Astigmatic Correlation between the Automated Refractometry and Dual Scheimpflug Analyzer in Pseudophakic Eyes

Seung Hun Park; In Seok Song; Min Cheol Seong; Hee Yoon Cho; Min Ho Kang

doi:10.3341/jkos.2016.57.3.361

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Park, Song, Seong, Cho, and Kang: Astigmatic Correlation between the Automated Refractometry and Dual Scheimpflug Analyzer in Pseudophakic Eyes

Original Article

J Korean Ophthalmol Soc 2016;57(3):361-368.

Published online: 3 September 2016

DOI: https://doi.org/10.3341/jkos.2016.57.3.361

Astigmatic Correlation between the Automated Refractometry and Dual Scheimpflug Analyzer in Pseudophakic Eyes

Seung Hun Park, MD¹, In Seok Song, MD, PhD², Min Cheol Seong, MD, PhD¹, Hee Yoon Cho, MD, PhD¹, Min Ho Kang, MD, PhD¹

¹Department of Ophthalmology, Hanyang University Guri Hospital, Hanyang University College of Medicine1, Guri, Korea

²Department of Ophthalmology, Hanyang University Hospital, Hanyang University College of Medicine, Seoul, Korea

Address reprint requests to Min Ho Kang, MD, PhD, Department of Ophthalmology, Hanyang University Guri Hospital, #153 Gyeongchun-ro, Guri 11923, Korea, Tel: 82-31-560-2350, Fax: 82-31-564-9479, E-mail: ocularimmunity@gmail.com

Received 22 May 2015 Revised 6 October 2015 Accepted 12 December 2015

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 examine the relationship between the refractive astigmatism by automated refractometry and the corneal astigmatism by a dual Scheimpflug analyzer in pseudophakic eyes.

Methods

Prospectively, 75 patients (100 eyes) were enrolled in the present study. Refractive astigmatism was obtained by automated refraction. Corneal astigmatism was obtained using automated keratometry (ARK-530A^®) and dual Scheimpflug scanning analysis (Galilei G4^®). All refractive values were converted to the power vector components J0 and J45 for comparison and regression analysis of refractive versus corneal astigmatism. Bland-Altman plots were created to estimate the agreement between measurements.

Results

The average astigmatism from each measurement was −1.11 ± 1.44 D (refractive astigmatism from automated refraction), −0.77 ± 1.06 D (corneal astigmatism from automated keratometry), −0.93 ± 1.02 D (simulated K from Galilei G4^®), and −1.11 ± 1.48 D (total corneal power from Galilei G4^®). Refractive J0 and keratometric J0 were significantly correlated (r = 0.557, p ≤ 0.001), as well as the corresponding J45 values (r = 0.655, p = 0.025). Refractive astigmatism and total corneal power components were also significantly correlated (J0: r = 0.618, p ≤ 0.001; J45: r = 0.608, p = 0.04). In the Bland-Altman plots, keratometric J0 and total corneal power J0 showed the best agreement.

Conclusions

The accuracy of measurements for corneal refraction and astigmatism in pseudophakic eyes is higher using the dual Scheimpflug analyzer, especially for total corneal power. This value of astigmatism can take into account the refractive astigmatism of pseudophakic eyes and can be used in evaluating postoperative corneal astigmatism.

Keywords: Dual Scheimpflug analyzer, Galilei G4^®, Pseudophakia, Refractive and keratometric astigmatism

References

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Figure 1.

Difference between corneal astigmatism measured by autokerotometer (ARK-530A, NIDEK, Gamagori, Japan) and dual Scheimpflug analyzer in pseudophakic eyes. Note that astigmatism is measured more in total corneal power of Scheimpflug analyzer than keratometric astigmatism of autokerotometer and simulated K of Scheimpflug analyzer (respectively p < 0.001, p < 0.001, paired t-test).

Figure 2.

Axis distribution (degrees) of refractive astigmatism, keratometric astigmatism, simulated K and total corneal pow er of Scheimpflug analyzer. Most of them are distributed in 90 degree axis and −1.0 diopter astigmatism. Astig = astigmatism; Sim K = simulated K; total = total corneal power; Ref = refractive astigmatism; kerato = keratometric astigmatism.

Figure 3.

Regression lines between refractive astigmatism J0 and keratometric astigmatism J0 (A) and J45 (B), refractive astigmatism J0 and Simulated K J0 (C) and J45(D) and refractive astigmatism J0 and total corneal power J0 (E) and J45 (F) by Jackson vector analysis. Refractive and keratometric astigmatism J0 were significantly correlated (r = 0.557, p < 0.001; A), and also the corresponding J45 values (r = 0.655, p = 0.025; B). Refractive and Simulated K astigmatic components were significantly correlated (J0: r = 0.623, p < 0.001; J45: r = 0.585, p = 0.025) (C, D). Refractive and total corneal power astigmatic components were significantly correlated (J0: r = 0.618, p < 0.001; J45: r = 0.608, p = 0.04) (E, F). A R = refractive astigm atism; A K = keratom etric astigmatism; Sim K = simulated K; TCP = total corneal power.

