Corneal epithelial dendritic cells, tear neuropeptides and corneal nerves continue to be affected more than 12 months after LASIK

Abstract

Purpose: LASIK causes corneal nerve damage and may affect the neuro-immune crosstalk. This study examined the effects of LASIK on corneal epithelial dendritic cells (CEDC) density and morphology and explored their relationships with corneal nerves and tear neuropeptides. A grading system was developed to assess CEDC morphology.Methods: Intra-and inter-observer repeatability of the CEDC morphology grading system was established using kappa (κ). In vivo confocal microscope images of the central cornea were captured from 20 participants who had undergone LASIK 12-16 months earlier and 20 controls (age 18-32 years, 55%F). CEDC density was counted manually, and CEDC morphology was assessed using a new grading system. CEDC sub-types (contacting nerves [CEDCc] and not contacting nerves [CEDCnc]) were also assessed. Differences in CEDC density and morphology were examined using mixed models and chi-squared test. Relationships between CEDC and corneal nerve parameters and tear substance P were explored using Spearman's correlation.Results: Excellent intra-and inter-observer repeatability was demonstrated for the grading system (κ = 0.82-0.97). In post-LASIK participants, CEDC density was lower compared with controls (5 [0-34] vs. 21 [7-77] cells/mm 2 ; p = 0.01), and the proportion of CEDC with thick dendrites was higher (55%-73% vs. 11%-21%, p < 0.003). Higher tear substance P levels were associated with higher CEDC density (rho = 0.48, p = 0.003). Fewer nerve interconnections were observed in participants in whom CEDC had dendrites (p = 0.03). CEDC sub-types followed a similar pattern to CEDC. Conclusions:The findings suggest that CEDC may remain altered more than 12 months post-LASIK. The association with substance P suggests a role for CEDC in corneal neurogenic inflammation.

Diurnal changes and topographical distribution of ocular surface epithelial dendritic cells in humans, and repeatability of density and morphology assessment

“…(54)(55)(56) The presence of thick dendrites is an indicator of migratory capacity of DC. (9,15,57) DC with migratory potential were evident mostly at the limbus. This may be due to their close proximity to limbal vessels which facilitate DC migration.…”

“…Bright/ hyperreflective cells at least 10 µm in size, with a linear/ curvilinear cell body, with or without dendrites (both short and long), located at the subbasal corneal epithelium and distributed among nerve fibres that do or do not cross them or conjunctival epithelium were considered as DC. (15) To minimise bias, DC density and morphology were assessed by an experienced investigator who was masked to the participants' identity and measurement timepoint.…”

“…DC body size and presence of dendrites at all locations were assessed using a grading system developed by our group. (15) Cell body size refers to the cell soma and does not include the dendrites and was graded as small (10-25 µm), medium (26-40 µm), or large (>40 µm), based on the largest cell body size observed in any of the 5 images (or in the single inferior whorl image). The measurement was based on an estimation of cell body size by using a pictorial reference as described previously by our group without further analysis by software to make it easy to use and accessible.…”

“…The measurement was based on an estimation of cell body size by using a pictorial reference as described previously by our group without further analysis by software to make it easy to use and accessible. (15) The presence of any dendrites, the presence of long dendrites and the presence of thick dendrites in any of the 5 images (or in the single inferior whorl image) were recorded. Images devoid of DC were not included in the DC morphology analysis.…”

“…(5) Changes in DC morphology can also be a marker of immune response activation, indicating the antigen capture and migratory capacity of these cells as summarised and reviewed. (2,(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) Ocular surface DC present in a steady state in ocular tissues that are in contact with the external environment and, in the event of an injury or insult, they undergo significant alteration to activate the immune response. (2) Upon activation, DC undergo morphological changes induced by the expression of surface markers such as major histocompatibility complex.…”