Congenital ocular abnormalities of Rocky Mountain Horses.

OBJECTIVE: To determine the incidence and describe ocular abnormalities in a cross-section of the population of Rocky Mountain Horses. Design: Prospective study. Animals: Five-hundred and fourteen Rocky Mountain Horses. Procedure: Ophthalmic examinations were performed using a slit-lamp biomicroscope and an indirect ophthalmoscope. Intraocular pressures were measured by applanation tonometry. Eyes from six horses were obtained for histologic examination. RESULTS: Cysts of the posterior iris, ciliary body, and peripheral retina were detected most frequently (249 horses), and were always located temporally. Curvilinear streaks of retinal pigmented epithelium extending from the peripheral temporal retina marked the boundary of previous retinal detachment in 189 horses. Retinal dysplasia was detected in 125 horses. Multiple ocular anomalies were evident in 71 horses and were always bilateral and symmetrical. Affected eyes had a large, clear cornea that protruded excessively and had an apparent short radius of curvature, a deep anterior chamber, miotic and dyscoric pupil, and iris hypoplasia. Pupillary light responses were decreased or absent and pupils failed to dilate after repeated instillation of mydriatic drugs in horses with multiple ocular anomalies. Less frequently encountered abnormalities included peripheral iridocorneal adhesions and goniosynechiae. Congenital cataract was always present in eyes with multiple abnormalities. Intraocular pressures did not differ among horses with normal eyes and horses with multiple ocular abnormalities. Histologic examination of eyes corroborated the clinical appearance.

Corneal thickness, intraocular pressure, and optical corneal diameter in Rocky Mountain Horses with cornea globosa or clinically normal corneas.

OBJECTIVE: To compare corneal thickness, intraocular pressure, and optical corneal diameter in Rocky Mountain Horses with cornea globosa and those with clinically normal corneas. ANIMALS: 129 Rocky Mountain Horses. PROCEDURE: Ultrasonic pachymetry was used to measure corneal thickness. Applanation tonometry was used to measure intraocular pressure. A Jameson caliper was used to measure optical corneal diameter. RESULTS: The central and temporal peripheral portions of the cornea were significantly thicker in horses with cornea globosa than in horses with clinically normal corneas, but corneal thicknesses in the dorsal, ventral, and medial peripheral portions of the cornea were not significantly different between groups. There were no differences in corneal thickness between male and female horses or between right and left eyes. However, there was a positive correlation between age and corneal thickness. Intraocular pressure was not significantly different between horses with cornea globosa and those with clinically normal corneas, or between right and left eyes, or male and female horses. Optical corneal diameter for horses with cornea globosa was not significantly different from diameter for horses with clinically normal corneas, but optical corneal diameter was positively correlated with age. CONCLUSIONS AND CLINICAL RELEVANCE: Cornea globosa in Rocky Mountain Horses is not associated with increased intraocular pressure. Corneal thickness and optical corneal diameter increase with age in Rocky Mountain Horses.

Evaluation of topically administered tissue plasminogen activator for intraocular fibrinolysis in dogs.

Fibrin clots were induced in eyes of dogs by injection of autogenous citrated plasma into the anterior chamber. Twenty-four hours after clot formation, one 50-microliters drop of tissue plasminogen activator at a concentration of 5 mg/ml (group 1, n = 7) was administered topically 9 times at 5-minute intervals, or a collagen shield that was hydrated with tissue plasminogen activator at a concentration of 5 mg/ml (group 2, n = 7) was applied. The contralateral eye served as a nontreated control. Serial photographs were taken of the fibrin clots after topical application of tissue plasminogen activator. Computerized morphometric analysis was then used to evaluate changes in cross-sectional surface area of the fibrin clot. There was no significant mean percentage decrease in clot surface area of treated eyes of group-1 dogs or in treated eyes of group-2 dogs. In addition, there was no significant difference in mean percentage decrease in clot surface area between treated eyes of group-1 and group-2 dogs.

Effects of three occlusive dressing materials on healing of full-thickness skin wounds in dogs.

