An evaluation of intracapsular lens extraction and transcorneal lens reduction for treatment of anterior lens luxation in dogs.

OBJECTIVE: The aim of the study was to evaluate success rate, complications, and outcomes in dogs with anterior lens luxation (ALL) treated with intracapsular lens extraction (ICLE) or transcorneal lens reduction (TCLR). PROCEDURE: Medical records of dogs with ALL undergoing ICLE or TCLR from 2014 to 2021 were reviewed. Signalment, presenting complaint, history, ophthalmic examination findings, short-term complications, and outcomes were analyzed. RESULTS: There were 20 ICLEs and 31 TCLRs; however, some cases were included in both groups. One ICLE was unsuccessful and four had undergone TCLR first, leaving 15 ICLEs. Three TCLRs were unsuccessful, four were lost to follow up, and three subsequently underwent ICLE due to recurrent ALL, leaving 21 TCLRs. Anterior uveitis was more common following ICLE than TCLR, p < .001 The frequencies of other short-term complications (post-operative hypertension and corneal ulceration) were not statistically different between groups. Median follow-up was 256 and 48 days for ICLE and TCLR, respectively. Vision was retained in 7/10 (70%) eyes following ICLE and 4/9 (44%) eyes following TCLR, p = .34. Enucleation was recommended for fewer eyes following ICLE (2/15 [13%]) than TCLR (7/21 [33%], p = .47). In total, lens extraction was achieved in 19/20 (95%) ICLEs and lens reduction was achieved in 28/31 (90%) TCLRs. Anterior lens luxation recurred in 10/24 (41%) TCLRs. CONCLUSIONS: The present study adds data to the current knowledge base regarding the treatment of ALL in dogs and highlights the need for future prospective studies containing a larger number of animals to help inform treatment decisions for dogs with ALL.

Ultrasound biomicroscopy of the equine iridocorneal angle.

BACKGROUND: The iridocorneal angle (ICA) is the major pathway of aqueous humour outflow from the anterior chamber of the eye. Ultrasound biomicroscopy (UBM) has been utilised to characterise the morphology of this drainage pathway in numerous species. UBM may allow for early recognition of aqueous humour outflow obstructions in horses, allowing for earlier recognition of risk for glaucoma, a vision-threatening and painful disease. UBM morphology of the normal equine ICA has yet to be described. OBJECTIVES: To determine the ultrasonographic morphology of the equine ICA by UBM in standing sedated horses. STUDY DESIGN: In vivo experimental study. METHODS: Thirty healthy adult horses underwent UBM of the ICA at four locations (superior, temporal, inferior, nasal) of each eye utilising standing sedation, topical anaesthesia and auriculopalpebral perineural anaesthesia. Anatomic structures were defined on ultrasound images through comparison to published histologic photomicrographs of the equine ICA. RESULTS: Ultrasound imaging of the ICA at all four locations was easily performed in standing, sedated horses. High-resolution images of the ICA allowed for identification of the pectinate ligament, corneoscleral trabecular meshwork (TM), uveal TM and supraciliary TM. MAIN LIMITATIONS: Pupil size was midrange in all eyes, but was not strictly controlled. Lighting conditions not controlled. Various breeds included. CONCLUSION: In vivo UBM of the equine ICA is feasible and provides high-resolution images of the structures of the aqueous humour outflow pathway.

Corneal thickness and anterior chamber depth of the normal adult horse as measured by ultrasound biomicroscopy.

OBJECTIVE: To determine corneal thickness (CT) and axial anterior chamber depth (ACD) using ultrasound biomicroscopy (UBM) in normal adult horses. To compare corneal thickness measurements between UBM and ultrasonic pachymetry. ANIMALS STUDIED: Sixty eyes of 30 healthy adult horses aged 8-24 years. PROCEDURES: Ultrasonic pachymetry (velocity of 1640 m/s) was utilized to obtain measurements of the central, superior, temporal, inferior, and nasal cornea. Triplicate images of the same corneal locations were acquired using UBM (50 MHz). Images of the axial anterior chamber were used to measure ACD. Intraocular pressure (IOP) was estimated using rebound tonometry, and axial globe length was measured using ultrasonographic biometry. RESULTS: CT (mean ± SD µm) measured by UBM was 854 ± 61 (central), 994 ± 58 (superior), 930 ± 57 (temporal), 979 ± 55 (inferior), and 898 ± 48 (nasal). CT measured by UBM was greater than that measured by ultrasonic pachymetry at all locations and was statistically significant at all locations except inferior (p = 0.0006-0.048). No sex nor age effect was detected for CT at any location. The repeatability of ultrasonic pachymetry was superior to that of UBM. Mean ± SD ACD was 5.74 ± 0.41 mm. A weak positive correlation was identified between central CT and IOP and between central CT and axial globe length. CONCLUSIONS: Normal data for CT and ACD of the adult horse obtained using UBM are provided. CT determined by UBM was greater relative to pachymetry at all corneal locations.