Figure 4.

Bland–Altman plots (solid line: mean, dotted lines: mean ± 1.96 SD) of the difference between refractive astigmatism J0 and keratometric astigmatism J0 against their mean (A), between refractive astigmatism J0 and Simulated K J0 against their mean (C), between refractive astigmatism J0 and total corneal power J0 by ray-tracing against their mean (E) and J45 (B, D, F), respectively. Bland-Altman plots show good agreement between refractive and keratometric J0 (difference: −0.78∼ 0.06) and J45 astigmatic components (difference: −0.20∼ 0.20; A, B, respectively). Agreement between refractive and simulated K J0 (difference: −0.66∼0.12) and J45 (difference: −0.20∼ 0.28) astigmatic components was good (C, D, respectively). Agreement between refractive and total corn eal pow er J0 (difference:-0.49∼ −0.31) and J45 (difference: −0.23∼ 0.29) astigmatic components was good E, F, respectively). SD = standard deviation; D= diopters.

Table 1.

Characteristics of patients included

	N	Mean	95% Confidence interval	Range
Age (years)	75	69.14	66.68∼71.46	40∼92
Cylinder
AR	100	−1.11 ± 0.72 D	−1.26∼-0.98	−4.0∼0
AK	100	−0.77 ± 0.52 D	−0.87∼-0.67	−3.25∼0
TCP	100	−1.11 ± 0.64 D	−1.27∼-0.97	−4.22∼0.87
Sim K	100	−0.93 ± 0.51 D	−1.02∼-0.83	−2.89∼-0.06
J0
AR	100	−0.37 ± 0.48 D	−0.47∼-0.28	−1.96∼1.50
AK	100	−0.01 ± 0.40 D	−0.09∼0.07	−1.43∼1.58
TCP	100	−0.29 ± 0.51 D	−0.38-0.19	−2.10∼0.75
Sim K	100	−0.1 ± 0.43 D	−0.19∼-0.01	−1.44∼0.92
J45
AR	100	0.05 ± 0.25 D	0∼0.10	−0.59∼0.75
AK	100	0.05 ± 0.23 D	0∼0.10	−0.39∼0.74
TCP	100	0.03 ± 0.33 D	−0.04∼0.09	−0.86∼1.11
Sim K	100	0.01 ± 0.28 D	−0.05∼0.06	−0.84∼0.83

Values are presented as mean ± SD unless otherwise indicated.

AR = automated refractive astigmatism; AK = automated keratometric astigmatism; TCP = total corneal power; Sim K = simulated K; D = diopter.

Table 2.

Difference between dual Scheimpflug analyzer readings and automated K readings

Parameter	Difference (D)		p-value
Parameter	Mean ± SD	95% Confidence interval	p-value
TCP-AR	0.02 ± 0.65	−0.11∼0.14	0.806^*
Sim K-AR	0.20 ± 0.72	0.05∼0.33	0.01
AK-AR	0.34 ± 0.78	0.20∼0.50	<0.001

Values are presented as mean ± SD unless otherwise indicated.

D = diopter; SD = standard deviation; TCP = total corneal power; AR = automated refractive astigmatism; Sim K = simulated K; AK = automated keratometric astigmatism.

^* No statistically significant difference.

Table 3.

The predictive aberration parameters for the total corneal power

	Group	Number	Mean (μm)	SD	p-value
Coma					0.097^*
	1	66	−0.1121	0.31658
	2	34	−0.0965	0.22625
Spherical					0.086^*
	1	66	0.1891	0.15227
	2	34	0.1679	0.11956
Trefoil					0.223^*
	1	66	−0.0197	0.33013
	2	34	−0.0341	0.25433
Total RMS					0.124^*
	1	66	1.7386	0.47463
	2	34	1.5303	0.31061
2nd RMS					0.188^*
	1	66	1.4447	0.43874
	2	34	1.3441	0.30329
3rd RMS					<0.001
	1	66	0.792	0.35752
	2	34	0.605	0.1951
4th RMS					0.095^*
	1	66	0.3867	0.20496
	2	34	0.2924	0.13527

Group 1 means ΔJ0 ≥ 0.25 or ΔJ0 ≤ −0.25, and Group 2 means −0.25 < ΔJ0 < 0.25 D.

SD = standard deviation; RMS = root mean square.

^* No statistically significant difference.

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