Abstract
Purpose :
Despite the clinical importance of evaporative dry eye, the inflammatory response and structural change that occur on the ocular surface in exposure keratopathy are not well understood. We hypothesized that the involvement of inflammatory cells, cytokines, and ocular epithelial pathologies in short term exposure keratopathy would result in a long recovery period post exposure termination.
Methods :
A short term exposure keratopathy model in New Zealand white rabbits was made by opening the right eyelids for 4 hours(h), then discontinuing the exposure for 0h, 4h, 8h and 24h (N=3x 4 groups=12). Ultrasound pachymetry and HRT in vivo confocal microscopy were used to detect central total corneal thickness, while in vivo confocal microscopy and impression cytology were used to evaluate the morphology of ocular surface epithelium and the infiltration of inflammatory cells. At 0h, 4h, 8h and 24h after discontinuation of exposure, immunohistochemistry was performed to stain for macrophages, neutrophils, CD4(+)T cells and CD8(+)T cells. Ocular surface change was detected via scanning electron microscopy (SEM). Tear film concentrations of IL-1, IL-2, IL-8, IL-17 and TNF-α were analyzed by multiplex immunobead assay.
Results :
After discontinuation of eye exposure, recovery of corneal thickness was found within 4h. In vivo confocal microscopy showed no morphological change in the peripheral corneal, limbal and perilimbal conjunctival epithelia at all examined time points. Time-dependent decrease in inflammatory cell infiltration was found, which consisted of macrophages, neutrophils and T cells (p<0.01). SEM of corneal surface after exposure termination showed time-dependent recovery in the intercellular gaps and epithelial cell sloughing, which previously increased during exposure. While our previous study found increased tear film concentrations of IL-8, IL-17 and TNF-α between 0h to 4h of exposure termination, these cytokines showed recovery at 24h with no significant difference from before 24h of exposure termination (p>0.05). There was no change in IL-1 and IL-2 concentrations during the entire observational period (p>0.05).
Conclusions :
Recovery of inflammatory response and ocular surface structure takes time after recovery of exposure keratopathy. Time-dependent decrease in several cytokines was found in tears within 24h after termination of eye exposure.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.