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Summary Two cases of distichiasis with subsequent recurrent superficial corneal ulceration are described in Friesian horses. Case 1 was a 9-year-old Friesian stallion with distichiae on the superior and inferior eyelids of both eyes corresponding to areas of recurrent superficial corneal ulceration. Case 2 was a 5-year-old Friesian gelding with a single distichia on the inferior lid associated with recurrent superficial corneal ulceration in the right eye. Case 1 underwent cryotherapy and epilation twice under standing sedation without resolution of distichiasis. A partial tarsal plate excision was then performed on the inferior left lid, which was the most severely affected. Cryotherapy was repeated one and 4 months post operatively due to recurrence. Cryotherapy was associated with skin depigmentation and repigmentation several months following the procedure. No recurrence has been reported up to 3 years following the fourth cryotherapy procedure. Case 2 was treated with epilation. Distichiasis should be included as a differential diagnosis when presented with a horse experiencing recurrent superficial corneal ulcerations. There has been no established breed association for Friesian horses and distichiasis but, due to the inherited nature of this condition in some human patients and dogs, this possibility should be investigated.

Objective To determine the long-term efficacy, complications, and duration of effect of a cyclosporine (CsA) suprachoroidal implant (CSI) in horses with equine recurrent uveitis (ERU). Methods Horses with ERU were treated with a 6-mm diameter, 25 mg, reservoir matrix CsA implant in the deep sclera adjacent to the suprachoroidal space. Horses with follow-up >1 year were examined for frequency of uveitis episodes, complications, and vision at last recheck. Results Data from 151 eyes of 133 horses from the USA and Europe that had CsA devices implanted for ERU were reviewed. Follow-up time ranged from 13 to 85 months after surgery, with a mean and median follow-up time of 28.9 and 26.3 months, respectively. Overall, at last follow-up 78.8% of eyes were considered visual and the overall mean frequency of uveitis episodes after CSI was 0.09 ± SD 0.08 episodes per month. The most common complications leading to vision loss at last follow-up were persistent uveitis episodes (54%), glaucoma (22%), mature cataracts (16%), and retinal detachment (6%). Persistent uveitis episodes tended to be the highest cause of vision loss in horses with 48 months of follow-up. Conclusions This study demonstrated the long-term maintenance of vision of horses with ERU implanted with a CSI. The increased vision loss related to uveitis episode of inflammation in eyes after the likely depletion of CsA from the CSI suggests that a repeat CSI may be required at or before 48 months after surgery.

Background: During hospitalization, horses typically undergo frequent blood sampling for diagnostic testing and monitoring. The need for numerous samples in hospitalized horses makes acquisition from an intravenous catheter (IVC) both convenient and less stressful to the patient. Hypothesis: We hypothesized that there would be no significant difference in the plasma chemistry and CBC variables from blood samples obtained from a jugular catheter as compared with direct jugular venipuncture. Animals: Fifty adult hospitalized horses; 25 receiving constant rate crystalloid therapy, and 25 receiving low volume IV medication. Methods: This study was conducted using a prospective, blinded, cross-over design. Samples were obtained sequentially by direct venipuncture of the jugular vein and aspiration from an IVC in the contralateral vein after an appropriate presample of blood was obtained and discarded. Samples were submitted for blinded analysis including CBC, plasma chemistry analysis, stall side plasma glucose concentration, PCV, and total protein concentration. Data obtained were analyzed using a Student's t-test with compensation for unequal variances between the 2 groups. Analyses were Bonferroni corrected for a 5% 2-tailed hypothesis test. Results: There were no statistically significant or clinically relevant differences associated with sampling method (venipuncture versus catheter) regardless of fluid administration status in any of the 24 analytes measured. Conclusions and Clinical Importance: Blood samples obtained by IVC have clinically equivalent values to those taken by direct venipuncture in commonly performed analyses. Additional investigation is warranted to establish if this technique is associated with increased complications such as phlebitis or bacteremia.

