Intraocular pressure in normal dairy cattle.

Intraocular pressure (IOP) was measured in normal dairy cows by applanation tonometry. In the first study of 15 Holstein and 17 Jersey cows the mean IOP by Mackay-Marg tonometry was 27.5 +/- 4.8 mmHg (range 16-39 mmHg); no significant differences (P < 0.92) were observed between the Holstein and Jersey breeds. In the second study of 15 Holstein and 12 Jersey cows, the mean IOPs by Mackay-Marg and TonoPen-XL tonometry were 28.2 +/- 4.6 mmHg (range 19-39 mmHg) and 26.9 +/- 6.7 mmHg (range 16-42 mmHg), respectively. Comparisons of the Mackay-Marg and TonoPen tonometers indicated no significant differences (P < 0.16). The mean and range of IOP in normal dairy cows within 2 SD (95% of the population) is 27 mmHg with a range of 16-36 mmHg.

Effects of intra-articularly administered endotoxin on clinical signs of disease and synovial fluid tumor necrosis factor, interleukin 6, and prostaglandin E2 values in horses.

In each of 4 horses, sterile synovitis was induced by intra-articular injection of 3 micrograms of Escherichia coli endotoxin (lipopolysaccharide, LPS) into one antebrachiocarpal joint; an equal volume (2 ml) of phosphate-buffered saline solution (PBSS) was injected into the opposite, control carpus. Blood and 1.5 ml of synovial fluid were obtained at postinjection hours (PIH) 0, 2, 4, 8, 12, 18, 42, 66, and 144. Synovial fluid sample collection was accomplished by use of an indwelling, intra-articular catheter through PIH 12, and by arthrocentesis subsequently. Joint fluid samples were analyzed for cell counts, protein concentration, cytologic variables, and tumor necrosis factor (TNF), interleukin 6 (IL-6), and prostaglandin E2 (PGE2) values. Tumor necrosis factor and IL-6 activities and WBC count were also measured in blood. To monitor local inflammation, skin temperature of each carpus was imaged, using a thermographic scanner prior to each sample collection time. Horses had minimal systemic effects. Mean (+/- SEM) rectal temperature increased significantly to 39.02 +/- 0.15 C only at PIH 18 after intra-articular injection of LPS. One horse had signs of mild depression from PIH 7 to 18, but its vital signs did not change appreciably. Each horse had mild signs of discomfort in the LPS-injected limb from PIH 1 to 3 until PIH 8 to 10. Mean peak surface temperature of the LPS-injected carpi was significantly higher than that of control carpi from PIH 8 to 144 (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of topically applied demecarium bromide and echothiophate iodide on intraocular pressure and pupil size in beagles with normotensive eyes and beagles with inherited glaucoma.

Topically applied demecarium bromide (0.125 and 0.25%) and echothiophate iodide (0.125 and 0.25%) solutions were evaluated in Beagles with normotensive eyes and Beagles with inherited glaucoma. In single-dose studies, the effects of intraocular pressure (IOP) and pupil size (PS) were measured in eyes before drug treatment and in drug- and nondrug-treated eyes. Both concentrations of the 2 drugs induced long-term miosis and decrease in IOP in normotensive eyes of Beagles and of eyes of Beagles with inherited glaucoma. Demecarium bromide (0.125 and 0.5%) decreased IOP for 49 and 55 hours, respectively. Echothiophate iodide (0.125 and 0.5%) reduced IOP for 25 and 53 hours, respectively. The miosis associated with both concentrations of the 2 drugs generally paralleled the decreases in IOP.

Effect of hyaluronidase on aqueous outflow resistance in normotensive and glaucomatous eyes of dogs.

The anterior chambers in 16 dogs with normotensive eyes and 3 Beagles with glaucomatous eyes were treated with 0, 25, 50, or 100 IU of bovine testicular hyaluronidase. Aqueous outflow resistance was then determined by constant-pressure perfusion of 0.9% NaCl solution for 30 or 60 minutes. In normotensive eyes, 25, 50, or 100 IU of hyaluronidase significantly (P less than 0.02) increased the rate of constant-pressure perfusion compared with that of untreated eyes during 30- or 60-minute perfusions. Treatment of glaucomatous eyes with 25, 50, or 100 IU of hyaluronidase did not significantly increase the rate of constant-pressure perfusion over controls during a 30-minute perfusion. Bovine testicular hyaluronidase at all doses removed the staining of colloidal iron from the trabecular meshwork in normotensive eyes. In Beagles with glaucoma, the trabecular meshworks remained stained with colloidal iron when treated with the hyaluronidase, which suggested that some glycosaminoglycans were resistant to this enzyme's action.

