Can the mfERG Be Used to Follow-up AMD Patients after PDT and Predict the Need for Retreatment?

Abstract

Abstract: : Purpose : A decrease in the central mfERG peak time latencies seems to occur following PDT. Our goal was to further document this finding in non-dilated eyes, before and after PDT and see if we could identify a latency criterion that could be used to predict the need for retreatment. Methods :18 AMD patients (mean age: 72±11 y.o.) with CNV had a mfERG followed by PDT. Stimulus consisted in a 61-hexagon matrix with the mean luminance set at 400 cd/m^-2. Recordings (DTL), were obtained using 16 segments of 15 sec each. Signal was filtered (10-100 Hz) and amplified (100,000x). P1 latency was measured for each Ring (5). Results : P1 latency of 35 msec or higher was present in 100%, 72%, 56%, 50% and 50% in Rings 1,2,3,4 and 5 respectively. The mean latency ±SD of Ring 1 and 2 were 38.9±3.5 msec and 37.1±3.5 msec respectively. One month after PDT in 10 patients retested so far, P1 latency in Ring 1, was significantly decreased by 3.0 msec on average (p=0.01). After 2-5 months, a return to pre-PDT value was observed in all 10 patients. Fluorescein angiogram obtained at 3-5 months after PDT in 6 patients so far, confirmed the presence of leakage along with a P1 latency of 35 msec or higher in Ring 1 (N=5) and Ring 2 (N=1; parafoveal leakage). Conclusions: Our data suggest that a latency of at least 35 msec is present in Ring 1 when CNV is present or when leakage (post-PDT) occurs. P1 latency in Ring1 appears to be useful to follow-up patients with CNV and predict the need for retreatment. The mfERG as obtained in non-dilated eye, could become a useful tool to follow-up patients more regularly especially if earlier retreatment is recommended in the near future.<br

Keywords: electroretinography: clinical • age-related macular degeneration • photodynamic therapy