Scanning electron microscopy of corrosion casts of the optic nerve microcirculation in dogs

Scanning electron microscopy of vascular corrosion casts of the optic nerve region in normal and glaucomatous Beagles demonstrated that the blood supply to the laminar optic nerve is derived from short posterior ciliary arteries, cilioretinal arteries, and longitudinal pial vessels. The short posterior ciliary arteries formed a ring of striated pillars around the scleral canal. The central retinal artery was not present in the dog. Differences between the casts in normal and glaucomatous dogs were not detected.     

Treatment of equine glaucoma by transscleral neodymium:yttrium aluminum garnet laser cyclophotocoagulation: a retrospective study of 23 eyes of 16 horses

Contact neodymium:yttrium aluminum garnet (Nd:YAG) laser transscleral cyclophotocoagulation (TSCP) was performed on 23 eyes of 16 horses for treatment of glaucoma. The mean highest preoperative IOP was 51 ± 17 mmHg. Follow-up evaluation was available for 19 eyes 1 day after surgery, 14 eyes from 1 to 2 weeks, 16 eyes from 4 to 6 weeks, 9 eyes from 12 to 16 weeks, and 10 eyes greater than 20 weeks after laser treatment. The mean intraocular pressure (IOP) the day following surgery was 34 ± 13 mmHg. The mean IOP for each follow-up period was: one to two weeks postoperative, 23 ± 9 mmHg; four to six weeks, 24 ± 7 mmHg; 12–16 weeks, 28 ± 10 mmHg; and  20 weeks, 22 ± 9 mmHg. IOP measurements were significantly different from pretreatment values for all follow-up intervals except for weeks 12–16 ( P < 0.05). Treatment success was defined as maintenance of IOP < 30 mmHg. Treatment success was achieved in 93%, 88%, 78%, and 70% of the treated eyes at the 1–2 weeks, 4–6 weeks, 12–16 weeks, and the  20 weeks re-evaluation, respectively. No significant difference was found between the number of eyes visual at presentation (52.2%) and visual at 20 weeks (60%). The most common laser complications were conjunctival hyperemia (21.7%) and corneal ulcers (13.0%). Results of this study indicate that Nd:YAG TSCP is an effective method of controlling IOP and preserving vision in horses with glaucoma. An effective Nd:YAG laser protocol for TSCP in the equine glaucomatous eye is a power setting of 11 W, duration of 0.4 s, applied 5 mm posterior to the limbus at 60 sites, resulting in a total energy dose of 264 J.     

Evaluation of various compounds to inhibit activity of matrix metalloproteinases in the tear film of horses with ulcerative keratitis

OBJECTIVE: To examine in vitro effects of various antiproteolytic compounds on activity of matrix metalloproteinase (MMP)-2 and -9 in the tear film of horses with active corneal ulcers. SAMPLE POPULATION: Samples of tear film obtained from the eyes of 34 horses with active ulcerative keratitis. PROCEDURE: Horses were sedated, and tear samples were collected from the lower fornix of 34 ulcerated eyes by use of capillary tubes. The protease inhibitors 0.2% EDTA, 0.1% doxycycline, 10% N-acetylcysteine (NAC), 0.1% solution of a modified dipeptide that contains hydroxamic acid (ie, ilomostat), 0.1% alpha1-proteinase inhibitor (PI), 0.5% alpha1-PI, and 100% fresh equine serum (ES) were used to treat pooled samples. Amount of latent and active MMP-2 and -9 was measured by optical density scanning of gelatin zymograms of treated and untreated tear samples. RESULTS: Pooled tear samples obtained from ulcerated eyes contained the latent and active forms of MMP-2 and -9. Compared with MMP activity in untreated samples, total MMP activity (sum of all bands detected) observed on the gelatin zymogram gels was reduced by 99.4% by EDTA, 96.3% by doxycycline, 98.8% by NAC, 98.9% by ilomostat, 52.4% by 0.1% alpha1-PI, 93.6% by 0.5% alpha1-PI, and 90.0% by ES. CONCLUSIONS AND CLINICAL RELEVANCE: We documented that EDTA, doxycycline, NAC, ilomostat, alpha1PI, and ES inhibited MMP activity in vitro. Because these compounds use different mechanisms to inhibit various families of proteases in the tear film of horses, a combination of these protease inhibitors may be beneficial for treatment of corneal ulcers in horses.     

Posterior lamellar keratoplasty for treatment of deep stromal absesses in nine horses

OBJECTIVE: To describe and evaluate the use of posterior lamellar keratoplasty as a surgical treatment for deep corneal stromal abscesses in horses. Animals studied Nine horses of various breeds and ages that presented with corneal stromal abscesses located in the posterior one-third of the cornea. Procedure Retrospective medical record study. RESULTS: Nine horses had deep corneal stromal abscesses that were treated with posterior lamellar keratoplasty. Median patient age was 3 years. Six patients were females and three were geldings. Medical therapy alone had been attempted prior to surgery in all nine animals. Corneal abscess culture and histopathology were performed in 8/9 horses. Cultures were positive for an infectious etiology in 4/8 (50%). Histopathology was positive for an infectious etiology in 5/8 (62.5%). Mean surgical time was 71.0 +/- 18.8 min and the average healing time was 23.7 +/- 5.2 days. Visual outcome was positive in 8/9 cases. Conclusion Posterior lamellar keratoplasty is a promising procedure for treatment of deep corneal stromal abscesses in horses. The procedure resulted in considerable shorter surgery time and healing time than had been observed with full-thickness penetrating keratoplasty. Scar formation with this procedure was not significantly different than with penetrating keratoplasty.     

Distribution of intraocular pressure in dogs

Intraocular pressure (IOP) was measured by four different applanation tonometers in normal dogs. By MacKay-Marg tonometry in 391 dogs (772 eyes) the mean ± SD IOP was 18.8 ± 5.5 mmHg (range 8–52 mmHg). Using Tono-Pen XL tonometry in 421 dogs (823 eyes) the mean IOP was 19.2 ± 5.9 mmHg, and the range was 4.42 mmHg. With MMAC-II tonometry in 80 dogs (158 eyes), the mean IOP was 15.7 ± 2.8 mmHg with a range of 10–30 mmHg. By pneumatonograph tonometry in 135 dogs (255 eyes), the mean IOP was 22.9 ± 6.1 mmHg and the range was 10–47 mmHg. In this study 53 breeds were represented. Of those breeds with six animals or more, no significant differences were detected in IOP between breeds ( P > 0.353) or sex ( P > 0.270). There was a significant decline of 2–4 mmHg ( P > 0.0001) in IOP as age increased from less than 2 years to greater than 6 years of age. This trend was present with all of the four tonometers. There were no significant differences between the MacKay-Marg and TonoPen-XL tonometers ( P > 0.198), but significant differences with the MMAC-II ( P > 0.001) and pneumatonograph ( P > 0.001) tonometers existed compared to the first two instruments. Based on this study and the literature, the mean IOP for the normal dog is 19.0 mmHg with a range of 11 (5%) and 29 (95%) mmHg.