Veterinary ophthalmology has its roots in Europe, and early publications starting in the 1880s focused mainly on the horse eye. However, major political conflicts in this region of the world delayed further development in veterinary ophthalmology until well after World War II. In America, based on the success of the American Society of Veterinary Ophthalmology, and the growth and sophistication of private small animal practices in the 1950s, the American College of Veterinary Ophthalmologists (ACVO) was established in 1970. Final approval of the College by the American Veterinary Medical Association occurred in 1974. Similar veterinary ophthalmology specialization has occurred in the United Kingdom (certificate and diploma programs), Japan, France, Norway, Sweden, and other countries. The common market countries of Europe, and most recently, the Latin America countries have formed multiple country veterinary ophthalmology certification programs.

Practice of veterinary ophthalmology in the private sector has become both profitable and a stimulating professional career. Development of the specialty colleges, such as the American College of Veterinary Ophthalmologists in America, have been critical in the establishment of higher standards for the practice of veterinary ophthalmology, training of veterinary ophthalmologists, and the genesis and distribution of the majority of new information and scientific studies. Continued vitality of the ACVO-based academic programs depends on increasing the number of successful cooperative programs with the private specialty practices for clinical training of veterinary students and residents, and for clinical research. The future for veterinary ophthalmology is indeed bright!

Significant medical and surgical advances have occurred in veterinary ophthalmology in the last fifty years. While the administration of topical ophthalmic preparations in small animals is usually simple, the use of the subpalpebral system for medication of the horse eye is of considerable benefit. New antibiotics have been introduced to combat bacterial resistance, which continues to be a problem. Topical antifungal agents remain for the most part, fungostatic, and additional drugs are needed. Drugs to control or eliminate endogenous proteinases and collaganase in corneal ulceration are urgently needed.

Medical therapy of the glaucomas has experienced continuous change with the introduction of topical beta antagonists, carbonic anhydrase inhibitors, alpha agonists, and most recently, prostaglandins. Of these agents, the prostaglandins (PGs) produce the greatest declines in intraocular pressure (IOP) in the normal and glaucomatous dogs. Preliminary reports of prostaglandins in normal cats indicate no or limited changes in IOP. New drugs that provide glaucomatous eye neuroprotection and/or neuroregeneration by the reduction of the damage associated with the release of the neurotransmittor, glutamate, and the influx of intraneuronal calcium, are forthcoming.

Cyclosporine A has markedly improved the therapy of keratoconjunctivitis sicca in dogs, causing the majority of these patients to secrete sufficient levels of tears to resolve the signs of this disease. Other immune-me-diated external eyes diseases, such as chronic superficial keratitis, and plasma cell infiltration of the nictitans, may also be controlled with topical cyclosporine A. Intracameral plasminogen tissue activator (tPA) has proven highly successful in producing fibrinolysis of blood clot and clotted fibrin of less than two weeks duration in all animal species. Medical and surgical attempts to control angiogenesis, inflammation, postoperative fibrosis, and lens capsular fibrosis are still early, but advances are forthcoming.

Opportunities for improved surgical procedures are considerable and will advance patient care with eyelid, corneal, lens and vitreoretinal disorders. Corneal grafts, improved glaucoma anterior chamber by-pass devices, improved IOLs, and higher success rates for vitreoretinal surgeries are predicted. Based on the past one-half century, significant and profound improvements in both pharmacological and surgical treatments of animal eye patients will be possible.

Retinal ganglion cells (RGCs) and their axons (optic nerve; ON) provide a good experimental model for research on damaged CNS neurons and their functional recovery. After the ON transection most RGCs degenerate retrogradely but they can be rescued and regenerated in some extent by transplantation of a piece of peripheral nerve (PN). When the nerve graft was bridged to the visual center, the central visual projection of regenerating RGC axons can be formed and the behaviors based on relatively simple visual function can be restored in rodents. Axotomized RGCs in adult cats are also shown to survive and regenerate their axons through the PN graft. Among the cat RGC types, Y cells (α-cells) tend to survive and regenerate axons better than others. X cells (β-cells), which are essential for central vision, suffer from rapid death after ON transection. To improve survival and axonal regeneration of axotomized RGCs, intravitreal injections of various neurotrophic factors and electrical stimulation to the ON are effective. To restore visual function in adult mammals with damaged optic pathway, the comprehensive and integrative strategies of multiple approaches will be needed.

Visually evoked cortical potentials (VECPs) were recorded in fifteen albino rats, which were typically used in toxicology studies, using a checkerboard with various stimulation patterns including various checker sizes, various stimulation frequencies and various stimulation luminances. The electrodes for recording the VECPs were implanted chronically on the surface of the visual cortex. Rats were anesthetized lightly with a mixture of xylazine and ketamine, and placed in front of a pattern-generating TV monitor which displayed checks becoming white and black. Reproducible waveforms with an initial positive wave (P1) followed by a large negative wave (N1) were recorded with checker sizes larger than 50mm. Steady-state responses were recorded with stimulation frequencies higher than 4Hz. No changes were found with variation in stimulus luminance. The P1 latencies were reproducible among animals and records. These results indicate that this technique for VECPs can be used to detect changes in visual function in albino rats.

GLC756 is an octahydrobenzo-quinoline which has combined dopamine D-1 antagonistic and dopamine D-2 agonistic properties. It may induce both a decrease in aqueous humor formation and an increase in uveoscleral outflow. The purpose of this study was to observe the effects on intraocular pressure (IOP) of topically administered 0.4% GLC756 solution, the duration of action, and any side effects in Rhesus monkeys with laser-induced ocular hypertension.

