It is widely accepted that an abnormal, hyperosmolar tear film cannot successfully support the ocular surface ultimately leading to a loss of mucin-producing goblet cells and an increase in conjunctival and corneal surface desquamation.
In general, the cell-to-cell junctions of the corneal epithelium are more resistant to the adverse effects of a dysfunional tear film than are those of the conjunctival epithelium. Hence, the earliest identifiable changes of a challenged ocular surface usually can be seen in the conjunctiva prior to those of the morphlogically more resilient cornea.
Vital dye staining of the ocular surface can highlight the disruption of the cellular junctions and identify cells that are devoid of mucin, devitalized and dead. Fluorescein is better suited to the former task, highlighting pathologic changes in the cornea. Rose Bengal and Lissamine Green have similar staining patterns, identifying the later groups, that is, cells in stress. Lissamine Green is better-tolerated and less toxic than Rose Bengal, making it the dye of choice to identify early changes in the conjuctival surface in ocular surface disease.