Summary Reasons for study: The effect of unilateral enucleation on vision and potential loss of performance in horses has received little study. Objective: To evaluate the likelihood of return to prior discipline following unilateral enucleation in horses, assessing the role of age at enucleation, equine discipline, reason for enucleation, time to vision loss and eye enucleated. Hypothesis: Unilateral enucleation has no significant effect on likelihood of return to work in horses, for both right and left eyes, across age and discipline. Method: A retrospective review of medical records identified 92 horses that underwent unilateral enucleation at the University of Pennsylvania New Bolton Center from April 2000–April 2008. Case variables determined from the medical record included breed and sex of horse, age at enucleation, which eye was enucleated, reason for enucleation and onset of vision loss. Pre- and post operative occupations were determined by telephone interview with the owner or trainer of each horse. Results: Based on hospital surgery logs, 92 enucleations were performed over the 8 year period and 77 records were available for review, with follow-up information available for 34 horses. Of these, 29/34 (85%) horses returned to work in pleasure or trail riding (11/13), flat racing (7/10), hunter/jumpers (4/4), dressage (3/3), group lessons (1/1), eventing (1/1), steeplechase (1/1) and as a broodmare (1/1). Four of 5 horses (4/34, or 12% sample) that did not return to work (2 pleasure and 2 racing) were retired due to anticipated or perceived decrease in performance or behaviour change following unilateral enucleation, with the remaining horse retired from racing for lameness issues unrelated to enucleation. Twenty-two of 25 horses (88%) with acute vision loss and 7/9 horses (78%) with gradual vision loss returned to their previous discipline. Conclusions: Horses are able to return to a variety of occupations after unilateral enucleation.

Summary The clinical features and outcomes of equine ulcerative keratitis with and without conjunctival graft surgery were assessed using a retrospective study. Medical records of horses hospitalised from July 2000-January 2006 for ulcerative keratitis were included if a diagnosis of melting ulcer, descemetocele or iris prolapse was made, or if surgery was recommended due to severity of corneal disease, and aggressive medical therapy using a subpalpebral catheter was instituted. Treatment and outcome variables were evaluated with and without conjunctival graft surgery. Forty-one horses, 21 that had surgery and 20 for whom surgery was recommended but not performed, were included. Horses were hospitalised for an average of 24 days, with 37/41 melting ulcers, 17/41 descemetoceles and 3/41 iris prolapses, with no statistical difference in frequencies between groups. Bacterial or fungal organisms were cultured from 22/39 cases, with 10 Aspergillus spp. and 8 Pseudomonas spp. Infectious organisms were seen on corneal cytology in 23/30 cases. Surgical cases were hospitalised for an average of 4.9 days prior to surgery. Abdominal discomfort was observed in 8/41 hospitalised horses, with 5/8 operated horses developing caecal impactions. Thirty-five horses retained an intact globe, including 18/20 treated medically and 17/21 that had surgery. Hospitalisation cost was 24% more for cases that had surgery than for medical cases. It was concluded that there was no statistical difference in length or cost of hospitalisation between surgical and nonsurgical groups. Outcomes from both groups were similar, with a high frequency of globe retention.

Summary The purpose of this study was to determine the clinical course and outcome associated with keratomycosis in horses in the mid-Atlantic USA. Records of horses diagnosed with keratomycosis at New Bolton Center from November 2006 to November 2007 with positive fungal culture were retrospectively studied. Neither horses with ulcerative keratitis and a negative fungal culture nor those with stromal abscesses were included. Subject details, history, clinical findings, therapy and outcome were recorded. Thirty horses fitted both inclusion criteria (diagnosis of keratomycosis and positive corneal fungal culture). Fourteen of 30 cases occurred during summer. Aspergillus was the most commonly cultured fungal genus (17/30, or 57%) followed by Alternaria (4/30). Seventeen horses had positive bacterial and fungal cultures. Fifteen of 30 horses were treated surgically by a keratectomy and amnion (8) or conjunctival (7) graft. Itraconazole was the most common topical anti-fungal therapy and was utilised in 25/30 horses. Globe survival was 97% (29/30). All surviving globes had a positive menace response and were visual at the last examination. It was concluded that in the mid-Atlantic USA, fungal keratitis is common, has the highest incidence in summer, and is usually associated with a positive outcome. Aspergillus may be a relatively more common corneal pathogen in this region than elsewhere in the USA. Surgical cases were more likely to have fungal hyphae identified on cytology and tended to be hospitalised longer than medical cases. There was no apparent association between surgical disease and all other patient, organism and treatment variables.

