comparison of corneal power and intraocular lens power calculation methods after lasik for myopia

نویسندگان

سیدمحمدرضا طاهری

seyed mohammad reza taheri آزیتا خیلتاش

azita kheiltash حسن هاشمی

hassan hashemi

چکیده

purpose : to evaluate the accuracy of the two methods the clinical history method (chm), and the contact lens method (clm), in refractive corneal power determination and comparing the accuracy of srk ii, srk t and holladay ii (h ii) formulas for intraocular lens (iol) power calculation in patients who had laser in situ keratomileusis (lasik) surgery for myopia with or without astigmatism methods : in this interventional prospective study, we evaluated 46 eyes of 32 patients who had undergone lasik for myopia with or without astigmatism and were visited at noor eye clinic during september 2001 to september 2006, for cataract surgery. the corneal power was determined with two methods chm and clm. then, iol power was calculated with three formulas srk ii, srk t and h ii. we used the results of chm+h ii formula for iol power selection. the manifest refraction (mr) one month after cataract surgery was regarded as the postoperative refraction. according to the rule that 1.5 diopter (d) change in iol power results in 1.0 d change in a patient’s refraction at the spectacle plane, we calculated the expected refractive results with iol powers based on other corneal power calculation methods and formulas, and compared them to results with chm+h ii formula. results : the mean difference between keratometry values by clm with chm methods was 2.53 ± 2.68 d (pearson correlation, 0.6 p<0.0001). the mean manifest spherical equivalent (seq) was -10.44 ± 3.92 d, before refractive surgery, -0.84 ± 1.33 d (range 1.00 to -5.00 d) before cataract formation, and -0.46 ± 1.04 d (range 1.87 to -2.62 d) after phacoemulsification and iol implantation with chm+h ii. the mean expected post-cataract surgery manifest seq using the chm with srk ii and srk t, were 1.39 ± 1.15 d and 0.56 ± 0.94 d, respectively. the mean expected post-cataract surgery manifest seq, using clm with h ii, srk ii and srk t, were calculated as 1.91 ± 2.37 d, 2.97 ± 2.17 d, and 2.59 ± 2.07 d, respectively. conclusion : chm appears to be more accurate than clm for true corneal power determination after lasik surgery for myopia with or without astigmatism. in this series of patients, the most accurate formulas for iol power calculation were h ii, srk t and srk ii, respectively.    iranian journal of ophthalmology 200921(4):45-54 © 2009 by the iranian society of ophthalmology

برای دانلود باید عضویت طلایی داشته باشید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

comparison of different methods for intraocular lens power calculation after corneal refractive surgery

with the increasing number of keratorefractive surgical procedures in the past years, an increasing number of cataract operations in eyes with previous keratorefractive surgery is anticipated. although cataract extraction seems to be feasible without major technical obstacles, intraocular lens (iol) power calculation remains problematic. insertion of measured k-readings after myopic photorefrac...

متن کامل

Intraocular Lens Power Calculation after Corneal Refractive Surgery

PURPOSE To determine the accuracy of a method of calculating intraocular lens (IOL) power after corneal refractive surgery. SETTING Department of Ophthalmology, Hospital de Gipuzkoa, San Sebastián, Spain. METHODS The SRK/T formula was modified to use the pre refractive surgery K-value (Kpre) for the effective lens position (ELP) calculation and the post refractive surgery K-value (Kpost) fo...

متن کامل

[Intraocular lens power calculation after corneal photorefractive surgery. Literature review].

OBJECTIVE Revision of methods for estimating corneal power (Kpost) and effective lens position (ELP) for cataract surgery after corneal refractive surgery. METHODS Review of medical literature. RESULTS To calculate the intraocular lens that achieves emetropia after corneal refractive surgery it is necessary to correct the Kpost and to estimate the effective lens position again correcting it...

متن کامل

intraocular lens power calculation after keratorefractive surgery

purpose: to determine corneal power for intraocular lens (iol) power calculation in eyes with previous keratorefractive surgery. methods: in 13 eyes of 9 patients with previous keratorefractive surgery undergoing phacoemulcification, iol power was calculated using the clinical history method (chm) in one case, manual keratometry (mkr) in 2, simk in 3, and flattest k (topographically derived) in...

متن کامل

Matrix formula for intraocular lens power calculation.

The matrix calculation was applied to Gaussian optics. Matrices were defined for a single diopter, a lens, an association of two centered systems having the same axis when the origins are taken at the vertices of the first and last refracting surfaces. The matrix formula then was used to calculate the power of the emmetropizing lens implant, and its results compared with the ones obtained by fi...

متن کامل

Intraocular lens power calculation for cataract surgery after photorefractive keratectomy.

OBJECTIVE To assess intraocular lens (IOL) power calculations in patients undergoing cataract surgery after excimer laser photorefractive keratectomy (PRK) for myopia. METHODS Four eyes of two patients underwent phacoemulsification with IOL implantation after PRK for myopia. The estimated refractive error that would have been induced had the IOL predicted for emmetropia been implanted was cal...

متن کامل

منابع من

با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید


عنوان ژورنال:
journal of current ophthalmology

جلد ۲۱، شماره ۴، صفحات ۴۵-۵۴

میزبانی شده توسط پلتفرم ابری doprax.com

copyright © 2015-2023