T1D Linked to Worse Contrast Sensitivity Function Among Patients Without Retinopathy

Individuals with type 1 diabetes (T1D) without diabetic retinopathy may experience worse contrast sensitivity function (CSF) than individuals without T1D, according to research published in Graefe's Archive for Clinical and Experimental Ophthalmology.

While it is known that CSF is impaired in patients with diabetes who also have retinopathy, there is limited evidence on the impact of diabetes on CSF in patients without any signs of retinopathy.

The current prospective, cross-sectional, case-control study included 80 patients aged between 11 and 47 years, with 40 patients with T1D and 40 without T1D. Both groups were mostly female and, in the T1D group, the mean (SD) T1D duration was 12.3 (8.7) years. Additionally, mean HbA1c was 7.44 (0.81) in the T1D group and 5.00 (0.19) in the control group (P < .001).

The groups also had similar characteristics regarding age, sex, visual acuity (VA), and refractive error (RE). All included patients had a distance and near corrected monocular VA better than 0.10 LogMAR, and an RE less than 4 diopters (sphere) and 3 diopters (cylinder).

The authors used the CSV-1000E test to assess CSF at 4 spatial frequencies—3, 6, 12 and 18 cycles/degree (cpd)—under 3 light conditions: high (550 lx), medium (200 lx) and low (< 2 lx). The loss in CSF among individuals with T1D was mainly at medium and high frequencies, and in all 3 light conditions analyzed, especially in medium and low-light conditions.

The spatial frequency most impacted by the presence of T1D was the highest frequency at 18 cpd, showing a statistically significant difference of 0.08 log units at high–, 0.10 log units at medium–, and 0.16 log units at low-light conditions in the mean CSF values. In contrast, the lowest decrease in CSF was observed at the lowest spatial frequency at 3 cpd, with no statistically significant difference between the groups (P > .05).

The authors also looked for any correlations between CSF and age, HbA1c, or T1D duration under different lighting conditions.

They observed a mild-moderate inverse statistically significant correlation between CSF and age for almost all spatial frequencies under all 3 lighting conditions. A weak inverse statistically significant correlation was also found between CSF and HbA1c at low-light conditions for 6 cpd, and at medium-light conditions for 12 cpd. However, no statistically significant correlations were observed at high-light conditions.

When considering T1D duration as 0 in the control group, a slight inverse correlation was found between CSF and T1D duration at all spatial frequencies under low-light conditions. However, when studying correlations between CSF and HbA1c, as well as CS and T1D duration only in the group with T1D, no significant correlations were observed between HbA1c and CSF. Meanwhile, a statistically significant correlation was found between T1D duration and CSF at 12 cpd under low-light conditions among individuals with T1D (ρ = -0.345, P = .029).

“This lower CS in people with T1DM, although it may have been statistically significant in some frequencies, depending on the illumination, was not clinically significant, as it was not enough to be able to discriminate when the vascular signs of DR would start, therefore, the follow- up of these patients over time is fundamental for early diagnosis,” the authors wrote.

Reference

Silva-Viguera MC, García-Romera MC, Bautista-Llamas MJ. Contrast sensitivity function under three light conditions in patients with type 1 diabetes mellitus without retinopathy: a cross-sectional, case-control study. Graefes Arch Clin Exp Ophthalmol. Published online April 11, 2023. doi:10.1007/s00417-023-06057-6