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G. Sun, R.H. Silverman, T. Raevski, G. Harmon, H. Lloyd, D.J. Coleman; Comparison of Gonioscopy and High Resolution Ultrasound for Evaluating Anterior Segment Anatomy in Glaucomatous Eyes . Invest. Ophthalmol. Vis. Sci. 2005;46(13):150.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Arc–scan very high frequency ultrasound (VHFU) allows visualization of the entire anterior segment (angle–to–angle and sulcus–to–sulcus) in a single image. Our aim was to measure and characterize the anterior chamber structures in open angle glaucoma with the use of very high frequency ultrasound and correlate these findings to clinical exam. Methods: Gonioscopy and VHFU (50 MHz) were performed on 16 eyes in 8 patients with clinical evidence of open angle or narrow angle glaucoma. Ultrasound was performed using a prototype arc–scan system developed in our laboratory. We measured anterior chamber depth (ACD), angle plane width (APW), sulcus plane width (SPW), and angle width (AW) (temporally and nasally) at 0.5 mm and 1.0 mm from the angle. Iris curvature was characterized by the ratio of AW measured at 1.0 and 0.5 mm. The AW was graded by gonioscopy and gonioscopic value correlated with ultrasound determined values. Inter– and intra–operator variability of ultrasound measurements was determined. Results: Ultrasound determined angle width was highly correlated with gonioscopic grade (R=.71, p=.002). Intra–operator variability was 21, 84 and 83 microns for ACD, APW and SPW, respectively. A second operator had variations of 28, 199 and 207 microns for ACD, APW and SPW from the first operator. Inter–operator AW variability was 2.8º and 2.3º at 0.5 mm and 1.0 mm from the angle, respectively, with a second operator difference from the first of 5.8º and 6.2º. Conclusions: VHFU is a technique that yields high resolution images and allows for both a qualitative and quantitative analysis of the anterior chamber structures. VHFU may be utilized to observe the anterior chamber angle in the presence of an opaque or edematous cornea, which could not be otherwise observed through a gonioscopic exam. VHFU allows a detailed image of the relevant structures of the anterior chamber, their dimensions, and their anatomic relationships. These relationships may shed light on possible anatomic causes of glaucoma. The high resolution cross–sectional images of the angle can be obtained chronologically for quantitative and qualitative assessment of change. The identification of such changes aids in clinical assessment of glaucoma and potentially allows for better treatment decisions.
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