Abstract
Purpose::
The purpose of this study was to investigate diurnal fluctuations in aberrations and blood glucose levels (BGLs) in diabetic patients and control subjects.
Methods::
Twenty-one type 2 diabetic subjects (age 56 ± 11 years), 20 type 1 diabetic subjects (age 38 ± 15 years) and 20 non-diabetic controls (age 49 ± 23 years) took part in the study. The distribution of refractive errors was similar between groups (p=0.96). Aberrations were measured with an OPD autorefractometer (NIDEK) and analysed for a 5mm pupil diameter. BGLs were measured using a finger stick test (Hemocue). All measurements were taken six times during the day, between 8AM and 8PM at approximately two-hourly intervals.
Results::
The coefficients of third order coma, fourth order spherical aberration, and higher-order RMS error were found to be higher in the diabetic compared to the control group. The mean variation in the third and fourth order aberrations over the twelve-hour period was found to be higher in the diabetic when compared to the control group; however, these differences were not statistically significant. The higher-order RMS error showed a negative correlation with time in the diabetic group compared to a positive correlation in the control group (gradient: -6.4 x 10-3 in type 2 diabetes, -24.4 x 10-3 in type 1 diabetes and 74.9 x 10-3 in control group; ANOVA p=0.025). In diabetic patients, increasing BGLs showed a negative trend with the third order horizontal coma (p=0.44) and fourth order spherical aberration coefficients (p= 0.61), while a positive trend was observed between BGLs and the third order vertical coma (p=0.58) and higher order RMS (p=0.47).
Conclusions::
Compared to controls, diabetic patients exhibit greater variation in higher order aberrations. Ocular aberration coefficients varied during the day, with fluctuating BGLs. The variation in ocular aberration coefficients is possibly due to the effect of large fluctuations in BGLs leading to hydration effects on the diabetic crystalline lens.