Abstract
Purpose: :
We demonstrated that repeated exposure to Jogging Board (JB) treatment under desiccating conditions induced abnormal tear dynamics and superficial punctate keratopathy (SPK) similar to that in humans. This study investigated changes in the structure of the corneal epithelial surface and tear film stability during dry eye induction.
Methods: :
A series of treatments were performed under continuous exposure to low–humidity airflow (25 ± 5%, 2–4 m/s). Seven–week–old SD rats were placed on a JB made of a plastic pipe for 7.5 h/d, then housed in individual cages without JB treatment for 16.5 hours. Morphological changes in the superficial layers of the corneal epithelium were examined by scanning electron microscopy (SEM). Rat tear film stability was evaluated using a noninvasive specular reflection video recording system (DR–1, Kowa Company Ltd., Tokyo, Japan) during sustained eye opening following forced blinking.
Results: :
On SEM examination, bright cells covered a large area and a high–density of microvilli and microplicae were noted in nontreated cornea. Apparent increase of the dark cells, covered by flat surface, was observed on day 5. In addition to the increase in dark cells, the mosaic–like pattern of epithelia was diminished on day 10. In nontreated eyes, there were no apparent changes after 5 minutes of sustained eye opening compared with the initial tear film images. In contrast, a number of distinct tear film break area appeared as dark spots within 5 minutes on day 10.
Conclusions: :
Our findings showed that loss of microvilli on surface cells and tear film instability were induced by our dry eye induction method. This model supports the importance of the fine structure of the corneal epithelial surface in maintaining the tear film status under dry eye conditions.
Keywords: cornea: tears/tear film/dry eye • cornea: epithelium • cornea: basic science