PURPOSE. To study the subbasal corneal plexus (SCP) in patients with diabetic retinopathy (DR) treated or nontreated with panretinal Argon laser photocoagulation (ALP). METHOD. Fifty consecutive patients with DR and 50 age- and sex-matched normal control subjects were examined with retinal tomography by a masked evaluator. The following subbasal plexus nerves parameters were considered: number per frame, tortuosity, and reflectivity. Diabetic patients were divided into two groups, according to the presence of proliferative versus nonproliferative retinopathy, according to the Early Treatment of Diabetic Retinopathy Study (ETDRS) classification. RESULTS. The number of fibers per frame and reflectivity were significantly lower in diabetic patients compared with control subjects (2.4 1 vs. 2.9 0.8, P 0.01 and 2.3 0.9 vs. 2.6 0.9, P 0.04, respectively). Tortuosity was significantly higher in diabetic patients (2.5 0.9 vs. 2.0 0.8, P 0.002). Number per frame and reflectivity were significantly lower in diabetic patients with proliferative diabetic retinopathy (PDR; respectively, 2.0 0.9 vs. 2.9 0.9, P 0.001, and 2.0 0.8 vs. 2.6 0.7, P 0.003). Tortuosity was significantly higher in the PDR group (2.2 0.8 vs. 2.8 0.9, P 0.008). The PDR group treated with ALP had significantly lower subbasal nerves number compared with the nontreated group (P 0.01). CONCLUSIONS. DR may induce substantial changes in the SCP. There is a difference between proliferative and nonproliferative retinopathy and in the former group between ALP treated and nontreated patients. (Invest Ophthalmol Vis Sci. 2009;50: 5155‐5158) DOI:10.1167/iovs.09-3384