Vertical Coma Aberration Research Articles

Ocular higher-order aberrations in a school children population

PurposeThe primary objective of the study was to explore the statistics of ocular higher-order aberrations in a population of primary and secondary school children. MethodsA sample of 557 children aged 10–15 years were selected from two primary and two secondary schools in Heraklion, Greece. Children were classified by age in three subgroups: group I (10.7±0.5 years), group II (12.4±0.5 years) and group III (14.5±0.5 years). Ocular aberrations were measured using a wavefront aberrometer (COAS, AMO Wavefront Sciences, USA) at mesopic light levels (illuminance at cornea was 4lux). Wavefront analysis was achieved for a 5mm pupil. Statistical analysis was carried out for the right eye only. ResultsThe average coefficient of most high-order aberrations did not differ from zero with the exception of vertical (0.076μm) and horizontal (0.018μm) coma, oblique trefoil (−0.055μm) and spherical aberration (0.018μm). The most prominent change between the three groups was observed for the spherical aberration, which increased from 0.007μm (SE 0.005) in group I to 0.011μm (SE 0.004) in group II and 0.030μm (SE 0.004) in group III. Significant differences were also found for the oblique astigmatism and the third-order coma aberrations. ConclusionsDifferences in the low levels of ocular spherical aberration in young children possibly reflect differences in lenticular spherical aberration and relate to the gradient refractive index of the lens. The evaluation of spherical aberration at certain stages of eye growth may help to better understand the underlying mechanisms of myopia development.

근시도가 나이에 따라 유발되는 고위수차의 변화에 미치는 영향

목적: 나이의 증가에 따른 고위수차의 변화를 분석하고, 근시도가 나이와 고위수차 변화와의 상관관계에 미치는 영향을 알아보고자 하였다. 방법: Hartmann-Shack 방식의 LADARWave 장비를 이용하여 20세에서 60세 931안의 고위수차를 분석하였고, 현성굴절검사를 통해 측정된 근시도가 고위수차에 미치는 영향을 분석하였다. 결과: 코마수차, 수직코마수차는 나이가 증가함에 따라 통계적으로 유의하게 감소하였으며, 수직난시수차는 통계적으로 유의하게 증가하였다. 코마수차, 수직코마수차, 구면수차, 수직트레포일수차, 수평트레포일수차, 수직난시수차, 수평난시수차, 수직테트라포일수차와 나이와의 상관관계는 근시도에 의해 영향을 받았으며 수평코마수차와 수평테트라포일수차는 영향을 받지 않았다. 결론: 본 연구에서는 근시도수가 나이에 따라 유발되는 고위수차의 변화에 영향을 줄 수 있음을 밝혔으며 시력교정술이나 시력교정용구 사용 시 시력의 질을 위하여 이의 고려를 제안하고자 한다. Purpose: The present study was aimed to investigate the change of higher-order aberrations induced by aging and the effect of myopic degree on the correlation between age and higher-order aberrations. Methods: The higher-order aberrations in 931 eyes aged from 20 to 60 were measured by using a LADARWave device employing Hartmann-Shack system to analyze the effect of myopic degree measured by manifest refraction test on higher-order aberrations. Results: Coma and vertical coma aberrations were significantly decreased by the increase of myopic degree while vertical astigmatic aberration was significantly increased. The correlations of age and coma, vertical coma, spherical, vertical trefoil, horizontal trefoil, vertical astigmatic, horizontal astigmatic and vertical tetrafoil aberrations depended on the myopic degree, except for horizontal coma and horizontal tetrafoil aberrations. Conclusions: It is suggested to consider the myopic degree for the refractive correction including the laser surgery based on the present result that higher-order aberrations are affected by the myopic degree.

