Experimental Study Of Swelling Corneai Microstructure And Opticai Properties

Purpose:To observe and assess the corneal changes in the macro-and micro-structure and light transmittance of two different models of corneal edema.Methods:Model A (endothelial cells (ECs) damage model):a cross with a length of2mm in both directions was made on the central corneal endothelium of the Healthy clean grade Sprague Dawley rats (SD rats) weighing about200g by using a needle, then immersed the eyeball in the ringer’s solution (sodium chloride:0.85%; potassium chloride:0.03%; calcium chloride:0.033%) at4℃and replenished the solution every24hours; observe the general structure (GS) and make a photograph for record according to different observation time points in order to calculate relative gray scale (RGS), ultrasonic corneal thickness measurement used to calculate the swelling rate, detect the corneal transmittance, observe the corneal microstructure and make a photograph for record under electron microscopy on the other group of specimens via the same procedures. Model B (hypotonic model):scrape the epithelium from the cornea of the SD rats and immerse the eyeball in the hypotonic solution at4℃, the remaining operations were the same as model A.Results:General structure (GS):as time prolonging, corneal edema showed a gradual worsening trend in anterior photography in both of the models. Relative gray scale (RGS):model A, with time prolonging, the RGS decreased gradually and a valley was met at day8, after which it remained at this level between8d and9d; model B, the RGS decreased gradually from instant to4w. Swelling rate (SR):model A, as time went by, SR showed a rapid increase firstly, and then a slow increase was visible up to the peak, following which was a stable state; model B, from instant to4w, SR increased rapidly at first and slowed down the increasing speed later. Electron microscopy:in either of the model, with the passage of time, the structure of corneal collagen fibers themselves was still regular while the spacing between them increased gradually within a certain period of time (Instant-24h); after that, the structure of collagen fibers became disordered and irregular as well as necrotic cell organelles and other unknown substances deposited. Light transmittance(LT):in both models, with time passing by, the LTs of the cornea showed a decreasing trend throughout the visible light range; further analysis of LTs at different measurement time points from three wavelength ranges of Red (R), green (G) and blue (B) displayed that the differences of LTs at different wavelength ranges(red, green, blue) were statistically significant (P<0.001) in model A which was in the opposite in model B (P>0.05).Conclusion:For two models of corneal edema, the cornea edema in macrostructure, the spacing between collagen fibers as well as the diameter themselves in microstructure and the light transmittance in central cornea showed a certain regularity.