Ultrasound biomicroscopy of the equine iridocorneal angle.
Abstract: 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. Objective: To determine the ultrasonographic morphology of the equine ICA by UBM in standing sedated horses. Methods: 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. Conclusions: Pupil size was midrange in all eyes, but was not strictly controlled. Lighting conditions not controlled. Various breeds included. Conclusions: In vivo UBM of the equine ICA is feasible and provides high-resolution images of the structures of the aqueous humour outflow pathway.
© 2022 EVJ Ltd.
Publication Date: 2022-06-15 PubMed ID: 35568989PubMed Central: PMC9547819DOI: 10.1111/evj.13585Google Scholar: Lookup
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- Journal Article
Summary
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The study explores the use of ultrasound biomicroscopy (UBM) to identify the elements of the iridocorneal angle (ICA) in horses, a critical area for the drainage of aqueous humour from the eye, whose blockages can lead to glaucoma.
Objective and Method
- The primary aim of the research was to examine the ultrasonographic morphology of the equine ICA by using UBM in standing sedated horses.
- The procedure involved 30 healthy adult horses, during which the ICA was studied from four different positions – superior, temporal, inferior, and nasal – while the subjects were standing under sedation.
- The approach also employed topical anaesthesia and auriculopalpebral perineural anaesthesia.
- The anatomical structures were characterized comparing the ultrasound images to previously published histologic photomicrographs of the equine ICA.
Results
- The researchers successfully performed ultrasound imaging of the ICA from all four positions in the standing, sedated horses.
- The high-resolution images produced by the UBM enabled the researchers to identify the pectinate ligament, corneoscleral trabecular meshwork (TM), uveal TM, and supraciliary TM, all key structures in the aqueous humour outflow pathway.
Conclusion
- Although various parameters, including pupil size and lighting conditions, were not strictly controlled, researchers found that using UBM to image the equine ICA in vivo (on living subjects) is practical and results in high-resolution images.
- The horse breeds taking part in the study were diverse.
- The study’s results suggest that UBM can provide detailed information about the ICA and thus can play a significant role in early detection of aqueous humour outflow obstructions, consequently facilitating early warning of glaucoma risk.
Cite This Article
APA
Knickelbein KE, Lassaline ME, Kim S, Thomasy SM.
(2022).
Ultrasound biomicroscopy of the equine iridocorneal angle.
Equine Vet J, 54(6), 1153-1158.
https://doi.org/10.1111/evj.13585 Publication
Researcher Affiliations
- Veterinary Medical Teaching Hospital, University of California-Davis, Davis, California, USA.
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, California, USA.
- Veterinary Medical Teaching Hospital, University of California-Davis, Davis, California, USA.
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, California, USA.
- Department of Ophthalmology and Vision Science, University of California-Davis, Davis, California, USA.
MeSH Terms
- Animals
- Anterior Chamber / diagnostic imaging
- Anterior Chamber / pathology
- Aqueous Humor / diagnostic imaging
- Eye Diseases / pathology
- Eye Diseases / veterinary
- Horse Diseases / pathology
- Horses
- Microscopy, Acoustic / methods
- Microscopy, Acoustic / veterinary
- Ultrasonography
Grant Funding
- P30 EY012576 / NEI NIH HHS
- P30 EY12576 / NIH HHS
- RM Cello Endowment / School of Veterinary Medicine, University of California, Davis
- VAF2019-2 / ACVO Vision for Animals Foundation
Conflict of Interest Statement
Competing interests: The authors have no competing interests to disclose.
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