Evaluation of a topically administered carbonic anhydrase inhibitor (MK-927) in normotensive and glaucomatous beagles.

A new topically administered anhydrase inhibitor, MK-927, was evaluated for its ocular hypotensive activity in normotensive and glaucomatous Beagles. Single- and multiple-dose studies were performed. Six concentrations of the drug were evaluated in the single-dose study and the 2% solution was used for multiple-dose evaluation. The decrease in intraocular pressure (IOP) was greater in glaucomatous Beagles at the higher concentrations of the drug. The 2 and 4% solutions of MK-927 significantly lowered IOP (mean, 5 mm of Hg; SEM +/- 1.6 and SEM +/- 1.2, respectively) in normotensive and glaucomatous Beagles. In the multiple-dose study, IOP was significantly decreased in the normotensive (mean, 4 mm of Hg; SEM +/- 0.74) and glaucomatous Beagles (mean, 9 mm of Hg; SEM +/- 1.2). The maximal effect was observed by day 4. A contralateral effect was found in glaucomatous Beagles, with the maximal effect on day 4.

Therapeutic management of ocular squamous cell carcinoma in the horse: 43 cases (1979-1989).

The records of 50 horses with ocular squamous cell carcinoma (OSCC) presented to the University of Florida Veterinary Medical Teaching Hospital over an 11 year period were reviewed to determine the influence of therapy on the outcome of the case. Follow-up information was obtained for 43 of the 50 cases. The disease was more prevalent in the light horse breeds; however, the draft breeds also were at risk. There was no sex predisposition and the average age was 11.8 years. Tumour recurrence was significant when surgery alone was performed. The eyelid and nictitating membrane were the primary sites for tumor recurrence. Cases in which adjunctive therapy was used correlated with a lower rate of recurrence.

Effect of topical prostaglandin PGA2, PGA2 isopropyl ester, and PGF2 alpha isopropyl ester on intraocular pressure in normotensive and glaucomatous canine eyes.

Topical instillations of 1.0, 10, and 20 micrograms/50 microliters of prostaglandin PGA2, 0.5 and 1.0 microgram/50 microliters of PGA2 isopropyl ester, and 0.5, 1.0, 5.0 and 10.0 micrograms/50 microliters of PGF2 alpha isopropyl ester were evaluated in the normal dogs and glaucomatous beagles eyes. Each concentration of drug was evaluated for a seven day period. On Day 1 baseline values were obtained, days 2-4, the drug was instilled (once a day) and on days 5-7 post-treatment values were measured. All concentrations of PGA2 failed to lower intraocular pressure (IOP) in the normal and the glaucomatous (P greater than 0.72) dogs. PGA2 isopropyl ester decreased IOP in the normal dogs and in the glaucomatous beagles (P less than 0.01). The declines in IOP were significant at 1/2 to 1 hour and continued for up to 5 hours. No significant change in IOP occurred in the non-treated fellow eye of the normotensive dog (P less than 0.54) and the glaucomatous beagle (P less than 0.29). All concentrations of PGF2 alpha isopropyl ester significantly decreased IOP in the treated eyes of the normotensive dog (P less than 0.05) and the glaucomatous beagle (P less than 0.01). The significant change in IOP occurred within one hour after the instillation of PGF2 alpha isopropyl ester. The IOP remained lower than the baseline pressures 24 hours post-treatment for both the normotensive and glaucomatous dogs. Maximal change in IOP for normal dogs was a decrease of 9 mm Hg while the glaucomatous beagle had a decrease of 19 mm Hg. No significant change in IOP occurred in the non-treated fellow eye of the normotensive animal (P less than 0.16) and the glaucomatous beagle (P less than 0.40). The side effects of PGF2 alpha isopropyl ester were miosis and mild conjunctival irritation.

