Astigmatism In Group Research Articles

Distribution and compensation mechanism of aberrations between anterior and posterior surface of the cornea in myopia and myopic astigmatism eyes

Objective: To study the compensation mechanism of aberrations between anterior and posterior corneal surface, and to investigate the correlations between corneal aberrations and K values, intraocular pressure and central corneal thickness. Methods: One hundred and sixty-one subjects (300 eyes) with myopia and myopic astigmatism were recruited randomly. Corneal aberrations (anterior, posterior and total) in three different optical zones (2 mm, 4 mm, and 6 mm) centered on the corneal vertex were assessed with a corneal topographer (Sirius). We also calculated compensation factors (CFs) as a measure of the relative efficiency of the aberration compensation mechanism. Astigmatism was divided into corneal astigmatism and non-corneal astigmatism. Mann-Whitney U test was utilized for the comparison of different aberrations and CFs between the two astigmatism groups. Spearman correlation was applied to analyze the correlations between corneal aberrations and K values, intraocular pressure and central corneal thickness. Results: As the order of the aberrations elevated from the second to the seventh, the RMS values decreased significantly. The larger the optical zone, the greater the values of aberrations and the lower the percentage of the compensation mechanism among all the Zernike terms. At the same time, as the order of the aberrations increased, the predominance of the compensation mechanism was increasingly obvious. Slight compensation of spherical aberration (Z40) was observed in the peripheral. In the center of the analyzing zones (2 mm), compensation mechanism represented in coma (Z3±1), and it disappeared in the peripheral. We detected slight compensation of the corneal astigmatism (Z2±2) in the surrounding zone, although the compensation factors were closed to zero in diverse optical zones. Superposition was found in trefoil (Z3±3) straightly. Nevertheless, a tendency towards compensation was discovered with the enlargement of the optical zones. And the secondary spherical aberration (Z60) behaved compensation continuously. However, similar compensation was discovered between the right eye and left eye in different analyzing optical zones. There were significant correlations between the flattest K values and Z2±2, Z3±3and Z40 in the anterior, posterior and total cornea. It was similar with the steepest K values. When the optical zone expanded to 6 mm, Z3±1 and Z40 significantly decreased with intraocular pressure (rcoma=-0.188, P<0.05. rspherical=-0.147, P<0.05). No correlation was found between various aberrations and central corneal thickness (P>0.05). Conclusions: Compensation dominated in the corneal center, while the percentage decreased gradually as the optical zone extended. Slight compensation in astigmatism and spherical aberration between the anterior and posterior cornea may be benificial to the scotopic visual quality. Corneal aberrations were significantly related to K values and intraocular pressure. (Chin J Ophthalmol, 2016, 52: 840-849).

Refractive error characteristics in patients with congenital blepharoptosis before and after ptosis repair surgery.

BackgroundWe examined the effect of surgical repair on the pattern of refractive errors in Korean patients with congenital blepharoptosis.MethodsWe reviewed the clinical records of 54 patients with congenital blepharoptosis who attended our hospital from 2006 to 2012 and underwent a detailed refractive examination before and after ptosis repair surgery. Among them, 21 of the patients whose refractive data was available for both before and after the surgery were included in order to observe the effect of ptosis repair surgery on refractive error characteristics. The astigmatism groups were divided into three subgroups: with-the-rule (WTR), against-the-rule (ATR), and oblique astigmatism (OA). We also evaluated the severity of astigmatism.ResultsBefore surgery, the ptotic eyes had more severe astigmatism and a greater percentage of OA than the fellow eyes. The changes in astigmatism magnitude before and after surgery were not significant, but the proportion of subjects with OA increased significantly. In ptotic eyes, amblyopia was found in 14 eyes (20.9 %). 3 eyes (4.5 %) were from solely occlusive visual stimulus deprivation due to severe ptosis, and 11 eyes were from refractive errors. Among refractive errors, amblyogenic astigmatism made up to the largest proportion of patients (8 patients, 11.9 %).ConclusionsPtotic eyes had more severe astigmatism and more OA than fellow eyes. Amblyogenic astigmatism was more common in ptotic eyes. A change in astigmatism toward the OA axis was significantly detected after surgery, and that can be possible amblyogenic cause. Therefore, the correction of astigmatism before and after ptosis repair surgery is very important to prevent amblyopia.

