Abstract
Abstract: :
Purpose:To use enucleated porcine eyes as a novel dry eye model with adjustable 'tear volume' and 'blink rate' to simulate dry eye condition, and to use the model to investigate the efficacy of artificial tears in protection of the corneal surface from desiccation. Methods: Porcine eyes were enucleated with the nictitating membrane, lacrimal gland and some connecting conjunctival tissue. The entire eyeball was placed in a holder with the cornea facing up, and the nictitating membrane was positioned to act as an eyelid, exposing the whole cornea to air when in the 'open' position. The lacrimal gland was held by a movable mechanical arm, and arranged so that the nictitating membrane could sweep over the corneal surface when the arm moved to and fro along the plane parallel to the corneal surface, simulating blinking. Just before 'blinking', a drop of PBS was applied to the limbal region next to the nictitating membrane by an infusion wing, thus spreading the drop of solution across the corneal surface during 'blinking'. Room temperature and humidity were maintained between 19–21°C and 50–60% respectively. The time interval between each 'lacrimation and blinking' cycle was 60s. An extra drop of artificial tears was applied onto the cornea every 5 minutes in the experimental group (n=5), and a drop of PBS at the same interval in the control group (n=5). The integrity of the cornea was assessed by fluorescein stain at the beginning and the end of the four–hour–experiment. The cornea was then stained by trypan blue dye and the numbers of stained corneal epithelial cells (central and peripheral) were counted. Results: There was a significant increase in the fluorescein grading of the cornea in the control group (p=0.042), but not in the experimental group (p=0.066). The number of stained cells in the peripheral cornea of the control group was significantly larger than those in the experimental group (p=0.008). However, there was no difference between the numbers of stained cells in the central cornea of the two groups (p=0.310). Conclusions: This novel porcine dry eye model, with lacrimation and blinking system, is a potentially useful biomonitoring tool for the study of exposure keratitis (dry eye syndrome), and these preliminary data will support future studies on the efficacy of artificial tears in corneal protection.
Keywords: cornea: tears/tear film/dry eye • cornea: epithelium