ULTRASOUND BIOMICROSCOPY - I - PRECISION OF MEASUREMENTS

Purpose: To evaluate the precision of anterior chamber dimensions meas ured by the 50 MHz Humphrey(R) Ultrasound Biomicroscope, the influence of various subprocedures, and the importance of clear definition of s tructures, Methods: Fourty-eight right eyes of 26 normal subjects and 22 glaucoma patients were scanned centrally and at the chamber angle a t three positions under standardized conditions. Eight different param eters were measured in angle images and two in images of central corne a and anterior chamber. Four variance components were calculated, Resu lts: Measurement of the dearest defined structures had the highest pre cision. In angle images the precision expressed as the coefficient of variation was <21%, except for measurement of iris-ciliary process (ra nge: 3-59%). All subprocedures contributed to the overall variance, im age to image variation the most. Conclusions: The precision of most me asured parameters seems reasonable for clinical use. All subprocedures contributed significantly to the overall variance. The parameters tha t were related to clearly defined structures had the highest precision .