Summary A 5-year-old Thoroughbred mare presented with an intermittently mildly painful right eye with a nonulcerative corneal opacity of several weeks' duration that had improved with topical steroids but recurred when steroids were withdrawn. Ophthalmic examination demonstrated a focal region of moderate corneal oedema and midstromal corneal infiltrate centrally but no other significant ocular abnormalities, and suggested a diagnosis of immune-mediated keratitis. Empirical courses of both topical and systemic anti-inflammatory drugs, both nonsteroidal and steroidal, led to initial improvement but bullous keratopathy developed when corneal oedema became profound. Due to the rapidly progressive nature of the bullous keratopathy combined with poor response to medical therapy, a keratectomy and conjunctival graft were performed under general anaesthesia. Intraoperative corneal culture of the keratectomy site grew Pseudomonas alcaligenes, a common soil and water contaminant. Histopathology of the keratectomy specimen revealed neutrophilic inflammation. Keratectomy and conjunctival graft led to resolution of ocular pain and inflammation, with an acceptable cosmetic and visual outcome. This report describes an unusual case of a nonulcerative Pseudomonas keratitis that responded well to surgical therapy, and underscores the complicated nature of nonulcerative keratitis in horses.

Objective—To measure duration of corneal anesthesia and time and degree of maximal anesthetic effect of 0.5% proparacaine hydrochloride by use of a Cochet-Bonnet aesthesiometer in horses. Animals—10 clinically normal adult horses. Procedures—Baseline corneal touch threshold (CTT) was measured in millimeters for 1 randomly selected eye of each horse by use of the aesthesiometer by applying the filament to the cornea at maximum length (60 mm) and decreasing in 5-mm increments until a consistent blink response was elicited. Following baseline CTT measurement, 0.2 mL of 0.5% proparacaine hydrochloride was instilled in the selected eye. The CTT was measured within 1 minute following proparacaine administration and every 5 minutes thereafter for 60 minutes. A mixed-model ANOVA with tested eye varying between subjects and measurement time varying within subject was used to test for main effects and any interaction between these factors. A contrast between means of baseline and each subsequent CTT identified the duration of corneal anesthesia as the time at which there was no difference from baseline. Maximal anesthetic effect occurred at the time with the lowest mean CTT. Results—Duration of corneal anesthesia achieved by use of proparacaine was 25 minutes, and maximal anesthetic effect occurred within 5 minutes, although CTT never went to 0 in any horse at any time. Conclusions and Clinical Relevance—Duration of corneal anesthesia in horses was shorter than in dogs, and degree of maximal effect was less than in cats and dogs, most likely because of increased sensitivity of the equine cornea, compared with corneal sensitivity in those species.

Objective To evaluate the visual outcome of three techniques of corneal transplantation surgery in treating severe inflammatory keratopathies in the horse. Design Retrospective medical records study. Animals studied Medical records of 206 horses that received corneal transplantation surgery at the University of Florida Veterinary Medical Center from 1993 to 2007 were reviewed. Procedure Data collected from the medical records included signalment, types of ocular lesions, type of transplant surgery performed, length of follow-up, complications, and visual outcomes. Results Full thickness penetrating keratoplasty (PK) was performed in 86 horses for melting ulcers, iris prolapse/descemetoceles, and medically nonresponsive full thickness stromal abscesses (SA). Posterior lamellar keratoplasty (PLK) and deep lamellar endothelial keratoplasty (DLEK) are split thickness penetrating keratoplasties that were utilized for medically nonresponsive deep stromal abscesses (DSA) in 54 and 66 eyes, respectively. The most common postoperative surgical complication was graft rejection and varying degrees of graft opacification. Wound dehiscence and aqueous humor leakage was also a common postoperative problem. A positive visual outcome was achieved for PK, PLK, and DLEK in 77.9%, 98.1%, and 89.4%, respectively. Conclusions Corneal transplantation is a tectonically viable surgery in the horse with an overall success rate of 88.5% in maintaining vision when treating vascularized and infected corneal disease in the horse.

