Volumes and routes of drug administration into different structures of the eye in laboratory animals

The modern rhythm of life leads to an intensive increase in the number of eye diseases, resulting in the need to develop new ophthalmic medicines. It is necessary to conduct preclinical studies on animals in order to register the drugs on the pharmaceutical market. The aim of the review is to systematize and summarize information about the structural features of the eye in animals used in preclinical studies, methods and volumes of drug administration into various structures of the laboratory animals’ eyes. Literature search was conducted in PubMed and Google Scholar databases. Publications that came out within the last 5 years were prioritized. This paper presents literature data on various volumes and methods of administration of ophthalmic drugs to such types of laboratory animals as mice, rats, pigs, rabbits, cats, dogs and non-human apes. The paper analyses interspecies differences in the structure of the eye in comparison with the human eye, which is reflected with the original illustrative material. The anatomical features of the eye of some species of laboratory animals are described, as it is necessary to keep this in mind in the determination of the administration volumes by different methods into the structures of the eye. The paper discusses local, intravitreal, intracameral and subconjunctival volumes of ophthalmic administration, taking into account the required instrument of administration and the type of anesthesia (for ophthalmic injections). It presents advantages and disadvantages of each administration method and the range of their use in veterinary and preclinical research. This paper assesses anatomical and physiological barriers for each route of administration into the eye, which can affect the delivery of the drug to a certain part of the eye and the achievement of the desired pharmacological effect. Determination of optimal injection volumes and their implementation in ophthalmic drug studies is important to ensure animal welfare and reduce animal stress in accordance with the rules of Good Laboratory Practice, the “3Rs” — concept, the principles of bioethics and humane treatment of animals.