Analysis of Factors that Influence on Accuracy of Intraocular Lens Power Calculation

Bo Hyuck Kim; Won Ryang Wee; Mee Kum Kim

doi:10.3341/jkos.2014.55.2.173

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Kim, Wee, and Kim: Analysis of Factors that Influence on Accuracy of Intraocular Lens Power Calculation

Original Article

J Korean Ophthalmol Soc 2014;55(2):173-181.

Published online: 7 September 2014

DOI: https://doi.org/10.3341/jkos.2014.55.2.173

Analysis of Factors that Influence on Accuracy of Intraocular Lens Power Calculation

Bo Hyuck Kim, MD^1,², Won Ryang Wee, MD, PhD^1,², Mee Kum Kim, MD, PhD^1,²

¹Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea

²Laboratory of Corneal Regenerative Medicine and Ocular Immunology, Seoul Artificial Eye Center, Seoul National University Hospital Biomedical Research Institute, Seoul, Korea

Address reprint requests to Mee Kum Kim, MD, PhD Department of Ophthalmology, Seoul National University Hospital, #101 Daehak-ro, Jongno-gu, Seoul 110-744, Korea, Tel: 82-2-2072-2665, Fax: 82-2-2741-3187, E-mail: kmk9@snu.ac.kr

Received 4 May 201326 June 2013 Accepted 8 January 2014

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 which factors primarily influence refractory errors between various formulas used to calculate intraocular lens (IOL) power.

Methods

Records of 266 eyes of 191 patients who underwent uneventful cataract surgery were reviewed retrospectively. IOL power was determined using SRK/T, HofferQ (H/Q), Master SRK/T (M/T), Master HofferQ (M/Q), Master Holladay (M/Hol), and Master Haigis (M/Hai). The mean absolute error (MAE) of each formula was compared; MAE was defined as the difference between the postoperative spherical equivalence (SE) determined 1 month after surgery and the predicted SE. Factors that could have influenced interformula refractive errors were analyzed. Patients were divided into 3 groups based on average keratometric value (Kavg) and the inter-group differences of the AE of each formula were analyzed. Effects of corneal curvature on changes in AE of each formula were evaluated by linear regression.

Results

The MAE was minimized in the M/T formula, followed by the M/Hol, M/Hai, SRK/T, H/Q, and M/Q formulas. Interformula MAE differences were not statistically significant. Kavg and AXL were significantly influenced by the different predictive values between formulas in univariate analysis, but only AXL was significant in multivariate analysis. The AE in each formula among the 3 groups according to keratometry was significantly different in SRK, M/Hol, and M/Hai. Linear regression analysis showed a significant negative correlation between Kavg, AE of SRK/T and the MHai formula. In partic-ular, this effect was more pronounced in those with short AXL (<22.5 mm).

Conclusions

There were no significant MAE differences between formulas. AXL was a significant factor that influenced the differences between formulas. SRK/T and M/Hai may be affected by outside the normal range of corneal curvatures. J Korean Ophthalmol Soc 2014;55(2):173-181

Keywords: Axial length, Corneal curvature, Intraocular lens power calculation, Refractive error

References

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Figure 1.

The proportion of eyes with an absolute error (AE) of less than 0.5 diopter and more than 0.5 diopter. The proportion of AE less than 0.5 D was greatest in the M/Hai formula (70.7%), followed by the M/T (68.7%), M/Hol (66.9%), SRK/T (64.2%), M/Q (63.1%), and H/Q (60.1) formulas. D = diopter; AE = absolute error; HofferQ = H/Q; Master SRK/T = M/T; Master HofferQ = M/Q; Master Holladay = M/Hol; Master Haigis = M/Hai.

Figure 2.

Comparison of mean absolute error in each formula between the 3 groups according to keratometry values. Significant difference of mean absolute error exists between group 1 and group 3 in SRK/T and between group 1 and group 2, group 1 and group 3 in M/Hol and M/Hai. Significance of the p is defined as less 0.05 by Turkey’s HSD test. HofferQ = H/Q; Master SRK/T = M/T; Master HofferQ = M/Q; Master Holladay = M/Hol; Master Haigis = M/Hai.

Figure 3.

Linear regression analysis. (A) Linear regression analysis shows a significant negative correlation between average K (x) and the AE of SRK/T and MHai formula (y). The best fit line has the equation y = 2.228 -0.04 x in SRK/T (R² = 0.038, p = 0.003) and y = 2.465-0.044x (R² = 0.025, p = 0.032). (B) Linear regression analysis shows an insignificant correlation between average K and the AE of H/Q (p = 0.748), M/T (p = 0.705), M/Q (p = 0.951), and M/Hol (p = 0.057) formulas. (C) Linear regression analysis shows a significant negative correlation between average K (x) and the AE of SRK/T formula (y) and M/Hai in the short axial length group. The best fit line has the equation y = 5.955-0.121x (R² = 0.237, p = 0.000,) in SRK/T and y = 5.955-0.121x (R² = 0.237, p = 0.000) in M/Hai. Kavg = average keratometric value; AE = absolute error; Master Haigis = M/Hai; HofferQ = H/Q; Master SRK/T = M/T; Master HofferQ = M/Q; Master Holladay = M/Hol.