The effects of 3 occlusive dressing materials and a standard, nonadherent dressing material on healing of full-thickness skin defects were evaluated in dogs. Two wounds measuring 2 x 2 cm were created bilaterally (4 wounds/dog) on the dorsolateral aspect of the trunk of 12 Beagles. Wound treatments were evenly distributed between 4 sites, using a Latin square design. Treatments evaluated were: equine amnion (group A), biosynthetic hydrogel dressing (group B), transparent polyethylene sheeting (group T), and a semi-occlusive rayon/polyethylene, nonadherent dressing (group C). Rates of contraction and epithelialization of group-A wounds were significantly greater than those of wounds of groups C, B, and T. On days 14, 21, and 28, mean percentage of wound contraction and mean percentage of total wound healed in group A exceeded those wounds in groups C, B, and T. On day 28, wounds in group A were significantly smaller than wounds in groups B and T, but were not significantly smaller than wounds in group C. All wounds in group A achieved 100% healing during the 28-day study period. Mean time for complete healing of group-A wounds was 21 days. The percentages of wounds completely healed by day 28 for groups B, C, and T were 25, 67, and 25%, respectively. Results indicate that use of equine amnion as an occlusive biological dressing on full-thickness wounds in dogs increases rate of healing.

Density of corneal endothelial cells and corneal thickness in eyes of euthanatized horses.

OBJECTIVE: To determine density of corneal endothelial cells and corneal thickness in eyes of euthanatized horses. SAMPLE POPULATION: 52 normal eyes from 26 horses. PROCEDURE: Eyes were enucleated after horses were euthanatized. Eyes were examined to determine that they did not have visible ocular defects. Noncontact specular microscopy was used to determine density of corneal endothelial cells. Corneal thickness was measured, using ultrasonic pachymetry or specular microscopy. RESULTS: Mean density of corneal endothelial cells was 3,155 cells/mm2. Cell density decreased with age, but sex did not affect cell density. Values did not differ significantly between right and left eyes from the same horse. Cell density of the ventral quadrant was significantly less than cell density of the medial and temporal quadrants. Mean corneal thickness was 893 microm. Sex or age did not affect corneal thickness. Dorsal and ventral quadrants were significantly thicker than the medial and temporal quadrants and central portion of the cornea. We did not detect a correlation between corneal thickness and density of endothelial cells in normal eyes of horses. CONCLUSIONS AND CLINICAL RELEVANCE: Density of corneal endothelial cells decreases with age, but corneal thickness is not affected by age or sex in normal eyes of horses. The technique described here may be useful for determining density of endothelial cells in the cornea of enucleated eyes. This is clinically relevant for analyzing corneal donor tissue prior to harvest and use for corneal transplantation.

Evaluation of short-term increased intraocular pressure on flash- and pattern-generated electroretinograms of dogs.

OBJECTIVE: To determine the electrodiagnostic and histologic response of short-term increases of intraocular pressure (IOP) on transient pattern electroretinograms (PERG) and flash electroretinograms (FERG) in the eyes of dogs. ANIMALS: 8 healthy mixed-breed dogs. PROCEDURE: Transient PERG and FERG waveforms were recorded from dogs (while anesthetized) as IOP was increased from baseline (7 to 19 mm Hg) to 90 mm Hg. One hundred mean PERG responses and a single FERG response were recorded at each step during 3 recording sessions. Globes of each dog were enucleated after euthanasia on posttreatment day 7 and evaluated by a pathologist. RESULTS: Increases in spatial frequency resulted in decreased amplitudes of N2 (second negative PERG peak). Increases in IOP resulted in decreases in all 3 PERG waveforms and the FERG waveform. All values began to return to baseline after short-term increases in IOP on day 0, and waveforms were not significantly different on posttreatment days 3 and 7 CONCLUSIONS: Data suggest that short-term increases in IOP affect PERG and FERG waveforms, and PERG waveforms are more sensitive to increases in IOP Differences were not detected between treated and control eyes on histologic examination. Further studies are necessary to determine at what IOP permanent damage to ganglion and photoreceptor cells will develop and whether PERG is a reliable clinical diagnostic technique for use in dogs to reveal retinal damage that is secondary to increased IOP prior to changes in waveforms generated by FERG in dogs.

Eosinophilic keratoconjunctivitis in a horse.

An 11-year-old Quarter Horse gelding was evaluated because of a persistent, raised band of 1- to 2-mm subepithelial plaques of the left cornea. Cytologic examination of corneal scrapings revealed numerous eosinophils and segmented neutrophils, with few mast cells, plasma cells, and lymphocytes. Bacteriologic culture yielded sparse growth of alpha-hemolytic Streptococcus and Staphylococcus spp. Histologically, the plaques consisted of subepithelial foci of fragmented and degenerated collagen fibers infiltrated by eosinophils and neutrophils, with few lymphocytes, plasma cells, and macrophages. Plaques were surrounded by a layer of brightly eosinophilic, acellular, granular material. Distribution of inflammatory cells in the conjunctiva was similar to cells in the cornea. After reepithelialization of the cornea, corticosteroid ointment was administered topically. Twenty-eight days after treatment with corticosteroids, the plaques had completely resolved. Histologic and cytologic diagnoses in this horse were similar to reports of eosinophilic keratitis in cats.

