Prevalence of Dry Eye Disease in Patients With Diabetes Mellitus: A Systematic Review.

Dry eye disease (DED) is a multifactorial disorder of the ocular surface increasingly recognised as a complication of diabetes mellitus (DM). Prevalence estimates in DM patients vary widely due to differences in diagnostic methods and populations. This systematic review aimed to synthesise contemporary evidence on DED prevalence in DM patients and explore factors influencing variability, particularly diagnostic approaches. A systematic search was conducted in four databases (PubMed, Embase, Scopus, Web of Science) for studies published between January 2015 and June 2025. Eligible studies included those reporting the prevalence of DED in patients with type 1 or type 2 DM, using clinical assessments or validated diagnostic methods. Only peer-reviewed, full-text studies published in English were included. Following an initial screening of 2053 records, 18 studies met the inclusion criteria for qualitative synthesis. Risk of bias was assessed using the Newcastle-Ottawa Scale. Prevalence ranged from 6.6% to 72.3%. Rates were lowest in large administrative studies using the International Classification of Diseases (ICD) codes (6.6-14.4%), intermediate in questionnaire-only assessments (34.8-51.7%), and highest in multimodal clinical evaluations combining symptoms with objective tests (17.5-72.3%). Where non-diabetic controls were included, DED prevalence was consistently higher in DM patients. DED is highly prevalent in DM patients, with estimates strongly influenced by diagnostic sensitivity. This suggests underdiagnosis where administrative data or symptoms alone are used. Routine screening with sensitive multimodal tools is recommended in DM care. Future research should adopt standardised diagnostics and broader geographic representation to enable quantitative synthesis.