Abstract
Purpose::
To determine the impact of long-term diabetic control and acute fluctuations in blood glucose levels on the visual function of patients with diabetes.
Methods::
Two study groups were recruited: Group 1 comprised 20 Type 1 diabetic patients (mean age 37.9±15.39y: range 17-66y). Group 2 comprised 21 Type 2 diabetic patients (mean age 56.33±11.09y: range 37-72y). Patients attended 6 visits at 2 hourly intervals over a 12h period. Blood samples were collected at the first visit to determine haemoglobin (HbA1c) levels; blood glucose levels (Hemocue 201+), visual acuity (100% and 10% logMAR), contrast sensitivity (Pelli Robson), central visual fields (Humphrey Field Analyser Program using 10-2 white-on-white and 10-2 short wavelength automated perimetry (SWAP)), were measured at each visit. A simultaneous regression model was used to explore the relationship between test parameters and predictor variables: type of diabetes, haemoglobin levels, duration of diabetes and glucose level for each visit. Mixed between-within subject ANOVA and post-hoc analysis assessed variation in test parameters over time for both groups.
Results::
A significant multiple regression model emerged for contrast sensitivity only at visits 1, 2, 3 and 4 (p=0.023, p=0.022, p=0.020 and p=0.043 respectively) with HbA1c making the largest statistically significant contribution in explaining the variance in contrast sensitivity (ß= -0.455, p=0.005; ß= -0.534, p=0.002; ß= -0.565, p=0.001, ß= -0.591, p=0.003 respectively). A similar trend was observed for visits 5 and 6 with HbA1c being the only significant predictor within the model (ß= -0.520, p=0.006 and ß= -0.445, p=0.009 respectively). Statistical differences occurred over time for reduced contrast (10%) logMAR acuity (p=0.030), Pelli Robson contrast sensitivity (p=0.000) and SWAP visual fields MD (p=0.023). However, 100% logMAR acuity, white-on-white perimetry (MD and PSD) and SWAP PSD were unaffected.
Conclusions::
Long-term metabolic control impacts the visual function in diabetic patients with an inverse relationship exhibited between contrast sensitivity scores and HbA1c levels. Acute changes to blood glucose levels result in fluctuations of visual function in diabetic patients and should be considered when interpreting clinical examination.
Keywords: diabetes • contrast sensitivity • visual acuity