(b)  

Vital dye staining
Study	Location	Year	Study design	Number of eyes	Major findings
Romero et al. [20]	Brazil	2013	Prospective case series	Pterygia (10) Actinic keratosis (10) Conjunctival intraepithelial neoplasia and conjunctival SCC (27)	Toluidine blue 1% is a good tool for the diagnosis of OSSN and premalignant lesions but the intensity of staining does not correlate with the degree of malignancy (sensitivity 100%, specificity 50%, PPV 73%, and NPV 100%).
Steffen et al. [21]	South Africa	2014	Prospective diagnostic validation	Malignant lesions including invasive SCC (16) and severe dysplasia (17) Benign or premalignant lesions (42)	Methylene blue 1% can exclude malignant lesions but cannot replace histopathology as the gold standard (sensitivity 97%, specificity 50%, PPV 60%, and NPV 95%).
Gichuhi et al. [22]	Kenya	2015	Cross-sectional, multicenter	OSSN (143) Non-OSSN (276)	Toluidine blue 0.05% is a good screening tool but not a good diagnostic tool due to a high frequency of false positives (sensitivity 92%, specificity 31%, PPV 41%, and NPV 88%).