Visual outcomes of phacoemulsification cataract surgery in horses: 1990-2013.

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.

Long-term outcome after implantation of a suprachoroidal cyclosporine drug delivery device in horses with recurrent uveitis.

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 <24 months and >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.

Effect of treatment with a topical ophthalmic preparation of 1% nalbuphine solution on corneal sensitivity in clinically normal horses.

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.

Evaluation of duration of corneal anesthesia induced with ophthalmic 0.5% proparacaine hydrochloride by use of a Cochet-Bonnet aesthesiometer in clinically normal 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.