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.

Evaluation of activity of selected ophthalmic antimicrobial agents in combination against common ocular microorganisms.

OBJECTIVE: To determine in vitro efficacy of gentamicin, tobramycin, and miconazole when used in combination, with or without atropine, against Pseudomonas or Aspergillus sp. PROCEDURE: Selected ophthalmic agents were combined for predetermined times. Sterile disks impregnated with the combined solutions were prepared and placed on Mueller-Hinton plates that were seeded with Pseudomonas or Aspergillus sp. Zones of growth inhibition were measured at postincubation hours 24 and 48. RESULTS: Tobramycin alone inhibited growth of Pseudomonas sp, whereas miconazole inhibited growth of Aspergillus sp. Significant differences in zones of growth inhibition when atropine was combined with tobramycin, when gentamicin was combined with miconazole, or when atropine was combined with miconazole and gentamicin, were not detected. CLINICAL RELEVANCE: Combining selected ophthalmic therapeutic agents for as long as 6 hours does not appear to alter the in vitro efficacy of the agents against microorganisms used in this study.

Ocular blastomycosis in dogs: 73 cases, 108 eyes (1985-1993).

OBJECTIVE: To evaluate clinical signs of ocular blastomycosis in dogs, to determine response of blastomycosis-infected eyes to treatment with systemically administered amphotericin B and ketoconazole, and to identify prognostic indicators of successful antifungal treatment. DESIGN: Retrospective study. ANIMALS: 73 dogs. PROCEDURE: Medical records were reviewed for all dogs with confirmed blastomycosis and ocular disease seen at our hospital between 1985 and 1993. RESULTS: 6 eyes had anterior segment disease, 24 had posterior segment disease, and 78 had endophthalmitis. 40 eyes were treated with a combination of amphotericin B and ketoconazole, and 16 of the 40 responded favorably. However, 16 of the 24 eyes that were not severely affected responded favorably, but none of the 16 eyes that were severely affected did. CLINICAL IMPLICATIONS: Dogs with blastomycosis had posterior segment disease, without complete retinal separation, had a good prognosis for retaining vision. Results of histologic examination suggested that secondary glaucoma was a manifestation of endophthalmitis and was indicative of a grave prognosis for response to antifungal and antiglaucoma treatment.

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.

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.

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.

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.

Ocular and disseminated candidiasis in an immunosuppressed cat.

Ocular and systemic candidiasis was diagnosed in an immunosuppressed and diabetic 12-year-old cat that initially was examined because of polyuria, polydipsia, and urinary tract disease. Bilateral recurrent corneal erosions and chorioretinitis, urinary tract infections attributable to bacteria or Candida sp, and renal dysfunction developed during the next 2 months. Examination of corneal scrapings revealed spherical to oval, budding, yeast-like cells. The cat's condition progressively deteriorated, and it was euthanatized. Toxoplasmosis was diagnosed by fecal flotation and from serum titers, and pituitary-dependent hyperadrenocorticism was detected at postmortem histologic evaluation. Candida budding yeasts and pseudohyphae with blastospores were detected in the corneas, vitreous bodies, retinas, CNS, pharynx, trachea, esophagus, kidneys, and urinary bladder at postmortem examination.

Evaluation of intraocular penetration of topically administered tissue plasminogen activator in dogs.

Topically administered tissue plasminogen activator (tPA) was evaluated for its penetration into aqueous humor of clinically normal dogs. Two concentrations of tPA (5 mg/ml and 10 mg/ml) were evaluated in a single-dose study, and a concentration of 5 mg of tPA/ml was used for a multiple-dose study. The contralateral eye served as a nontreated control. Enzyme substrate analysis of aqueous humor was used to determine tPA activity. The activity of tPA in aqueous humor was significantly (P < or = 0.05) greater in treated eyes of all dogs, compared with that in control eyes. Significant differences in activity of tPA were not detected at different doses in treated eyes.

