Tear Film Alterations in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

Area of Science:

• Ophthalmology
• Endocrinology
• Systematic Review & Meta-Analysis

Background:

• Type 2 diabetes mellitus (T2DM) is increasingly recognized for its effects beyond the retina, impacting the ocular surface.
• Chronic hyperglycemia in T2DM can lead to meibomian gland dysfunction, reduced tear secretion, and impaired corneal sensitivity.
• These factors contribute to tear film instability and dry eye disease symptoms, though previous findings have been variable.

Purpose of the Study:

• To systematically review and meta-analyze observational studies on tear film parameters in adults with T2DM compared to non-diabetic controls.
• To clarify the extent of ocular surface alterations in T2DM.

Main Methods:

• Adherence to PRISMA guidelines for systematic review and meta-analysis.
• Inclusion of observational studies comparing tear film parameters (tear break-up time, Schirmer test, tear meniscus height, OSDI) in T2DM adults versus controls.
• Analysis of data from 24 studies involving approximately 3500 eyes.

Main Results:

• Most studies reported significantly reduced tear stability and secretion in T2DM participants.
• Shorter tear break-up times and lower Schirmer test results correlated with diabetes duration and glycemic control.
• Modestly reduced tear meniscus height and generally higher Ocular Surface Disease Index (OSDI) scores were observed in T2DM patients.

Conclusions:

• T2DM is strongly associated with tear film instability, reduced tear secretion, and increased dry eye symptoms.
• Routine ocular surface assessment should be integrated into diabetic care.
• Standardized, longitudinal investigations are needed to further understand these associations.