Longitudinal Changes in Refractive Error in a Pediatric Referral Population in Korea.

To investigate changes in the spherical equivalent (SE) refractive error and astigmatism in a pediatric referral population in Korea with longitudinal follow-up and to evaluate the effect of risk factors on changes in refractive error. This was a retrospective case series. In total, 221 patients who presented to a tertiary care hospital when aged 3 to 9 years and who underwent at least 10 years of follow-up were enrolled. The patients were divided into groups in terms of the initial extent of SE refractive error, the initial extent of astigmatism, sex, and ocular alignment. Changes in SE and astigmatism were compared among the groups. The patients were followed up for a mean of 11.19 ± 1.81 years. An overall negative shift in SE refractive error and increasing tendency in astigmatism during the follow-up period were noted. The negative shift in SE refractive error in the myopia group was significantly greater than those in the emmetropia and hyperopia groups. The change in astigmatism in the myopia group was significantly greater than that in the hyperopia group. The change in astigmatism in the low astigmatism group was significantly greater than those in the moderate and high astigmatism groups. Sex did not influence the changes in SE refractive error or astigmatism. A pediatric referral population in Korea showed a negative shift in SE refractive error and increasing tendency in astigmatism during childhood. Changes in refractive error may be influenced by the initial degree of SE refractive error and astigmatism. [J Pediatr Ophthalmol Strabismus. 2017;54(1):43-51.].

Threshold limit of postoperative astigmatism for patient satisfaction after refractive lens exchange and multifocal intraocular lens implantation

To determine the degree of tolerance toward different magnitudes of residual refractive astigmatism and corneal astigmatism and the angles of corneal astigmatism after implantation of an asymmetric multifocal intraocular lens (IOL). Cathedral Eye Clinic, Belfast, United Kingdom. Retrospective comparative case series. The study enrolled patients having refractive lens exchange and implantation of a Lentis Mplus LS-312 MF30 IOL. Uncorrected (UDVA) and corrected distance visual acuities, uncorrected near and intermediate visual acuities, and quality-of-vision questionnaires were evaluated. Groups were categorized based on the magnitude of refractive astigmatism and corneal residual astigmatism. Refractive astigmatism of less than 0.50 diopter (D) and more than 0.50 D and corneal astigmatism of 0.50 D or less, 0.51 to 0.75 D, 0.76 to 1.00 D, and more than 1.00 D were categorized. The study comprised 117 patients (234 eyes). There was a significant difference in UDVA (P=.003), refractive sphere (P=.001), and defocus equivalent (P≤.001) between the residual refractive astigmatism groups; however, there was no difference in quality of vision (P=.28). The same was found for corneal astigmatism with UDVA (P≤.001) and quality of vision (P=.16). The angle of corneal astigmatism in relation to IOL placement did not statistically affect postoperative outcomes. The IOL appeared to subjectively tolerate residual astigmatism well despite a statistically significant difference in UDVA with higher magnitudes of residual astigmatism. The angle of residual corneal astigmatism in relation to IOL placement did not have a significant effect on postoperative outcomes. None of the authors has a financial or proprietary interest in any material or method mentioned.

Evaluation of Opposite Clear Corneal Incision in Controlling Astigmatism in Cataract Patients Undergoing Phacoemulsification Surgery