Use of 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, 0.01 ml of tissue plasminogen activator at a concentration of 1 microgram/100 microliters (group 1, n = 5) or 25 micrograms/100 microliters (group 2, n = 5) was injected into 1 anterior chamber of each dog. The contralateral eye served as a nontreated control. Serial photographs were taken of the fibrin clots after intracameral injection of tissue plasminogen activator. Computerized morphometric analysis was then used to evaluate changes in cross-sectional surface area of the fibrin clot. Significant (P less than 0.001) fibrin-clot lysis was detected in treated eyes of group-2 dogs, but was not found in treated eyes of group-1 dogs. A mean decrease of greater than 90% in clot surface area was detected by 120 minutes after injection in treated eyes of group-2 dogs.

Effects of intracameral injection of tissue plasminogen activator on corneal endothelium and intraocular pressure in dogs.

Contact wide-field specular microscopy was performed on eyes of 16 healthy dogs after tissue plasminogen activator at a concentration of 25 micrograms/100 microliters (group 1, n = 8) or 50 micrograms/100 microliters (group 2, n = 8) was injected into 1 anterior chamber of each dog. The contralateral eye served as a nontreated control. Applanation tonometry was used to measure intraocular pressure in both eyes for up to 168 hours. By use of computerized morphometric analysis and pachymetry, changes from baseline values in endothelial cell density, cell morphologic features, and corneal thickness were evaluated at postinjection hours 24, 48, and 168. Significant mean differences in intraocular pressure were not detected between treated eyes of group-1 dogs and those in group 2 at designated times, or between treated and nontreated eyes of dogs in either group. Mean corneal thickness of treated and nontreated eyes was similar in both groups through postinjection hour 168. Changes in mean percentage of endothelial cell sides were observed only in treated eyes of group-2 dogs, with the mean percentage of hexagons at postinjection hour 168 decreasing by 18%, a decrease that was significantly (P less than 0.05) greater than the decrease in nontreated eyes. The mean percentage of 6-sided cells in treated eyes of group-2 dogs was significantly (P less than 0.05) less than that in treated eyes of group-1 dogs at postinjection hour 168.

In vitro evaluation of ocular irritants using corneal protein profiles.

This report represents the first application of tissue isoelectric focusing to establish reference human and rabbit corneal protein profiles and to study the corneal response to ocular irritants. The methods developed in this study provide a direct, semiquantitative comparison of tissue-irritant interactions without the potential limitations of standard homogenization and extraction procedures. The in vitro exposure of corneal sections to acetic acid (1 and 4%) and ammonium hydroxide (0.25 and 2%) solutions resulted in selective modifications of tissue protein profiles which were evaluated by scanning densitometry. Direct comparison of the rabbit and human corneal protein changes induced by in vitro irritant action revealed a similar acid/base effect on a common rabbit and human corneal protein band (pI 8.1).

Effects of intracameral injection of viscoelastic solutions on corneal endothelium in dogs.

Contact in vivo wide-field specular microscopy was performed on right eyes of 20 healthy dogs after sodium hyaluronate (1%, n = 5), sodium chondroitin sulfate (4%) and sodium hyaluronate (3%, n = 5), hydroxypropyl methylcellulose (2%, n = 5), or balanced salt solution (control, n = 5) was injected into the anterior chamber. Using computerized morphometric analysis and pachymetry, changes in endothelial cell density, cell morphologic features, and corneal thickness from baseline values were evaluated at postinjection hour (PIH) 72 and PIH 168. Changes were not seen in endothelial cell density or cell morphologic features in any treated eye. The mean corneal thickness of all treated eyes at PIH 72 increased 6%, significantly greater than that of the nontreated eyes (P = 0.03). Mean corneal thickness of treated and nontreated eyes was similar at baseline and PIH 168 in all treatment groups.

Microbiology of the canine and feline eye.