Evaluation of three applanation tonometers in dogs.

The Mackay-Marg, Tono-Pen, and Challenger applanation tonometers were evaluated in vivo in 12 clinically normal eyes of 6 dogs. Tonometric measures of intraocular pressure (IOP) were compared with closed manometric IOP measurements from the anterior chamber of anesthetized dogs. The tonometers were evaluated at IOP that ranged from 5 to 100 mm of Hg. The Mackay-Marg tonometer was the most reliable instrument when evaluated at IOP from 5 to 100 mm of Hg (r2 = 0.996) and from 10 to 30 mm of Hg (r2 = 0.962). The Tono-Pen tonometer was also reliable (r2 = 0.967) over the range of IOP, but consistently overestimated IOP at lower pressures and underestimated IOP at higher pressures. The Mackay-Marg and Tono-Pen measurements were essentially linear. When evaluated from 10 to 30 mm of Hg, r2 was 0.828 for the Tono-Pen tonometer. The Challenger tonometer, although reliable over the full range of IOP (r2 = 0.965), proved to be less accurate, as indicated by lack of a good linear equation.

Tonometric and tonographic studies in the normal pony eye.

Tonometric and tonographic techniques were evaluated in the normal pony and compared to other species. Applanation tonometry was utilised to calculate the ocular ridigity of the normal equine eye. The mean intraocular pressure for the pony eye was established as 23.5 mm Hg (sd +/- 4.5). Comparing the non-anaesthetised and anaesthetised pony eye (xylazine-ketamine and glycerol guaiacolate) no significant change in intraocular pressure occurred (P < 0.49). Mean aqueous outflow facility was 0.88 microliter/min/mm Hg (sd +/- 0.65) which is significantly higher (P < 0.01) than the canine and human species. The ocular rigidity values for the pony eye were higher which indicates that the eye is more rigid than either the canine or human eye.

Ultrastructural changes in the aqueous outflow apparatus of beagles with inherited glaucoma.

Spontaneous glaucoma in the beagle was exhibited after 6 months of age by elevated intraocular pressures and open iridocorneal angles followed by secondary changes. In order to appreciate alterations of the aqueous outflow apparatus in dogs with this autosomal recessive disorder, the eyes of beagles with inherited glaucoma at ages 1 day through 34 months were examined by light, scanning and transmission electron microscopy. Developmentally, no notable differences were observed between normal and preglaucomatous outflow channels through 7 months of age. In 12-month-old glaucomatous chamber angles clustered basement membrane-like material was found scattered throughout the outer corneoscleral trabecular meshwork. In this region elastin-like fibers appeared to be more numerous and arranged less regularly than age-matched normal eyes. Occasional trabecular cells within the corneoscleral trabecular meshwork possessed small clusters of serrated, opaque rods within their cytoplasm. In the older glaucomatous dogs these changes were more generalized and extensive throughout the entire corneoscleral trabecular meshwork. In some individual eyes the anterior chamber angles were observed to be narrow both clinically and histologically. These outflow apparatuses were additionally characterized by compressed, less organized trabeculae with a concomitant build-up of extracellular materials. No correlation was found between the shallowness of the iridocorneal angle and increase in intraocular pressure. Primary glaucoma in the beagle during its earlier phases compared more positively to open-angle glaucoma in man than any of the other spontaneous types in animals.

Effects of 4% pilocarpine gel on normotensive and glaucomatous canine eyes.

A 4% pilocarpine gel applied topically to eyes was evaluated in glaucomatous Beagles and normotensive Miniature Schnauzers to determine its efficacy in reducing intraocular pressure (IOP) and to assess any side effects. Pilocarpine gel significantly (P less than 0.05) reduced IOP for 24 hours after treatment, compared with baseline (pre-drug) values, untreated fellow eyes, and placebo-treated eyes. The IOP remained significantly lower (P less than 0.05) during 3 treatment days, as well as the first 2 days after treatment. The pupil sizes were significantly smaller (P less than 0.01) in all treated dogs after the first administration of pilocarpine, compared with baseline values, untreated eyes, and placebo-treated eyes. The subsequent pilocarpine gel administrations induced significant miosis (P less than 0.01), compared with baseline values, but the extent of miosis and duration were significantly less (P less than 0.01) as the number of treatments increased. Conjunctival irritation and blepharospasm were observed mainly in the first 2 days of treatment and were minimal after subsequent applications. There was no contralateral effect on IOP or pupil size, compared with baseline values and placebo-treated eyes.

