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Objective The gene (myocilin: MYOC) has been attributed to be involved in over 6% of inherited types of human glaucoma, the highest correlation for any gene to date. This study determines myocilin protein levels in the aqueous humor (AH) of normal laboratory quality, genetic carrier (offspring of normal laboratory quality and POAG Beagles), and primary open angle glaucoma (POAG) Beagles. Materials and methods Eighteen dogs were used and classified as either normal, carrier or having mild, moderate or advanced POAG. A 0.1-mL sample of AH was drawn from the anterior chamber of each dog in the study and frozen on dry ice. A modified Coomassie stain and Western blot, using a polyclonal rabbit antihuman myocilin antibody (Santa Cruz Biotechnologies, Santa Cruz, CA), was run on each sample to compare the myocilin levels. A purified human trabecular meshwork excreted myocilin protein sample was used as a control (Alcon Research Laboratories, Fort Worth, TX) and its band/densitometry measurement was defined as one unit of myocilin for comparisons. Results Comparisons of AH myocilin levels differed among normal laboratory quality, genetic carrier, and POAG Beagles at different stages of the disease. In the normal laboratory, Beagles the AH myocilin measured 0.817 ± 0.075 units (mean ± SEM); in the carrier Beagles the AH myocilin was 3.117 ± 0.290 units. As POAG progressed, myocilin protein levels also increased to 6.097 ± 0.810, 8.844 ± 1.079, and 17.228 ± 1.198 units in the early, moderate, and advanced forms, respectively. Overall comparisons between normal, carrier and all POAG Beagles combined showed significant differences (P

Objective To evaluate the visual outcome of three techniques of corneal transplantation surgery in treating severe inflammatory keratopathies in the horse. Design Retrospective medical records study. Animals studied Medical records of 206 horses that received corneal transplantation surgery at the University of Florida Veterinary Medical Center from 1993 to 2007 were reviewed. Procedure Data collected from the medical records included signalment, types of ocular lesions, type of transplant surgery performed, length of follow-up, complications, and visual outcomes. Results Full thickness penetrating keratoplasty (PK) was performed in 86 horses for melting ulcers, iris prolapse/descemetoceles, and medically nonresponsive full thickness stromal abscesses (SA). Posterior lamellar keratoplasty (PLK) and deep lamellar endothelial keratoplasty (DLEK) are split thickness penetrating keratoplasties that were utilized for medically nonresponsive deep stromal abscesses (DSA) in 54 and 66 eyes, respectively. The most common postoperative surgical complication was graft rejection and varying degrees of graft opacification. Wound dehiscence and aqueous humor leakage was also a common postoperative problem. A positive visual outcome was achieved for PK, PLK, and DLEK in 77.9%, 98.1%, and 89.4%, respectively. Conclusions Corneal transplantation is a tectonically viable surgery in the horse with an overall success rate of 88.5% in maintaining vision when treating vascularized and infected corneal disease in the horse.

Purpose To document differences in the levels of the endothelin-1 peptide, nitric oxide, and glutamate in aqueous humor and vitreous in the dog eye with spontaneous glaucoma compared to the normal dog eye. Methods Samples of aqueous humor and vitreous from enucleated normal eyes (n = 21) of 14 dogs and glaucomatous eyes (n = 8) of eight dogs were collected. Levels of endothelin-1, nitric oxide, and glutamate were measured by enzyme immunoassay. Results Endothelin-1 aqueous humor levels (mean +/- SD) increased significantly from 3.05 (+/- 1.66) pg/mL for the normal eyes to 6.22 (+/- 2.83) pg/mL for the glaucomatous eyes (P = 0.0054). The increase in vitreous from 1.83 (+/- 1.66) pg/mL for the normal eyes to 2.86 (+/- 1.31) pg/mL for the glaucomatous eyes was not significant (P = 0.0840). Nitric oxide levels (mean +/- SD) increased significantly in aqueous humor from 4.12 (+/- 2.64) microM for the normal eyes to 12.95 (+/- 14.42) microM for the glaucomatous eyes (P = 0.0141). The vitreous levels increased from 4.86 (+/- 3.92) microM for the normal eyes to 15.33 (+/- 16.22) microM for the glaucomatous eyes (P = 0.0179). Glutamate levels (mean +/- SD) decreased nonsignificantly in aqueous humor from 2.35 (+/- 3.84) microM for the normal eyes to 1.61 (+/- 0.74) microM for the glaucomatous eyes (P = 0.9377) and in vitreous from 1.37 (+/- 1.89) microM for the normal eyes to 1.02 (+/- 1.11) microM for the glaucomatous eyes (P = 0.3303). Conclusion Endothelin-1 and nitric oxide increased in aqueous humor and vitreous of dogs with spontaneous glaucoma while the changes in glutamate varied.