Use of orally administered succimer (meso-2,3-dimercaptosuccinic acid) for treatment of lead poisoning in dogs.

OBJECTIVE: To determine whether succimer (meso-2,3-dimercaptosuccinic acid) would be effective in reducing blood lead concentration in dogs with naturally acquired lead poisoning and whether treated dogs would develop clinically important adverse effects. DESIGN: Prospective case series. ANIMALS: 13 dogs with moderate-to-high blood lead concentrations (39 to 120 micrograms/dl) and clinical signs of lead poisoning. PROCEDURE: Dogs were treated with succimer (10 mg/kg of body weight, PO, q 8 h) for 10 days. Blood and urine samples were analyzed for lead concentration before, during, and after treatment with succimer. RESULTS: Mean blood lead concentrations on days 0, 3, 7, and 20 were 70.6, 32.7, 16.8, and 27.6 micrograms/dl, respectively. Mean blood lead concentrations decreased 53.6, 76.2, and 60.9% from pretreatment value on days 3, 7, and 20, respectively. Mean urine lead concentrations on days 0, 3, 7, and 20 were 70.0, 485.4, 254.3, and 28.3 micrograms/dl, respectively. CLINICAL IMPLICATIONS: In dogs with naturally acquired lead poisoning, succimer administered orally for 10 days effectively reduced blood lead concentrations and eliminated clinical signs of lead poisoning.

Intraocular silicone prosthesis implantation in eyes of dogs and a cat with intraocular neoplasia: nine cases (1983-1994).

OBJECTIVE: To determine the outcome of implantation of an intraocular silicone prosthesis (ISP) in the eyes of dogs and cats with intraocular neoplasia. DESIGN: Retrospective case series. ANIMALS: Eight dogs and 1 cat with histologically confirmed intraocular neoplasia. PROCEDURE: Signalment, clinical signs before and after surgery, results of microscopic examination of eviscerated intraocular tissues, follow-up information, and necropsy findings, if available, were recorded for each animal. RESULTS: Five dogs and 1 cat had primary intraocular neoplasms. Two of the dogs developed regrowth of the neoplasm around the ISP 6 to 24 months after implantation, and the eyes were enucleated. The cat developed signs compatible with systemic metastasis 4 years after surgery and was euthanatized. Three dogs had multicentric or metastatic neoplasia involving the eye. Two of these dogs were euthanatized because of their systemic disease 1.5 to 7 months after ISP implantation. The third dog is alive without evidence of regrowth 3 years after surgery. CLINICAL IMPLICATION: Intraocular neoplasia is not an absolute contraindication to ISP implantation.

Feline chlamydia and calicivirus infections.

Feline conjunctivitis is common and often presents a clinical challenge to the veterinarian. Chlamydia psittaci is an important pathogen and should always be considered when evaluating cats with conjunctivitis. FCV is an infrequent cause of conjunctivitis and only causes the disease in conjunction with other clinical signs of this infection, such as oral mucosal ulcers and upper respiratory tract disease.

Surgery of the orbit.

Orbital surgery is performed infrequently but when necessary, requires detailed understanding of orbital anatomy and the probable biologic behavior and extent of the pathologic process affecting the orbit. Thorough preoperative characterization of an orbital disease allows the surgeon to develop a surgical strategy. Inaccurate or hasty preoperative localization, determination of extension, and diagnosis may result in selection of an inappropriate surgical approach or discretionary surgery when medical treatment is indicated. In most instances, diagnostic images (MR, CT, echography) should always be made and fine-needle aspiration be done before orbital surgery is performed. The choice of surgical approach or combination of approaches is determined primarily by the type, location, size, and extent of disease present. Extensive surgical exposure of the orbit is limited to centimeters or fractions of a centimeter because of the compact anatomy and tight confines of the orbital region. Careful tissue manipulation, surgical dissection, and postoperative assessment are necessary to preserve the globe and functional vision when orbital disease endangers function.

Primary adenocarcinoma of the gland of the nictitating membrane in a cat.

An 11-year-old, neutered, male domestic shorthair was presented with a five-month history of recurrent, unilateral, seromucoid discharge from the right eye. A verrucous mass extended from the posterior aspect of the nictitating membrane. Adenocarcinoma of the gland of the nictitating membrane (GNM) was diagnosed upon biopsy. The cat subsequently developed metastases to the lungs, pleura, mediastinum, liver, and kidneys and died six months after clinical signs first were observed. Little is known about the biological behavior of adenocarcinoma of the GNM in cats. This is the first report that describes the natural progression of this disease.