Aim: To evaluate the role of clear corneal incision combined with opposite clear corneal incision in controlling astigmatism in patients undergoing phacoemulsification surgery for cataract. Design: Prospective clinical study. Methods: 45 consecutive patients planned for phacoemulsification were divided into three equal groups of fifteen patients each: Group 1 presenting without corneal astigmatism, Group 2 having WTR (with-the-rule) and Group 3 having ATR (against-the-rule) astigmatism. All underwent phacoemulsification through 2.8mm clear corneal incision. In Group 1 the temporal clear corneal incision (CCI) was enlarged to 3.2mm before IOL insertion along with 2.2mm superior CCI to neutralise the astigmatism induced by main cataract incision. In Group 2 the superior CCI was enlarged to 3.2mm before IOL insertion, followed by 3.2mm inferior opposite CCI. In Group 3 the temporal CCI was enlarged to 3.2mm before IOL insertion followed by 3.2mm nasal opposite CCI. Results: In Group 1, the overall mean postoperative astigmatism observed was 0.28 ± 0.2D WTR, with 4 out of 15 patients (26.66%) continuing to have nil astigmatism. In Group 2, the mean postoperative astigmatism was reduced from 1.16 ± 0.32D WTR preoperatively, to 0.46 ± 0.28D WTR at 3 months postoperatively. In Group 3, the preoperative astigmatism of -1.25 ± 0.32DATR reduced to -0.38 ± 0.31D ATR, 3 months postoperatively. The reduction in astigmatism was statistically significant in both WTR and ATR astigmatism groups (p < 0.001). Conclusion: More than 50% reduction in astigmatism was achieved in both groups with astigmatism. Thus opposite clear corneal incision (OCCI) is a simple, predictable, safe and effective procedure in reducing mild to moderate preexisting corneal astigmatism in cataract surgery.

Topography-Guided Transepithelial Surface Ablation in the Treatment of Moderate to High Astigmatism.

To analyze the outcomes of treatment of astigmatism of 2.00 diopters (D) or greater with topography-guided transepithelial surface ablation. Retrospective analysis of a series of 206 eyes divided into two groups: myopic astigmatism (153 eyes) and mixed astigmatism (53 eyes). All cases were treated with topography-guided transepithelial surface ablation. Efficacy, safety, and predictability were evaluated, and vector analysis of cylindrical correction was performed. The median preoperative spherical equivalent was -2.63 and -0.63 D for the myopic and mixed astigmatism groups, respectively, with median cylinder of -2.50 D. Postoperative uncorrected distance visual acuity was 20/20 or better in 92% and 83% of eyes in the myopic and mixed astigmatism groups, respectively; the corresponding efficacy indices were 1.00 and 0.96 and residual astigmatism of 0.50 D or less was present in 82.4% and 56.7% of eyes in the myopic and mixed astigmatism groups, respectively. The arithmetic mean magnitude of the difference vector was 0.38 (myopic) and 0.65 (mixed) D. Difference vector magnitude was positively correlated with the magnitude of target induced astigmatism in both groups. The geometric mean coefficient of adjustment index was 1.04 and 1.19, representing undercorrection of 4% and 19% in the myopic and mixed astigmatism groups, respectively. Topography-guided transepithelial ablation is a safe, effective, and predictable treatment for moderate to high astigmatism. [J Refract Surg. 2016;32(6):418-425.].

Higher Order Aberration and Astigmatism in Children with Hyperopic Amblyopia.

PurposeTo investigate the changes in corneal higher-order aberration (HOA) during amblyopia treatment and the correlation between HOA and astigmatism in hyperopic amblyopia children.MethodsIn this retrospective study, a total of 72 eyes from 72 patients ranging in age from 38 to 161 months were included. Patients were divided into two groups based on the degree of astigmatism. Corneal HOA was measured using a KR-1W aberrometer at the initial visit and at 3-, 6-, and 12-month follow-ups. Correlation analysis was performed to assess the association between HOA and astigmatism.ResultsA total of 72 patients were enrolled in this study, 37 of which were classified as belonging to the higher astigmatism group, while 35 were assigned to the lower astigmatism group. There was a statistically significant difference in success rate between the higher and lower astigmatism groups. In both groups, all corneal HOAs were significantly reduced during amblyopia treatment. When comparing the two groups, a significant difference in coma HOA at the 12-month follow-up was detected (p = 0.043). In the Pearson correlation test, coma HOA at the 12-month follow-up demonstrated a statistically significant correlation with astigmatism and a stronger correlation with astigmatism in the higher astigmatism group than in the lower astigmatism group (coefficient values, 0.383 and 0.284 as well as p = 0.021 and p = 0.038, respectively).ConclusionsHOA, particularly coma HOA, correlated with astigmatism and could exert effects in cases involving hyperopic amblyopia.

