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SUMMARY

Objective

To determine ocular dimensions (using A-scan ultrasound biometry) and corneal curvature (using keratometry) in the feline eye and to calculate the appropriate dioptric power for a prototype posterior chamber intraocular lens (IOL) necessary to achieve emmetropia in the eyes of cats undergoing lens extraction.

Animals

25 clinically normal adult mixed-breed cats and 10 eyes from 10 clinically normal adult mixed-breed cat cadavers.

Procedure

A-scan ultrasonic biometry was performed on both eyes of each live cat. Cats were tranquilized, and keratometry was performed on each eye. Biometry was performed on the cadaver eyes. Five of the cadaver eyes had the lens extracted and an IOL, designed for use in dogs, was implanted. Biometry was repeated to estimate postoperative IOL position. Using 3 theoretical IOL formulas, data from biometry, keratometry, and postoperative IOL position were used to predict IOL strength required to achieve emmetropia after lens extraction in cats.

Results

Mean axial length of eyes in live cats was 20.91 ± 0.53 mm. Mean preoperative anterior chamber depth (ACD) was 5.07 ± 0.36 mm, and mean lens thickness was 7.77 ± 0.23 mm. Predicted postoperative ACD was calculated to be 10.84 mm. Measured postoperative ACD in the 5 cadaver eyes was 8.28 mm. Required IOL strength calculated, using the predicted postoperative ACD, was 73 to 76 diopters. The required IOL strength calculated, using the measured postoperative ACD, was 53 to 55 diopters.

Conclusions and Clinical Relevance

An IOL of substantially higher diopter strength than that needed in dogs is required to achieve emmetropia after lens extraction in average cats; an IOL strength of approximately 53 to 55 diopters will likely be required. (Am J Vet Res 1998;59:131–134)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the use of an intravitreal sustained-release cyclosporine (CsA) delivery device for treatment of horses with naturally occurring recurrent uveitis.

Animals—16 horses with recurrent uveitis.

Procedures—Horses with frequent recurrent episodes of uveitis or with disease that was progressing despite appropriate medication were selected for this study. Additional inclusion criteria included adequate retinal function as determined by use of electroretinography, lack of severe cataract formation, and no vision-threatening ocular complications (eg, retinal detachment, severe retinal degeneration, and posterior synechia). Sustained-release CsA delivery devices (4 µg of CsA/d) were implanted into the vitreous through a sclerotomy at the pars plana. Reexaminations were performed 1, 3, 6, and 12 months after implantation, then continued annually. Ophthalmic changes, number of recurrent episodes of uveitis, and vision were recorded.

Results—The rate of recurrent episodes after device implantation (0.36 episodes/y) was less than prior to surgery (7.5 episodes/y). In addition, only 3 horses developed episodes of recurrent uveitis after surgery. Vision was detected in 14 of 16 affected eyes at a mean follow-up time of 13.8 months (range, 6 to 24 months).

Conclusions and Clinical Relevance—This intravitreal sustained-release CsA delivery device may be a safe and important tool for long-term treatment of horses with chronic recurrent uveitis. (Am J Vet Res 2001;62:1892–1896)

Full access
in American Journal of Veterinary Research

SUMMARY

Intraocular pressure (iop) was measured, using applanation tonometry, in both eyes of 20 horses after topical application of 0.5% proparacaine to the cornea. Ultrasonic pachymetry was used to measure central, mid-peripheral, and peripheral corneal thickness (ct) in all 4 quadrants of both eyes of 25 horses. All measurements were repeated after auriculopalpebral nerve block, sedation by iv administration of xylazine, or combination of nerve block and sedation. Mean iop after topical anesthesia of the cornea was 20.6 ± 4.7 mm of Hg for the left eye and 20.35 ± 3.7 mm of Hg for the right eye. Mean central ct was 793.2 ± 42.3 μm. The peripheral part of the cornea was significantly (P < 0.05) thicker, on average, than the central part of the cornea. Auriculopalpebral nerve block had no significant effect on iop or ct. Intravenous administration of xylazine resulted in a significant (P < 0.05) decrease in iop, but had no effect on ct.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine penetration of topically and orally administered voriconazole into ocular tissues and evaluate concentrations of the drug in blood and signs of toxicosis after topical application in horses.

Animals—11 healthy adult horses.

Procedure—Each eye in 6 horses was treated with a single concentration (0.5%, 1.0%, or 3.0%) of a topically administered voriconazole solution every 4 hours for 7 doses. Anterior chamber paracentesis was performed and plasma samples were collected after application of the final dose. Voriconazole concentrations in aqueous humor (AH) and plasma were measured via high-performance liquid chromatography. Five horses received a single orally administered dose of voriconazole (4 mg/kg); anterior chamber paracentesis was performed, and voriconazole concentrations in AH were measured.

