Scleral Changes Induced by Intravitreal Injection of Atropine in an Experimental Model of Myopia in Chickens

Abstract

Purpose: : To determine the effect of different atropine dose in the sclera of experimental model of myopia in chickens.

Methods: : New born White Leghorn chickens (Gallus gallus domesticus), underwent induction of experimental myopia by monocular application of diffusers for 12 days starting at the day of hatching. Six groups of 6 animals were measured: negative control (non manipulated animals), positive control (experimental myopia induced by diffusers) and 4 experimental groups that get 12.5µl of intravitreal injections of 250, 750 and 2500 µg of atropine in saline and a group with only saline. Injections were performed ones a day starting on day 9 for 4 days. Refractive errors (RE) were measured by automated infrared (IR) photoretinoscopy and scleral changes in the posterior pole of the eye were evaluated by histopathology (classic light histology and cellular proliferation with 5-bromo-2'-deoxyuridine, BrdU, a commonly marker which is detected with an indirect immunohistochemical technique).

Results: : Animals develop experimental myopia (-3 D) with changes in scleral thickness and cell proliferation (increase in the cartilaginous layer and decrease in the fibrous layer).These changes were modulated by atropine in terms of reductions of RE and changes in the two layers of scleral tissue: cartilaginous and fibrous layer. Interesting, BrdU positive cells were increased by atropine in the fibrous layer and decreased in the cartilage.

Conclusions: : Intravitreal injection of atropine revert the effect of experimental myopia induced by diffusers with histological changes in the scleral layers:In the fibrous layer the cellular proliferation and the thickness were increase while in the cartilage the cellular proliferation and thickness were decrease.

Keywords: myopia • sclera • refractive error development