Endoscopic-guided diagnosis of and interventional stent placement for nasolacrimal duct obstruction in a horse.

OBJECTIVE: To describe the successful use of endoscopy to visualize and place a soft canine ureteral stent to relieve a chronic nasolacrimal duct (NLD) obstruction in a horse. ANIMAL STUDIED: A 7-year-old, Quarter horse gelding. PROCEDURE: Under general anesthesia, retrograde nasolacrimal endoscopy was performed using an 8.5 Fr Storz Flex XC ureteroscope through the nasal punctum (NP). An obstructive web of fibrous tissue was visualized approximately 20 cm proximal to the NP. A 0.035″/150 cm hydrophilic guidewire was passed normograde from the ventral lacrimal punctum and used to puncture the stenotic tissue. Then, a 5.0Fr/70 cm open-end ureteral catheter was threaded normograde over the guidewire and NLD patency was re-established. The catheter confirmed a NLD length of 30 cm and was then removed. A 5.0Fr/22-32 cm Universa© Soft Ureteral Stent was threaded normograde over the guidewire until the loops of the stent were exposed at each end. The guidewire was removed and the stent loops were sutured in place. RESULTS: The stent was withdrawn 1 month after the procedure. Telephone follow-up with the client reported significant improvement in the amount of ocular discharge and decreased sensitivity around the face and ears. CONCLUSION: Endoscopy is a safe and effective procedure allowing for definitive diagnosis of NLD obstruction and to assist in interventional procedures. Placement of a canine indwelling ureteral stent seems to be an effective alternative treatment option for equine NLD obstruction compared to conventional invasive surgical procedures.

Evaluation of equine corneal disease using ultrasound biomicroscopy.

OBJECTIVE: To describe the clinical use of ultrasound biomicroscopy (UBM) to evaluate equine corneal disease. METHODS: Images were obtained using a 50-MHz probe ultrasound biomicroscopy system (Quantel Aviso) and Clear Scan® probe cover. Six horses with corneal disease were evaluated via UBM for lesion size, lesion depth, and continuity of Descemet's membrane. Horses were sedated and received auriculopalpebral nerve blocks and application of topical anesthetic prior to UBM. RESULTS: Ultrasound biomicroscopy was easily performed in all cases. UBM evaluation of three cases of corneo-limbal squamous cell carcinoma yielded information regarding lesion depth for planning of keratectomies using fixed-depth keratomes and subsequent ß-radiation therapy. Corneal depth and continuity of Descemet's membrane were determined in two horses with stromal abscesses and allowed for planning of therapeutic options. In one horse with a corneal foreign body, UBM contributed to accurate assessment of the foreign body's stromal depth, which could not be assessed during ophthalmic examination due to extensive corneal cellular infiltrate. The information regarding corneal depth allowed for more accurate pre-surgical planning in patients with opaque corneal lesions. CONCLUSIONS: Ultrasound biomicroscopy was easily performed and provided useful information regarding lesion depth and continuity of Descemet's membrane for patients with corneo-limbal squamous cell carcinoma, stromal abscesses, and a corneal foreign body, allowing for increased precision in pre-surgical planning and development of therapeutic protocols.

Double drape tectonic patch with cyanoacrylate glue for surgical repair of corneal defects: 8 cases.

OBJECTIVE: To describe the use of a double drape tectonic patch with cyanoacrylate glue technique for the treatment of deep or penetrating corneal defects in cats and dogs. ANIMALS STUDIED: Eight client-owned animals of which five were cats and three were dogs. PROCEDURE: Eight cases: Four with descemetoceles, three with corneal perforations, and one with a deep stromal ulcer were treated with a double layer of plastic drape material adhered to the cornea with a cyanoacrylate (2-octyl or 2-octyl, N-butyl)-based tissue adhesive. The patch was then covered with a third eyelid flap. RESULTS: Seven of the eight eyes healed uneventfully with a median time to healing time of 20 days (range 14-28 days). After healing, the glue patch had loosened and was removed. One eye of one cat developed bacterial keratitis with an iris prolapse adjacent to the patch and was subsequently enucleated. Only two of the eight eyes had increased corneal neovascularization. CONCLUSION: Treatment of deep or penetrating corneal defects with a double drape tectonic patch and cyanoacrylate glue is a viable option which may be a faster and less expensive alternative to other globe sparing surgical options.