Results—Mean ± SD voriconazole concentrations in AH after topical administration of 0.5%, 1.0%, and 3.0% solutions (n = 4 eyes for each concentration) were 1.43 ± 0.37 μg/mL, 2.35 ± 0.78 μg/mL, and 2.40 ± 0.29 μg/mL, respectively. The 1.0% and 3.0% solutions resulted in significantly higher AH concentrations than the 0.5% solution, and only the 3.0% solution induced signs of ocular toxicosis. Voriconazole was detected in the plasma for 1 hour after the final topically administered dose of all solutions. Mean ± SD voriconazole concentration in AH after a single orally administered dose was 0.86 ± 0.22 μg/mL.

Conclusions and Clinical Relevance—Results indicated that voriconazole effectively penetrated the cornea in clinically normal eyes and reached detectable concentrations in the AH after topical administration. The drug also penetrated noninflamed equine eyes after oral administration. Low plasma concentrations of voriconazole were detected after topical administration.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether a chemokine (RANTES)-like protein expressed by ciliary epithelium plays a role in uveitis.

Sample Population—3 clinically normal horses intradermal, 5 eyes from 5 horses with recurrent uveitis, and 10 normal eyes from 5 age- and sex-matched horses.

Procedure—Cross-reactivity and sensitivity of recombinant human (rh)-regulated upon activation, normal T-cell expressed and secreted (RANTES) protein were evaluated in horses by use of intradermal hypersensitivity reactions and a chemotaxis assay. Aqueous humor and ciliary body of eyes from clinically normal horses and horses with uveitis were examined for RANTES expression by use of an ELISA and reverse transcription-polymerase chain reaction (RT-PCR). Expression of RANTES mRNA and protein content of primary cultures of equine ciliary pigmented epithelial cells (RT-PCR) and culture supernatant (ELISA) were measured 6 or 24 hours, respectively, after cultures were stimulated with interleukin-1β and tumor necrosis factor-α.

Results—Strong reactions to intradermal hypersensitivity testing and significant chemotaxis of equine leukocytes to rh-RANTES wereas observed. Aqueous humor of eyes from horses with uveitis contained increased concentrations of rh-RANTES-like protein (mean ± SD, 45.9 ± 31.7 pg/ml), compared with aqueous humor from clinically normal horses (0 pg/ml). Ciliary body from horses with uveitis expressed RANTES mRNA, whereas ciliary body from clinically normal horses had low mRNA expression. Stimulated ciliary pigmented epithelial cells expressed increased amounts of rh-RANTES-like protein (506.1 ± 298.3 pg/ml) and mRNA, compared with unstimulated samples.

Conclusions and Clinical Relevance—Ciliary epithelium may play a role in recruitment and activation of leukocytes through expression of RANTES. (Am J Vet Res 2002;63:942–947)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the degree of ocular penetration and systemic absorption of commercially available topical ophthalmic solutions of 0.3% ciprofloxacin and 0.5% moxifloxacin following repeated topical ocular administration in ophthalmologically normal horses.

Animals—7 healthy adult horses with clinically normal eyes as evaluated prior to each treatment.

Procedures—6 horses were used for assessment of each antimicrobial, and 1 eye of each horse was treated with topically administered 0.3% ciprofloxacin or 0.5% moxifloxacin (n = 6 eyes/drug) every 4 hours for 7 doses. Anterior chamber paracentesis was performed 1 hour after the final dose was administered, and blood samples were collected at 24 (immediately after the final dose), 24.25, 24.5, and 25 hours (time of aqueous humor [AH] collection). Plasma and AH concentrations of ciprofloxacin or moxifloxacin were determined by use of high-performance liquid chromatography.

Results—Mean ± SD AH concentrations of ciprofloxacin and moxifloxacin were 0.009 ± 0.008 μg/mL and 0.071 ± 0.029 μg/mL, respectively. The AH moxifloxacin concentrations were significantly greater than those of ciprofloxacin. Mean ± SD plasma concentrations of ciprofloxacin were less than the lower limit of quantification. Moxifloxacin was detected in the plasma of all horses at all sample collection times, with a peak value of 0.015 μg/mL at 24 and 24.25 hours, decreasing to < 0.004 μg/mL at 25 hours.

Conclusions and Clinical Relevance—Moxifloxacin was better able to penetrate healthy equine corneas and reach measurable AH concentrations than was ciprofloxacin, suggesting moxifloxacin might be of greater value in the treatment of deep corneal or intraocular bacterial infections caused by susceptible organisms. Topical administration of moxifloxacin also resulted in detectable plasma concentrations.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine appropriate intraocular lens (IOL) implant strength to approximate emmetropia in horses.

Sample Population—16 enucleated globes and 4 adult horses.

Procedures—Lens diameter of 10 enucleated globes was measured. Results were used to determine the appropriate-sized IOL implant for insertion in 6 enucleated globes and 4 eyes of adult horses. Streak retinoscopy and ocular ultrasonography were performed before and after insertion of 30-diopter (D) IOL implants (enucleated globes) and insertion of 25-D IOL implants (adult horses).

