Purpose: To report the density and morphology of probable-Langerhans cells (LC) in the cornea and their association with clinical parameters in keratoconus (KC).
Methodology: This pilot study included 16 KC subjects aged between 18-65 years. Central corneal sub-basal nerve plexus was imaged using in vivo confocal microscopy and montaged using Adobe Photoshop. The nerve fibre density in a cropped 1 mm2 image was calculated using Neuron J software. Nerve fibre tortuosity was graded on a scale 0-5. For LC density, the number of LC were manually counted and averaged across three images. LC morphology was graded on a 0-3 scale, where grade 3 indicates LCs with long visible dendrites. The data from the more severe eye of each subject were included in the analysis. Associations of LC with other clinical variables were evaluated using Spearman’s correlation and statistical significance was set at p < 0.2 for this pilot study.
Results: 75% of subjects were male, 50% had severe KC (keratometry ≥52D) and 50% were contact lens wearers. The median LC density for the whole cohort was 15 cells per mm2 (IQR: 4-20). LC morphology of grades 2 or 3 (with short or long dendrites) was seen in 63% of subjects. LC density was significantly higher in males (p=0.033), those who frequently rubbed their eyes (p=0.117), and was associated with nerve fibre density and tortuosity (rho and p values = -0.451,0.106 and 0.495,0.072 respectively). LC morphology was associated with nerve fibre tortuosity, duration of the disease and systemic allergy (rho and p-values = 0.492,0.074; 0.372,0.156; 0.397,0.128). There was no significant association with age, severity, contact lens wear, ocular symptoms or tear variables.
Conclusion: This is the first study to examine LC density and its associations in KC. Based on the association of LC cell density and morphology with nerve parameters, we speculate the possibility of inflammation as the underlying cause for corneal nerve changes that observed in KC.