근시도와 고위수차와의 상관관계

목적: 특정 범위의 근시도 및 난시도에서 근시도 변화에 따른 고위수차의 증감 분석을 통해 근시도와 고위수차의 상관관계 알아보고자 하였다. 방법: Hartmann-Shack방식의 LADARWave 장비를 이용하여 총 992 안의 고위수차를 분석하였고, 현성굴절검사로 측정된 근시도값의 증가와 고위수차의 상관관계를 알아보았다. 결과: 전체 실험대상안에서 근시도가 증가함에 따라 총코마수차와 구면수차가 통계적으로 유의하게 증가하였으며, 트레포일 수차, 난시수차, 테트라포일 수차는 감소하였다. 근시도가 작은 군일수록 근시도에 따른 총코마수차의 변화가 더 급격하였으며 근시도가 작은 군에서는 통계적으로도 유의한 변화가 나타났다. 근시도가 -3.00 D 미만인 군은 근시도에 따른 구면수차값의 변화가 크지 않은 반면에 -3.00 D 이상인 군과 -6.00 D 이상인 군에서는 근시도에 따른 변화의 폭이 컸다. 특정 난시도 범위에서 근시도와 고위수차의 상관관계를 알아보았을 때 총코마수차는 난시도가 -1.00 D 이하인 군에서만 통계적으로 유의한 감소가 나타났다. 구면수차의 경우는 난시도가 작은 군일수록 근시도 증가에 따른 구면수차의 증가 폭이 더 커졌으며 모든 난시군에서 통계적으로 유의한 변화가 나타났다. 수평 및 수직코마수차는 특정 근시도 및 특정 난시도군별 일관성있는 증감관계가 성립하지 않았으며 통계적으로도 유의하지 않았다. 결론: 본 논문에서 밝힌 저위수차와 고위수차와의 상관관계를 통하여 시력의 질과 관련된 이해와 시력의 질 향상에 도움을 줄 수 있을 것으로 보여진다. Purpose: The present study was aimed to investigate the correlation between higher-order aberration and myopic degree by the analysis of fluctuation of high-order aberration according to the change of myopic degree in certain ranges of myopia and astigmatism. Methods: The high-order aberration in a total of 992 eyes was analyzed by using a LADARWave device employing Hartmann-Shack system, and the relation between high-order aberration and myopia by the change of myopic degree through manifest refraction test. Results: In all subjects, spherical aberration and total coma aberration were significantly increased by the increase of myopic degree, however, trefoil aberration and astigmatic aberration and tetrafoil aberration were decreased. With the group of lower myopic degree, the change of coma aberration was greater by myopic degree and its change was significantly different. The change of spherical aberration by myopic degree was greatly large in the a group of -3.00 D or more and the group of -6.00 D or more where as its change was not large in the group of lower than -3.00 D. The significant decrease of coma aberration was observed only in the group of astigmatic degree of -1.00 D or less when analyzing the correlation between the higher-order aberrations and myopia in the certain groups of astigmatic degree. In the case of spherical aberration, the significant change was shown in all astigmatic groups, however, its increase was larger with the increase of myopic degree in lower degree of astigmatism. The consistent relationship in variations of horizontal and vertical coma aberration in certain myopic and astigmatic groups was neither established nor statistically significant. Conclusions: It is concluded that the correlation between the higher-order aberration and low-order aberration obtained from the results of the present study can help the understanding related to vision quality and the improvement of vision quality.

Ocular Monochromatic Aberrations in a Rural Chinese Adult Population

To investigate the distribution of monochromatic aberrations in a rural Chinese adult population and the possible effect of aberrations on the development of refractive error. A total of 404 Chinese adults who grew up in rural Yongnian County, Handan City, Northern China, were included. Monochromatic aberrations of left eyes were measured using iTrace Dynamic Laser Refraction at 5.0-mm pupil size without cycloplegia. Mean age of all participants was 49.9 ± 10.5 years (range, 31 to 86 years). Mean spherical equivalent was 0.22 ± 1.14 diopters (D) (range, -7.06 to +3.62 D). With age, the refraction demonstrated a significant hyperopic shift (r = 0.25, p < 0.01). Oblique trefoil (C3), vertical coma (C3), horizontal coma (C3), and spherical aberration (SA) (C4) significantly differed from zero (-0.065 ± 0.133 μm, -0.043 ± 0.161 μm, +0.070 ± 0.115 μm, and +0.058 ± 0.082 μm, respectively). Total root mean square values of higher-order aberrations (HOAs) were 0.296 ± 0.147 μm, with predominant ones of coma (0.180 ± 0.115 μm), trefoil (0.151 ± 0.116 μm), and SA (0.081 ± 0.060 μm). Root mean square values of total HOAs, coma, trefoil, SA, and third- to seventh-order aberrations significantly increased with age (p < 0.01). Total HOAs, SA, coma, and trefoil were not significantly different between hyperopic, emmetropic, and myopic eyes after adjusting for age (p = 0.26, 0.15, 0.24, and 0.28, respectively). Zernike coefficient of SA showed a significant difference between hyperopic (0.076 ± 0.086), emmetropic (0.056 ± 0.079), and myopic (0.028 ± 0.088) eyes (p = 0.00). Ocular refraction in rural Chinese adults showed significantly hyperopic shift with age. Magnitudes of HOAs in rural Chinese adults were similar to that of other populations and significantly increased with age but showed no differences in myopic, emmetropic, and hyperopic adults. The existence of HOAs is not, in itself, sufficient to account for the myopia epidemic in China.

