple photodynamic therapies in age-related macular degeneration: a report of cases

Purpose: To monitor retinal function after multiple laser treatments by photodynamic therapy (PDT) with the multifocal electroretinogram (mfERG) in age-related macular degeneration (AMD). Methods: Five eyes of five subjects with AMD were investigated before the first and I month after each of three PDT treatments. Function was assessed using the cone- and rod-mediated mfERG, high-contrast distance visual acuity, central visual fields and contrast sensitivity. For each subject the local first-order mfERG results before treatment were used as a template and fitted against the local post-treatment results (Matlab, Mathworks). Results: We found transient reduction of the cone- and rod-mediated amplitudes between the first and second treatments but stable or improved mfERG function in four of five eyes for the cone-mediated mfERG and in all eyes for the rod-mediated mfERG after three treatments. Visual acuities and contrast sensitivities remained stable between treatments in four and two eyes respectively, whereas visual fields showed substantially higher mean defects in two subjects after all treatments. Conclusion: As found in previous studies of the cone-mediated mfERG after one PDT treatment, objective function was stabilized after multiple treatments in this case report. Similarly, although poor at baseline, rod-mediated function was not further compromised. Transiently reduced amplitudes after I month possibly reflected choroidal hypoperfusion. A larger sample size is needed to confirm if additional evaluation using electrophysiological criteria might be helpful in re-treatment decisions during PDT.