Purpose: To determine how Conjunctival Impression Cytology (CIC), Schirmer test, Tear Film Break up Time (TBUT) and Rose Bengal Stain (RBS) correlate with dry eye symptoms. To calculate the sensitivity, specificity and likelihood ratio (LR) of these tests for diagnosis of dry eye.
Methods: A case control study was done at two referral eye centers in northern part of the Indian subcontinent. Symptomatic patients with dry eye were recruited based on their response to a questionnaire of dry eye related symptoms (Table 1). Age and sex matched healthy subjects served as controls. Sensitivity and specificity, as estimated by the area under receiver operating characteristic (ROC) curve were primary outcome measures and the correlation between dry eye symptoms (DESS) and ocular surface tests, were secondary outcome measures.
Results: Eyes of 320 symptomatic patients were compared to 350 eyes of age and sex matched healthy controls. The mean symptom score in cases and controls was 8±2.6 and 1.2±2, respectively (P<0.001). The diagnostic accuracy of these tests was CIC (AUC=0.957) >TBUT (AUC=0.793)>Schirmer (AUC= 0.765)>RBS (AUC=0.723). There was a stronger correlation between symptoms, CIC (Pearson’s coefficient, Adjusted R2=0.774) and TBUT (R2=0.580). However, the correlation of RBS (R2=0.361) and Schirmer (R2=0.475) with dry eye symptoms although positive, was less significant (R2<0.5).
Conclusions: CIC correlates best with dry eye symptoms and has excellent specificity and sensitivity in diagnosing dry eye as compared to other tests evaluated in the study.