Analysis of Age-Dependence of the Anterior and Posterior Cornea With Scheimpflug Imaging

To assess keratometric and higher-order aberrations of the anterior and posterior cornea and their age-related changes. This study investigated one healthy eye of 227 patients (mean age: 55.15 ± 21.2 years; range: 16 to 90 years; 135 right eyes, 92 left eyes). Images were captured from each eye with Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) using automatic mode. Keratometric, astigmatism data, and corneal higher-order aberrations were analyzed. With respect to laterality, no deviance was found in any of the parameters (P > .05). Mean refractive error was 0.52 ± 0.23 diopters. The level of astigmatism decreased significantly with advancing age for both the anterior and posterior corneal surfaces (P < .05). The overall root mean square of the higher-order aberration increased continuously with age (r = 0.517; P < .01), which can be explained by the combined effect of the increased in both the anterior and posterior corneal root mean square higher-order aberrations. Of the higher-order aberrations, the constant increase of the primary and secondary spherical aberration with aging (P < .01) is caused by the spherical aberration growth of the anterior surface. Apart from these, only the vertical coma aberration of the posterior surface and the vertical trefoil aberrations of both the anterior and posterior surfaces showed a significantly positive correlation with aging (P < .05). Corneal astigmatism showed a significant decrease with aging. Of the higher-order aberrations, primary and secondary spherical aberrations, vertical coma, and vertical trefoil significantly increase with age, whereas other higher-order aberrations show no correlation with aging.

Higher-Order Aberrations and Anisometropia

Purpose/aim: Myopia incidence is increasing around the world. Myopization is considered to be caused by a variety of factors. One consideration is whether higher-order aberrations (HOA) influence myopization. More knowledge of optics in anisometropic eyes might give further insight into the development of refractive error.Materials and methods: To analyze the possible influence of HOA on refractive error development, we compared HOA between anisometropes and isometropes. We analyzed HOA up to the 4th order for both eyes of 20 anisometropes (mean age: 43 ± 17 years) and 20 isometropes (mean age: 33 ± 17 years). HOA were measured with the Shack-Hartman i.Profiler (Carl Zeiss, Germany) and were recalculated for a 4 mm pupil. Mean spherical equivalent (MSE) was based on the subjective refraction. Anisometropia was defined as ≥1 D interocular difference in MSE. The mean absolute differences between right and left eyes in spherical equivalent were 0.28 ± 0.21 D in the isometropic group and 2.81 ± 2.04 D in the anisometropic group. Interocular differences in HOA were compared with the interocular difference in MSE using correlations.Results: For isometropes oblique trefoil, vertical coma, horizontal coma and spherical aberration showed significant correlations between the two eyes. In anisometropes, all analyzed higher-order aberrations correlated significantly between the two eyes except oblique secondary astigmatism and secondary astigmatism. When analyzing anisometropes and isometropes separately, no significant correlations were found between interocular differences of higher-order aberrations and MSE. For isometropes and anisometropes combined, tetrafoil correlated significantly with MSE in left eyes.Conclusions: The present study could not show that interocular differences of higher-order aberrations increase with increasing interocular difference in MSE.

Comparison of wavefront aberrations under cycloplegic, scotopic and photopic conditions using WaveScan

