الفهرس 
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Abstract
present study was performed to evaluate accuracy of calculation of the dioptric power of IOL by both instruments (The optical biometry & ultrasonic biometry ) . For IOLM) optical) patients 48 (96%) had postop spherical refraction in range of −0.50 to +0.50 and 2 (4%) were outside this range. for A-scan (ultrasonic) patients 40 (80%) had postop spherical refraction in range of −0.50 to +0.50 and 10 (20%) were outside this range . That means the more accuracy of the Optical biometry than the Ultrasonic biometry in measuring the IOL.
Modern technology has significantly improved our ability to accurately measure ocular biometrical parameters. Hence, today, we are more confident fulfilling patient expectations. However, it is still very important to pay attention to, accurate biometry, and right IOL power formula selection. Eventually, the highest variable parameter is going to establish the outcome.
In order to increase accuracy in ocular biometry practice, one must have sought the following realizations: properly calibrated instrument and an experienced operator, repeating measurements, using optical biometry rather than contact biometry, using last generation IOL formulae and tailoring the IOL constants accordingly, and evaluating refractive outcomes regularly. By following each step carefully understanding strengths and weaknesses during all these steps, successful outcomes are achievable.
IOL master Biometry was found to be more accurate in the measurement of the ocular axial length than applanation ultrasonography. It has improved significantly the refractive results of cataract surgery in this carefully selected cohort. However it has number of limitations, the presence of outliers indicates the need for further improvements in the ocular biometry and IOL power prediction methods.
In our study, we used Haigis formula (a fourth generation formula) to IOL power calculation in the A scan guided biometry device and the IOL master device for biometry, which give best refractive outcomes.
The Haigis formula, a fourth-generation formula, may have performed better than the others because of its inclusion of the IOL master-measured anterior chamber depth (ACD).
Third-generation formulae such as the Hoffer Q, and SRK/T are 2-variable formulae that rely on AL and central corneal power to predict the postoperative IOL position. These formulae do not use actual measurements of the ACD; they assume that short eyes will have shallower ACDs and long eyes will have deeper ACDs.
We can conclude that IOL measurements performed with the Zeiss IOL master, using partial coherence interferometry, yielded significantly better IOL power prediction and therefore refractive outcome in cataract surgery than Applantion US biometry.