Use of high-resolution ultrasound as a diagnostic tool in veterinary ophthalmology

Abstract

The recent development of a 20-MHz, high-frequency ultrasound probe has allowed tissue to be visualized at resolutions of 20 to 80 microm, which is similar to a low-power histologic view. This high degree of resolution, however, limits tissue penetration to 5 to 10 mm, which is ideal for examination of the anterior segment of the eye. The detail provided by high-resolution ultrasound readily permits the clinician to distinguish between various anterior segment entities that may appear similar but are treated quite differently, such as anterior uveal tumors, iridociliary cysts, and iris bombé. High-frequency ultrasound is also a valuable aid in creating a surgical plan for treatment of ocular disorders in which the cornea is opaque, such as feline corneal sequestrum and tumor invasion into the cornea. Other applications of this technology include elucidation of the pathogenesis of glaucoma in veterinary patients and evaluation of regions of the lens that are difficult to examine directly.

Relação entre a biometria ultrassonográfica ocular e os parâmetros morfométricos do crânio, idade, peso e gênero em gatos domésticos

“…Aubin et al (2003) utilizaram transdutor de alta frequência (50 MHz) em gatos e referiram ser possível mensurar a espessura da córnea, a profundidade da câmara anterior (D1) e da primeira porção do processo ciliar à base da íris e o ângulo iridocorneano. Bentley et al (2003) relataram que transdutores de frequência superior a 20 MHz possibilitaram a visualização de imagens de estruturas do segmento anterior do olho (córnea, cápsula posterior do cristalino e íris) devido a sua maior definição de imagem e poder de penetração, aproximadamente, 20 a 80 µm e limite de penetração de 5 a 10 mm em gatos e cães.…”

Ultrasonographic and ecobiometric findings in the eyes of adult goats

“…Compared with conventional 10 MHz probes that have resolutions of 300 to 400μm, high-frequency probes (20MHz) enable imaging at resolutions comparable to low-power microscopic views (20μm) (FOSTER et al, 2000). However, in the equipment used in the present study, the minimum power of penetration is limited to 20mm, not reaching lower tissue penetrations of 5 to 10mm, which are necessary to visualize structures such as the ciliary cleft (BENTLEY et al, 2003).…”

“…For these reasons, in the present research, it was decided to calculate all measurements using Amode ultrasonography. The high-resolution 20MHz transducer used in our study offers a power of penetration ranging from 2 to 6cm, which is necessary to visualize the entire globe, without the formation of reverberation artifacts in the anterior chamber (BENTLEY et al, 2003). Compared with conventional 10 MHz probes that have resolutions of 300 to 400μm, high-frequency probes (20MHz) enable imaging at resolutions comparable to low-power microscopic views (20μm) (FOSTER et al, 2000).…”

“…Corneal edema is a common clinical sign of corneal ulceration, keratitis, anterior uveitis, and many systemic diseases, and precludes the direct visualization of intraocular structures by ophthalmoscopy (WHITTAKER et al, 2003). Under such conditions, alternative diagnostic methods for intraocular diseases must be explored (BOROFFKA et al, 1998;BENTLEY et al, 2003;SCOTTY et al, 2004).…”

“…Knowledge of the ultrasonographic appearance and normal dimensions of the eye would serve as a basis for ultrasonographic examinations when ocular disease may have caused alterations in the dimensions and appearance (BENTLEY et al, 2003;SCOTTY et al, 2004;POTTER et al, 2008). For this reason, the aim of this research was to study the dimensions (ecobiometry) and the ultrasonographic aspect of adult goats.…”