Commercial amniotic membrane extract for treatment of corneal ulcers in adult horses.

BACKGROUND: Amniotic membrane extract enhances the rate of epithelialisation after corneal ulceration in several species but has not been studied in the equine cornea. OBJECTIVES: To evaluate the effect of amniotic membrane extract on re-epithelialisation of equine corneal ulcers compared with ulcers treated with antibiotic, antifungal and mydriatic medical therapy alone, and to evaluate equine corneal healing after experimentally induced superficial ulceration. STUDY DESIGN: Masked, randomised, controlled experimental trial. METHODS: Superficial, 8 mm corneal ulcers were created bilaterally in each horse. One eye was treated with amniotic membrane extract and the opposite was control. Both eyes were treated with medical therapy. Treatment eyes received amniotic membrane extract, and control eyes received the amniotic membrane extract vehicle. Ulcers were stained with fluorescein and photographed in 12-hour increments until completely healed. Ulcer surface area was determined by analysing photographs with ImageJ. A mixed linear model was used to compare ulcer surface area and hours until healing between treatment groups. A regression model was also used to calculate corneal re-epithelialisation rate over time. RESULTS: Regardless of therapy, healing occurred in two phases: an initial rapid phase of 0.88 mm2 /hr (95% CI: 0.81-0.94 mm2 /hr) for approximately 48-54 hours followed by a second, slow phase of 0.07 mm2 /hr (95% CI: 0.04-0.09 mm2 /hr). Most eyes healed within 135.5 ± 48.5 hours. Treatment (amniotic membrane extract vs. control) was not significantly associated with size of ulcers over time (P = .984). Discomfort was minimal to absent in all horses. MAIN LIMITATIONS: Results achieved experimental studies may differ from outcomes in the clinical setting. CONCLUSIONS: There was no significant difference in healing rate with addition of amniotic membrane extract to medical therapy for equine superficial corneal ulcers. A biphasic corneal healing process was observed, with an initial rapid phase followed by a slow phase. Further study will be needed to determine whether amniotic membrane extract will be helpful for infected or malacic equine corneal ulcers.

Golden retriever pigmentary uveitis: Vision loss, risk factors for glaucoma, and effect of treatment on disease progression.

OBJECTIVE: In previous reports, almost half of Golden Retrievers with Pigmentary Uveitis (GRPU) have lost vision in an eye within a year of diagnosis. The purpose of this study was to determine the proportion of GRPU affected dogs with vision loss, risk factors for the development of glaucoma, and effect of treatment on disease progression. ANIMALS STUDIED: Client owned Golden Retrievers. PROCEDURES: Two complete ophthalmic examinations were performed at least 6 months apart. Visual status, presence of glaucoma, GRPU score, and treatment were recorded. A proportional odds (ordinal logistic) model was fitted to determine whether the use of topical steroidal or non-steroidal (NSAID) ophthalmic preparations was associated with a change in GRPU scores. RESULTS: Twenty-nine Golden Retrievers, 58 eyes, were included. One eye was enucleated after the first examination. On first examination, 57/58 (98.3%) eyes and 29/29 (100%) dogs were visual. At the second examination, 48/57 (84.2%) eyes and 25/29 (86.2%) dogs were visual. Vision loss in 7/9 (77.8%) eyes was secondary to glaucoma. Posterior synechia and fibrinous material in the anterior chamber were significant risk factors for the development of glaucoma (P < .001). There was no significant difference in the change in GRPU score between eyes receiving topical steroids and topical NSAIDs (P = .14). Time between examinations was a significant factor in disease progression (increased GRPU score; P = .016). CONCLUSION: The number of eyes and dogs that retained vision was higher than previous reports. No topical treatment was superior in slowing disease progression. Golden Retriever Pigmentary Uveitis is a slowly progressive disease.