To evaluate the differences of wavefront aberrations under cycloplegic, scotopic and photopic conditions. A total of 174 eyes of 105 patients were measured using the wavefront sensor (WaveScan® 3.62) under different pupil conditions: cycloplegic 8.58 ± 0.54 mm (6.4 mm - 9.5 mm), scotopic 7.53 ± 0.69 mm (5.7 mm - 9.1 mm) and photopic 6.08 ± 1.14 mm (4.1 mm - 8.8 mm). The pupil diameter, standard Zernike coefficients, root mean square of higher-order aberrations and dominant aberrations were compared between cycloplegic and scotopic conditions, and between scotopic and photopic conditions. The pupil diameter was 7.53 ± 0.69 mm under the scotopic condition, which reached the requirement of about 6.5 mm optical zone design in the wavefront-guided surgery and prevented measurement error due to the pupil centroid shift caused by mydriatics. Pharmacological pupil dilation induced increase of standard Zernike coefficients Z(3)(-3), Z(4)(0) and Z(5)(-5). The higher-order aberrations, third-order aberration, fourth-order aberration, fifth-order aberration, sixth-order aberration, and spherical aberration increased statistically significantly, compared to the scotopic condition (P<0.010). When the scotopic condition shifted to the photopic condition, the standard Zernike coefficients Z(4)(0), Z(4)(2), Z(6)(-4), Z(6)(-2), Z(6)(2) decreased and all the higher-order aberrations decreased statistically significantly (P<0.010), demonstrating that accommodative miosis can significantly improve vision under the photopic condition. Under the three conditions, the vertical coma aberration appears the most frequently within the dominant aberrations without significant effect by pupil size variance, and the proportion of spherical aberrations decreased with the decrease of the pupil size. The wavefront aberrations are significantly different under cycloplegic, scotopic and photopic conditions. Using the wavefront sensor (VISX WaveScan) to measure scotopic wavefront aberrations is feasible for the wavefront-guided refractive surgery.

Fellow-eye comparison of 2 aspheric microincision intraocular lenses and effect of asphericity on visual performance

To evaluate visual performance and aberrations with aspheric and spherically neutral microincision intraocular lenses (IOLs) and assess the influence of asphericity on visual performance, wavefront aberration, and depth of focus. St. Thomas' Hospital, London, United Kingdom. Clinical trial and cohort study. In the first study, patients with bilateral cataract were randomized to receive an aspheric Acri.Smart 36A IOL or a spherically neutral Akreos MI60 IOL in the first eye. The other IOL was implanted in the second eye within 3 weeks. Assessments at 3 months were 100% and 9% corrected distance visual acuity (CDVA) and distance-corrected near visual acuity (DCNVA). Aberrations and depth of focus were computed using iTrace software. In the second study, data from the other published study was combined to assess the visual performance, aberration, and depth of focus in groups of spherical, spherically neutral, and negatively aspheric (asphericity -0.17 μm) IOLs. In part 1, there was no difference in 100% or 9% CDVA, DCNVA, or depth of focus between the 2 microincision IOLs. Total spherical aberration was lower with the aspheric IOL. In part 2, the CDVA and DCNVA were not different between the spherical (n = 44), spherically neutral (n = 32), or aspheric (n = 76) IOLs. Total spherical (P<.01) and vertical coma aberrations decreased with increasing IOL asphericity (P<.01). Depth of focus (4.0 mm pupil) also decreased with increasing asphericity and was significant between the spherical IOL and aspheric IOLs. The DCNVA did not differ between groups. Asphericity of IOLs did not affect distance visual acuity. The difference in depth of focus was significant only between negatively aspheric and spherical IOLs. Asphericity differences up to 20 μm did not influence depth of focus.

Dynamic Changes in Ocular Zernike Aberrations and Tear Menisci Measured with a Wavefront Sensor and an Anterior Segment OCT

To measure dynamic change characteristics of spatial and temporal variations in the post-blink tear film of normal eyes. A wavefront sensor was used to measure dynamic changes in wavefront aberrations, up to the seventh order, for 10 seconds in a group of 33 normal young adults. Tear menisci were imaged with an anterior segment optical coherence tomography (AS-OCT) system and tear film break-up times (TFBUTs) were determined. Systematic changes in main axis astigmatism (R(2) = 0.933, P < 0.0001), vertical coma (R(2) = 0.935, P < 0.0001) and spherical aberrations (R(2) = 0.879, P = 0.0002) occurred during the 10-second post-blink period. Both lower tear meniscus height and area increased by 10 seconds compared with the initial levels (P < 0.0001 for each). The change of vertical coma had significant correlation with the increase of lower tear meniscus areas during the 10-second post-blink period (R(2) = 0.181, P = 0.014). Subjects with TFBUTs < 15 seconds had significantly increased main axis astigmatism, vertical coma, and spherical aberrations by 10 seconds. Subjects with longer TFBUTs did not have any significant wavefront aberrations during that period. Systematic changes in some Zernike aberrations after blinking are associated with the changes in tear menisci and TFBUT. There was a substantial individual variation in dynamic changes of Zernike aberrations, suggesting the necessity to explore individual differences in tear quality and tear performance. Dynamic wavefront measurement combined with anterior segment optical coherence tomography could provide a useful tool to understand spatial and temporal processes of the tear film in clinical practice.

