Effects of Axial Length and Vitrectomy on Refractive Error after Cataract Surgery Using SRK/T Formula

Min Kyu Lee; Kyu Yeon Hwang; Man Soo Kim

doi:10.3341/jkos.2013.54.2.257

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Lee, Hwang, and Kim: Effects of Axial Length and Vitrectomy on Refractive Error after Cataract Surgery Using SRK/T Formula

Original Article

J Korean Ophthalmol Soc 2007;54(2):257-264.

Published online: 24 August 2007

DOI: https://doi.org/10.3341/jkos.2013.54.2.257

Effects of Axial Length and Vitrectomy on Refractive Error after Cataract Surgery Using SRK/T Formula

Min Kyu Lee, MD, Kyu Yeon Hwang, MD, Man Soo Kim, MD, PhD

Department of Ophthalmology and Visual Science, The Catholic University of Korea School of Medicine, Seoul, Korea

Address reprint requests to Man Soo Kim, MD, PhD, Department of Ophthalmology, The Catholic University of Korea, Seoul St. Mary's Hospital, #222 Banpo-daero, Seocho-gu, Seoul 137-701, Korea Tel: 82-2-2258-6197, Fax: 82-2-599-7405, E-mail: mskim@catholic.ac.kr

Received 25 September 201223 October 2012 Accepted 7 January 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 investigate the error tendency between preoperative target diopter and postoperative manifest refraction in cataract surgery cases and the effect of axial length and vitrectomy on refractive error (RE).

Methods

We retrospectively studied 90 eyes of 90 patients who underwent cataract surgery. The power of intraocular lens (IOL) was calculated by SRK/T formula. Patients were devided into four groups based on axial length (AXL) and the past history of vitrectomy.

Results

The mean of RE showed no significant difference between groups. But an increasing AXL was associated with increased myopic shift with normal range AXL (≤24.4 mm) (r = −0.502, p = 0.005) and increased hyperopic shift with long AXL (>24.4 mm) (r = 0.718, p < 0.001). In vitrectomized eyes, it showed no significant refractive shift with both normal range and long AXL.

Conclusions

When determining IOL power using SRK/T formula in nonvitrectomized eyes, postoperative refractive shift based on axial length should be considered.

Keywords: Axial length, Cataract surgery, Effective lens position, Refractive error, Vitrectomy

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Figure 1.

Correlation between axial length and refractive error after cataract surgery. Correlation is more significant at 2 month than 1 month after surgery in nonvitrectomized patient (A, B). Vitrectomized patient showed no significant correlation in both normal range (C) and long axial length (D). Refractive error = (Postoperative spherical equivalent) - (Target diopter); r = Pearson correlation coefficient in A and B; r = Spearman rho in C and D.

Table 1.

Demographics of patients

Patient group	Simple		Post-vitrectomy
Patient group	Group A AXL ≤ 24.4 mm	Group B AXL > 24.4 mm	Group C AXL ≤ 24.4 mm	Group D AXL > 24.4 mm
Number of eyes	30	30	15	15
Mean age (years)	69.0 ± 13.3	54.7 ± 11.0	65.1 ± 6.3	56.9 ± 14.2
Gender (M/F)	10/20	15/15	7/8	9/6
Axial length (mm)	23.45 ± 0.71	28.87 ± 2.56	23.26 ± 0.74	26.41 ± 2.61
	(21.6-24.4)	(25.3-35.1)	(22.0-24.4)	(24.5-34.3)
Preoperative SE (D)	-0.12 ± 2.19	-12.78 ± 7.90	-0.54 ± 1.53	-5.86 ± 4.25
Preoperative K (D)	44.35 ± 1.27	44.15 ± 1.41	44.07 ± 1.29	43.28 ± 1.27

Values are presented as mean ± standard deviation.

SE = Spherical equivalent; K = corneal power; D = diopter; AXL = axial length.

Table 2.

Comparison of postoperative refractive error

	Group A	Group B	Group C	Group D	p-value^∗
Preoperative
Spherical equivalent (D)	-0.12 ± 2.19	-12.78 ± 7.90	-0.54 ± 1.53	-5.86 ± 4.25
Target diopter	-0.51 ± 0.49	-1.80 ± 1.04	-0.31 ± 0.15	-1.45 ± 1.15
Postoperative 1 month
Spherical equivalent (D)	-0.63 ± 0.74	-2.02 ± 1.54	-0.11 ± 0.61	-1.54 ± 1.54
Refractive error^† (D)	-0.12 ± 0.60	-0.21 ± 1.02	0.20 ± 0.61	-0.01 ± 0.46	0.429
Postoperative 2 months
Spherical equivalent (D)	-0.57 ± 0.84	-2.05 ± 1.34	-0.03 ± 0.67	-1.44 ± 1.58
Refractive error (D)	-0.06 ± 0.72	-0.25 ± 0.94	0.27 ± 0.67	0.12 ± 0.49	0.239

Values are presented as mean ± standard deviation.

D = diopter.

^∗Tested by Kruskal-Wallis test; ^†(Postoperative spherical equivalent) - (Target diopter).

Table 3.

Change of corneal power after cataract surgery

	Group A		Group B		Group C		Group D
	K^†	p-value^∗	K^†	p-value	K^†	p-value	K^†	p-value
Preoperative	44.35 ± 1.27		44.15 ± 1.41		44.52 ± 1.32		43.28 ± 1.27
Postoperative
1 month	44.41 ± 1.16	0.267	44.25 ± 1.48	0.088	44.56 ± 1.29	0.622	43.39 ± 1.22	0.085
2 months	44.46 ± 1.15	0.080	44.30 ± 1.48	0.052	44.59 ± 1.32	0.181	43.38 ± 1.23	0.056

Values are presented as mean ± standard deviation.

^∗Comparison with preoperative K, tested by paired t-test in Group A, B and by Wilcoxon signed rank test in Group C, D; ^†Corneal power.

Table 4.

Comparison of refractive error in different type of intraocular lens

IOL type	Group A		Group B		Group C		Group D
IOL type	Ref. error^†	p-value^∗	Ref. error^†	p-value^∗	Ref. error^†	p-value^∗	Ref. error^†	p-value^∗
1-piece	0.03 ± 0.81	0.371	0.03 ± 0.81	0.061	0.33 ± 0.29	0.354	0.16 ± 0.30	0.906
	(n = 20)		(n = 19)		(n = 7)		(n = 6)
3-piece	-0.23 ± 0.49		-0.23 ± 0.49		0.09 ± 0.09		0.12 ± 0.15
	(n = 10)		(n = 11)		(n = 8)		(n = 9)

Values are presented as mean ± standard deviation.

^∗Tested by Mann-Whitney test; ^†(Postoperative spherical equivalent) - (Target dioptre).

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