Apparent accommodation in pseudophakic eyes with refractive against-the-rule, with-the-rule and minimum astigmatism

AimTo compare the magnitude of apparent accommodation in pseudophakic eyes with refractive against-the-rule (ATR), with-the-rule (WTR) and minimum astigmatism. Factors associated with apparent accommodation were also examined in each group.MethodsIn...

The Unevenness and Non-orthogonal State of Distribution of Corneal Thickness and the Influence on Correction of Myopic Astigmatism by LASEK

To observe and calculate the unevenness and the non-orthogonal state of distribution of corneal thickness and the relationshipbetween them using Pentacam and to investigate the influence of unevenness and the non-orthogonal state on correction of myopic astigmatism by laser subepithelial keratomileusis (LASEK). 230 eyes with myopic astigmatism treated with LASEK were divided into two groups: 114 eyes as the low astigmatism group (-0.25 to -0.75 DC) and 116 eyes as the midrange-high astigmatism group (-1.00 to -4.50 DC). With the help of the diagram of keratoconus evaluation program of the Pentacam, the D 3.0 and D 6.5 were calculated for the index of distribution of unevenness of the corneal thickness, and the absolute value of the angle between the maximum and minimum progression-index orientation (M 90) for the index of non-orthogonal states. The correction of myopic astigmatism by LASEK was based on standard vector analysis and power vector analysis. The follow-up period was for 3months. The preoperative M 90 was 22.14°±20.87°, D 6.5 was 58.66±21.32μm, and D 3.0 was 16.11±4.28μm for the 230 eyes that were tested. The D 6.5 of low astigmatism group (55.62±20.81)μm was significantly lower than that of midrange-high astigmatism group (61.65±21.48)μm (P<0.05). Of the 230 eyes, the M 90 was positively correlated with D 6.5 (r=0.37, P<0.001), and D 6.5 was positively correlated with D 3.0 (r=0.56, P<0.001). 3months postoperatively, the absolute error vector (|EV|) of low astigmatism group (0.46±0.34) was significantly lower than that of midrange-high astigmatism group (0.53±0.29) (P<0.01). The error of magnitude of low astigmatism group (-0.10±0.31) was significantly lower than that of midrange-high astigmatism group (0.08±0.41) (P<0.001). The absolute error of angle (|EA|)of low astigmatism group (26.10±27.24) was significantly higher than that of midrange-high astigmatism group (9.99±17.32) (P<0.001). The correction ratio of low astigmatism group (1.45±1.21) was significantly higher than that of midrange-high astigmatism group (0.94±0.33) (P<0.01). The error ratio (ER) of low astigmatism group (1.34±1.40) was significantly higher than that of midrange-high astigmatism group (0.42±0.27) (P<0.001). In low astigmatism group, M 90 was positively correlated with |EV| (r=0.30, P<0.001). In midrange-high astigmatism group, M 90 was positively correlated with ER (r=0.31, P<0.001) and D 6.5 was positively correlated with |EV| and B, respectively (r=0.34, 0.33, P<0.001). The relationship between unevenness and non-orthogonal state of distribution of corneal thickness could influence the correction of astigmatism by LASEK. Therefore, more attention should be paid to the correction of midrange-high astigmatism group by excimer surgery.

Distribution of posterior corneal astigmatism according to axis orientation of anterior corneal astigmatism.