Effect of intraocular lens asphericity on vertical coma aberration

To analyze the effect of asphericity of intraocular lenses (IOLs) on vertical coma aberration after implantation of spherical, spherically neutral, and aspheric IOLs. Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom. This observational study recruited patients from previous prospective randomized fellow-eye controlled studies comparing aspheric and spherical IOLs (3 spherical, 1 spherically neutral, and 2 aspheric IOLs). At postoperative follow-up visits, maximum pupil dilation was achieved and aberrometry was performed using an iTrace aberrometer with a pupil scan size of 5.0 mm. Data on Zernike coefficients Z(3,-1) (vertical coma), Z(3,+1) (horizontal coma), and Z(4,0) (spherical aberration) and on IOL power were extracted. Two hundred eyes of 100 patients were recruited. Ninety-two eyes had a spherical IOL, 32 eyes had a spherically neutral IOL, and 76 eyes had an aspheric IOL. Vertical coma Z(3,-1) and spherical aberration Z(4,0) values were highest with the spherical IOLs and lowest with the aspheric IOLs (P = .0163 and P<.0001, respectively). There was no difference in horizontal coma aberration between the 3 IOL groups. There was no correlation between IOL power and vertical coma aberration (r(2) = 0.0135, P = .1169). Conventional spherical IOLs induced more vertical coma than newer aspheric and spherically neutral IOLs. Vertical coma aberration enhances the depth of focus; thus, newer aspheric and spherically neutral designs of IOLs may negatively affect uncorrected near vision.

Customized hydrogel contact lenses for keratoconus incorporating correction for vertical coma aberration

To study the effects on visual performance of a novel custom hydrogel contact lens, which employs a correction for vertical coma aberration, in keratoconic eyes. Six subjects (8 eyes) with mild or moderate keratoconus were recruited for the study. Preliminary measurements included corneal topography, wavefront aberrometry, subjective refraction, visual acuity (VA) and 50% contrast VA. Based on the aberrometry data, customized lenses were made and fitted to the subjects. Evaluation of the on-eye performance of the lenses was carried out, including wavefront aberrometry, over-refraction, VA and 50% contrast VA. In two of the subjects, both eyes were fitted with the customized lenses, and binocular performance was evaluated. Monocular visual performance with a 4 mm pupil, with the lenses worn, was improved, and reached the mean values of -0.003 (LogMar units) of 100% high contrast VA, and 0.049 (in LogMar units) of 50% contrast VA. Vertical coma aberration and total higher-order aberrations (HOAs) were reduced (naked eyes: -0.64 +/- 0.21 root mean square (rms) of vertical coma and 0.86 +/- 0.15 rms of total HOAs; with the lenses worn: -0.29 +/- 0.23 rms of vertical coma and 0.57 +/- 0.17 rms of total HOAs, all for a 4 mm pupil). Binocular VA results from two of the subjects were on average -0.040 (LogMar units) 100% high contrast acuity and -0.060 (LogMar units) 50% contrast visual acuity. Customized hydrogel contact lenses implementing correction of vertical coma, have been found to improve both monocular and binocular visual performance of eyes affected with mild or moderate keratoconus.

Wavefront aberrations in eyes with decentered ablations

To compare the refractive and functional outcomes and wavefront profiles in eyes with decentered ablations and eyes with well-centered ablations. Medical Research Foundation, Chennai, Tamil Nadu, India. This retrospective analysis comprised eyes with topographically diagnosed decentered ablations after laser in situ keratomileusis (LASIK). Refraction, contrast sensitivity, and ocular wavefront aberrations were measured preoperatively and 1 month postoperatively. The induced aberrations in these eyes were compared with those in eyes with well-centered ablations. Forty-six eyes (38 patients) had decentered ablations and 60 eyes (32 patients), well-centered ablations. The mean decentration in the study group was 0.86 mm +/- 0.29 (SD) (range 0.35 to 1.61 mm). There was no significant correlation between decentration and attempted refractive correction. There was, however, a statistically significant (P<.05) linear correlation between the distance of decentration and the magnitude of induced tilt (r = -0.31), coma (r = -0.41), and secondary astigmatism (r = 0.36). The induced changes in tilt, oblique astigmatism, vertical coma, and spherical aberration were statistically significantly higher in eyes with decentered ablations than in eyes with well-centered ablations. A statistically significantly higher percentage of eyes (87%) with well-centered ablations than eyes with decentered ablations (70%) had a postoperative uncorrected visual acuity (UCVA) of 20/20 or better. There was no significant difference in contrast sensitivity between groups. Eyes with decentered ablations had a significantly higher magnitude of induced aberrations and lower UCVA than eyes with well-centered ablations.

