Biomedical Engineering Reference
In-Depth Information
Fig. 5 Ocular fundus photograph of a guinea pig demonstrating a paurangiotic
pattern of retinal vasculature. This vascular pattern is typical of guinea pigs,
some marsupials, and horses and is characterized by retinal vasculature
restricted to the peri-papillary portion of the optic disc
The second goal is to determine if an appropriate dose can
reach the ocular target tissue and be effective in the eye using a
dosing route and frequency that is clinically feasible. These studies
would determine the pharmacokinetics and pharmacodynamics of a
specific route of administration of a drug, typically in a normal eye,
then repeated using the optimal dosing and routes in eyes of
models of the disease state. For this second group of studies to be
clinically valid in most instances, the animal models would have to
have eyes anatomically similar to the target species and in the case of
humans, use of the dog, pig, or primate eye would be most appro-
priate. Finally, when selecting the appropriate animal model, the
target tissue and disease state has to be paired with the most
appropriate route of therapy (Fig.
6
). This determination is impor-
tant for pharmacokinetic, toxicologic, and efficacy studies.
When evaluating living ocular tissues for evaluation of ocular phar-
macokinetics, pharmacodynamics, and toxicity, normal animals are
typically studied, the more uniform to each other the better to
minimize biologic variability (and thus increase statistical power
of the experiments). These animals are purpose bred for biomedical
studies, and in the case of rodents, have similar if not identical
genetic background.
To determine the effect of a drug on ocular disease, whether
the disease is induced or naturally occurring, animal models of the
4.1.2 Induced Models
Versus Naturally Occurring
Models of Ocular Disease
