Conjunctival MUC5AC+goblet cell index: relationship with corneal nerves and dry eye

PurposeTo evaluate the relative proportion of conjunctival MUC5AC+ and MUC5AC- goblet cells in a post-LASIK population and their association with dry eye indicators and corneal nerve morphology using a MUC5AC+ Goblet Cell Index.MethodsTwenty subjects who had undergone LASIK >12months previously and 20 age-matched controls were recruited. Dry eye symptoms, tear breakup time, osmolarity, meniscus area and corneal nerve morphology were examined. Conjunctival impression cytology samples were collected from inferior-temporal bulbar conjunctiva using Millicell (R) inserts. Total goblet cell density was determined from positive cytokeratin-7 (CK7) immunolabelling; MUC5AC+ goblet cell density was determined from both CK7+- and MUC5AC+-immunolabelled cells. The ratio of MUC5AC+ to total density was defined as the MUC5AC+ Goblet Cell Index. Differences in variables between groups and the associations between goblet cell variables and clinical assessments were examined.ResultsNo significant differences in the total and MUC5AC+ goblet cell density and tear film parameters were found between groups, although greater ocular discomfort was reported in the post-LASIK group (P=0.02). A higher MUC5AC+ Index was associated with worse/greater dry eye symptoms (=0.55, P=0.01) and higher nerve tortuosity (=0.57, P=0.01) in the post-LASIK group; lower nerve density and thickness was found in controls (>-0.45, P<0.05), but not associated with tear film parameters.ConclusionsThe MUC5AC+ Goblet Cell Index provides an indicator of mucin secretion for assessing the goblet cell function in dry eye. In the post-LASIK participants, we found an increased MUC5AC+ Index associated with worse dry eye symptoms and adverse changes in corneal nerve morphology.