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Abstract
Purpose
To report the distribution of ocular higher-order aberrations in candidates for refractive surgery measured by Zywave® II aberrometer.
Methods
The present study included 232 eyes of 116 subjects. Ocular aberration data were obtained by measurements per eye using Zywave® II aberrometer. The mean Zywave spherical equivalent (SE) and higher order aberrations (HOAs) calculated in the central 6-mm zone and expressed as root mean square (RMS) values were analyzed. Correlation analysis was performed to assess the association between ocular HOAs and gender, age, SE refractive error, or central corneal thickness (CCT) and investigate the aberration symmetry between right and left eyes.
Results
The average SE was −4.67 ± 1.83 diopters (D). The mean RMS values of total HOA, 3rd, 4th or 5th summated HOAs, coma, trefoil and spherical aberration (SA) were 0.421 ± 0.201 gm, 0.346 ± 0.206 gm, 0.202 ± 0.105 gm, 0.087 ± 0.048 gm, 0.241 ± 0.172 gm, 0.225 ± 0.154 gm and 0.136 ± 0.102 gm, respectively. There was no significant differences of the mean total HOA, summated HOAs, coma, trefoil and SA between genders, age and refractive errors, but the 3rd order trefoil was strongly related with myopia (r = −0.900, p = 0.008). There was symmetry of ocular aberrations between both eyes and the ocular aberrations were not correlated with CCT.
References
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Figure 1.
(A) Error bar showing inter-subject averages and standard deviations for all higher order true Zernike coefficients (6-mm pupils). (B) Error bar showing inter-subject averages and standard deviations of all absolute values for higher order Zernike coefficients (6-mm pupil).
Figure 2.
Graph of summated RMS value (horizontal line) ± 1 standard deviation (ends of vertical lines) for 3rd- to 5th-order aberrations (RMS = root mean square; Sph Abb = spherical aberration).
Figure 3.
Scattergrams of total higher order aberration (third to fifth order) as a function of age; RMS = root mean square.
Figure 5.
Scattergram of 3rd trefoil as a function of spherical refractive error; RMS = root mean square.
Table 1.
Signed and absolute values of the Zernike coefficients in the study population
|
Mean ± SD (μm) |
Range (μm) |
|||
|---|---|---|---|---|
| Zernicke Coefficient* | Signed value | Absolute value | Minimum | Maximum |
| 3rd order | ||||
| Z(-3,3) | 0.067 ± 0.23 | 0.172 ± 0.16 | −1.09 | 0.81 |
| Z-1,3) | −0.089 ± 0.25 | 0.190 ± 0.18 | −1.29 | 0.55 |
| Z(1,3) | −0.019 ± 0.14 | 0.105 ± 0.09 | −0.41 | 0.41 |
| Z(3,3) | 0.005 ± 0.14 | 0.110 ± 0.08 | −0.35 | 0.32 |
| 4th order | ||||
| Z(-4,4) | −0.012 ± 0.17 | 0.056 ± 0.05 | −0.37 | 0.21 |
| Z(-2,4) | −0.001 ± 0.05 | 0.038 ± 0.03 | −0.13 | 0.12 |
| Z(0,4) | −0.101 ± 0.14 | 0.136 ± 0.10 | −0.53 | 0.23 |
| Z(2,4) | 0.019 ± 0.08 | 0.064 ± 0.06 | −0.17 | 0.38 |
| Z(4,4) | −0.014 ± 0.09 | 0.065 ± 0.06 | −0.39 | 0.32 |
| 5th order | ||||
| Z(-5,5) | 0.010 ± 0.05 | 0.032 ± 0.04 | −0.14 | 0.32 |
| Z(-3,5) | −0.004 ± 0.04 | 0.030 ± 0.02 | −0.13 | 0.1 |
| Z(-1,5) | 0.004 ± 0.04 | 0.035 ± 0.03 | −0.3 | 0.17 |
| Z(1,5) | 0.004 ± 0.03 | 0.022 ± 0.02 | −0.08 | 0.08 |
| Z(3,5) | 0.007 ± 0.03 | 0.023 ± 0.02 | −0.07 | 0.11 |
| Z(5,5) | 0.006 ± 0.04 | 0.032 ± 0.03 | −0.22 | 0.14 |
Table 2.
Ocular aberrations of the subjects
Table 3.
Correlation between age and higher order aberrations
Table 4.
Correlation between spherical equivalent and higher order aberrations
Table 5.
Comparison of HOAs in present patient population with those in other studies
| Parameter | Current Study (Korea) | Prakash et al12 (India) | Wei et al13 (Singapore) | Salmon and Van de Pol11 (USA)* |
|---|---|---|---|---|
| Sample size | 232 | 412 | 166 | 2,560 |
| Ethnicity | Korean | Indian | Chinese | Mixed |
| Aberrometric principle and instrument used | Hartmann Shack, Zywave II | Hartmann Shack, Zywave | Hartmann Shack, Zywave | Hartmann-Shack, multiple aberrometers |
| HOA RMS | 0.421 ± 0.20 | 0.36 ± 0.266 | 0.49 ± 0.16 | 0.33 ± 0.13 |
| Summated RMS of 3rd to 5th order μm) | ||||
| 3rd order† | 0.346 ± 0.206 | 0.23 ± 0.15 | 0.37 ± 0.16 | 0.25 ± 0.12 |
| 4th order† | 0.202 ± 0.105 | 0.17 ± 0.09 | 0.29 ± 0.11 | 0.169 ± 0.09 |
| 5th order† | 0.087 ± 0.048 | 0.08 ± 0.38 | 0.08 ± 0.04 | 0.067 ± 0.03 |
| Ratio of means of 3rd:4th:5th order | 1:0.58:0.25 | 1:0.7:0.3 | 1:0.78:0.002 | 1:0.68:0.3 |
| Difference (%) of 3rd-5th order means; | ||||
| Korean versus other populations‡ | ||||
| 3rd order† | 33.5 | −6.9 | 27.7 | |
| 4th order† | 15.8 | −43.5 | 16.3 | |
| 5th order† | 8.0 | 8.0 | 22.9 | |
| Major HOAs | ||||
| Coma† | 0.241 ± 0.17 | 0.14 ± 0.10 | 0.27 ± 0.14 | NS |
| Trefoil† | 0.225 ± 0.154 | 0.16 ± 0.12 | NS | NS |
| Spherical aberration† | 0.136 ± 0.102 | 0.03 ± 0.05 | 0.22 ± 0.14 | 0.13 ± 0.09 |
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