Evaluation of the Krupin-Denver valve implant in normotensive and glaucomatous beagles.

The Krupin-Denver valve was implanted unilaterally in 2 normotensive and in 6 glaucomatous Beagles. The fellow eye of each dog had an external trabeculectomy. Before and after surgery, all dogs were evaluated serially by gonioscopy, biomicroscopy, tonometry, and tonography. The valve implant remained patent in 2 normotensive and in 2 glaucomatous Beagles throughout the 12 months of observation. Valve function was lost in 4 glaucomatous Beagles 4 to 6 weeks (3 dogs) and 6 months (1 dog) after implantation. Light microscopic and scanning electron microscopic evaluations of early loss of implant function revealed occlusion of the lumen and/or valve mechanism by inflammatory debris and cells. The late loss of valve function was related to chronic inflammatory response and fibrosis about the valve mechanism and tubing within the sclera.

Aqueous outflow in the beagle: unconventional outflow, using different-sized microspheres.

Normal drainage of aqueous humor from the anterior chamber of the canine eye occurred through the angular aqueous plexus and uveoscleral route. In order to understand more clearly, uveoscleral outflow with regard to larger sized tracer particles and the possible influence that varying intraocular pressure (IOP) may have on them, microspheres of 3 sizes, 0.5, 1.0, and 3.0 micron, were perfused at 3 different IOP (20, 50, and 75 mm of Hg) for 3 different times (30, 60, and 90 minutes). Presence of spheres was detected by light microscopy and scanning electron microscopy, and verified by transmission electron microscopy. By 30 minutes of perfusion, all 3 sphere sizes thoroughly infiltrated the anterior uveal trabecular meshwork. At normotensive pressure (20 mm of Hg), spheres of each size penetrated the outer anterior extension of the ciliary musculature and entered the supraciliary space. Only 0.5- and 1.0-micron spheres moved posteriorly into the suprachoridal space. At hypertensive pressures, movement of the tracer particles increased markedly toward the posterior uveal trabecular meshwork. However, 3.0- and 1.0-microns spheres did not enter the supraciliary space and suprachoroidal space, respectively. Spheres also entered the iris, mostly at its root. They remained comparably sparse at different perfusion times and IOP. The present study supported evidence for uveoscleral outflow (vs uveovortex) in the dog and indicated that passage of materials through this pathway may be influenced by IOP when these substances are within a critical size range.

Quantitation of uveoscleral outflow in normotensive and glaucomatous Beagles by 3H-labeled dextran.

In uveoscleral outflow, aqueous humor leaves the anterior chamber and passes caudally through the trabecular meshwork and the sclerociliary cleft to enter the supraciliary and suprachoroidal spaces. The fluid is then absorbed by choroidal and scleral circulations. Using 3H-labeled dextran, uveoscleral outflow was quantitated in normotensive and glaucomatous Beagles under general anesthesia. The intrascleral plexus was isolated and 3H-labeled dextran was injected into the anterior chamber. Intrascleral plexus contents were sampled every 5 minutes over a 30- to 60-minute period. The eyes were enucleated, sectioned, and prepared for scintillation counting. Uveoscleral outflow accounted for 15% and 3% of the total aqueous humor outflow in the normotensive dogs and in the advanced glaucomatous dogs, respectively. In the advanced glaucomatous Beagle, conventional and uveoscleral outflow pathways were reduced and contributed to the etiopathogenesis of glaucoma.

Morphologic studies of uveoscleral outflow in normotensive and glaucomatous beagles with fluorescein-labeled dextran.