Golden retriever pigmentary uveitis: Challenges of diagnosis and treatment.

Pigmentary uveitis (PU), also known as Golden Retriever Pigmentary Uveitis (GRPU), is a common ocular condition of Golden Retrievers that has severe, vision-threatening ocular complications and can require surgical intervention. In order to ensure consistency in the diagnosis of GRPU between examiners, a specified set of diagnostic criteria must be applied. This is critical to ensure owners, breeders, and veterinary ophthalmologists maintain confidence in the ocular certification process. Therefore, current and former members of the American College of Veterinary Ophthalmologists' Genetics Committee came together to draft this Viewpoint Article on the challenges of diagnosis and treatment of Golden Retriever Pigmentary Uveitis for veterinary ophthalmologists, Golden Retriever owners, and Golden Retriever breeders.

Antibacterial activity and safety of commercial veterinary cationic steroid antibiotics and neutral superoxidized water.

Antibiotic resistance of bacteria common to the ocular surface is an evolving problem. Thus, novel treatment options with new modes of action are required. We investigated the antibacterial activity and safety of three commercially available topical veterinary ophthalmic products (cationic steroid antibiotics, products A and B, and a neutral superoxidized water, product C) to determine their potential use as antimicrobial alternatives. The minimum inhibitory concentrations (MIC) of the three products were determined against 17 antibiotic resistant bacterial clinical isolates from the ocular surface. Using a standard cytotoxicity assay, the products at varying concentrations were evaluated with a corneal fibroblast cell line and a macrophage-like cell line to determine their potential toxic effect in vitro. The commercial ophthalmic solutions, ofloxacin 0.3%, tobramycin 0.3% and gentamicin 0.3% were used as positive controls for the MIC and tobramycin 0.3% was used as positive control for the cytotoxicity assays. For the MIC, Product C showed no inhibition of growth for any organisms, while Products A and B showed inhibition of growth similar to slightly less than the positive controls. For the cytotoxicity assays, Product C exhibited minimal toxicity while Products A and B exhibited toxicity similar to the controls. In conclusion, Product C had no antibacterial activity in these assays, while Products A and B had antibacterial profiles similar to slightly less than common topical ophthalmic antibiotics and cytotoxicity profiles similar to common topical ophthalmic antibiotics. To our knowledge, this is the first report on the antibacterial activity and safety of the cationic steroid antibiotics and superoxidized water.

Disease and Surgery of the Equine Lens.

Examination of the lens is critical, particularly when evaluating horses with visual impairment or performing prepurchase examinations. To adequately evaluate the lens, the pupil must be pharmacologically dilated. A cataract is any lens opacity. The size, density, and position of a cataract determine the impact on vision. Cataracts may be congenital or inherited or occur secondary to trauma or equine recurrent uveitis. Surgical removal is the only treatment option for vision impairing cataracts, but careful selection of surgical candidates is critical for successful outcomes.

Canine panuveitis: a retrospective evaluation of 55 cases (2000-2015).

OBJECTIVE: To determine the most common etiologies of panuveitis in a group of dogs, patient response to therapy, and visual outcome. DESIGN: Retrospective study. MATERIALS AND METHODS: Medical records of 55 dogs diagnosed with panuveitis at the Purdue University Veterinary Teaching Hospital between December 2000 and December 2015 were reviewed. Data collected included signalment, season of diagnosis, descriptions of ocular lesions, diagnostic testing, treatment protocols, etiologic diagnoses (when determined), and visual outcome. RESULTS: The most common clinical sign in the anterior segment was aqueous flare and in the posterior segment was serous retinal detachment. The most common diagnosis was idiopathic/immune-mediated disease followed by systemic blastomycosis, lymphoma, and other causes (leptospirosis, aspergillosis, and histoplasmosis). Of the 43 dogs for which follow-up was available, 40% of dogs had resolution of visible inflammation and retinal reattachment, 32% of dogs had slight to moderate improvement, and 28% of dogs had no improvement or deterioration of lesions. Mean follow-up time was 11 months, and mean time to resolution of visible inflammation and retinal reattachment was 32 days. Sixty-five percent of dogs either retained or regained vision in one or both diseased eyes with initial medical therapy. CONCLUSIONS: Idiopathic/immune-mediated panuveitis was the most common diagnosis. Dogs with idiopathic/immune-mediated panuveitis tended to respond more favorably to medical therapy than dogs with infectious panuveitis. Visual outcome was favorable in those dogs that responded to initial medical therapy, but long-term therapy was required in many dogs to maintain vision and prevent recurrence of disease.

