Purpose:
To compare scanning laser polarimetry (SLP) measurements of the peripapillary retinal nerve fiber layer (RNFL) thickness in diabetic patients with healthy subjects.
Methods:
A cross–sectional study was carried. A total of 20 diabetic patients (35 eyes) and 13 healthy volunteers (25 eyes) were included. All subjects underwent a complete ophthalmic evaluation. Patients with significant ocular disease other than diabetic retinopathy were excluded. Scanning laser polarimetry with variable corneal compensation (GDx–VCC) was performed to obtain RNFL thickness measurements. The following GDx–VCC parameters were analyzed: TSNIT (temporal–superior–nasal–inferior–temporal) Average, Superior Average, Inferior Average, TSNIT SD, The Number, Superior Maximum, Inferior Maximum, Normalized Superior Area, Normalized Inferior Area, Ellipse SD and Ellipse Average. The mean of two optimal image scans of each eye was used for statistical analysis.
Results:
All GDx–VCC parameters analyzed demonstrated statistically significant alterations (P<0.001) when comparisons were made between healthy individuals and diabetic patients with retinopathy. The diabetic patients had thinner RNFL thickness than healthy subjects (P<0.001). This difference was mainly due to the diabetic patients that had previously undergone panretinal photocoagulation (PRP). The mean (± SD) TSNIT average thickness in diabetic patients with PRP, diabetic patients without PRP and healthy subjects was 42.9 ± 6.1 µm, 55.8 ± 5.7 µm and 56.0 ± 6.2 µm, respectively (P<0.001). The parameter The Number was significantly greater in diabetic patients with PRP (53.2 ± 12.1) than in diabetic patients without PRP (20.0 ± 10.1; P<0.001) and healthy subjects (13.9 ± 9.4; P<0.001).
Conclusions:
Diabetic patients have thinner peripapillary RNFL thickness than healthy individuals. This fact should be taken into account when evaluating RNFL thickness of glaucomatous patients with diabetic retinopathy, especially those who underwent PRP.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • nerve fiber layer • diabetic retinopathy