Developing a rat model of UVB-induced ocular surface and eyelid injuries mimicking ocular rosacea

Abstract

Purpose : Ocular Rosacea (OR) is a common chronic inflammatory and neurovascular disease of the ocular surface and eyelids associated with meibomian gland (MG) dysfunction. Despite the vision threatening consequences, OR is underdiagnosed and incurable. There is also a lack of experimental models for pathophysiological study and candidate drug screening. UVB is a well-known triggering factor for cutaneous rosacea through the production of ROS and inflammatory cytokines. We aimed to develop a rat model of UVB-induced ocular surface and eyelid injuries mimicking ocular rosacea.

Methods : Eyes of adult SD rats (n=12 ) were exposed to 380 µW/cm² of UVB light (wavelength, 280-315 nm) for 4 min daily for 5 days. Eyelids (n=16) were shaved and exposed to 1.4 mW/cm² of UVB for 10 min daily for 3 days. Corneal morphology was evaluated in vivo by Micron III optical coherence tomography (OCT). Corneal smoothness and opacity were graded under slit lamp, and fluorescein-stained corneal epithelial defects were quantified. Eyelids were also observed macroscopically and microscopically. Rats were then euthanized, corneas and eyelids were dissected for histologic analysis.

Results : OCT and slit lamp showed a significant increase in corneal thickness (p＜0.001), corneal irregularity and opacity after UVB exposure. Corneal epithelial defects were observed in all rat eyes with an average size of 20% of corneal surface. Histology showed loss of corneal epithelial cells, stromal edema and infiltration of inflammatory cells. Eyelid skin was red and edematous, and covered with yellowish secretion after UVB irradiation. Slit lamp microscopy revealed telangiectasia with hyperemia of eyelid margins, drop out of some eye lashes and exudation in both eyes. Histology of eyelid showed cell infiltration in the epidermis and conjunctiva, and loss of hair follicles. Morphological abnormalities of MG include irregular epithelial layout, cell shedding and inflammatory exudation in gland ducts, and cavitations and nuclei distortion in acinar cells.

Conclusions : UVB-induced corneal, eyelid and MG damages are similar to clinical features of ocular rosacea. Changes in ocular surface innervation, immune cell population, oxidative stress status and MG function need to be further characterized. Chronic effects of UVB exposure on ocular surface and eyelid will also be investigated.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.