Background: Diabetes mellitus has a wide spectrum of effects on the ocular surface. Conjunctival impression cytology (CIC) is a relatively easy and non-invasive technique that allows for the evaluation of the morphology of the conjunctival epithelium and changes in the conjunctival goblet cells.

Objective: To assess conjunctival impression cytology patterns in controlled and uncontrolled diabetic patients and correlate cytological findings with HbA1c levels.

Materials and Methods: A comparative observational cross sectional study conducted in the Department of Ophthalmology, National Institute of Medical Sciences and Research, Jaipur, for 18 month. The total 216 patients with type 2 diabetes mellitus were divided into two groups: controlled (HbA1c level was ≤6.5%) and uncontrolled (HbA1c level was >6.5%). Ophthalmological detailed examination and impression cytology of the conjunctiva were carried out. The nasal bulbar conjunctiva was sampled under topical anaesthetic, stained for cytological examination and classified using Nelson’s classification. Descriptive statistics and Student’s t-test were used in SPSS and Microsoft software for data analysis.

Results: 216 subjects participated in the study, with a mean age of 59.3 ± 10.2 years. The goblet cells were more common in the controlled group (80.0%) than in the uncontrolled group (59.4%), while the metaplastic cells were more common in the uncontrolled group (24.5% vs 10.0%). Nelson Grade 0 was mainly seen in controlled patients and Grades 2 and 3 were more common in uncontrolled patients (p=0.001). There was a significant association among fundus findings and HbA1c status (p=0.001) with the uncontrolled group having more cases of proliferative DR and clinically significant ME. Nelson grade (p=0.008) was significantly associated with the duration of diabetes. Patients with HbA1c >6.5% were more likely to have reduced corneal sensation (10.18%) compared with patients with HbA1c <6.5% (p=0.001) who had no reduced corneal sensation. Conclusion: There were positive associations between glycaemic control and duration of diabetic disease and increasing severity of abnormalities in the conjunctival epithelium. CIC may be a helpful non-invasive tool for early detection of changes in the ocular surface in diabetic patients