Spatiotemporal Contrast Sensitivity in Patients With Type 2 Diabetes Mellitus

Abstract

Abstract: : Purpose: To evaluate the spatiotemporal contrast sensitivity in patients with Type 2 diabetes mellitus (DM) with no or minimal background diabetic retinopathy. Methods: 20 patients with Type 2 DM, aged 59.0 (SD 9.9) years and 23 age matched controls aged 55.9 (SD 13.4) years were recruited. Duration of DM was 8.60 (SD 6.0) years. Spatiotemporal contrast sensitivity (CS) was assessed at spatial frequencies of 0.025, 0.5 and 10c/d at temporal frequencies of 2.17, 6.50 and 21.66Hz. The stimuli were vertical sinusoidal gratings generated by a VSG 2/5(Cambridge Research System Ltd) and presented either on monitor or back projected with minimal distortion on a curved diffusing screen using a video projector. Visual fields (HFA Program 24–2 and the SITA Standard) and FDT (Full Threshold C–20 Program) perimetry were also assessed. Results: Three spatiotemporal frequencies were significantly reduced in the DM patients; 0.025c/d at 2.17Hz, 0.025 c/d at 6.50 Hz and 10 c/d at 21.66 Hz (p<0.05). The mean sum log CS (sum of the log CS for all 9 spatiotemporal frequencies) was also found to be reduced in the DM patients (p<0.05). Significant reductions in the MD, PSD were found in the DM patients using the HFA (p<0.05). No significant differences were found for the FDT indices. Conclusions: The spatiotemporal CS and visual fields were reduced in patients with no or minimal background diabetic retinopathy. These findings appear to suggest that both the P and M pathways could be affected in the early stages of diabetic retinopathy.

Keywords: diabetes