Pars plana vitrectomy for the treatment of ophthalmomyiasis interna posterior in a dog.

Unilateral chorioretinitis caused by ophthalmomyiasis interna posterior in a 5-month-old, female spayed Dachshund is reported. Larva removal by pars plana vitrectomy was performed after an unsuccessful photocoagulation of the organism. The larva was intact after surgical removal and was identified as a first stage instar Cuterebra spp. larva. The eye remains visual and comfortable with no signs of residual or recurrent inflammation postoperatively. This report describes, for the first time, the successful surgical retrieval of an intravitreal fly larva in a dog using vitrectomy techniques without sacrificing either the globe or vision, and taxonomic identification of the parasite.

Periocular neurofibrosarcoma in a horse.

A periocular neurofibrosarcoma was debulked and treated with intralesional cisplatin in a 5-year-old Thoroughbred mare. The horse presented with a 1-year history of a large slowly progressing subcutaneous mass over the right supraorbital process. The mass was surgically debulked, and intralesional cisplatin (1.0 mg/cm3) was injected in 3 doses at 2 weeks, 5 weeks, and 8 weeks postoperatively. No recurrence was noted over a 15-month follow-up period. Histopathology of the mass indicated neurofibrosarcoma.

Development of glaucoma after cataract surgery in dogs: 220 cases (1987-1998).

OBJECTIVE: To examine postoperative ocular hypertension (POH) and other variables as predictors of the risk of developing glaucoma after cataract surgery in dogs. DESIGN: Retrospective study. ANIMALS: 220 dogs that had cataract surgery. PROCEDURE: Medical records of 220 dogs (346 eyes) that had extracapsular cataract removal or phacoemulsification of cataracts were reviewed. With respect to glaucoma development, 8 variables were analyzed, which included development of POH, breed, sex, age at time of surgery, eye (right vs left), phacoemulsification time, intraocular lens (IOL) placement (yes or no), and stage of cataract development. Eyes developed glaucoma within 6 or 12 months of surgery or did not have signs of glaucoma at least 6 or 12 months after cataract surgery. RESULTS: Of 346 eyes, 58 (16.8%) developed glaucoma after surgery. At 6 months, 32 of 206 (15.5%) eyes examined had glaucoma; at 12 months, 44 of 153 (28.8%) eyes examined had glaucoma. Median follow-up time was 5.8 months (range, 0.1 to 48 months). Mixed-breed dogs were at a significantly lower risk for glaucoma, compared with other breeds. Eyes with IOL placement were at a significantly lower risk for glaucoma, compared with eyes without IOL placement. Eyes with hypermature cataracts were at a significantly higher risk for glaucoma, compared with eyes with mature or immature cataracts. CONCLUSIONS AND CLINICAL RELEVANCE: Multiple factors appear to contribute to the onset of glaucoma in dogs after cataract surgery. Complications prohibiting IOL placement during cataract surgery may lead to a high risk of glaucoma development.

Rose bengal positive epithelial microerosions as a manifestation of equine keratomycosis.

Purpose To describe the clinical appearance of corneal epithelial cell microerosions associated with keratomycosis in the horse. METHODS: Retrospective clinical study. RESULTS: Multifocal, punctate, superficial corneal opacities with positive rose bengal retention were noted in six horses with presumed 'viral keratitis'. Faint fluorescein staining was also present in three cases. Equine herpesvirus tissue culture inoculation was negative for a cytopathic effect in three cases. Aspergillus (n = 3), Curvularia (n = 1), and an unidentified fungus (n = 1) were cultured in five horses, and hyphae found on corneal cytology from the sixth. Mixed bacterial infections were present in three eyes. The eyes of two horses with Aspergillus progressed to deep melting corneal ulcers that required surgical therapy. The microerosions remained superficial, but persistent in the other four eyes. Natamycin was utilized topically in all six horses. Transmission electron microscopy from case 6 revealed mucin layer disruption, an intact corneal epithelial cell layer, and fungal attachment to degenerating epithelial cells. The visual outcome was positive in all six horses, although healing was prolonged (48.5 +/- 14.5 days on average in the horses with no surgery; 62 days on average in the two horses that required surgery). CONCLUSIONS: Complete removal or full-thickness penetration of the corneal epithelial cell barrier may not be necessary to allow fungal adherence and initiation of keratomycosis in the horse. Prior to colonization and invasion of the horse cornea, fungi may induce changes in the mucin layer of the tear film that result in or are associated with rose bengal positive microerosions of the superficial corneal epithelium. Horses with painful eyes, and eyes with superficial, multifocal corneal opacities should have their corneas stained with both fluorescein and rose bengal as fungal microerosions may stain weakly, or not at all, with fluorescein, and may thus be mistaken for presumed 'viral keratitis' of the horse.

