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Comparisons of Wavefront Refraction, Autorefraction, and Subjective Manifest Refraction

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Comparisons of Wavefront Refraction, Autorefraction, and Subjective Manifest Refraction Tzu Chi Medical Journal 25 (2013) 43e46 Contents lists available at SciVerse ScienceDirect Tzu Chi Medical Journal journal homepage: www.tzuchimedjnl.com Original Article Comparisons of wavefront refraction, autorefraction, and subjective manifest refraction Hong-Zin Lin a,b, Chien-Chung Chen c, Yuan-Chieh Lee a,b,c,d,* a Department of Ophthalmology, Buddhist Tzu Chi General Hospital, Hualien, Taiwan b Graduate Institute of Medical Sciences, Tzu Chi University, Hualien, Taiwan c Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan d Department of Medicine, Tzu Chi University, Hualien, Taiwan article info abstract Article history: Objectives: To compare cycloplegic wavefront refraction, autorefraction, and subjective manifest Received 5 November 2012 refraction. Received in revised form Materials and Methods: Thirty-one myopic eyes in 17 patients were studied. Subjective manifest refraction 10 December 2012 was measured and deemed as the true refraction status. After inducing cycloplegia by administering 1% Accepted 27 December 2012 tropicamide, cycloplegic autorefraction was measured using a Topcon autorefractor, and wavefront refrac- tion was measured with an Allegretto wave analyzer. Refraction data were presented as the spherical Keywords: equivalent and astigmatism. Astigmatismwas converted tovector powerand analyzed by the Alpins method. Autorefraction Subjective manifest refraction Results: Both cycloplegic wavefront refraction and autorefraction showed good correlations with sub- 2 Wavefront refraction jective refraction. The adjusted R value was 0.9726 between cycloplegic autorefraction and subjective manifest refraction, and 0.9693 between cycloplegic wavefront refraction and subjective manifest refraction. Compared with subjective manifest refraction, a myopic shift of À0.14 Æ 0.06 D was noted in cycloplegic wavefront refraction (p ¼ 0.0182). However, cycloplegic autorefraction was not different from subjective manifest refraction (p ¼ 0.55). Astigmatism in both wavefront refraction and autorefraction differed from subjective astigmatism (p < 0.0001 for both). The difference of astigmatism vector power from subjective refraction was 0.16 D larger in the cycloplegic wavefront refraction group than in the cycloplegic autorefraction group (p ¼ 0.0039). Conclusion: Autorefraction gives a better estimate of subjective manifest refraction than wavefront refraction in both the spherical equivalent and astigmatism. Copyright Ó 2013, Buddhist Compassion Relief Tzu Chi Foundation. Published by Elsevier Taiwan LLC. All rights reserved. 1. Introduction astigmatism, both of which can be measured by autorefractors and wavefront aberrometers. However, detection of high-order aber- The primary goal of refractive surgery is to achieve indepen- rations can only be done by wavefront aberrometers. Concomitant dence from spectacles and contact lenses. However, along with the elimination of high-order aberrations, instead of correction of only dramatic advances introduced by new technologies such as exci- defocus and regular astigmatism, relies on wavefront aberrometers mer laser platforms with higher repetition rates, faster eye trackers, for the measurement of all aberrations. However, the accuracy and and customized ablation profiles, the primary goal of refractive efficacy of this advanced technology and complicated instrument surgery has evolved and aims to provide “super vision”. still need to be validated. Therefore, the purpose of this study was Monochromatic aberrations include low-order and high-order to compare the measurements of cycloplegic autorefraction, aberrations. The two most common low-order aberrations are wavefront refraction, and subjective manifest refraction. defocus (myopic and hyperopic spherical errors) and regular 2. Materials and methods * Corresponding author. Department of Ophthalmology, Buddhist Tzu Chi Gen- This research followed the tenets of the Declaration of Helsinki, eral Hospital, 707, Section 3, Chung-Yang Road, Hualien, Taiwan. Tel.: þ886 38561825x3255; fax: þ886 38577161. and informed consent was obtained from each patient before the E-mail address: [email protected] (Y.-C. Lee). study. The patients were excluded if they had any other ocular 1016-3190/$ e see front matter Copyright Ó 2013, Buddhist Compassion Relief Tzu Chi Foundation. Published by Elsevier Taiwan LLC. All rights reserved. http://dx.doi.org/10.1016/j.tcmj.2013.01.006 44 H.