The Application of in vivo laser scanning confocal microscopy as a tool of conjunctival in vivo cytology in the diagnosis of dry eye ocular surface disease

PURPOSE To evaluate the applicability of in vivo laser scanning confocal microscopy as a tool of conjunctival cytology in a prospective case-control study. METHODS Nineteen right eyes of 19 Sjogren's syndrome dry eye patients (19 females; mean age: 55.8±15 years), and 18 right eyes of 18 normal healthy control subjects (12 females and 6 males; mean age: 50.8±14 years) were evaluated in this study. The eyes were analyzed by the Heidelberg retina tomography (HRTII)/Rostock cornea module (RCM). Ocular surface and tear function tests including vital stainings (fluorescein and Rose Bengal), Schirmer test, tear film break up time (BUT), and conjunctival impression cytology were performed. After obtaining the confocal microscopy images, the mean individual epithelial cell area (MIECA), and nucleocytoplasmic (N/C) ratio were analyzed. The correlation between confocal microscopy and impression cytology parameters was also investigated. RESULTS The BUT, Schirmer test values, vital staining scores and squamous metaplasia grades in impression cytology were significantly worse in dry eye patients compared to controls (p<0.0001). The MIECA and the mean N/C ratios were worse in dry eye subjects compared to controls both in impression cytology and in vivo confocal microscopy (p<0.0001) with no significant differences between these parameters when the two examination techniques were compared. The MIECA and N/C ratio in conjunctival impression cytology showed significant correlation with the corresponding confocal microscopy parameters (MIECA, r2:0.557 ; N/C, r2:0.765). CONCLUSIONS Laser scanning confocal microscopy seems to be an efficient non-invasive tool in the evaluation of phenotypic alterations of the conjunctival epithelium in dry eye disease. N/C ratio and MIECA appear to be two promising and new parameters of in vivo confocal cytology in the assessment of the ocular surface in dry eye disease.