Uveitic glaucoma in the horse

Equine pectinate ligament descemetization is associated with age

PURPOSE

To evaluate the correlation between equine pectinate ligament descemetization and ocular disease.

METHODS

The pathology database of the North Carolina State University Veterinary Medical Center was searched from 2010-2021 for all equine globes. Disease status was then assigned as affected by glaucoma, uveitis, or "other" based upon clinical records. The iridocorneal angles (ICA) of each globe were evaluated for the presence of pectinate ligament descemetization, the length of descemetization, as well as for the degree of angle collapse and the extent of cellular infiltrate or proteinaceous debris. One slide from each eye was evaluated by two separate, blinded investigators (HW & TS).

RESULTS

A total of 66 eyes from 61 horses were identified, with a total of 124 sections of ICA of sufficient quality to review. 16 horses were affected by uveitis, 8 by glaucoma, 7 by both glaucoma and uveitis, and 30 horses by other ocular disease, most commonly ocular surface disease or neoplasia, which served as controls. Pectinate ligament descemetization was most prevalent in the control group compared to the glaucoma and uveitis groups. Pectinate ligament descemetization length was positively correlated with age, with an increase of 13.5 μm per year of age (p = .016). Infiltrate scores and angle closure scores were higher in both the glaucoma and uveitis group compared to the control group (p < .001).

CONCLUSIONS

Equine pectinate ligament descemetization appears to be correlated with increased age and should not be used as a histologic marker for the presence of glaucoma.

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.

Effects of 0.0015% preservative-free tafluprost on the equine eye

OBJECTIVE

The purpose of this study was to determine the effects and potential side effects of topical preservative-free (PF) tafluprost 0.0015% in ophthalmologically normal horses.

ANIMALS

Five adult grade horses.

PROCEDURES

One of the eyes of each horse was randomly chosen as the "treatment" eye, and consequently, the contralateral eye served as the "control." A single dose of PF tafluprost 0.0015% (0.2 mL) was instilled in the treated eye of each horse. Intraocular pressure (IOP), Schirmer's tear test (STT) levels of each eye, and an ophthalmic examination were performed at T0 (baseline), T30, T120, T24 h, and T48 h.

RESULTS

The mean IOP values of the treated eyes at baseline (T0), T30, T120, T24 h, and T48 h were 25.4 ± 4.8 mmHg, 21.2 ± 1.92 mmHg, 15.20 ± 2.48 mmHg, 18.40 ± 1.51 mmHg, and 24.60 ± 1.94 mmHg, respectively. Significant differences were observed between the mean baseline IOP level and the T120 and T24 h time points (p = .001 and p = .009). The mean STT levels at each time point showed insignificant fluctuations during the study (p = .140). Adverse effects such as chemosis and episcleral injection were observed 30 min after the instillation of tafluprost 0.0015% (T30). Blepharospasm and conjunctival hyperemia were observed 120 min (T120) after the administration of the medication.

CONCLUSION AND CLINICAL RELEVANCE

Tafluprost 0.0015% showed potential in reducing IOP, but due to its local side effects, it is not a good candidate for management of glaucoma in horses. Tafluprost did not notably affect STT.

Use of autologous fascia lata graft to repair a complex corneal ulcer in a mare

Background

Application of an autogenous fascia lata graft in the treatment of keratomalacia in the horse has not been reported. The present case describes the use of an autologous fascia lata graft to surgically treat a complicated corneal ulcer in a horse.

Case presentation

A 12-year-old Arabian mare was admitted to Sharjah Equine Hospital with a history of right eye ulcerative keratitis of unknown duration. Following a week of aggressive medical treatment, the condition deteriorated and a keratectomy and pedicle conjunctival graft were performed. A week later, the conjunctival graft partially dehisced and the ulcer continued to degrade.

In attempting to preserve the integrity of the globe a second grafting procedure was performed when a segment of fascia lata harvested from the ipsilateral hind leg was grafted onto the corneal lesion.

Response to surgery was positive and the mare was discharged from the hospital on Day 31 post diagnosis (17 days after the second surgery) with a comfortable eye.

Follow-up12 months later revealed a comfortable but only partially visual eye due to corneal scarring.

Conclusion

Although the graft actually failed from the point of view of tissue integration, fascia lata appears to be a readily available, effective and affordable autografting material and we believe this technique has potential for short term physical and structural support of severe malacic or other complex corneal ulcers.

Ophthalmologic Disorders in Aged Horses

Ocular abnormalities are a common finding in aged horses. Although these seldom cause overt visual deficits detected by their owners, they can be a source of chronic or acute discomfort so early detection, and treatment when available, is essential. Some of these abnormalities are specific to old horses, whereas others are a result of ongoing disease or inflammation that started earlier in life but that becomes more evident when the damage sustained to the eye is advanced. If vision is significantly affected, consideration of human safety and animal welfare is paramount.