Historically used as a food additive, lissamine green (LG) is an organic, high-visibility dye and is indicated for aiding the diagnosis of ocular surface disease. LG stains dead and degenerate cells and mucus. This can help optometrists evaluate ocular surface damage by highlighting changes in the conjunctiva that are associated with a lack of tear flow, excessive dryness and redness. 

The importance of the dye in assessing and monitoring severity in dry eye disease was reinforced by the publication of the Dry Eye Workshop Report II (DEWS II) by the Tear Film and Ocular Surface Society (TFOS, 2017). 

In contact lens patients experiencing discomfort, LG staining of the circumlimbal region of the eye may indicate that the lens is too tight or has a sharp edge. Other uses include assessment of epithelial damage in cataract surgery. 

So why, given its apparent advantages, has LG been under-utilised by practitioners? Reasons include a lack of understanding or confidence over its use in eye assessments, a belief that fluorescein is sufficient for both bulbar conjunctiva staining and for the cornea, and the comparative cost and time taken to sufficiently view staining by LG compared with fluorescein.