The role of hormonal regulation in the impact of blood glucose fluctuations on refractive changes in individuals with and without diabetes

Background and Aim: Fluctuations in blood glucose levels, especially during hyperglycemia, have been linked to visual disturbances in diabetic patients, though the mechanisms remain unclear . It is known that blood glucose fluctuations can influence refractive values, but whether these changes lead to myopia or hyperopia is uncertain . This study investigates whether hormonal regulation (cortisol, IGF-1, GH, or insulin) modulates the relationship between blood glucose and refractive changes.

Methods: A total of 61 participants were included, with 58 completing the full procedure. Among them, 40 without diabetes: 22 with obesity (BMI≥30 kg/m²) and 18 healthy without obesity. 18 participants with type 2 diabetes were included. Participants without diabetes underwent a 1-hour glucose tolerance test. Blood glucose levels, hormones (insulin, cortisol, IGF-1, GH) and refraction measurements were taken during fasting and at defined time points. Participants with diabetes had measurements taken throughout the day, pre- and postprandial. To explore the relationship between blood glucose fluctuations and refractive changes, univariate linear regression was performed. Group differences were examined using a Fisher's Z-test. A chi-square test compared the distribution of refractive changes between groups. Repeated measures correlation between blood glucose and refractive values was performed, separately for non-diabetics and diabetics. Moderation and mediation effects of fasting hormone levels on the relationship between blood glucose and refraction were analyzed.

Results: Maximal blood glucose fluctuations showed a significant correlation with maximal refractive changes in the univariate linear regression (F(1,56)=6.19; p=0.016). A Fisher's Z-test revealed no significant differences between groups regarding the relationship between maximal blood glucose increase and maximal refractive changes (healthy/obesity: Z=0.74; healthy/diabetes: Z=0.85; obesity/diabetes: Z=0.16). A chi-square test showed no significant differences in refractive category distribution (χ²(1)=7.43, p=0.16). No significant correlation between blood glucose and refraction was found in both diabetics (r=0.0425, p=0.469) and non-diabetics (r=-0.1235, p=0.327). Cortisol was found to significantly moderate the relationship between fasting glucose and fasting refraction, with a significant interaction effect (p=0.0401). Other moderation and mediation analyses did not yield significant results [1] [2].

Conclusion: No direct relationship between blood glucose concentration and refraction was found. However, maximal blood glucose increases were associated with maximal refractive changes: strong blood glucose spikes were linked to hyperopia, while smaller spikes correlated with myopia. Additionally, cortisol appears to moderate glucose-dependent refraction, potentially promoting myopia.

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Artikel online veröffentlicht:
28. Mai 2025

• Literatur

• 1 Gwinup G., Villarreal A.. Relationship of serum glucose concentration to changes in refraction. Diabetes 1976; 25: 29-31
• 2 Calvo-Maroto A.M., Perez-Cambrodí R.J., Albarán-Diego C., Pons A., Cerviño A.. Optical quality of the diabetic eye: a review. Eye 2014; 28: 1271-1280