Evaluation of tear film proteinases in horses with ulcerative keratitis.

Ulcerative keratitis is a common and potentially blinding ocular disease of horses, capable of progressing to corneal perforation in as little as 24 h. This rapid stromal degeneration is mediated in part by exogenous and endogenous proteinases. We measured and compared the concentrations of two matrix metalloproteinases (MMP-2 and MMP-9) and a serine proteinase (neutrophil elastase) present in the precorneal tear film of normal horses and horses with rapidly progressing ulcerative keratitis. Precorneal tear film samples were collected from 23 ulcerated and 21 unaffected eyes of 23 horses with unilateral ulcerative keratitis, and from 33 normal eyes of 17 control horses. MMP-2, MMP-9, and neutrophil elastase were identified by casein and gelatin zymography and quantified by computerized image analysis. Median MMP-9 levels were significantly higher in the precorneal tear film of young control horses vs. older control horses (P = 0.005). Median MMP-2, MMP-9, and neutrophil elastase levels were significantly higher in the precorneal tear film of ulcerated eyes when compared to age-matched normal controls (P = 0.004, P = 0.001, and P = 0.012, respectively). Median MMP-2 levels were also significantly higher in the precorneal tear film of contralateral eyes of affected horses when compared to age-matched normal controls (P = 0.004). No significant differences in median proteinase levels were detected between 'sterile' ulcers and those from which bacteria or mixed infections (bacteria and fungi) were isolated. However, median MMP-2 and neutrophil elastase levels were significantly higher in the precorneal tear film of eyes with 'sterile' ulcers when compared with ulcerated eyes from which fungi were isolated (P < 0.05). The results of this study support the use of topical antiproteinase therapy which targets both MMPs and serine proteinases in progressive equine ulcerative keratitis.

Ulcerative keratitis caused by beta-hemolytic Streptococcus equi in 11 horses.

Purpose To describe 11 clinical cases of ulcerative keratitis in horses associated with beta-hemolytic Streptococcus equi in Florida, USA. METHODS: Retrospective clinical study (1996-99). RESULTS: Beta-hemolytic Streptococcus equi was cultured from 11 horses with deep ulcers, descemetoceles or iris prolapse (n = 8), a suture abscess found with a penetrating keratoplasty for a stromal abscess (n = 1), and ulceration that developed following keratectomy/irradiation for corneal squamous cell carcinoma (n = 2). Beta-hemolytic Streptococcus equi subspecies zooepidemicus was found in 10 eyes and subspecies equi in one. Marked signs of uveitis including miosis and hypopyon were present in 8/11 (72.7%) eyes. Keratomalacia was severe in all eyes. The mean diameter of the ulcers associated with beta-hemolytic Streptococcus was 10.2 +/- 6.1 mm. Eight of the eyes required conjunctival flap surgery (four grafts dehisced) and one eye corneal transplantation. Two eyes were treated with medication only. Isolate sensitivity to antibiotics included ampicillin (6/11), bacitracin (11/11), cephalothin (11/11), chloramphenicol (11/11), gentamicin (5/11), polymyxin B (2/11), and tobramycin (1/11). All isolates were resistant to neomycin. The average healing time was 44.7 +/- 26.7 days. The visual outcome was positive in 8/11 eyes, and the globe retained in 9/11 eyes. CONCLUSIONS: Although Gram-positive bacteria predominate in the normal conjunctival microflora of horses throughout the world, Gram-negative bacteria and fungi are more often isolated from equine ulcers. Beta-hemolytic Streptococcus spp. are associated with a very aggressive ulcerative keratitis with the capability to digest conjunctival graft tissue. Clinical signs are pronounced. Aggressive surgical and intensive medical therapy with topical antibiotics and protease inhibitors is indicated.

In vitro flow characteristics of the Ahmed and self-constructed anterior chamber shunts.