Comparison of the in vitro anticollagenase efficacy of homologous serum and plasma on degradation of corneas of cats, dogs, and horses.

OBJECTIVE To compare the anticollagenase efficacy of fresh feline, canine, and equine serum and plasma on in vitro corneal degradation. SAMPLE Grossly normal corneas from recently euthanized dogs, cats, and horses and fresh serum and plasma from healthy dogs, cats, and horses. PROCEDURES Serum and plasma were pooled by species and used for in vitro experiments. Corneas were collected and stored at -80°C. Sections of cornea were dried, weighed, and incubated in saline (0.9% NaCl) solution with clostridial collagenase and homologous fresh serum or plasma. Corneal degradation was assessed as the percentage of corneal weight loss and hydroxyproline concentration, compared with results for positive and negative control samples. RESULTS Homologous fresh serum and plasma significantly reduced the percentage of corneal weight loss, compared with results for positive control samples. No significant difference was found in percentage of corneal weight loss between incubation with serum or plasma for feline, canine, and equine corneas. Canine serum and plasma significantly reduced hydroxyproline concentrations, whereas inclusion of feline and equine serum or plasma did not, compared with results for positive control samples. Hydroxyproline concentrations were moderately correlated with percentage of corneal weight loss for feline samples and weakly correlated for equine samples, but they were not correlated for canine samples. CONCLUSIONS AND CLINICAL RELEVANCE In this study, the anticollagenase efficacy of fresh feline, canine, and equine serum was not different from that of plasma. Plasma should be an acceptable substitute for serum in the topical treatment of keratomalacia.

An association between systemic cyclosporine administration and development of acute bullous keratopathy in cats.

OBJECTIVE: To determine whether any association exists between the onset of feline acute bullous keratopathy (ABK) and administration of systemic corticosteroid or immunosuppressive therapy. ANIMALS STUDIED: Medical records of cats diagnosed with ABK between the years of 2000 and 2008 were retrospectively reviewed. Breed, age at diagnosis, weight, systemic disease status, eye affected, ophthalmic examination findings, systemic and topical therapy instituted, dosage and duration of therapy, visual outcome and histopathological analyses were recorded in cases meeting the inclusion criteria. RESULTS: A total of 12 cats of a surveyed population of 70 167 met the inclusion criteria with 17/24 eyes affected by ABK. Medical and/or surgical therapy was utilized for management of ABK with 13/17 eyes remaining sighted at the time of last follow-up. In a subset of cases corneal cytology, aerobic bacterial culture, FHV-1 PCR, virus isolation and/or histopathology were performed; no infectious organisms were identified. A rupture in Descemet's membrane of the cornea was identified histologically in two globes. A total of 10 of 12 cats had been previously diagnosed with ongoing systemic disease. A total of 10 of 12 cats were receiving systemic therapy, and a significant association (P < 0.001) was noted between systemic administration of corticosteroids and/or cyclosporine A and the development of ABK. A total of 8 of 10 cats were administered oral prednisolone at doses between 1-2 mg/kg every 12-24 h. A total of 5 of 8 cats receiving oral prednisolone were concurrently administered oral cyclosporine at doses of 1.5-7 mg/kg every 12-24 h. Systemic cyclosporine therapy was found to be a significant risk factor (P < 0.001) for ABK development, while systemic prednisolone was not significant (P = 0.10). CONCLUSIONS: Systemic cyclosporine administration appears to be a risk factor for development of ABK in the population of cats studied.