Potential Higher-Order Aberration Cues for Sphero-Cylindrical Refractive Error Development

To investigate analytically whether higher-order wavefront errors comprising combinations of trefoil along 30 degrees (trefoil30), vertical coma, and spherical aberration could provide cues to sphero-cylindrical refractive error development. A total of 25 test wavefronts, subdivided into five different types and five levels of higher-order root mean square errors (HO-RMS), were created for the study. One type contained spherical aberration only, producing HO-RMS levels between 0.1 and 0.5 microm. Four wavefront types contained coma, trefoil, and spherical aberration of various sign combinations also producing HO-RMS levels between 0.1 and 0.5 microm. From the 25 wavefronts, refractive power maps were created and 2025 different sphero-cylindrical combinations were added to each refractive power map. For each sphero-cylinder combination, the visual Strehl ratio based on the modulation transfer function (VSMTF) was calculated. Retinal images and refractive power histograms were calculated for the refractive power maps corresponding to the peak of the VSMTF. Spherical aberration affected the best focal plane thereby inducing spherical or defocus cues. The VSMTF produced by vertical coma and trefoil30, in combination with spherical aberration, could be improved with sphero-cylinders of various magnitudes and directions (i.e., with-the-rule, against-the rule, myopic astigmatism, or hyperopic astigmatism). Clinical significance of sphero-cylinders (i.e., >or=0.25 D) was reached at HO-RMS levels between 0.2 and 0.3 microm for a 5-mm pupil zone. In the context of compensatory blur driven eye growth, commonly occurring combinations of the three considered higher-order aberrations have the potential to produce cues to eye growth resulting in myopia and with-the-rule astigmatism.

Influence of eyelid position on wavefront aberrations

To investigate the influence of eyelid position on wavefront aberrations. In study 1, the right eyes of 43 non-cyclopleged subjects were evaluated using the Complete Ophthalmic Analysis System (COAS) aberrometer. In study 2, the right eyes of the 23 cyclopleged subjects were evaluated using the Optical Pathway Difference Scan aberrometer. Measurements were made with wide-open and deliberately narrowed palpebral apertures in these subjects. In study 3, the influence of eyelashes on the COAS output was investigated in 20 subjects by placing artificial eyelashes in front of the eye, in close proximity to the natural eyelashes. For study 1, the total root mean square (RMS) of the third- and fourth-order aberrations with the wide-open lids was significantly different from the narrowed lid position after the correction for multiple comparisons. There was a difference in the Zernike coefficient of the defocus (C4), 90/180 astigmatism (C5), vertical coma (C7) and spherical aberration terms (C12) between the narrowed and wide-open positions. For study 2, changes were observed with the narrowed lid position in the overall RMS of the third and fourth orders, and total coma aberrations, as well as the specific Zernike coefficients of the C5 and C7 terms. However, none of these changes were significant after the multiple comparison correction. The corneal topography also showed remarkable changes in the superior corneal zone. Placing artificial eyelashes in front of the eye significantly affected some Zernike terms and the RMS of the second and fourth orders, and total coma aberrations, for particular pupil sizes. Deliberate narrowing of the palpebral aperture can influence the wavefront aberrations significantly. The corneal curvature distortion in response to eyelid pressure may account for some of the effect on aberration change. Eyelashes interfering with the light path within the pupil zone distort the output from the COAS, causing significant errors.