Additional Evidence for DDB2 T338M as a Genetic Risk Factor for Ocular Squamous Cell Carcinoma in Horses.

Squamous cell carcinoma (SCC) is the most common periocular cancer in horses and the second most common tumor of the horse overall. A missense mutation in damage-specific DNA-binding protein 2 (DDB2, c.1012 C>T, p.Thr338Met) was previously found to be strongly associated with ocular SCC in Haflinger and Belgian horses, explaining 76% of cases across both breeds. To determine if this same variant in DDB2 contributes to risk for ocular SCC in the Arabian, Appaloosa, and Percheron breeds and to determine if the variant contributes to risk for oral or urogenital SCC, histologically confirmed SCC cases were genotyped for the DDB2 variant and associations were investigated. Horses with urogenital SCC that were heterozygous for the DDB2 risk allele were identified in the Appaloosa breed, but a significant association between the DDB2 variant and SCC occurring at any location in this breed was not detected. The risk allele was not identified in Arabians, and no Percherons were homozygous for the risk allele. High-throughput sequencing data from six Haflingers were analyzed to ascertain if any other variant from the previously associated 483 kb locus on ECA12 was more concordant with the SCC phenotype than the DDB2 variant. Sixty polymorphisms were prioritized for evaluation, and no other variant from this locus explained the genetic risk better than the DDB2 allele (P = 3.39 × 10-17, n = 118). These data provide further support of the DDB2 variant contributing to risk for ocular SCC, specifically in the Haflinger and Belgian breeds.

Equine eosinophilic keratoconjunctivitis in California: retrospective study of 47 eyes from 29 cases (1993-2017).

OBJECTIVE: (a) To evaluate the epidemiology of equine eosinophilic keratoconjunctivitis (EK) in the western United States, (b) to ascertain the efficacy of keratectomy and diamond burr debridement vs medical management alone, (c) to determine the efficacy of various medical therapies, and (d) to further characterize the histopathologic findings of the disease in horses. ANIMALS STUDIED: Twenty-nine horses (47 eyes) diagnosed with EK from 1993 to 2017. PROCEDURE: Retrospective medical record review; owner questionnaire. RESULTS: Average age of presentation was 11 ± 4 years. Warmbloods were significantly overrepresented (P = 0.024). Twenty horses were treated with medical therapy alone, five were treated with superficial lamellar keratectomy, and four were treated with diamond burr debridement. Follow-up data were available for 38 eyes of 23 horses. Median time to resolution for horses treated with either superficial keratectomy or diamond burr debridement (62 days) was not statistically significantly different from those that underwent medical therapy alone (46 days; P = 0.33). Eyes treated with topical steroids had a statistically significant longer median time to resolution (61 days) compared to those that did not receive topical steroid (44 days; P = 0.023). Common histopathologic findings in keratectomy samples included the presence of eosinophils, vascularization, and an eosinophilic membrane spanning areas of ulceration. CONCLUSION: In this population, time to EK resolution was similar for horses treated with medical and surgical management. The use of topical steroids was associated with a prolonged time to resolution. Keratectomy samples from horses with EK had similar findings to those reported in other species.

Traumatic phacocele in an American Miniature Horse.

