Experimental study to investigate the safety of new intraocular bio-degradable implant for drug delivery to the posterior segment of an eye

Purpose: to prove the safety of dexamethasone-free and dexamethasone-loaded intraocular implants in the experiment in vivo. 

Materials and methods. The study included 60 Chinchilla rabbits (120 eyes). In the first series of animals,dexamethasone-free implants were inserted into the anterior chamber of the eye in the rabbits of the 1st group, and into the vitreous cavity in the rabbits of the 2nd group. In the second series, dexamethasone-containing implants were inserted into the anterior chamber of the eye in the rabbits of the 3rd group, and into the vitreous cavity in the rabbits of the 4^th group. The intraocular structures were evaluated by ophthalmologic examinations: slit lamp biomicroscopy, fundus photographic images, electroretinography (ERG) performed before the implantation and in dynamics. In the same time period, the animals were withdrawn from the experiment, the eyes enucleated, and morphological studies performed. 

Results. Being inserted into the anterior chamber of the eyes in the rabbits of the 1st and 3rd group, the implants settled on a surface of an iris, occupied the position in the anterior chamber bottom. The implants were resorbed within 31–33 days. Throughout the whole study period, no intraocular structure abnormalities were identified by the slit lamp biomicroscopy in the rabbits of the 1st and 3rd groups. Morphological studies of the eyes demonstrated no structural abnormalities in the cornea, iris, or the ciliary body, either. While studying the effects of dexamethasone-free and dexamethasone-containing implants on the posterior structural segments of the eyes in the rabbits of the 2nd and 4^th groups immediately after intravitreous implantation, the implants were identified positioned in the anterior third of the vitreous of a rabbit eye. Their gradual resorption took the whole study period. Implants were not identifiable any more in the vitreous body at day 35. No evident abnormalities were seen in the structures of the eye anterior segments, vitreous body, or retina throughout the study period. Histological examination showed no abnormalities of the retinal or other intraocular structures. 

Conclusions: in the experimental study in vivo, the developed implant has proved to be an inert, biocompatible intraocular system for drug delivery and posing no toxic effects on eyeball structures of a rabbit.

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