Aqueous humor leaves the anterior chamber through 2 pathways: the trabecular meshwork of the iridocorneal angle and the unconventional uveoscleral route. In the latter route, aqueous humor leaves the anterior chamber, passes caudally through the trabecular meshwork and sclerociliary cleft to enter the supraciliary and suprachoroidal spaces. The fluid is absorbed by the choroidal and scleral circulation. Fluorescein-labeled dextran was slowly infused into the posterior chamber of healthy and glaucomatous Beagles for 30 minutes. The eyes were fixed in a mixture of 70% alcohol and formalin, placed in epoxy resin for histologic evaluation, and examined by fluorescent microscopy. Fluorescence was detected in the healthy dogs throughout the uveoscleral pathway. In the glaucomatous dogs, the uveoscleral outflow was decreased or completely absent.

Kinetics of phagocytosis in the normal canine iridocorneal angle.

Microspheres of 3 different sizes were infused separately into the eyes of dogs with normotensive and hypertensive intraocular pressures. Latex spheres (0.5 or 1.0 micron) or 3.0 micron plastic spheres were added to Ringer's solution with 6% gelatin. Initially, this mixture was injected into the anterior chamber of dogs with intraocular pressures of 20, 50, or 75 mm of Hg. After 10, 20, 30, 60, or 90 minutes had elapsed, the dogs were euthanatized and the gelatin was hardened. Tissues were subsequently studied by light and transmission electron microscopies. Phagocytosis of the 0.5 and 1.0 micron spheres by trabecular cells was first detected within 10 minutes and within 20 minutes for the 3.0 microns spheres. Migration of cells in the corneoscleral trabecular meshwork was observed after 30 minutes. Phagocytosis was less active at hypertensive pressures and had larger sphere sizes. Microspheres in the uveal trabecular meshwork were ingested mostly by macrophages and polymorphonuclear leukocytes.

Maturation of the retina of the canine neonate as determined by electroretinography and histology.

Retinal potentials were obtained by electroretinography from birth to maturity of dogs. Amplitudes, time latency, and flicker fusion frequencies under scotopic conditions were compared to the histologic development of the retina. There was no electroretinogram (ERG) recorded during the 1st week of life, but in the 2nd week, a small negative wave (not exceeding 5 microV) was detected. Small ERG waveforms appeared in dogs at 3 weeks of age; these markedly increased in amplitude and latency between the 3rd and the 4th weeks of age. Additional changes in the ERG amplitudes were evident in the 5th to the 8th weeks of life approximating amplitudes of the adult dog. Similarly, the greatest changes in flicker fusion frequencies occurred between the 3rd and the 5th weeks and the 7th and the 8th weeks. Latency of the a-wave indicated little change in the age groups studied. The greatest decrease in latency occurred in the b- and c-waves between the 3rd and 5th weeks of age. The rod and cone inner and outer segments were first observed microscopically in the 3rd week after the dogs were born. Further differentiation of the rod and cone segments and other retinal layers occurred from the 5th to the 8th weeks.

Dose response of topical carbamylcholine chloride (carbachol) in normotensive and early glaucomatous beagles.

Single-dose loading with a placebo (0.5% methylcellulose) and 0.75%, 1.5%, 2.25%, or 3% carbamylcholine chloride (carbachol) was evaluated in normotensive and glaucomatous Beagles to determine dose response. The 4 carbachol concentrations significantly (P less than 0.05) lowered intraocular pressure and reduced pupil size in the normotensive and early glaucomatous Beagles at most time intervals as compared with base-line values, nontreated fellow eyes, and placebo-treated eyes. There were no significant (P less than 0.24) effects on intraocular pressure or pupil size by unilateral carbachol instillations as compared with base-line values or placebo-treated eyes.

Dose response of topical pilocarpine-epinephrine combinations in normotensive and glaucomatous Beagles.

Dose responses to single-dose loadings with a placebo (0.50% methylcellulose) and 1%, 2%, 3%, 4%, and 6% pilocarpine combined with 1% epinephrine were determined in normotensive and glaucomatous Beagle dogs. All combinations of pilocarpine and 1% epinephrine significantly (P less than 0.007) reduced pupil size and intraocular pressure in the normotensive and glaucomatous-treated eyes at most measurement times, as compared with base-line (predrug) values, untreated fellow eyes, and placebo-treated eyes. There were no significant (P less than 0.11 or greater) contralateral effects on pupil size and intraocular pressure by unilateral pilocarpine-epinephrine instillations as compared with base-line values or placebo-treated eyes.