The use of 1% toluidine blue eye drops in the diagnosis of ocular surface squamous neoplasia.

Purpose: To evaluate the use of in vivo toluidine blue (TB) dye in the diagnosis of ocular surface squamous neoplasia and to correlate staining intensity with the histopathological diagnosis.

Methods: A prospective study was performed at the Federal University of Sao Paulo, Brazil. Patients with conjunctival epithelial lesions were examined by slit-lamp biomicroscopy, with and without 1% TB eye drops, and the results were photo documented. Before the instillation of the dye, 1% proxymetacaine HCl eye drops were used. All patients were submitted to surgery and histopathological analysis to confirm the diagnosis. The patients were grouped according to the histopathological aspects of the lesions into 3 groups: group 1-patients with ocular surface squamous neoplasia; group 2-patients with premalignant lesions; and group 3-patients with pterygium. The digital images were analyzed by 2 masked examiners who had no previous access to the histopathological results. The photographs were classified according to the positivity and intensity of the staining. The statistical analysis method chosen depended on the type of data, with the level of significance set as P < 0.05.

Results: Forty-seven patients were included in the study: 10 had benign lesions (pterygium), 10 had premalignant lesions (actinic keratosis), and 27 had malignant lesions (conjunctival intraepithelial neoplasia and conjunctival squamous cell carcinoma). Agreement between observers regarding the analysis of the digital photographs was 100% for positivity and 82.9% for intensity of staining (κ = 0.938). Ninety percent of patients with premalignant lesions and all patients with malignant lesions showed positive staining with 1% TB. One patient had positive staining, but histopathological examination revealed a benign lesion (false positive).

Conclusions: The use of 1% TB eye drops is an efficient method for the clinical diagnosis of ocular surface squamous neoplasia and premalignant lesions. Nevertheless, the intensity of the staining does not correlate with the degree of malignancy of these tumors.