An 18-year-old American Miniature Horse mare was presented with a complaint of a scleral swelling affecting the right eye and a history of suspected trauma 6 weeks prior to evaluation. Clinical findings included severe blepharospasm, a bulbous swelling of the dorsotemporal bulbar conjunctiva, and phthisis bulbi. Ocular ultrasound was recommended but declined. Enucleation was elected for the blind, painful eye and was performed standing. Gross and histopathologic examinations of the globe were consistent with extrusion of the lens to the episcleral space, which is classified as a traumatic phacocele when associated with naturally occurring trauma. The location of lens entrapment suggested globe rupture occurred at the limbus, which is described as one of the weakest points of the equine globe. Subconjunctival dislocation of the lens and development of a traumatic phacocele should be considered as a differential diagnosis for horses presenting with subconjunctival masses, apparent aphakia, and historical trauma.

Effect of topical application of 0.5% proparacaine on corneal culture results from 33 dogs, 12 cats, and 19 horses with spontaneously arising ulcerative keratitis.

OBJECTIVE: To investigate the effect of topically applied proparacaine on bacterial and fungal culture results and to compare cytologic and culture results in patients with ulcerative keratitis. PROCEDURE: Corneal samples were collected from 33 dogs, 19 horses, and 12 cats with spontaneously arising ulcerative keratitis. Samples for bacterial (dogs, cats, horses) and fungal (horses) cultures were collected prior to and following application of 0.5% proparacaine or saline. All patients then received a topical anesthetic, and samples were collected for cytology. Frequency of cultivatable bacteria before (Swab 1) and after (Swab 2) application of proparacaine or saline was compared using Fisher's exact test. Homogeneity of culture and cytology results was assessed using McNemar's test. RESULTS: No difference was detected in number of animals from which bacteria were isolated from Swab 1 or Swab 2 for proparacaine (21/37 and 17/37, respectively) or saline (10/27 and 12/27, respectively). Small numbers prevented analysis of fungal culture results in horses between Swab 1 and Swab 2 for proparacaine (2/12 and 1/12, respectively) or saline (both, 1/8). Bacteria were isolated from 10 of 20 horses and detected cytologically in 3 of these; fungi were isolated from 3 of 20 horses and detected cytologically in 2 of these. Bacteria were detected more frequently using culture (31/64) than cytology (19/64). CONCLUSION: Proparacaine did not significantly alter bacterial or fungal culture results in cats, dogs, or horses; however, clinical significance warrants investigation. Culture and cytology provided complementary data; both should be performed to maximize organism detection in patients with ulcerative keratitis.

Limbal squamous cell carcinoma in a Rocky Mountain Horse: Case report and investigation of genetic contribution.

OBJECTIVE: To document a case of limbal squamous cell carcinoma (SCC) in a Rocky Mountain Horse stallion determined to be homozygous for the genetic risk factor (DDB2 c.1013C>T) strongly associated with the disease in Haflinger and Belgian horses, and to determine the frequency of this allele in a larger population of Rocky Mountain Horses. ANIMALS STUDIED: One privately owned Rocky Mountain Horse and 84 Rocky Mountain Horses screened for allelic frequency. PROCEDURES: A complete ophthalmic examination was performed on a Rocky Mountain Horse stallion for assessment of a mass affecting the right eye. A clinical diagnosis of suspected limbal SCC was made, and routine keratoconjunctivectomy and adjunctive strontium irradiation were performed. Genotyping for the DDB2 c.1013C > T (rs1139682898) risk variant was performed utilizing an allele-specific PCR assay on DNA isolated from whole blood and hair follicles. RESULTS: Histopathology confirmed the limbal mass to be consistent with SCC. The horse was genotyped as homozygous for the DDB2 c.1013C >T risk variant. The frequency of the variant allele among a population of 84 Rocky Mountain Horses was found to be 0.20. CONCLUSION: The Rocky Mountain Horse breed possesses the DDB2 variant allele determined to be a significant risk factor for ocular SCC in the Haflinger and Belgian breeds. Genotyping additional Rocky Mountain Horses diagnosed with ocular SCC as well as confirmed healthy controls for this variant should be undertaken to determine whether a significant association exists between ocular SCC and the variant in the Rocky Mountain Horse breed.

Equine amniotic membrane transplantation for corneal ulceration and keratomalacia in three horses.