-Z. Lin et al. / Tzu Chi Medical Journal 25 (2013) 43e46 disease or previous ocular surgery that would affect the refractive Table 1 status. During the visit, a series of evaluations was carried out as Sphere, cylinder, and spherical equivalent of three measurements. follows: (1) a baseline subjective manifest refraction was deter- Subjective Cycloplegic Cycloplegic mined by fogging, duochrome tests, and astigmatism dials with manifest wavefront autorefraction trial lenses, including cross-cylinder refraction. (2) Two drops of refraction refraction tropicamide (Mydriacyl 1% ophthalmic solution, Alcon Labora- Spherical error (D) À5.87 Æ 0.32 À5.93 Æ 0.30 À5.77 Æ 0.33 À À À À À À tories, Fort Worth, TX, USA) were administered to the studied eyes ( 2.5 to 8.5) ( 2.73 to 8.71) ( 2.50 to 9.0) Cylindrical error (D) À0.47 Æ 0.08 À0.64 Æ 0.05 À0.47 Æ 0.08 with an interval of 10 minutes for mydriasis and cycloplegia. (0 to À1.25) (À0.19 to À1.19) (0 to À1.25) Twenty minutes after the second drop, when the photopic pupil SE (D) À6.10 Æ 0.32 À6.25 Æ 0.30 À6.07 Æ 0.33 sizes were no less than 7 mm, cycloplegic autorefraction was (À2.375 to À8.5) (À2.93 to À9.11) (À2.63 to À9.00) measured using an autorefractor (RM-A7000; Topcon, Tokyo, p compared with d 0.0182* 0.5529 subjective SE Japan) by automatically averaging three measurements of the central 3 mm of the entrance pupil. (3) Finally, three consecutive Data are expressed as means Æ SEM. fi wavefront measurements were performed using the Allegretto *Statistically signi cant. SE ¼ spherical equivalent. wave analyzer (WaveLight Laser Technologies AG, Erlangen, Ger- many). Fogging of the accommodation target was turned off during Compared with subjective manifest refraction in the spherical measurements. An optic zone of 6 mm was chosen for wavefront equivalent, there was a significant myopic shift of cycloplegic analysis. wavefront refraction by À0.14 Æ 0.06 D (p ¼ 0.0182), while cyclo- Through mathematical calculation, the wavefront sphere (SPH) plegic autorefraction was not significantly different from subjective and wavefront cylinder (CYL) can be estimated from the three manifest refraction (p ¼ 0.55). second-order modes: C4 for defocus; C3, and C5 for astigmatism. Both cycloplegic wavefront refraction and autorefraction 8 1 showed good correlations with subjective refraction (Figs. 1 and 2). SPH ¼ C À CYL 2 OZ 4 2 The adjusted R value was 0.9726 for the correlation between cycloplegic autorefraction and subjective manifest refraction, and qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 8 0.9693 for that between cycloplegic wavefront refraction and CYL ¼ C2 þ C2 OZ 3 5 subjective manifest refraction. Cycloplegic autorefraction showed a higher correlation with subjective manifest refraction than where OZ ¼ wavefront diameter. cycloplegic wavefront refraction. On the basis of subjectively sensing the clearest image, subjective The measured astigmatism and calculated difference vector are manifest refraction is therefore considered the gold standard in shown in Table 2. While analyzing astigmatism, the difference from estimating the true refractive status. Wavefront refraction and subjective manifest refraction was 0.44 Æ 0.04 D (p < 0.0001) in the cycloplegic autorefraction were compared with subjective manifest cycloplegic wavefront refraction group and 0.28 Æ 0.05 D refraction, which stood for the true refraction status. Both the (p < 0.0001) in the cycloplegic autorefraction group. The difference spherical equivalent and astigmatism were calculated and com- of astigmatism vector power from subjective refraction was 0.16 D pared. The Alpins method of astigmatism analysis was used for larger in the cycloplegic wavefront refraction group than in the comparing astigmatism [1,2]. The magnitude and the axis of the cycloplegic autorefraction group (p ¼ 0.0039). Using subjective cylinder were converted to vector power [1,2]. The discrepancy of manifest refraction as the standard, astigmatism measured by vector power between wavefront refraction and subjective manifest cycloplegic autorefraction was more precise than that measured by refraction and that between autorefraction and subjective manifest cycloplegic wavefront refraction. refraction were calculated and the assumed residual astigmatism after astigmatism correction in each group was compared. 4. Discussion 2.1. Statistical analysis Several techniques for wavefront sensing are available, such as HartmanneShack and Tscherning systems, Tracey ray-tracing, and Data were expressed as means Æ standard error of the mean. A paired t test was used to compare the spherical equivalent and astigmatism between autorefraction and subjective manifest refraction, and between wavefront refraction and subjective man- ifest refraction, as well as the discrepancy of astigmatism vector power from subjective manifest refraction in cycloplegic wavefront refraction and cycloplegic autorefraction. Simple linear regression was used to study the correlation between the spherical equivalent of wavefront refraction and that of subjective manifest refraction, and between autorefraction and
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