To investigate the diurnal variation of subjective visual symptoms of diabetic patients and to evaluate its correlation with visual acuity, blood pressure, blood glucose and OCT-measured macular thickness.

Fifty-five diabetic patients (56 eyes) who were hospitalized for the operation of the fellow eye were enrolled in the study. They underwent optical coherence tomography (OCT) measurements of macular thickness with retinal mapping protocol of OTI/SLO OCT at 5PM, 8PM on operation day, and at 7AM, 10AM on following day. Visual acuity (log MAR), refraction, intraocular pressure, blood glucose and blood pressure were also measured at each time. We surveyed the patients' symptomatic visual variation and its pattern if there is any change over a day.

Thirteen patients (25%) had reported changes in their subjective visual symptom over a day according to their blood glucose level. Among twenty-four cases with changes in their subjective visual acuity throughout the exam, only ten showed their real visual acuity change in accordance with their symptoms.

One fourth of our diabetic patients stated fluctuation in their vision according to their blood glucose level, but there were no correlations between visual acuity, blood glucose level and macular thickness.