Ten male monkeys with argon laser-induced ocular hypertension in one eye were sedated with ketamine hydrochloride, and the IOP measured in both eyes at 7:00 am, 7:30 am, and then hourly until 1:00 pm with a Tonopen^TM XL applanation tonometer (Mentor^®, Norwell, MA, U.S.A). During the first week, IOP baselines were obtained. The following week, 0.4% GLC756 solution was administered at 7:00 am in the hypertensive eye and the IOP measurements repeated hourly until 1:00 pm. Baseline and drug response curves, and intraocular pressure time profiles for both eyes in each animal were developed.

The baseline IOP was significantly higher in the experimental hypertensive eye than in the normal eye (29.9±2.7 versus 14.5±0.7 mmHg, p<0.0001). The mean IOP in the lasered eye treated with 0.4% GLC756 at 7:00 am decreased from 7:00 to 9:00 am, and then slightly increased until 1:00 pm. The maximal mean IOP decrease (8.5 mmHg) occurred one hour after application of the drug solution. A significant IOP lowering effect was observed 30 minutes after administration of the solution and remained low for two hours. No ocular (such as itching or pain) or systemic side effects to the medication were observed. The IOP in the control eye varied slightly from 7:00 am to 1:00 pm. GLC756 at a concentration of 0.4% significantly lowers the IOP in Rhesus monkeys with laser-induced ocular hypertension. This differs from previous studies performed in humans and rabbits. The IOP lowering effects are more pronounced, but only for a short period of time, in monkeys when compared to the effects observed in humans and rabbits.

GLC756 could be a useful and well-tolerated ocular hypotensive agent and should be investigated further.

The bilateral vacuolar cataract that has been previously reported in Crj: Hartley guinea pigs was further investigated. The incidence reached to 52% by ophthalmological examination. The onset of the vacuolar cataract was all within 28 weeks of age. The vacuoles were ophthalmoscopically first detected along the equator of the lens. Then, the vacuoles that developed only at a focal region disappeared within 12 weeks without any treatment, whereas those that developed throughout the equator progressed to prominent vacuoles extending from the equator toward the anterior pole of the lens. Histopathological examination of the lens with an advanced stage of the vacuolar cataract revealed vacuolation, degeneration and disarrangement of the cortical lens fibers.

High blood glucose levels were noted in all the guinea pigs that showed the vacuolar cataract, suggesting a relationship between the high blood glucose level and development of the vacuolar cataract. This assumption led us to conduct a diet restriction study where the blood glucose level was lowered by reducing a daily diet supply by approximately 50% of the standard consumption. As a result, the lens vacuoles were unequivocally reduced in number and size when animals with an advanced stage of the vacuolar cataract were maintained for 7 weeks under the restricted feeding regimen. And, the cataract was again progressed when these animals were returned to and kept on the ad libitum feeding regimen for 5 weeks. The decrease and increase in the blood glucose levels were well associated with the severity of the cataract, respectively. Thus, it can be concluded that high blood glucose levels are heavily involved in development of the vacuolar cataract. The vacuolar cataract found in Crj: Hartley guinea pigs that showed high blood glucose levels is regarded as a spontaneous diabetic cataract. Guinea pigs cannot synthesize ascorbic acid (vitamin C) de novo. Since ascorbic acid plays an important role in preventing diabetic cataract, Crj: Hartley guinea pigs can be a potential useful animal model for diabetic cataract in humans.

Ectopic retina was observed histopathologically within the beginning of the optic nerve in 19 of 80 male (23.8%) and 21 of 80 female (26.3%) Crj: CD (SD) IGS rats. No abnormal findings were detected ophthalmoscopically in the optic disk of these affected eyes. The ectopic retinal tissues consisted of irregularly-aggregated photoreceptor cells or of tissue segments of the photoreceptor segment, outer nuclear, outer plexiform, and inner nuclear layers. There were no age-related changes or no sex difference in the occurrence of the lesions. These results suggest that the ectopic retina in the optic nerve in Crj: CD (SD) IGS rats may develop in a congenital manner such as overgrowth of the inner layer of the optic cup.

A 13-year old male Maltese diagnosed as generalized arteriolar sclerosis was admitted with aqueous hemorrhage in the left eye. On the physical examination, the congestive conjunctiva and superior sclera were observed in both eyes. The aqueous humor was turbid in the right eye and aqueous hemorrhage was detected in the left eye. The ocular pressure was moderately elevated in both the eyes, suggesting secondary glaucoma. After the treatment with an ocular-pressure lowering agent, styptic and an anti-inflammatory agents, all abnormal findings in the anterior segments were recovered, however senile cataract, decrease of the tapetum reflection, hyaloid hemorrhage, retinal hemorrhage, and retinal detachment were detected.

As the ophthalmic abnormalities are frequently associated with the age related diseases, including generalized arteriolar sclerosis, ophthalmic examination is an available diagnostic technique for these diseases.

Effects of ketamine hydrochloride anesthesia on the intraocular pressure-reducing effect of timolol maleate were evaluated in male cynomolgus monkeys of 5-6 years of age. Intraocular pressure (IOP) was measured following several minutes after ketamine hydrochloride anesthesia at each measurement interval.

A statistically significant or slight increase in IOP was noted in anesthetized animals as compared to conscious animals. After instillation of timolol maleate, IOP was measured under ketamine hydrochloride anesthesia. IOP values in animals anesthetized at 5 mg/kg were comparable to those in conscious animals; whereas, the values were more decreased in animals anesthetized at 10 mg/kg as compared to those in animals anesthetized at 5 mg/kg and in conscious animals.

An increase in dose level of ketamine anesthetic enhanced the IOP-reducing effect of timolol maleate and individual differences in the depth of anesthesia resulted in appreciable variations in IOP. Therefore, determination of IOP in monkeys is considered to be desirable to be conducted using well-trained conscious monkeys.