الفهرس 
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Abstract
Cataract is the leading cause of preventable blindness worldwide. Cataract extraction with implantation of an intraocular lens (IOL) is the most frequently performed ophthalmic surgical procedure worldwide. Accurate calculation of the IOL power for attaining the desired postoperative refraction remains a research issue.
Several factors affect the refractive outcome after cataract surgery, including axial length, keratometry, and lens formulas. Of these factors the preoperative axial length measurement is a key determinant in the choice of intra-ocular lens (IOL) power.
This study aimed to determine whether intraocular lens (IOL) power calculations for cataract surgery as measured by postoperative refractive error using IOL master are more accurate in improving postoperative outcomes than applanation ultrasounic biometry (AUS) in emmetropic versus highly myopic eyes. Traditionally, contact A-scan ultrasonography is used. This measures the time taken for sound to traverse the eye and converts it to a linear value (spikes) using a velocity formula. The distance between the corneal and retinal spikes gives the axial length of the eye. Keratometry reading (K1&K2) taken by automated keratometer.
The IOLmaster 700 device is a computerized biometry device consisting of an OCT system to measure distances within the human eye along the visual axis, a Keratometer system to measure the corneal surface.
38 eyes from patients scheduled for phacoemulsification were included in the study. A scan biometry was done to 18 of them where 9 eyes were myopic and 9 eye were emmetropic. IOL master biometry
Summary
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was done to the other 20 eyes where 10 of eyes were highly myopic and 10 eyes were emmetropic.
Results show that the axial length measured using the IOL master was 0.6 mm longer than that measured using A- scan which was statistically significant (p<0.001).
In the high myopic group, we found that the mean difference between the two methods was 0.75 mm, which was statistically significant (p<0.001). In the emmetropic group, the mean difference between the two methods was 0.44 mm, which was statically significant (P<0.001).
We can conclude that The IOL master provides an accurate axial length measurement and results in accurate intraocular lens power calculation. However, IOL master has a failure rate, particularly in the presence of dense cataracts.