Evaluation of species differences and the effects of storage duration and temperature on the anticollagenase efficacy of canine, feline, and equine serum on in vitro corneal degradation.

OBJECTIVE To evaluate species differences and effects of storage duration and temperature on the anticollagenase efficacy of canine, feline, and equine serum on in vitro corneal degradation. SAMPLES Corneas and serum from dogs, cats, and horses. PROCEDURES Clinically normal corneas from dogs, cats, and horses were harvested within 2 hours after euthanasia. Serum samples from dogs, cats, and horses were collected and pooled by species. Corneal specimens were incubated with collagenase derived from Clostridium histolyticum, 5mM calcium chloride in saline (0.9% NaCl) solution, and feline, canine, or equine serum that had been stored for 0, 30, 90, or 180 days at -20° or -80°C. Following incubation, the corneal weight loss percentage and hydroxyproline concentration in the incubation fluid were calculated and compared among experimental combinations. RESULTS Feline serum was more effective than canine or equine serum for minimizing corneal weight loss. Incubation with feline or equine, but not canine, serum significantly reduced hydroxyproline production. Serum storage duration did not affect corneal weight loss, but the hydroxyproline concentration was greater for corneal specimens that were incubated with serum that was stored for 90 days, compared with that for corneal specimens incubated with serum that was stored for 0, 30, or 180 days. Serum storage temperature did not affect corneal weight loss or hydroxyproline concentration. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that serum reduced corneal degradation in vitro, and the duration and temperature at which serum was stored did not affect its anticollagenase efficacy.

Comparison of ultrasound biomicroscopy and standard ocular ultrasonography for detection of canine uveal cysts.

OBJECTIVE: To compare ultrasound biomicroscopy (UBM) with standard ocular ultrasonography for detection of canine uveal cysts and to determine the sensitivity, specificity, and interobserver agreement for detection of uveal cysts with UBM. SAMPLE: 202 enucleated eyes from 101 dogs. PROCEDURES: 2 examiners examined 202 eyes by means of UBM (50 MHz) to identify uveal cysts. A board-certified radiologist then examined 98 of the 202 eyes by means of standard ocular ultrasonography (7- to 12-MHz linear transducer). Subsequently, 1 examiner dissected all 202 eyes under magnification from an operating microscope to definitively identify uveal cysts. Each examiner was masked to other examiners' findings. Sensitivity, specificity, and interobserver agreement were calculated for detection of cysts by UBM. RESULTS: Cysts were detected by use of UBM in 55 of 202 (27%) eyes by one examiner and 29 of 202 (14%) eyes by the other. No cysts were detected in the 98 eyes examined with standard ocular ultrasonography. Dissection results revealed that cysts were present in 64 of 202 (32%) eyes, including 29 of 98 (30%) eyes examined by standard ocular ultrasonography. Mean sensitivity of UBM for cyst detection was 47%; mean specificity was 92%. Uveal cysts not identified with UBM were often small (mean diameter, 490 üm). Interobserver agreement was high (κP = 0.81). CONCLUSIONS AND CLINICAL RELEVANCE: UBM was more effective than standard ocular ultrasonography for detection of uveal cysts in enucleated eyes. Small-diameter cysts were difficult to visualize even with UBM.

Prevalence of methicillin-resistant Staphylococcus spp. in the conjunctival sac of healthy dogs.

OBJECTIVES: To determine the prevalence of selected coagulase-positive methicillin-resistant Staphylococcus aureus (MRS) in the conjunctival sac in a group of healthy dogs and to compare the prevalence of ocular MRS colonization with colonization of typically assessed body sites including the nasal cavity and rectum. ANIMALS STUDIED: 123 healthy dogs were used in the prevalence study: 40 dogs from a shelter and 83 privately owned dogs. PROCEDURES: The sampling procedure included culturing three separate sites per subject in the following order: the lower conjunctival fornices, the nares, and rectum. RESULTS: A low prevalence of 1.6% (2/123) of MRS was detected in healthy dogs. Methicillin-resistant Staphylococcus pseudintermedius was isolated from two dogs, one from a conjunctival swab and the other from a rectal swab. CONCLUSION: The survey data indicate the ocular surface is a potential site of MRS colonization, although the prevalence was low in healthy dogs.

