Comparison of Four Systems of IOL Calculation after Keratorefractive Surgery in Eyes Requiring Cataract Surgery

Woo Seok Lee; Sang Jeong Moon; Kyung Heon Lee; Dong Jun Lee

doi:10.3341/jkos.2013.54.12.1810

Journal List > J Korean Ophthalmol Soc > v.54(12) > 1009552

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Lee, Moon, Lee, and Lee: Comparison of Four Systems of IOL Calculation after Keratorefractive Surgery in Eyes Requiring Cataract Surgery

Original Article

J Korean Ophthalmol Soc 2013;54(12):1810-1817.

Published online: 7 September 2013

DOI: https://doi.org/10.3341/jkos.2013.54.12.1810

Comparison of Four Systems of IOL Calculation after Keratorefractive Surgery in Eyes Requiring Cataract Surgery

Woo Seok Lee, MD, Sang Jeong Moon, MD, Kyung Heon Lee, MD, Dong Jun Lee, MD

Sungmo Eye Hospital, Busan, Korea

Address reprint requests to Dong Jun Lee, MD Sungmo Eye Hospital, #409-1 Haeundae-ro, Haeundae-gu, Busan 612-823, Korea, Tel: 82-51-743-0775, Fax: 82-51-743-0776, E-mail: hanwave2@gmail.com

Received 19 July 20137 October 2013 Accepted 20 November 2013

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To report the evaluation and comparison of true corneal power after corneal refractive surgery through ARK, Orbscan II^®, Pentacam and IOL master.

Methods

Target IOL (Intraocular lens) power calculated with the SRK/T formula using SMK (Sungmo Eye Hospital keratometry), which is a new method for measuring corneal refractive power, was compared with the back-calculated ideal IOL power after cataract surgery for 30 eyes that required cataract surgery and had previously undergone refractive surgery. Target IOL powers calculated using 4 systems were compared with IOL power calculated using the clinical history method for 64 eyes that had undergone refractive surgery.

Results

Using SMK with the SRK/T formula, the actual refraction was within ±0.5 diopter (D) of the intended refraction for 63.8% of eyes and within ±1.0 D for 90.9% of eyes. Compared with target IOL power calculated with the clinical history method, target IOL power calculated by SMK with the SRK/T formula had a difference of 1.95 ± 0.86 D, which was similar to the results calculated by the Haigis-L formula and by TNP with Haigis.

Conclusions

The method of IOL calculation using SMK with the SRK/T formula showed the best predictability in patients after corneal refractive surgery. Comparatively accurate results were produced in IOL power calculations using the Haigis-L formula, and the TNP with Haigis method.

Keywords: Corneal refractive power, IOL power calculation, Refractive surgery

References

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Figure 1.

The SMK calculation based on Gaussian optic formula. This method calculates anterior corneal power and posterior corneal power, respectively and the final keratometry value is the sum of each other. Anterior corneal radius is measured by RK and orbscan. Posterior radius is measured by Orbscan. Anterior and posterior radius is measured on 3 mm in best fit sphere.

Figure 2.

Clinical Result of SMK with SRK/T formula. From 2008, there are 22 patients who have received cataract surgery after LASIK or PRK. We compared retrograde calculated ideal IOL power after cataract surgery with attempted IOL power by SMK with SRK/T formula. As a result, 63.6% patients have difference within ±0.5 diopter and 90.9% within ±1.0 diopter. The blue line shows range of ±1.0 diopter as a refer-ence marker.

Figure 3.

Comparison with a back calculated ideal IOL power There were no statistically significant difference between Haigis-L, TNP (True net power from Pentacam) with Haigis formula, and SMK with SRK/T formula. TOP = total optical power map. ^* p > 0.05.

Figure 4.

Comparison with multiple keratomerty values from variable devices. Anterior corneal curvature were measured by Orbscan II® (ORB). and autorefractokeratometer (RK), and posterior curvature were measured by Orbscan II® (ORB) and Pentacam (PEN). SMK calculated with anterior curvature data from higher values of ORB or RK, and posterior curvature from ORB. Two IOL calculation formulas were used (Haigis formula and SRK/T formula), respectively. There were no statistically significant difference between multiple keratometry values with multiple formulas and SMK with SRK/T formula. TNP = true net power from Pentacam; ORB = Orbscan II®; PEN = Pentacam®; RK = refractive keratometry.

Figure 5.

Comparison of estimated keratometry value (Ks) in the SMK, true net power (TNP) and history-derived Ks. Estimated Ks were statistically significantly different between SMK and TNP (p < 0.05).

Figure 6.

Compared with clinical history method in SRK/T formula. Target IOL power calculated with SRK/T formula using variable keratometry value. Target IOL power has statistically significantly different compared with SMK with SRK/T. TNP = true net power from Pentacam; ORB = Orbscan II®; PEN = Pentacam®; RK = refractive keratometry. ^* p < 0.05.

Figure 7.

Compared with clinical history method in Haigis Formula. Target IOL power calculated with Haigis formula using variable keratometry value. Target IOL power have statistically significantly different compared with TNP with Haigis. ^* p < 0.05.

Figure 8.

In comparison with a clinical history method. 64 eyes of 32 patients who received only LASIK have been evaluated. Compared with target IOL power calculated with the clinical history method, target IOL power by SMK with SRK/T formula was different by 1.95 ± 0.86 D. Blue line shows similar results of Haigis-L, TNP with Haigis and SMK with SRK/T which was not statistically sinificantly different from each other. ^* p > 0.05.

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