Tracking oscillatory potential delays in patients with diabetes and no retinopathy after short-term levodopa treatment

Abstract

Purpose : Dim flash oscillatory potential (OP) delays have previously been shown to be an early indicator of retinal dysfunction in both diabetic rodents and in patients with diabetes mellitus (DM) and no fundus abnormalities. Our previous work showed two weeks of levodopa treatment to have restorative effects on OP delays in patients. While OP timing is progressively more delayed with duration of DM in rodents, whether OP timing in patients changes with DM progression is not known. This study aimed to assess dim flash OP implicit times in DM patients multiple years after receiving a short-term treatment of levodopa.

Methods : Participants (n=9) were recruited from the Motz et al. 2020 study cohort, comprised of DM patients who had OP delays and no diabetic retinopathy (DR) randomized to high or low dose Sinemet (levodopa+carbidopa) treatment for two weeks. OP timing was measured in each eye of participants using a handheld electroretinogram (ERG) at a visit 4.5-6 years after levodopa treatment. OP measures from each participant’s most delayed eye were selected for analysis. ERGs and OPs from baseline, immediately post-levodopa treatment (IPT), and the extended post-levodopa treatment (EPT) visit were marked using the same filtering and analysis software (ERGassist, Feola et al. 2023). The presence of diabetic retinal vascular pathology was assessed using fundus photography and scored by an ophthalmologist. One-way ANOVA was used for analysis of the data.

Results : As shown previously, the OP implicit time delays decreased from baseline (values are mean +/- std for OP2: 47.29±4.67 ms) compared to IPT (42.63±5.22 ms). At the EPT visit, OP implicit times (45.75±6.89 ms) increased compared to IPT but did not surpass the baseline delays. Three participants developed clinical fundus signs of diabetic retinopathy within this period.

Conclusions : During this multi-year period, the OP implicit times became more delayed, compared to IPT measures, nearly returning to baseline levels. Surprisingly, the OPs did not become more delayed than baseline, suggesting that the short duration of levodopa may have provided lasting benefit. Alternatively, OP delays may not progress as rapidly in patients with DM compared to observations in diabetic rodents. Future randomized-controlled, clinical studies examining levodopa’s effect on OP delay progression in DM are needed.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.