الفهرس 
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Abstract
There are several problems which affect the accuracy of the IOL power calculation. The two main problems encountered are the measurement of the proper axial length to be used in calculation due to the presence of the posterior staphyloma and the lack of accuracy of the available formulas that calculate the power of the IOL in cases of high myopia
The presence of a posterior staphyloma can lead to significant errors in A-scan AL measurements and should always be considered if there is difficulty obtaining a distinct retinal spike.
A number of formulas for IOL power calculation have been published for better prediction of the postoperative refractive error especially for long and short eyes.
Till now no ideal formula for all eyes.
Our study was carried out on 45 eyes of 56 patients including 32 males (71.12 %) and 13 females (28.88%) with age range from (24-67 years). The mean age of the studied patients was 53.039 ± 7.73 years with an axial length from 25.22 mm to 32.85 mm.
The present study concluded that SRK II formula and Haigis formula tended to cause a hyperopic refractive error postoperatively.
When range of AL from 25.22mm to 27mm; The SRK II formula caused the smallest mean error,(-0.04D).The Haigis formula showed a higher mean error than the SRK II formula (+0.32D).But mean error increase with increase axial length so in group II (axial length from 27-29mm) The Holladay formula caused a myopic postoperative refractive error, -0.25D).The mean error in the axial length subcategories ranged from -0.04D to +0.32 D in group I, from -0.25Dto +0.21 D in group II, and from -0.22D to +0.33D in group III.
In the present study, there was no statistically significance difference between the mean error of the three formulas used in the overall performance or in the axial length subcategories.
There was a positive correlation between the axial length and the mean errors of the SRK II and while show a negative correlation between the axial length and the mean errors of the Holladay formula (the mean errors decreases with longer axial length) Within limit and Haigis formula showed a lower ME than the SRK II formula in AL longer than 28 mm.
In the present study, the SRK II and Haigis formulas have a tendency to over minus the power of the IOL to be implanted specially in group II resulting in postoperative hyperopia, while Holladay formula tend to over plus the power of the IOL implanted which result in a postoperative myopia which preferred to patient as adaptation and near work purpose.
Haigis formula is the best one when minus power IOL is implanted.
The new technique of laser interferometry in measurement of the axial length proved a better precision over the Amplitude scan. However, still there is some limitation in its use in a wide range of different type of cataract.
In the future power IOL will be implanted undergo other expensive and complex techniques as lenstar® and intraoperative biometry, also with mulifocal IOL styles.