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Comparison of manufacturer constant and optimized constant for IOL power

Poster Details

First Author: M.Diab SAUDI ARABIA

Co Author(s):    S. Eeisa              

Abstract Details


Early postoperative refraction after cataract surgery in children is commonly different from what had been predicted. To the best of our knowledge, no pediatric study has evaluated impact of optimized constant on early postoperative refraction. We compared deviation of the postoperative refraction from the targeted refraction using the manufacturer’s and an optimized surgeon-specific A-constant in children.


Magrabi Hospital Aseer


Data from children who have undergone cataract surgery by single surgeon using SN60WF IOL were reviewed. Exclusion criteria: traumatic cataract, uveitis, nonbag fixation and secondary IOL, unavailability of refraction within 3-months postoperative period. The estimated refraction was evaluated by inputting manufacturer’s A-constant into Holladay software. It calculates personalized ACD for each eye, and gives personalized surgeon factor for Holladay-1 formula (and Personalized Lens Constant for SRK/T). The estimated postoperative refraction was reevaluated by inputting optimized constant into Holladay software. The deviations of refraction using both constants were compared with paired T test.


n=100; Age at surgery:6.1±5.4 years; Preoperative immersion AL: 22.5±2.2mm. Follow-up refraction was obtained at median of 32 days. Mean deviation of refraction was 0.23D using manufacturer’s A-constant (surgeon factor 1.62, equivalent constant 118.7), while -0.03D using optimized constant (SF 1.812, equivalent constant 119.229) (<0.001). Absolute mean deviation was 0.77 and 0.72D (P = 0.03). Deviation was <0.5D in 41% eyes using manufacturer constant, while 48% using optimized constant


Discussion: Use of optimized constant is one of the preventable causes of early postoperative refractive error. Conclusion: The use of a optimized surgeon-specific A-constant could potentially decrease early postoperative refractive error in children.

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