Effects of acute in vivo exposure of rabbit cornea and conjunctiva to artificial sunlight

Abstract

AbstractPurpose Acute exposure of ocular and periocular tissues to natural or artificial light can induce inflammatory responses, attributed mainly to the UVB range of the spectrum. In this study, we have used a model of acute exposure of rabbit eyes to artificial sunlight, to study possible alterations in the architecture of corneal and conjunctival tissue as well as in the expression of tumor necrosis factor (TNF) and platelet activating factor (PAFR) in these tissues.Methods New Zealand albino rabbits were immobilized opposite a 300W light bulb and exposed for 30 min to an equivalent of 7,500 Jm‐1 of UVB irradiation, in the range of the reported threshold for corneal damage. Corneal and conjunctival tissue samples were removed from exposed eyes at 2, 6 and 24 hours following the end of the exposure to the bulb light, and were subsequently processed for histochemical staining or RNA extraction. The gene expression of TNF and PAFR was monitored with RT‐PCR.Results Histopathological examination revealed minor changes in the corneal architecture. A distinctive eosinophilic infiltration was observed, as early as 2 hrs post‐exposure, in the conjunctiva of the third eyelid, both in the epithelial layer and the basal lamina, which had apparently subsided by t = 24 hrs. The gene expression of TNF and PAFR was monitored with RT‐PCR.Conclusion Acute exposure to artificial sunlight caused a marked accumulation of eosinophils in rabbit conjunctival epithelium but only minor changes in the corneal epithelium. Neither TNF nor PAFR gene expression was affected appreciably