Measuring the refractive properties of the diabetic eye during blurred vision and hyperglycaemia using aberrometry and Scheimpflug imaging

This study aimed to measure the refraction and geometry in the diabetic eye during the presence and absence of hyperglycaemia and blurred vision, using aberrometry and Scheimpflug imaging. Aberrometry and Scheimpflug imaging were used to examine ocular refraction and higher-order aberrations, as well as the shape of the cornea and the lens, in 25 patients with diabetes mellitus. From these parameters, the equivalent refractive index of the lens was calculated. Using paired t-tests, comparisons were made between a first series of measurements (Visit 1) taken in the presence of blurred vision and hyperglycaemia (> 10.0 mu mol/l), and a second series of measurements (Visit 2) taken under normal conditions. The mean difference in blood glucose between Visits 1 and 2 was 5.9 mmol/l (standard deviation [SD] 3.1) (p < 0.0001). Both small hyperopic and myopic shifts of equivalent refractive error (ERE) were found in nine patients (mean absolute difference ERE: 0.38 D [SD 0.12]; p = 0.02). Furthermore, higher-order aberrations (root mean square [RMS] error) were slightly increased in four patients (mean difference RMS error: 0.07 mu m [SD 0.02]; p = 0.04) at Visit 1, compared to Visit 2. No significant changes were observed in the shape of the cornea or lens in any of the patients. No significant correlations were found between changes in blood glucose levels and the measured parameters in diabetic eyes. The present study suggests that subjective symptoms of blurred vision during hyperglycaemia are not necessarily caused by changes in the refractive properties of the diabetic eye.