Longitudinal changes in Langerhans cell density of the cornea and conjunctiva in contact lens-induced dry eye

BackgroundThe aim was to determine longitudinal changes in Langerhans cell density (LCD) in the human cornea and conjunctiva during asymptomatic and symptomatic contact lens wear. MethodsTwenty-five participants with contact lens-induced dry eye (CLIDE) and 35 without CLIDE (NO-CLIDE), diagnosed using a range of symptom questionnaires and objective tests (tear film break up, cotton thread tear test and corneal staining) were enrolled. The central cornea and nasal bulbar conjunctiva were examined using a Heidelberg laser scanning confocal microscope at baseline and following one, four and 24 weeks wear of daily disposable hydrogel contact lenses. Twenty-three non-contact lens-wearing controls were also examined. Langerhans cells were counted manually from randomly selected images. ResultsIn the cornea, mean and standard error of the mean LCD was greater after one week of lens wear in CLIDE (55 7 cells/mm(2)) versus NO-CLIDE (43 +/- 4 cells/mm(2)) (p = 0.041) and controls (27 +/- 4 cells/mm(2)) (p < 0.001). LCD was also greater in NO-CLIDE versus controls (p = 0.010). At week 4, LCD was greater in CLIDE (41 +/- 6 cells/mm(2)) versus controls (27 +/- 4 cells/mm(2)) (p = 0.004). There were no other significant differences between groups at weeks four or 24. In the conjunctiva, LCD was greater after one week of lens wear in CLIDE (17 +/- 1 cells/mm(2)) (p = 0.003) and NO-CLIDE (17 +/- 3 cells/mm(2)) (p = 0.001) versus controls (7 +/- 1 cells/mm(2)). There were no significant differences between groups at weeks four or 24. ConclusionsThe initial transient increase in corneal and conjunctival LCD in CLIDE (versus NO-CLIDE) suggests an inflammatory component in the aetiology of this condition.