Uveal cysts in dogs were previously considered to be a benign, incidental finding.1 In 1998, uveal cysts were reported to cause glaucoma in Great Danes.2 In each affected eye, cysts could be visualized filling the posterior chamber and anteriorly displacing the iris, resulting in a shallow anterior chamber and difficulty visualizing the iridocorneal angle.2 At approximately the same time, Deehr and Dubielzig3 described an association between the presence of uveal cysts and the development of glaucoma in Golden Retrievers. Uveal cysts in Golden Retrievers were found to originate from the ciliary body epithelium and were typically located within the iridociliary sulcus on histologic examination.4 Uveal cysts have become a hallmark histologic finding in the condition now described as Golden Retriever pigmentary uveitis.4,5 Clinically, the cysts typically appear round, are pigmented, and trans-illuminate; may be single or multiple; and are located within the anterior chamber, at the pupillary margin, or within the posterior chamber.6 In Golden Retrievers, cysts at the pupillary margin or in the posterior chamber are most often located nasally.6 Clinical identification of these uveal cysts has been difficult, with detection rates as low as 1 of 15 to 3 of 13 in eyes with cysts confirmed histologically.3,5
The development of UBM, which uses a high-frequency (50-MHz) transducer for the imaging of eyes, provides a noninvasive technique that enables 360° visualization of the anterior segment, including the cornea, iridocorneal angle, iris, posterior chamber, iridociliary sulcus, and ciliary body.7 Ultrasound biomicroscopy has a resolution 5 to 10 times that of a 10-MHz ultrasound probe.7 With UBM, resolution to 200 üm is possible, although penetration is limited to 4 to 5 mm. Therefore, the posterior segment cannot be visualized with this method.8 Physician ophthalmologists have successfully used UBM to detect uveal cysts within the iridociliary sulcus, typically in the inferior or temporal quadrants.8 Through the use of UBM, an association has been identified between the presence of uveal cysts and development of angle closure glaucoma in humans.9,10 Cysts within the posterior chamber have been shown to mechanically displace the iris anteriorly, thereby compromising the filtration angle.10
In the veterinary literature, UBM has been described as an effective tool for evaluation of corneal disease, anterior uveal neoplasia, and iridocorneal angle morphology.11–13 Examinations via UBM have been performed successfully in dogs and cats with manual restraint and application of a topical anesthetic.11,13 In 1 report,11 bilobed cysts within the posterior segment causing anterior iridal displacement were identified with this method. In a recent clinical report14 describing glaucoma associated with uveal cysts in 3 American Bulldogs, UBM allowed detection of multiple cysts within the iridociliary sulcus. It appears that UBM could be a useful tool to further elucidate the role of uveal cysts in glaucoma and in Golden Retriever pigmentary uveitis.
Most veterinarians do not currently have access to UBM technology; instead, most use a 7.5- to 10-MHz standard ultrasound probe to perform examination of intraocular structures.15 Whether the difference in resolution between UBM and standard ocular ultrasonography results in one imaging modality being superior to the other for detection of uveal cysts is not known. To our knowledge, the accuracy and reproducibility of UBM or standard ocular ultrasonography for detection of uveal cysts in any species have not yet been determined. The objectives of the study reported here were to compare the use of UBM versus standard ocular ultrasonography to detect uveal cysts; to determine the sensitivity and specificity of each method for this purpose, compared with dissection; and to determine interobserver agreement for detection of these cysts with UBM. We hypothesized that UBM would have a higher sensitivity and specificity for detection of uveal cysts, compared with standard ocular ultrasonography.
This manuscript represents a portion of a thesis submitted by Dr. Taylor to the Purdue University Department of Veterinary Clinical Sciences as partial fulfillment of the requirements for a Master of Science degree.
Supported in part by the Vision for Animals Foundation.
Presented in abstract form at the 44th Annual Conference of the American College of Veterinary Ophthalmologists, Rio Grande, Puerto Rico, November 2013.
ClearScan ultrasound cover, ESI Inc, Plymouth, Minn.
50-MHz linear scan transducer, Aviso, Quantel Medical, Cedex, France.
iU22 Ultrasound, Philips, Andover, Mass.
Leica F40, Leica Microsystems, Buffalo Grove, Ill.
Digimatic 500-151-20 caliper, Mitutoyo Corp, Aurora, Ill.
STATA/SE, version 12.1, StataCorp, College Station, Tex.
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