RNFL thinning in diabetic peripheral neuropathy
Progressive thinning of the retinal nerve fibre layer (RNFL) in the superior quadrant is apparent in patients with diabetic peripheral neuropathy (DPN), a new prospective longitudinal study has found. This thinning is more pronounced in older individuals.
In the study population of 105 type 1 diabetes mellitus (T1DM) patients (mean age 45±15 years), 61 percent did not have obvious diabetic retinopathy (DR) while 36 percent had mild retinopathy. Moderate nonproliferative retinopathy was observed in two participants, while mild proliferative retinopathy was reported in one.
Grouping according to the Toronto criteria showed that 20 percent (n=21) had DPN (DPN+ve), while the remaining 80 percent (n=84) did not (DPN-ve). Diabetes duration (10.0 vs 33.5 years; p<0.01) was significantly longer and baseline total RNFL (102.5 vs 109.5 µm; p=0.01) was significantly thinner in DPN+ve participants.
Linear mixed models with overall RNFL thickness (p=0.02) and thickness of the RNFL superior quadrant (p=0.01) as dependent variables revealed that changes in RNFL thickness in relation to neuropathy status over time were significant.
In contrast, when thickness of the RNFL nasal (p=0.05), inferior (p=0.79) and temporal (p=0.40) quadrants were designated as dependent variables, RNFL changes over time, in relation to neuropathy status, did not reach statistical significance.
“DPN is a common and potentially debilitating complication of diabetes and its diagnosis relies on traditional measures of neuropathy,” explained researchers. While previous cross-sectional studies have shown that RNFL thickness is decreased in DPN, there has thus far been a scarcity of relevant longitudinal information. [Diabet Med 2012:29:e106-e11; Curr Eye Res 2016;41:1359-1366]