Effect of total higher-order aberrations on accommodation in pseudophakic eyes

To analyze the effect of total higher-order aberrations (HOAs) on the range of accommodation in pseudophakic eyes and the size of near-vision optotypes. Department of Ophthalmology, Nara Medical University, Nara, Japan. The study comprised 30 patients (44 eyes) who were diagnosed with cataract at Nara University of Medical Science Hospital and Municipal Oyodo Hospital. Inclusion criteria included no other eye disorder and a best corrected distance acuity of 20/20 or better 1 month after cataract surgery. All patients had small-incision phacoemulsification followed by in-the-bag implantation of a monofocal intraocular lens (SA60AT, Alcon). All incisions were self-sealing. Accommodation in pseudophakic eyes was measured by the lens-loading method in an examination room under constant illumination. Ocular HOAs were measured using the KR-9000PW Hartmann-Shack wavefront analyzer (Topcon). The mean patient age was 75.8 years +/- 5.4 (SD) (range 64 to 83 years). The Pearson correlation coefficient (r) showed a significant positive correlation between the range of accommodation and Z7 (vertical coma) for a 4.0 mm pupil using the 1.0 near-vision optotype. There was a significant negative correlation between the range of accommodation and Z12 (spherical aberration) for a 4.0 mm pupil using the 1.0 near-vision optotype (r = .311, P = .040 for Z7;r = -.365, P = .015 for Z12). No other parameter was significantly correlated with the range of accommodation. Measurement of accommodation in pseudophakic eyes by the lens-loading method using the 1.0 near-vision optotype showed that eyes with larger vertical coma aberrations achieved a larger range of accommodation. In contrast, eyes with larger spherical aberrations had smaller amounts of accommodation. The size of the near-vision optotype may affect accommodation analysis in pseudophakic eyes.

Influence of diameter of optical zone ablation on LASIK-induced higher order optical aberrations in myopia

To analyze the effects of optical zone ablation diameter on LASIK-induced higher order optical aberrations in myopia. Four hundred and sixty-one eyes of 236 patients treated with LASIK for myopia were divided into high, moderate and low myopia group according to preoperative spherical equivalent diopter. In each group, eyes were divided into four subgroups according to optic zone ablation diameter. Before and after surgery 6 months, monochromatic wavefront aberrations of each eye were objectively measured using WASCA Analyzer Aberrometer. F test and q test were used to analyze the difference of total high order, horizontal coma, vertical coma, and spherical aberrations among four subgroups in each group at 4, 5, and 6 mm pupil size. Before surgery no significant difference of higher order aberrations among four subgroups was found. After surgery, there was significant difference of total high order, and spherical aberrations among four subgroups. Total high order, and spherical aberrations in larger optical zone ablation diameter subgroup were significantly lower than that in smaller one. The difference was significant at 4, 5, and 6 mm pupil size in high myopia group, and 6 mm pupil size in low myopia group. At 6 mm pupil size, the difference was significant between each subgroup in high myopia group and subgroup I and subgroup IV in low myopia group. There was no significant difference of horizontal coma, and vertical coma aberrations among four subgroups. Optical zone ablation diameter has influence on LASIK-induced higher order optical aberrations. Larger optical zone can decrease total higher order and spherical aberrations after LASIK. The effects are more significant in high myopia group than in low myopia group.

Prediction of flap response

To find predictors of the induced biomechanical and optical effects of lamellar flap creation on the cornea. Optimed Eye and Laser Clinic, Pretoria, South Africa, and the Department of Ophthalmology and Biomedical Engineering Center, The Ohio State University, Columbus, Ohio, and Bausch & Lomb Vision Research Laboratory, Rochester, New York, USA. This prospective study monitored the refractive, wavefront aberration, and corneal topographic changes in 29 eyes of 15 patients for 3 months after the creation of a corneal lamellar flap. The main outcome measures for statistical analysis were refraction, total corneal thickness, residual corneal bed thickness, horizontal white-to-white corneal diameter, horizontal flap diameter, topography data, and wavefront data. Statistically significant changes were seen in the autorefraction mode. Wavefront data showed significant change in 4 Zernike modes-90/180-degree astigmatism, vertical coma, horizontal coma, and spherical aberration. The topography data indicated the corneal biomechanical response was significantly predicted by stromal bed thickness in the early follow-up period and by total corneal pachymetry and flap diameter in a 2-parameter statistical model in the late follow-up period. Uncomplicated lamellar flap creation is responsible for systematic changes in corneal topography and induction of higher-order optical aberrations. Predictors of this response include stromal bed thickness, flap diameter, and total corneal pachymetry.