Table 1.

Information of four intraocular lens subtypes and number of uses

	SA60AT	AR40e	SN60WF	Tecnis ZCB00
Company	Alcon	AMO	Alcon	AMO
Optic type	Spheric	Spheric	Aspheric	Aspheric
A constant	118.4	118.4	118.7	118.8
Piece(s)	1	3	1	1
Eyes (numbers)	77	14	155	20

Table 2.

Comparison of mean absolute errors (MAE) between formulas and number of eyes with mean absolute errors less than 0.5 diopter, more than 1 diopter, and more than 2 diopter

	SRK/T	H/Q	M/T	M/Q	M/Hol	M/Hai	Sig
MAE (diopter)	0.46 ± 0.37	0.47 ± 0.39	0.43 ± 0.39	0.47 ± 0.43	0.44 ± 0.48	0.44 ± 0.49	p = 0.893
Number of eyes	266	266	266	266	266	202
MAE < 0.5 D	171 (64%)	160 (60%)	183 (68%)	168 (63%)	178 (66%)	143 (71%)
MAE > 1 D	24 (9%)	22 (8%)	23 (8%)	26 (9%)	25 (9%)	21 (10%)
MAE > 2 D	1 (0.3%)	1 (0.3%)	1 (0.3%)	2 (0.7%)	2 (0.7%)	4 (2%)

Values are presented as mean ± SD.

D = diopter; MAE = mean absolute error; HofferQ = H/Q; Master SRK/T = M/T; Master HofferQ = M/Q; Master Holladay = M/Hol; Master Haigis = M/Hai.

Table 3.

Characteristics of 3 groups classified on average keratometry values

	Group 1^*	Group 2^†	Group 3^‡	Total	Sig^§
Eyes (number)	46	95	125	266
Mean age (years)	63.5 ± 18.0	67.4 ± 9.1	68.4 ± 10.3	67.23 ± 10.7	p = 0.156
Kavg (diopter)	41.18 ± 0.69	43.10 ± 0.55	45.47 ± 0.97	43.86 ± 1.83	p = 0.000
AXL (mm)	25.63 ± 2.40	24.91 ± 2.90	23.75 ± 2.58	24.50 ± 2.76	p = 0.000
ACD (mm)	2.63 ± 0.45	2.54 ± 0.42	2.64 ± 0.48	2.61 ± 0.45	p = 0.238
MAE (diopter)
SRKT	0.59 ± 0.48	0.49 ± 0.35	0.39 ± 0.32	0.46 ± 0.37	p = 0.018
H/Q	0.53 ± 0.48	0.45 ± 0.39	0.45 ± 0.35	0.46 ± 0.37	p = 0.639
M/T	0.54 ± 0.50	0.38 ± 0.38	0.43 ± 0.35	0.43 ± 0.39	p = 0.129
M/Q	0.56 ± 0.49	0.39 ± 0.40	0.49 ± 0.41	0.47 ± 0.43	p = 0.081
M/Hol	0.61 ± 0.51	0.38 ± 0.39	0.42 ± 0.36	0.44 ± 0.41	p = 0.009
M/Hai	0.69 ± 0.74	0.37 ± 0.49	0.39 ± 0.30	0.44 ± 0.49	p = 0.006

Values are presented as mean ± SD.

Kavg = average keratometric value; AXL = axial length; ACD = anterior chamber depth; MAE = mean absolute error; HofferQ = H/Q; Master SRK/T = M/T; Master HofferQ = M/Q; Master Holladay = M/Hol; Master Haigis = M/Hai.

^* Kavg < 42 D

^† 42 D ≤ Kavg < 44 D

^‡ 44 D ≤ Kavg

^§ One way ANOVA test.

Table 4.

Characteristics of 3 groups classified according to axial length values

	Group a^*	Group b^†	Group c^‡	Total
Eyes (numbers)	55	142	69	266
Mean age (years)	67.3 ± 12.3	70.3 ± 7.5	61.1 ± 13.4	67.23 ± 10.7
AXL (mm)	21.96 ± 0.40	23.7 ± 0.64	28.24 ± 2.84	24.50 ± 2.76
Kavg (diopter)	45.15 ± 1.72	43.7 ± 1.69	43.12 ± 1.69	43.86 ± 1.83
ACD (mm)	2.28 ± 0.33	2.57 ± 0.40	2.97 ± 0.36	2.61 ± 0.45

Values are presented as mean ± SD.

Kavg = average keratometric value; AXL = axial length; ACD = anterior chamber depth.

^* AXL < 22.5 mm

^† 22.5 mm ≤ Kavg < 25 mm

^‡ 25 mm ≤ Kavg.

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