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Bệnh nhân được đặt ở một vị trí ngồi trong một chiếc ghế trong phòng kiểm tra với người đứng đầu reclined nhẹ nhàng chống lại tựa đầu. Trung bình "Tổng chiều dài" báo cáo của đơn vị đã được nhập vào công thức tính điện II Holladay IOL. Đối với Thạc sĩ IOL, chiều dài trục được lựa chọn với tỷ lệ tín hiệu-to-noise cao nhất đã được sử dụng làm cơ sở để so sánh. | 12 M. Packer I.H. Fine R.S. Hoffman IOL Master Zeiss Humphrey Systems Jena Germany with measurements obtained by immersion ultrasound using the Axis II Quantel Medical Clermont-Ferrand France . We have also examined the postoperative refractions of patients undergoing cataract extraction with posterior chamber IOL implantation to determine the accuracy of the immersion ultrasound technique. Fifty cataractous eyes underwent preoperative axial length measurement with both the Axis II and the IOL Master. For the Axis II immersion technique the Praeger shell was employed. Patients were placed in a sitting position in an examination room chair with the head reclined gently against the headrest. The average Total Length reported by the unit was entered into the Holladay II IOL power calculation formula. For the IOL Master the selected axial length with the highest signal-to-noise ratio was used as the basis for comparison. The measured axial lengths were plotted and a linear regression trendline fitted to the data. The Pearson correlation coefficient was determined to assess the relationship between the immersion and the optical measurements according to the formula ọ 1 1-n S x - p s y - p s . Keratometry was performed with the IOL Master. The three reported sets of values were compared for consistency and correlated with the axis and magnitude of the eye s preoperative astigmatism. Either an averaged value of three measurements or of the two closest measurements in case one measurement appeared to be an outlier was entered into the formula. In selected cases autoker-atometry HARK 599 Zeiss Humphrey Systems Jena and or computerized corneal topography EyeSys Technologies Houston were utilized to delineate better the preoperative keratometry. The corneal white-to-white diameter was determined with the Holladay-Godwin Corneal Gauge. One surgeon IHF performed all surgery. The Holladay II IOL power calculation formula was used to select the intraocular lens for implantation .
