Longer axial length and higher axial length-to-cornea ratio are possible protective factors against diabetic retinopathy either developing or  progressing,, according to a study published in Acta Ophthalmologica. Refractive status, on the other hand, was not significantly associated with the condition or visual threatening diabetic retinopathy.

The cross-sectional study examined the association between ocular biometric parameters, myopia, and diabetic retinopathy in 1838 Chinese adults with type 2 diabetes mellitus. Of those studied, 1455 (79.2%) patients did not have diabetic retinopathy and 383 (20.8%) did.

Study authors took measurements of the patients’ corneal diameter, central corneal thickness (CCT), corneal curvature (CC), anterior chamber depth (ACD), lens thickness (LT), and axial length (AL). They calculated lens power and axial length-to-cornea radius ratio (AL/CR ratio) and determined spherical equivalent with auto-refraction following pupil dilation. They also used multivariate logistic regression analyses to find any associations of ocular biometry related to diabetic retinopathy and vision threatening diabetic retinopathy (VTDR).


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“After adjusting confounding factors, any diabetic retinopathy was independently associated with AL (OR 0.84 per 1 mm increase, 95% confidence interval (CI): 0.74, 0.94) and AL/CR ratio (OR 0.26 per 1 increase, 95% CI: 0.10, 0.70),” researchers report.

“Similarly, the presence of VTDR was independently related to AL (OR 0.67 per 1 mm increase, 95%CI: 0.54, 0.85) and AL/CR ratio (OR 0.04 per 1 increase, 95%CI: 0.01, 0.25). The lens power may not be significantly correlated with presence of any diabetic retinopathy or VTDR. The CC, corneal diameter and refractive status were not significantly correlated with presence of diabetic retinopathy or VTDR,” the study says.

Investigators say that more longitudinal studies are needed, to determine if the refractive status and AL-associated parameters “contribute to the occurrence and progression of diabetic retinopathy in type 2 diabetes mellitus.”

Limitations of the study include how a casual relationship between biometry parameters and diabetic retinopathy needs to be verified with a longitudinal, not cross-sectional study, as this is. All patients in this group had type 2 diabetes, so more research will be needed in the type 1 diabetes patient population. And then there’s this: “The AL is not an easily obtained parameter for low income and resource poor population, which may limit the clinical application for the risk stratification based on AL-related parameters.”

Finally, this research was conducted in communities in only Guangzhou, China, and because myopia has an ethnic heterogeneity, it’s tough to generalize conclusions from the study, researchers write. “Multi-ethnic and multi-centre studies are warranted to verify our findings.”

Reference

Wang L, Liu S, Wang W, et al. Association between ocular biometrical parameters and diabetic retinopathy in Chinese adults with type 2 diabetes mellitus. Acta Ophthalmologica Published online ahead of print 2020 Nov 16. doi: 10.1111/aos.14671