Maintenance and repair of corneal stromal extracellular matrix (ECM) requires a tightly coordinated balance of ECM synthesis, degradation and remodeling in which proteolytic enzymes (proteinases) perform important functions. There are natural proteinase inhibitors present in preocular tear film (PTF) and cornea simultaneously with proteinases that prevent excessive degradation of normal healthy tissue. Disorders occur when there is an imbalance between proteinases and proteinase inhibitors in favor of the proteinases, causing pathologic degradation of stromal collagen and proteoglycans in the cornea. Two matrix metalloproteinases (MMPs), MMP-2 and MMP-9, are of major importance in terms of remodeling and degradation of the corneal stromal collagen. Immunohistochemical studies have shown different origins of MMP-2 and -9. MMP-2 is synthesized by corneal keratocytes and performs a surveillance function in the normal cornea, becoming locally activated to degrade collagen molecules that occasionally become damaged. Alternatively, MMP-9 may be produced by epithelial cells and polymorphonuclear neutrophils following corneal wounding. Because the cornea is in close contact with the preocular tear film (PTF), proteinases have been evaluated in the PTF. In damaged corneas, total proteolytic activity in the tear fluid was found to be significantly increased compared to normal eyes and contralateral eyes. Studies analyzing the proteolytic activity in serial PTF samples during corneal healing led to the following conclusions: ulcerative keratitis in animals is associated with initially high levels of tear film proteolytic activity, which decrease as ulcers heal; proteinase levels in melting ulcers remain elevated leading to rapid progression of the ulcers. The success of medical and surgical treatment of the corneal ulcers is reflected by the proteolytic activity in tears. In animals, successful treatment leads to a rapid reduction in tear film proteolytic activity that corresponds with the improvement in the clinical signs of corneal ulceration. The in vitro effects of various compounds on proteolytic activity in the tear fluid of animals with ulcerative keratitis have been evaluated and their important inhibitory effects have been confirmed. Because these various compounds utilize different mechanisms to inhibit various families of proteinases, a combination of these proteinase inhibitors may be beneficial.

Objective The purpose of this study was to evaluate the effectiveness of postoperative beta-irradiation with strontium-90 as an adjunctive treatment to superficial keratectomy and permanent bulbar conjunctival graft for removal of equine corneolimbal squamous cell carcinoma (SCC), in decreasing recurrence rate. Study The retrospective case study included 38 horses diagnosed and treated for SCC of the eye that involved the limbus and/or cornea. The patients were treated between 1990 and 2002, with strontium-90 irradiation immediately after corneal and conjunctival graft surgery. Recurrence was defined as the postoperative and postirradiation regrowth of SCC in the same site and globe that was previously treated. Results The Appaloosa was the most commonly represented breed and horses that had more than one base coat color represented the majority of the cases (53%). The coat colors of white, chestnut/sorrel and gray were the most commonly represented colors of the horses treated. Eight horses (21%) could not be assessed for tumor recurrence due to lack of two or more post-treatment examinations, and another horse was enucleated 6 days postoperatively due to progressive corneal ulceration. Twenty-four horses (63% of the entire study population; 83% of the followed cases) had a mean ± SD of 1754 ± 1319 days without tumor recurrence, ranging from 14 days to 5110 days. Five horses (13% of the entire study population; 17% of the assessed horses) had tumor recurrence at a mean ± SD of 449 ± 339 days with a range of 29 days to 900 days. For the five recurrences, treatment included local excision (n = 1), enucleation (n = 2), and additional strontium-90 therapy (n = 3). Conclusions The combination of superficial keratectomy, β-irradiation and permanent bulbar conjunctival grafts for limbal, corneal or corneolimbal SCC in horses is effective in at least 83% of the horses. Recurrence occurred in about 17% of the horses. Multiple biannual re-examinations are recommended to observe for tumor recurrence.