Results—In enucleated globes, mean ± SD lens diameter was 20.14 ± 0.75 mm. Preoperative and postoperative refractive state of enucleated globes with 30-D IOL implants was −0.46 ± 1.03 D and −2.47 ± 1.03 D, respectively; preoperative and postoperative difference in refraction was 2.96 ± 0.84 D. Preoperative anterior chamber (AC) depth, crystalline lens thickness (CLT), and axial globe length (AxL) were 712 ± 0.82 mm, 11.32 ± 0.81 mm, and 40.52 ± 1.26 mm, respectively; postoperative AC depth was 10.76 ± 1.16 mm. Mean ratio of preoperative to postoperative AC depth was 0.68. In eyes receiving 25-D IOL implants, preoperative and postoperative mean refractive error was 0.08 ± 0.68 D and −3.94 ± 1.88 D, respectively. Preoperative AC depth, CLT, and AxL were 6.36 ± 0.22 mm, 10.92 ± 1.92 mm, and 38.64 ± 2.59 mm, respectively. Postoperative AC depth was 8.99 ± 1.68 mm. Mean ratio of preoperative to postoperative AC depth was 0.73.

Conclusions and Clinical Relevance—Insertion of 30-D (enucleated globes) and 25-D IOL implants (adult horses) resulted in overcorrection of refractive error.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To describe the immunopathologic characteristics of superficial stromal immune-mediated keratitis (IMMK) immunopathologically by characterizing cellular infiltrate in affected corneas of horses.

Animals—10 client-owned horses with IMMK.

Procedures—Immunohistochemical staining was performed on keratectomy samples with equine antibodies against the T-cell marker CD3 and B-cell marker CD79a (10 eyes) and the T-helper cytotoxic marker CD4 and T-cell cytotoxic marker CD8 (6 eyes). Percentage of positively stained cells was scored on a scale from 0 (no cells stained) to 4 (> 75% of cells stained). Equine IgG, IgM, and IgA antibodies were used to detect corneal immunoglobulin via direct immunofluorescence (10 eyes). Serum and aqueous humor (AH) samples from 3 horses with IMMK were used to detect circulating and intraocular IgG against corneal antigens via indirect immunofluorescence on unaffected equine cornea.

Results—Percentage scores (scale, 0 to 4) of cells expressing CD3 (median, 2.35 [range, 0.2 to 3.7]; mean ± SD, 2.36 ± 1.08) were significantly greater than scores of cells expressing CD79a (median, 0.55 [range, 0 to 1.5]; mean, 0.69 ± 0.72). All samples stained positively for CD4- and CD8-expressing cells, with no significant difference in scoring. All samples stained positively for IgG, IgM, and IgA. No serum or AH samples collected from horses with IMMK reacted with unaffected equine cornea.

Conclusions and Clinical Relevance—Pathogenesis of superficial stromal IMMK included cell-mediated inflammation governed by both cytotoxic and helper T cells. Local immunoglobulins were present in affected corneas; however, corneal-binding immunoglobulins were not detected in the serum or AH from horses with IMMK.

Full access
in American Journal of Veterinary Research

Abstract

Case Description—A 12-year-old castrated male mixed-breed dog was evaluated because of blepharospasm and blindness affecting both eyes.

Clinical Findings—During examination and diagnostic testing of the dog, fine-needle aspirates of splenic nodules were examined microscopically and stage Vb multicentric large-cell lymphosarcoma was identified. Aqueocentesis was performed, and sample analysis revealed intraocular lymphosarcoma; B-cell neoplasia was confirmed by use of a PCR assay for antigen receptor rearrangement (PARR) performed on samples of aqueous humor. Secondary uveitis and glaucoma were detected bilaterally in addition to chronic superficial corneal ulcerations in the left eye.

Treatment and Outcome—Treatment for abdominal and intraocular lymphosarcoma involving administration of vincristine, l-asparaginase, cyclophosphamide, doxorubicin, and prednisone was initiated. Secondary uveitis and glaucoma were controlled with topical treatment; however, the corneal ulceration did not resolve. Seven weeks following diagnosis, the dog died as a result of complications related to systemic neoplasia and chemotherapy.

Clinical Relevance—In the dog of this report, intraocular lymphosarcoma was diagnosed via PARR performed on samples of aqueous humor. Moreover, the immunophenotype of the neoplastic cells was determined by use of that diagnostic technique. Because secondary uveitis is a common finding in dogs and cats with systemic lymphosarcoma, intraocular lymphosarcoma should be considered as a differential diagnosis; furthermore, investigation (eg, PARR performed on aqueous humor samples) to identify the presence of intraocular lymphosarcoma is warranted, thereby allowing targeted interventions to be considered in management of those patients.

Full access
in Journal of the American Veterinary Medical Association

  • Nutritional deficiency of vitamin E in dogs can lead to oxidative damage and degeneration of the photoreceptors of the retina.

  • Clinical and pathologic changes associated with vitamin E deficiency in dogs are similar to those described for central progressive retinal atrophy and equine lower motor neuron disease, which suggests that these diseases share a common pathogenesis.

Free access
in Journal of the American Veterinary Medical Association