PURPOSE: Amniotic membrane has antifibrotic, anti-angiogenic and antiprotease properties. This retrospective study was designed to investigate the use of equine amniotic membrane transplants (AMT) at preserving vision, maintaining the structural integrity of the globe and maximizing cosmesis in equine eyes with corneal ulceration and severe keratomalacia. METHODS: Equine amnion had previously been aseptically harvested from a 12-year-old Thoroughbred mare during an elective Cesarean section. Sections of amnion were stored at -80 degrees C and thawed as needed. Records of equine cases at the University of Florida with keratomalacia that received an AMT without adjunctive conjunctival grafting were examined. Clinical description, details of medical and surgical treatment, globe survival and visual outcome were documented. Etiologies were determined by cytology, culture or histology. RESULTS: Three horses with corneal ulceration and severe keratomalacia received an AMT without conjunctival graft between December 2002 and April 2003. Pseudomonas spp. were cultured from all three eyes, with evidence of a concurrent fungal infection in two eyes. The three ulcers were 50, 72, and 76% of corneal diameter, and each one worsened in the face of aggressive medical therapy. In all three cases, the AMT sloughed over a 4 to 6-week period. At last follow-up, all three eyes receiving AMT were comfortable and receiving no medication, with light perception and an inconsistent location-dependent menace response. All three horses returned to their prior work. CONCLUSIONS: Results of a small number of equine AMT suggest that amnion can be used successfully to preserve both globe structure and limited vision, as well as optimize cosmesis, in horse eyes with corneal ulceration and severe keratomalacia.

Orbitotomy for retrobulbar malignant fibrous histiocytoma in a dog.

A retrobulbar malignant fibrous histiocytoma was diagnosed in a 12-year-old castrated male Keeshond dog. The mass was excised with a lateral orbitotomy and zygomatic arch resection. Vision was preserved in the affected eye, and no recurrence was noted up to 10 months postoperatively. Malignant fibrous histiocytoma originates from primitive mesenchymal stem cells. The malignant fibrous histiocytoma seen in our patient was most consistent with the storiform-pleomorphic variant, given the storiform arrangement of spindle cells, the presence of histiocytoid cells, and a mixed inflammatory infiltrate, without giant cells. The metastatic potential of malignant fibrous histiocytoma in general, and the storiform variant in particular, is unknown. Seventeen months later the dog was presented to the referring veterinarian with anorexia, diarrhea, weight loss and bilateral purulent nasal exudates. The dog was euthanized without necropsy.

Evaluation of various compounds to inhibit activity of matrix metalloproteinases in the tear film of horses with ulcerative keratitis.

OBJECTIVE: To examine in vitro effects of various antiproteolytic compounds on activity of matrix metalloproteinase (MMP)-2 and -9 in the tear film of horses with active corneal ulcers. SAMPLE POPULATION: Samples of tear film obtained from the eyes of 34 horses with active ulcerative keratitis. PROCEDURE: Horses were sedated, and tear samples were collected from the lower fornix of 34 ulcerated eyes by use of capillary tubes. The protease inhibitors 0.2% EDTA, 0.1% doxycycline, 10% N-acetylcysteine (NAC), 0.1% solution of a modified dipeptide that contains hydroxamic acid (ie, ilomostat), 0.1% alpha1-proteinase inhibitor (PI), 0.5% alpha1-PI, and 100% fresh equine serum (ES) were used to treat pooled samples. Amount of latent and active MMP-2 and -9 was measured by optical density scanning of gelatin zymograms of treated and untreated tear samples. RESULTS: Pooled tear samples obtained from ulcerated eyes contained the latent and active forms of MMP-2 and -9. Compared with MMP activity in untreated samples, total MMP activity (sum of all bands detected) observed on the gelatin zymogram gels was reduced by 99.4% by EDTA, 96.3% by doxycycline, 98.8% by NAC, 98.9% by ilomostat, 52.4% by 0.1% alpha1-PI, 93.6% by 0.5% alpha1-PI, and 90.0% by ES. CONCLUSIONS AND CLINICAL RELEVANCE: We documented that EDTA, doxycycline, NAC, ilomostat, alpha1PI, and ES inhibited MMP activity in vitro. Because these compounds use different mechanisms to inhibit various families of proteases in the tear film of horses, a combination of these protease inhibitors may be beneficial for treatment of corneal ulcers in horses.