OBJECTIVE: To compare in vitro opening pressures (OP) and closing pressures (CP) of the Ahmed VS-1 and VS-2 glaucoma valves with those of several self-constructed valve 'prototypes,' and to assess their ability to maintain perfusion pressures between 6 and 21 mm of Hg. SAMPLE POPULATION: Ahmed VS-1 (n = 6), 2 groups of Ahmed VS-2 (group 1: n = 12; group 2: n = 14), and self-constructed valves with linear incisions in the long axis of the tube wall (n = 6) or X-shaped incisions in the tube walls (n = 2). PROCEDURE: Valves were perfused with deionized water, lactated Ringer's solution (LRS), Dulbecco's modified Eagle's medium (DMEM), DMEM plus 50% equine serum (ES), and 100% ES. Flow rates of 2.85, 4.2, 6.0, 9.0, and 12.0 microliter/min were used for each perfusate. Valves were tested 3 times for reproducibility, and OP/CP were compared for each system. RESULTS: OP/CP of the VS-1, VS-2 (group 1), VS-2 (group 2), and linear 1.0-cm incisional valves with thick tubing consistently increased with increasing perfusion rate. Linear 0.5-cm (thick tubing) and 1.0-cm (thin tubing) incisional valves had increasing OP/CP with increasing perfusion rate in all but a few instances. Mean OP/CP decreased with increasing perfusate osmolarity for all perfusates except LRS, using the VS-1 and V-2 (group 2) valves. Mean OP/CP were consistently lower for VS-1 than VS-2 (group 1) valves at any given flow rate and for any given perfusate. Mean OP/CP were consistently lower for VS-2 (group 1) than VS-2 (group 2) valves at any given flow rate and for any given perfusate. The linear 0.5-cm incisional valves with thick and thin tubing induced the highest mean OP/CP, maximizing at > 30 mm of Hg. CONCLUSIONS: Only the VS-2 (group 2) valves consistently had mean OP/CP between 6 and 21 mm of Hg for all perfusates and at all flow rates. CLINICAL RELEVANCE: Anterior chamber shunts, although imperfect, appear to offer a physiologically sound alternative for glaucoma management.

Evaluation of multiple doses of 4 and 6% timolol, and timolol combined with 2% pilocarpine in clinically normal beagles and beagles with glaucoma.

Topically applied 4% timolol, 4% timolol combined with 2% pilocarpine, 6% timolol, and 6% timolol combined with 2% pilocarpine were evaluated in clinically normal Beagles and Beagles with glaucoma. The drugs were instilled twice daily for 5 days. Changes in intraocular pressure (IOP), pupil size, and heart rate were recorded on days 1, 3, and 5 at 0, 2, 5, and 8 hours, starting at 8:30 AM. In clinically normal dogs, 4 and 6% topically administered timolol did not cause consistent reductions in IOP; however, with addition of 2% pilocarpine, IOP was consistently lower. In the Beagles with glaucoma, 4 and 6% timolol and, to a greater extent, 4 and 6% timolol combined with 2% pilocarpine lowered IOP. The combinations lowered IOP and reduced pupil size consistently. In all test groups, either 4 or 6% topically applied timolol caused approximately 10% decrease in mean heart rate.

Histomorphometry of the optic nerves of normal dogs and dogs with hereditary glaucoma.

The beagle dog with hereditary primary open-angle glaucoma, unlike other animal models of human glaucoma, possesses a slowly progressive, sustained elevation of intraocular pressure. The effects of this insidious elevation in intraocular pressure on the axons of the optic nerves of three beagles at early stages of glaucoma and two beagles with advanced signs of glaucoma were compared to the optic nerves of four age-matched normal dogs. Plastic embedded optic nerve cross-sections (1 micron) 1 mm posterior to the lamina cribrosa were osmicated and stained with Toluidine Blue. Axons from 0.2 to > 2.0 microns in diameter were counted and measured in 16 cross-sectional regions of equal size within the whole optic nerve using a computerized image analysis system. The mean optic nerve axon diameters in the normal, early glaucomatous, and advanced glaucomatous dogs were 1.53, 1.25 and 1.13 microns respectively. The average total optic nerve axon count in the normal dogs was 148,303. Approximately 16% of the total axonal fibers were counted in each nerve. The counts of optic nerve axons 2.0 microns or greater in diameter were reduced by up to 60% in the central regions of the optic nerves of affected beagles. The large diameter axons of the peripheral optic nerve of the beagle dogs with glaucoma were more resistant to the elevated intraocular pressure. The counts of axons > 0.6 to 0.8 micron in diameter were significantly increased in glaucomatous beagles.