Knowledge of the microbiology of the canine and feline eye in normal and pathologic states is an important aspect of the clinician's assessment of external ocular disease. Gram-positive bacteria predominate in surveys of microbial flora in normal and diseased eyes. These same organisms are routinely isolated from skin and the upper respiratory tract. Injury to the eye may result in proliferation and potential pathogenicity of normal ocular flora. A variety of bacterial, fungal, viral, and other microbial isolates affect the diagnosis and treatment of external ocular disease.

Effects of intracameral injection of viscoelastic solutions on intraocular pressure in dogs.

Intraocular pressure (IOP) was determined in right eyes of 20 healthy dogs after sodium hyaluronate (1%, n = 5), sodium chondroitin sulfate (4%) and sodium hyaluronate (3%, n = 5), hydroxypropyl methylcellulose (2%, n = 5), or balanced salt solution (control, n = 5) was injected into the anterior chamber. Applanation tonometry was used to measure IOP in both eyes of each dog for up to 168 hours. The 3 viscoelastic solutions resulted in an increased mean IOP by postinjection hours (PIH) 2; from PIH 12 until PIH 72, the IOP was significantly (P less than 0.001) lower than baseline. The control group did not have an increase in IOP at PIH 2; mean IOP decreased below baseline measurements within 2 hours and remained lower until PIH 72. Mean differences in IOP were not found among treated eyes (P = 0.50), and a significant interaction of any treated eyes in a group was not detected (P = 0.21). By PIH 168, the IOP approached baseline values in all groups.

Pathogenic bacteria and fungi associated with external ocular diseases in dogs: 131 cases (1981-1986).

Medical records of 131 dogs with external ocular diseases were reviewed. Bacteriologic culture of swab specimens from 151 eyes revealed 100 eyes (66.2%) were considered positive for potentially pathogenic microorganisms. Of 127 species of microorganisms (bacterial and fungal) isolated, 50 (39.3%) were Staphylococcus spp (S intermedius, 17.3%). Streptococcus spp were the next most frequently isolated organism at 32 (25.2%), (Str canis, 16.5%). beta-Hemolytic streptococci (17%) were isolated more frequently than were alpha-hemolytic streptococci (9%), and coagulase-positive staphylococcal species (29%) were isolated almost 3 times as often as were coagulase-negative species (11%). Fungal and yeast organisms were isolated from 4.6% of the eyes. In vitro, most Staphylococcus spp were susceptible to cephalothin, bacitracin, and gentamicin, whereas most Streptococcus spp were susceptible to chloramphenicol, erythromycin, carbenicillin, and cephalothin. Pseudomonas spp were sensitive to tobramycin, gentamicin, and amikacin.

Glaucoma associated with a high number of mast cells in the uveal tract of an African lion cub.

An 8-week-old male lion cub (Panthera leo) was referred for evaluation of an enlarged and reddened left eye. Ocular examination revealed a buphthalmic left globe, with corneal edema, superficial neovascularization, moderate episcleral injection, a fixed dilated pupil, and an intraocular pressure of greater than 41.5 mm of Hg as measured by the Schiotz tonometer and a human conversion chart. A diagnosis of glaucoma was made. A silicone prosthesis was implanted after evisceration of the intraocular contents. Histologic examination of the eviscerated uveal tissue revealed numerous congested and dilated vessels of various sizes. Neutrophils were marginated along the vascular endothelium, and the uveal stroma was infiltrated by a few lymphocytes and numbers (3 to 30/hpf) of widely disseminated, well-differentiated mast cells with abundant, well-granulated cytoplasm.

Pupillotonia in a dog.

A 5-year-old German Shepherd Dog was examined because of anisocoria. Pupillatonia because of parasympathetic denervation of iris sphincter muscle was diagnosed. This finding, most commonly referred to as Adie's tonic pupil in human medical literature, illustrated such a case in a species other than man. Diagnosis consisted of measuring the change in size of the pupillary aperture in response to topical administration of 0.1% pilocarpine. It is hoped that this report will help practitioners to be cognizant of pupillatonia when sorting out anisocorias.