The unique sensitivity of the rabbit eye to x-ray-induced ocular inflammation

Marijuana-derived material-induced changes in monkey ciliary processes differ from those in rabbit ciliary processes

The morphologic changes in ciliary processes and the associated intraocular pressure (IOP) were observed in owl and squirrel monkeys after intravitreal (IVT) and intravenous (IV) injections of water soluble marijuana-derived material (MDM). The response in monkeys differed from that reported in rabbits wherein IV injection induced severe ciliary swelling and a significant decrease in IOP. Only moderate swelling occurs in monkey processes after IV injection of relatively high dose of MDM, and this change, which includes disruption of the basal lamina of the pigment epithelium, is not associated with a change in IOP. Severe swelling occurs in the crests of monkey ciliary processes after IVT injection, which is accompanied by a fall in IOP. The difference in the response in monkey versus rabbit ciliary processes after IV injection of MDM may be due to a more compact stroma in the monkey processes.

Intraocular microendoscopy of the ciliary-process vasculature in albino rabbits: effects of vasoactive agents

The reactions of the ciliary-process microvasculature following administration of various vasoactive substances were studied in the albino rabbit using a new method of intraocular microendoscopy. This technique allows an in vivo observation of arterioles, capillaries and venules of the ciliary body and iris. As long as these tissues are not traumatized, the newly described method of intraocular microendoscopy produces no reactive changes in the vasculature. The video images of microendoscopy were also evaluated quantitatively. Administration of substance P caused a short-term ischemic phase in the ciliary-process vasculature which preceded a long-term hyperaemia. After topical administration of epinephrine as well as intra-arterial administration of epinephrine, phenylephrine and isoproterenol, rapid and intense vasoconstrictory or vasodilatory reactions were seen in the terminal arterioles of the vascular territories in the ciliary processes. The terminal arterioles of the iridial ciliary processes responded faster and more intensely than those of the major ciliary processes. It is concluded that the terminal arterioles play an important role in blood-flow regulation of the ciliary processes and function as special afferent vessel segments which control the circulation within the ciliary-process capillaries.

SEM studies on the functional morphology of the rabbit ciliary process vasculature

Architecture and functional reactions of the blood vessels of the rabbit ciliary processes were studied after administration of epinephrine and isoproterenol. A new corrosion cast technique was applied which allows the analysis of different functional stages in the vascular system by scanning electron microscopy. The ciliary process vasculature is divided into three different vascular territories, each supplied by individual arterioles: (1) the iridial ciliary processes; (2) the anterior (pre-lenticular) portion of the major ciliary processes; and (3) the minor ciliary processes localized post-lenticularly between the major processes. The three vascular territories differ not only in form and architecture of the capillaries but also in their reactions on vasoactive agents. After epinephrine, the earliest reactions were seen in the first vascular territory followed by the second, the third vascular territory being least sensitive. The most intense vasoconstrictory changes were found in the terminal arterioles which supply each vascular territory separately. This afferent vascular segment might therefore be considered to be the most important structure for regulation of blood flow through the ciliary processes.

Species differences in the responses of the eye to irritation and trauma: a hypothesis of divergence in ocular defense mechanisms, and the choice of experimental animals for eye research

Information published during the past century, especially the last decade, has identified pronounced species differences, not only in the morphological organization of ocular structures, but also in the functional responses of the eyes of different mammals to experimental and surgical procedures, as well as to drugs and autacoids. For the most part, these differences have been regarded as peculiarities or weakness rather than as fundamental evolutionary adaptations optimally suited to the environment and behavior of each species. This paper proposes a working hypothesis of evolutionary divergence in ocular defense mechanisms, based on some of the known morphological and functional differences among mammals, and discusses the implications of these differences with regard to the choice of appropriate animals for use as models in different areas of ophthalmic research.

Comparison of the ocular hypotensive efficacy of eicosanoids and related compounds

It has recently been shown that prostaglandin (PG)E2 or F2 alpha reduces the intraocular pressure (IOP) of cats and primates when applied topically to the eye in very small doses, and that reduced IOP can be maintained in these species as long as the topical application of one of these PGs is repeated daily or twice daily. In the present study the ocular hypotensive efficacy and some of the ocular side-effects of 15 eicosanoids and related compounds, especially derivatives of PGF2 alpha, were compared and were also compared to some clinically used ocular hypotensive agents. Derivatives of PGF2 alpha were found that had short-term and long-term ocular hypotensive potencies some 10- to 50-fold greater than PGF2 alpha itself.