Mechanical ventilation and management of an adult horse with presumptive botulism.

OBJECTIVE: To describe the clinical course, management, and outcome of a horse with a presumptive diagnosis of botulism treated with long-term mechanical ventilation. CASE SUMMARY: A 6-year-old Quarter Horse gelding with a history of esophageal obstruction was evaluated for progressive tetraparesis. Generalized and progressive skeletal muscle weakness characterized by recumbency, decreased tongue, tail, eyelid, and anal tone, and respiratory failure was observed. Anticholinergic signs including decreased salivation, xerophthalmia, and ileus were also noted. A presumptive diagnosis of botulism was made, although mouse inoculation and spore identification testing were negative. Pentavalent botulism antitoxin was administered on Day 3. The horse was maintained on a water mattress and was managed with mechanical ventilation for 2 weeks. Complications encountered included necrotic rhinitis, intertrigo, decubital ulceration, jugular and cephalic vein thrombophlebitis, corneal ulceration, and transient ventricular tachycardia. The horse showed marked improvement in skeletal muscle strength and parasympathetic nervous system function, allowing it to be successfully weaned from the ventilator but suffered large colon volvulus on Day 21 and was euthanized. NEW OR UNIQUE INFORMATION PROVIDED: To the authors' knowledge, this is the first report of successful weaning from long-term mechanical ventilation and management of recumbency using a water mattress in an adult horse with presumptive botulism.

Prevalence of uveal cysts and pigmentary uveitis in Golden Retrievers in three Midwestern states.

OBJECTIVE: To determine the prevalence of uveal cysts and pigmentary uveitis (PU) in Golden Retrievers in 3 Midwestern states. DESIGN: Prospective cross-sectional study. ANIMALS: 164 American Kennel Club-registered Golden Retrievers in the states of Illinois, Indiana, and Michigan. PROCEDURES: For all dogs, biomicroscopic and binocular indirect ophthalmoscopic examinations of both eyes were performed after pupillary dilation. A finding of pigment deposition in a radial pattern or in zones on the anterior aspect of the lens capsule of 1 or both eyes was required for a diagnosis of PU. RESULTS: Eighty of the 328 (24.4%) eyes and 57 of the 164 (34.8%) dogs had visible uveal cysts. Of those 80 eyes with cysts, 41 (51.3%) had a single cyst located nasally and posterior to the iris, 33 (41.3%) had multiple uveal cysts, and 6 (75%) had a single, free-floating cyst. A diagnosis of PU was made for 9 (5.5%) dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Prevalences of uveal cysts (34.3%) and PU (5.5%) in the examined Golden Retrievers were both higher than prevalences reported previously (5.4% for uveal cysts and 1.5% for PU) in the Canine Eye Registry Foundation's 2009 All-Breeds Report. Study findings have indicated that PU is not a rare condition and should be considered as a differential diagnosis for Golden Retrievers with ocular disease.

Ocular and neural distribution of feline herpesvirus-1 during active and latent experimental infection in cats.

BACKGROUND: Herpes simplex virus 1 (HSV-1) and varicella zoster virus (VZV) cause extensive intra-ocular and neural infections in humans and are closely related to Felid herpes virus 1 (FeHV-1). We report the extent of intra-ocular replication and the extent and morphological aspects of neural replication during the acute and latent phases of FeHV-1 infection. Juvenile, SPF cats were inoculated with FeHV-1. Additional cats were used as negative controls. Cats were euthanized on days 6, 10, and 30 post-inoculation. RESULTS: FeHV-1 was isolated from the conjunctiva, cornea, uveal tract, retina, optic nerve, ciliary ganglion (CG), pterygopalatine ganglion (PTPG), trigeminal ganglion (TG), brainstem, visual cortex, cerebellum, and olfactory bulb of infected cats during the acute phase, but not the cranial cervical ganglion (CCG) and optic chiasm. Viral DNA was detected in all tissues during acute infection by a real-time quantitative PCR assay. On day 30, viral DNA was detected in all TG, all CCG, and 2 PTPG. Histologically mild inflammation and ganglion cell loss were noted within the TG during acute, but not latent infection. Using linear regression, a strong correlation existed between clinical score and day 30 viral DNA copy number within the TG. CONCLUSIONS: The correlation between clinical score and day 30 viral DNA copy number suggests the severity of the acute clinical infection is related to the quantity of latent viral DNA. The histologic response was similar to that seen during HSV-1 or VZV infection. To the author's knowledge this is the first report of FeHV-1 infection involving intraocular structures and autonomic ganglia.