A 9-week-old miniature mule foal presented to the Veterinary Medical Teaching Hospital for acute blindness, ataxia, and depression following an overdose of an over-the-counter ivermectin-based de-worming medication. Ophthalmic examination and electrodiagnostic evaluation eliminated outer retinal abnormalities as the primary cause of the bilateral blindness, implicating instead a central neurologic effect of the drug. With symptomatic and supportive care, the foal recovered fully and regained its vision.

Objective To detect and categorize time-specific variations in daytime intraocular pressure (IOP) found in Rhesus monkeys with laser-induced ocular hypertension. Procedures Ten male monkeys with argon laser-induced ocular hypertension in one eye were anesthetized with ketamine hydrochloride, and the IOP measured in both eyes at 7 a.m., 7.30 a.m., and then hourly until 1 p.m. with a Tonopen trade mark XL applanation tonometer. Intraocular pressure time profiles for both eyes in each animal were developed. The means +/- SD of the IOPs for both eyes were calculated for the whole 6-h study period, and the values compared statistically. The difference between the lasered eye mean IOP standard deviation and the normal eye mean IOP standard deviation for each animal during the 6-h follow-up was also calculated and compared. Results Mean IOP (+/- SD) in the glaucoma and normal eyes for the 10 animals during the 6-h study was 32.6 +/- 2.5 and 14.9 +/- 2.5 mmHg, respectively. The IOP was significantly higher in the experimental eye than in the normal eye (P = 0.0008). The mean IOP in the lasered eye did not significantly change during the study period, whereas a slight but significant increase in IOP of the normal eye over the study period was recorded (P = 0.003). The variance in IOP in the hypertensive eyes was considerably greater than that in the untreated control eyes. From 7 a.m. to 1 p.m. the IOP declined in five eyes and increased in the other five eyes with laser-induced ocular hypertension. Conclusions The time-specific IOP variation pattern in the daytime in the laser treated eyes is significantly greater than the variation in the normotensive eyes. This shows that in order to detect statistical differences between IOP variations induced by an IOP-reducing drug, and the exaggerated spontaneous IOP variations present in the laser-induced hypertensive eye, sufficient animals should be included in any study. Understanding the time-specific IOP variation present in a group of monkeys with laser-induced ocular hypertension is essential prior to using the model for the evaluation of IOP-reducing drugs.

Electroretinogram (ERG) and visual-evoked potentials (VEPs) are used in veterinary ophthalmology to assess the functional integrity of the retina and the central visual pathway. The interpretation of altered electrophysiologic potentials in diseases can be of great diagnostic value, although it is important to be aware of technical factors and the limitations of these techniques which may result in over-interpretation and misinterpretation of the recordings, such that they are similar to those found in disease-related electrophysiologic changes. The recorded potentials represent the differences in voltage between the active and reference electrodes. The ground electrode serves as zero. A differential or instrumentation amplifier selectively amplifies signals of interest while rejecting noise. Differences between inputs are amplified, whereas common signals are rejected in a process called common mode rejection (CMR). In order for CMR to be most effective in reducing noise, the electrode impedances should be balanced. Filters are part of the differential amplifier as they remove unwanted noise of a certain frequency. The frequency bandwidth, or passband, is the range of frequencies between low- and high-frequency filter settings that are not filtered out. Major sources of noise that cause interpretation artifacts are power lines, amplifier noise, physiologic activity, electrochemical electrode noise and circular grounds. Noise reduction is achieved with high amplifier input impedance, balanced electrode impedances, CMR, filters and signal averaging. Maintaining electrodes in good condition, achieving proper contact between electrode and animal, and keeping electrode leads short aid in achieving noise reduction.