Association between Sickle Cell Trait and the Prevalence and Severity of Diabetic Retinopathy.

Purpose: To determine whether Sickle cell trait (SCT) is associated with an increased severity of diabetic retinopathy.

Methods: This was a single center retrospective study case control study of 100 eyes of 100 patients with diabetes mellitus (DM) with SCT (SCT group) and 100 eyes of 100 age-matched patients with DM without SCT (control group). The main outcome measure was the difference in the prevalence of sight threatening DR [here defined as diabetic macular edema (DME) and/or proliferative diabetic retinopathy (PDR)], between the SCT and control groups. Secondary outcome measures included differences in visual acuity, ocular comorbidities, intraocular pressure, glycemic control as assessed by random blood glucose measurement, diabetes duration, nephropathy, hyperlipidemia and hypertension.

Results: The SCT group had statistically significantly shorter duration of DM (median [25% quartile] 15 [8.3] years versus 20 [14.7] years, respectively)(P<0.001) and presented with statistically better metabolic control (mean difference 1.6 mmol/l, (95% confidence interval [CI], 0.1-3.3;P = 0.03). The prevalence of PDR and/or DME was significantly lower in the SCT group (58%) compared to the control group, (95%)(P<0.001). The absence of SCT (adjusted odds ratio [AOR] = 24; 95% CI, 8-72; P<0.001) and longer duration of DM (AOR = 1.1 [95% CI, 1.02-1.13]; P = 0.003) were independent predictors of PDR and/or DME.

Conclusions: SCT seems to protect against the development and progression of DR. This may have implications for monitoring and screening. Prospective studies are required to confirm this association. If true, this association may indicate an increased blood glucose buffering capacity of abnormal hemoglobin.