Effects of action of proparacaine and tetracaine topical ophthalmic formulations on corneal sensitivity in horses.

OBJECTIVE: To compare the corneal anesthetic effects and duration of action of 2 ophthalmic anesthetic agents in horses. DESIGN: Prospective, randomized masked crossover study. ANIMALS: 8 clinically normal adult horses. PROCEDURES: Corneal sensitivity was determined by measuring each eye's corneal touch threshold (CTT) with a Cochet-Bonnet esthesiometer. Each eye's baseline CTT was recorded prior to anesthetic instillation at 0 minutes and every 10 minutes thereafter for 60 minutes. Each eye was randomly assigned to receive 2 of 4 treatments: 0.5% aqueous proparacaine ophthalmic solution (aqueous proparacaine; 8 eyes); 0.5% aqueous tetracaine ophthalmic solution (aqueous tetracaine; 8 eyes); 0.5% viscous tetracaine ophthalmic solution (viscous tetracaine; 8 eyes); and saline (0.9% NaCl) eyewash solution (8 eyes) as a negative control. There was a 48-hour washout period. Every horse received all treatments. RESULTS: Median baseline CTT of eyes was 4.5 cm (range, 0.5 to 6 cm). Median CTT for saline solution-treated eyes never differed significantly from baseline. The maximum anesthetic effect with the other 3 treatments occurred at 10 minutes. Median CTT of eyes at 10 minutes was 0.5 cm (range, 0 to 2.5 cm) with aqueous proparacaine treatment, 0.25 cm (range, 0 to 2.0 cm) with aqueous tetracaine treatment, and 0 cm (range, 0 to 0.5 cm) with viscous tetracaine treatment. Maximum anesthetic duration was 20 minutes with aqueous proparacaine and aqueous tetracaine treatments and 30 minutes with viscous tetracaine treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment of eyes with viscous tetracaine resulted in the greatest decrease in CTT and the longest duration of action, compared with treatment with aqueous proparacaine or aqueous tetracaine.

Association of height, body weight, age, and corneal diameter with calculated intraocular lens strength of adult horses.

OBJECTIVE: To determine whether differences exist in the calculated intraocular lens (IOL) strengths of a population of adult horses and to assess the association between calculated IOL strength and horse height, body weight, and age, and between calculated IOL strength and corneal diameter. ANIMALS: 28 clinically normal adult horses (56 eyes). PROCEDURES: Axial globe lengths and anterior chamber depths were measured ultrasonographically. Corneal curvatures were determined with a modified photokeratometer and brightness-mode ultrasonographic images. Data were used in the Binkhorst equation to calculate the predicted IOL strength for each eye. The calculated IOL strengths were compared with a repeated-measures ANOVA. Corneal curvature values (photokeratometer vs brightness-mode ultrasonographic images) were compared with a paired t test. Coefficients of determination were used to measure associations. RESULTS: Calculated IOL strengths (range, 15.4 to 30.1 diopters) differed significantly among horses. There was a significant difference in the corneal curvatures as determined via the 2 methods. Weak associations were found between calculated IOL strength and horse height and between calculated IOL strength and vertical corneal diameter. CONCLUSIONS AND CLINICAL RELEVANCE: Calculated IOL strength differed significantly among horses. Because only weak associations were detected between calculated IOL strength and horse height and vertical corneal diameter, these factors would not serve as reliable indicators for selection of the IOL strength for a specific horse.