Objective To evaluate the long-term visual outcome of phacoemulsification lens extraction surgery in foals and horses and identify any unique postoperative complications that affect the visual outcome. Procedure This is a retrospective medical records study of phacoemulsification cataract surgery in 95 foals and horses from 1990 to 2013. Results Cataracts were removed by phacoemulsification from 111 eyes of 95 horses ranging in age from 22 days to 26 years (average 8.0 ± 5.7 years). Forty-four of the 95 animals were foals (46.3%). Sixteen horses or foals had surgery bilaterally. One hundred and two eyes were blind preoperatively with 97 eyes (95.1%) having evidence of vision immediately postoperatively. Ninety of the 95 horses (94.7%) regained vision in the immediate postoperative period. Five horses did not recover vision postoperatively. Twenty-four horses had cataracts associated with equine recurrent uveitis (ERU). Trauma was noted as the cause of cataract in 10 horses, and no specific cause for the cataract identified in 61 horses. The combined visual outcome data from horses with all types of cataracts (n = 95) found 83 (87.3%) horses to be visual ≤1 month postoperatively, 47 (49.4%) horses visual for >1–6 months postoperatively, 33 (34.7%) horses visual from >6 to 12 months postoperatively, and 25 horses (26.3%) visual >24 months postoperatively. Conclusion The results of phacoemulsification cataract surgery in horses indicate at least 26.3% of horses are still visual and able to continue their natural activity for 2 years or more postoperatively.

The purpose of this review is to discuss the evolution of equine cataract surgery over the past 50 years to its current stage. Equine cataract surgery is performed similarly compared with the techniques used in human ophthalmology and in other veterinary species. However, enough differences exist to make surgical lens removal and intraocular lens implantation in the horse an intrinsically unique endeavour. Due to the size of the adult equine globe, the introduction of species-specific instrumentation has provided the cornerstone to many of the changes made regarding surgical technique over the last 15-20 years. The continuing development of an equine specific, foldable intraocular lens implant (IOL) has provided much needed data supporting the use of such lenses in the horse to improve upon the post operative visual outcome. Finally, the methods utilised to assess visual capacity and the effects of intraocular lens implantation on the globe (e.g. ocular ultrasonography, electroretinography and streak retinoscopy) are gradually becoming more important in preoperative patient assessment and IOL development in the horse. It is the hope of the authors that a broader group of equine veterinarians will become aware of the many changes that have taken place in equine cataract surgery over the last half-century. Although aspiration was implemented nearly 40 years ago in foals for the treatment of congenital cataracts, phacofragmentation (phacoemulsification) techniques have only recently become routine in mature horses undergoing lens extraction.

Objective—To assess the effect of treatment with a topical ophthalmic preparation of 1.2% nalbuphine solution on corneal sensitivity in clinically normal horses. Animals—8 horses. Procedures—Baseline corneal touch threshold (CTT) was measured (defined as the mean filament length [mm] at which a consistent blink response was elicited) for both eyes of each horse by use of a Cochet-Bonnet aesthesiometer. Subsequently, 0.2 mL of 1.2% nalbuphine solution was instilled in 1 randomly selected eye of each horse, and 0.2 mL of artificial tears solution was instilled in the contralateral eye (control treatment). For all 8 horses, CTT of each eye was measured within 1 minute following nalbuphine or artificial tears administration and every 15 minutes thereafter for 60 minutes. For 5 of the 8 horses, CTT was also measured in both eyes at 120 minutes. Changes in CTT values from baseline over time were assessed, as were differences between treated and control eyes. Results—At any time point, corneal sensitivity following nalbuphine treatment did not differ significantly from control treatment findings. Mean CTTs for nalbuphine-treated and control eyes were 38.8 and 37.9 mm, respectively. In both groups, CTT was significantly lower than baseline value at 15, 45, 60, and 120 minutes. No tearing or redness developed in any eye treated with nalbuphine. Conclusions and Clinical Relevance—Topical administration of ophthalmic 1% nalbuphine solution had no effect on corneal sensitivity in clinically normal horses. The topical ocular treatment was not associated with local irritation.

Amniotic membrane transplantation (AMT) is an effective clinical therapy for reconstruction of the ocular surface in human and veterinary patients. Amnion is avascular and strong, contains antiangiogenic and antiinflammatory properties and growth factors, and has properties that prevent or decrease fibrosis in healing tissue. Indications for its use are steadily growing and include grafting to replace diseased, missing or excised tissue, patching to support diseased tissue during the healing process and as a substrate for the expansion of epithelial cells for transplantation to the cornea. AMT through a combination of mechanical and biologic factors can preserve the integrity of the globe, optimize the visual outcome, and minimize scarring in severely diseased corneas.