Ligneous conjunctivitis in four Doberman pinschers.

Ligneous conjunctivitis (LC) was diagnosed in four unrelated Doberman pinschers. Thick, opaque membranes of the palpebral conjunctivae and nictitating membranes were present bilaterally. Three dogs had concurrent signs of multisystemic disease. A thick, amorphous, eosinophilic, hyaline-like material in the substantia propria of the conjunctiva--containing a moderate, mononuclear cell infiltrate--was evident on histological examination. A predominance of T lymphocytes, few macrophages, and weak positive staining for immunoglobulin G (IgG) and immunoglobulin A (IgA) were evident by immunohistochemical staining. The clinical and histological appearance of LC in Doberman pinschers and humans is similar.

The horse homolog of congenital aniridia conforms to codominant inheritance.

Anterior segment dysgenesis syndrome occurs frequently in Rocky Mountain horses and has two distinct ocular phenotypes: (1) large cysts originating from the temporal ciliary body or peripheral retina and (2) multiple anterior segment anomalies including ciliary cysts, iris hypoplasia, iridocorneal adhesions and opacification, nuclear cataract, and megalocornea. To determine if anterior segment dysgenesis syndrome is heritable in horses we performed ophthalmic examinations and collected pedigree information on horses (n = 516) in an extended Rocky Mountain horse pedigree. Logistic regressive segregation analysis of a subset of animals (n = 337) in which the ocular phenotypes of progeny and both parents were known indicated that the codominant inheritance model best fit the data. This model predicted cyst phenotype expression in heterozygous animals and multiple anterior segment anomalies in homozygous animals. Several cases of nonpenetrance of the cyst phenotype were detected in one lineage. The close resemblance between the inheritance and lesions observed in Small eye mice and rats, humans with congenital aniridia or anterior segment malformation, and horses with anterior segment dysgenesis syndrome supported the conclusion that anterior segment dysgenesis syndrome in the horse may be homologous to similar ophthalmic anomalies in other species.

Persistent fetal intraocular vasculature in the European ferret (Mustela putorius): clinical and histological aspects.

OBJECTIVE: To describe the clinical and histological appearance of persistent fetal intraocular vasculature in a colony of ferrets. Design Prospective study. ANIMALS STUDIED: Eighty-six European ferrets (Mustela putorius). Procedure Both eyes of 76 genetically related progeny and 10 breeding, adult, colony-raised ferrets were studied using a slit lamp biomicroscope and an indirect ophthalmoscope. Ferret progeny were examined after eyelid opening at 5-6 weeks of age, and at 12 months of age. After euthanasia, globes were enucleated and examined histologically. RESULTS: Persistent fetal intraocular vasculature was evident in 21 progeny ferrets at 5-6 weeks of age and in three mature progenitor ferrets. Clinical appearance of diminutive vasculature was characterized by focal remnants of the posterior tunica vasculosa lentis, muscae volitantes, and an occluded hyaloid artery extending from the optic papilla and terminating in the anterior vitreous body. Extensive persistent vasculature was characterized by a perfused hyaloid artery, vasa hyaloidea propria and posterior tunica vasculosa lentis, posterior cortical and capsular cataract, and proliferation of fibrovascular tissue along the posterior lens capsule. Fetal vasculature persisted in 7 of 21 progeny ferrets at one year of age and in three progenitor ferrets. Results of histologic examination showed persistence of the hyaloid vasculature, proliferation of retrolental fibrovascular tissue with osseous metaplasia, posterior capsular and cortical cataract, and occasional retinal detachment. CONCLUSIONS: Persistent fetal intraocular vasculature in ferrets appears similar clinically and histologically to persistent fetal intraocular vasculature reported in humans and dogs. The ferret may be a suitable animal model for vasculogenic mechanisms of persistent fetal intraocular vasculature and for evaluating vasoinhibitory growth factors and angiostatic test compounds.

Ophthalmic manifestations and complications of dental disease in dogs and cats.

Ophthalmic manifestations of dental disease may occur in dogs and cats because of the proximity between posterior maxillary teeth and the orbit. Ophthalmic disorders may be diagnosed promptly, but the initiating dental disease may be overlooked. Inappropriate diagnosis and treatment of dental disease may result in loss of teeth, irreversible vision-threatening ophthalmic disease, or, ultimately, loss of the globe. When ophthalmic examination results are suggestive of a primary dental disorder, thorough examination of the maxillary teeth is imperative to diagnose appropriately the underlying dental disease. Therapy should include treatment of the dental disease and secondary ophthalmic disorders.