City Research Online

Abstract

Background and aims: The refractive error of the eye is dependent on its axial length. Refractive error is known to fluctuate significantly in poorly controlled diabetic patients. Recently it has been reported that human eyes fluctuate in axial length during the day. However, this change is not detectable in all subjects, suggesting physiological influences such as diet. The purpose of this study was to investigate fluctuations in axial length and blood glucose levels (BGLs) in diabetic patients and control subjects, using partial coherence interferometry.

Material and methods: Periodic axial length measurements were taken with an IOLMaster (Zeiss, Oberkochen, Germany) in 21 type 2 diabetic subjects (age 56 ± 11 years), 19 type 1 diabetic subjects (age 38 ± 15 years) and 18 non-diabetic controls (age 46 ± 22 years). Additionally, BGLs were measured using a HemoCue Beta glucose analyser (HemoCue, Ängelholm, Sweden). Measurements were taken between 8AM and 8PM at approximately two hourly intervals. The ocular length variability was mapped against time of day and related to BGLs, age, and the degree of diabetic retinopathy.

Results: Axial length variations were found to be significant with time (ANOVA, P=.003) and there was a significant effect for the interaction between group and time of day (ANOVA, P<.0005). DM type 1 and control subjects showed a significantly increased axial length in the afternoon compared to in the morning (t-test, P<.0005). No significant change was observed among DM type 2 subjects. Axial length fluctuated sinusoidally with time of day. A three-parameter sinusoidal curve was used to fit each set of axial length measurements, which resulted in a correlation coefficient R2 ≥0.7 in 62% of type 2 diabetic subjects, 78% of type 1 diabetic subjects and 72% of control subjects. Multiple regression analysis established that neither BGLs, age, nor the degree of diabetic retinopathy had a significant effect on the fluctuations of the axial length (P>.05)

Conclusion: Axial length varies throughout the day in diabetic and control subjects; however, this change does not appear to be significant in every individual. The data suggest a maximum axial length value in the afternoon. Changes in axial length from baseline did not correlate with BGLs, age, or the degree of diabetic retinopathy. Therefore, blood glucose levels may not be the main physiological influence in axial length fluctuations.

Publication Type:	Conference or Workshop Item (Paper)
Subjects:	R Medicine > RC Internal medicine R Medicine > RE Ophthalmology
Departments:	School of Health & Psychological Sciences > Optometry & Visual Sciences

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