PurposeTo investigate the distribution of posterior corneal astigmatism in eyes with with-the-rule (WTR) and against-the-rule (ATR) anterior corneal astigmatism.MethodsWe retrospectively examined six hundred eight eyes of 608 healthy subjects (275 men and 333 women; mean age ± standard deviation, 55.3 ± 20.2 years). The magnitude and axis orientation of anterior and posterior corneal astigmatism were determined with a rotating Scheimpflug system (Pentacam HR, Oculus) when we divided the subjects into WTR and ATR anterior corneal astigmatism groups.ResultsThe mean magnitudes of anterior and posterior corneal astigmatism were 1.14 ± 0.76 diopters (D), and 0.37 ± 0.19 D, respectively. We found a significant correlation between the magnitudes of anterior and posterior corneal astigmatism (Pearson correlation coefficient r = 0.4739, P<0.001). In the WTR anterior astigmatism group, we found ATR astigmatism of the posterior corneal surface in 402 eyes (96.6%). In the ATR anterior astigmatism group, we found ATR posterior corneal astigmatism in 82 eyes (73.9%). Especially in eyes with ATR anterior corneal astigmatism of 1 D or more and 1.5 D or more, ATR posterior corneal astigmatism was found in 28 eyes (59.6%) and 9 eyes (42.9%), respectively.ConclusionsWTR anterior astigmatism and ATR posterior astigmatism were found in approximately 68% and 91% of eyes, respectively. The magnitude and the axis orientation of posterior corneal astigmatism were not constant, especially in eyes having high ATR anterior corneal astigmatism, as is often the case in patients who have undergone toric IOL implantation.

Assessment of aberrations and visual quality differences between myopic and astigmatic eyes before and after contact lens application.

OBJECTIVE:To evaluate the aberration and visual quality differences between myopic and astigmatic eyes before and after contact lens application by using corneal aberrometer and low- contrast sensitivity chart.METHODS:Eighty eyes of 40 patients were included in this study. Patients were divided into two groups as myopic (40 eyes, n=20) and astigmatic groups (40 eyes, n=20). We used aspheric Balafilcon A (Purevision and Purevision Toric Bausch&Lomb, Rochester, USA) lenses for each group. Corneal aberrations and low-contrast sensitivity values were measured and compared for each patient in both groups.RESULTS:There were no statistically significant differences between myopic and astigmatic groups when we compared low-contrast sensitivity values for both on- and off-eyes. Mean total higher-order aberration (HOA) values for off-eye, were 0.29±0.10 μm, and 0.33±0.10 μm for on-eye in the myopic group, while they were 0.42±0.14 μm in off-eye and 0.37±0.23 μm in on-eye in the astigmatic group. Off-eye mean coma, irregular astigmatism and total higher-order aberration RMS (root-mean-square) values were significantly higher in the astigmatic group compared to the myopic group (p=0.006, p=0.001, p=0.001) but mean on-eye RMS values were not.CONCLUSION:Myopic and astigmatic patients differ in terms of high-order aberrations and these differences cannot be equalized after contact lens application, but visual quality can be improved in both patients by using contact lenses.

The Change in Corneal Astigmatism after Cataract Surgery in Patients with Small Amount of Astigmatism

Purpose: To analyze the change in posterior corneal astigmatism and total corneal astigmatism in patients with anterior corneal astigmatism less than 1.0 diopter (D). Methods: In the present study we evaluated 52 eyes with anterior corneal astigmatism less than 1.0 D. Patients were divided into 2 groups according to steep axis: Group 1 included 33 eyes with within-the-rule (WTR) astigmatism and Group 2 included 19 eyes with against-the-rule (ATR) astigmatism. Anterior, posterior and total corneal astigmatism were measured using Scheimpflug imaging (Pentacam). Results: In Group 1, preoperative anterior astigmatism, posterior astigmatism and total astigmatism were 0.55 ± 0.44 D, 0.31 ± 0.14 D and 0.30 ± 0.72 D, respectively. At postoperative 2 months, anterior astigmatism, posterior astigmatism and total astigmatism were 0.51 ± 0.67 D, 0.31 ± 0.15 D and 0.35 ± 0.81 D, respectively. There was no statistically significant difference between preoperative and postoperative anterior, posterior and total corneal astigmatism in Group 1. In Group 2, preoperative anterior astigmatism, posterior astigmatism and total astigmatism were -0.48 ± 0.46 D, 0.26 ± 0.09 D and -0.51 ± 0.65 D, respectively. At postoperative 2 months, anterior astigmatism, posterior astigmatism and total astigmatism were -0.17 ± 0.68 D, 0.25 ± 0.13 D and -0.30 ± 0.55 D, respectively. There was no statistically significant difference between preoperative and postoperative anterior, posterior and total corneal astigmatism in the 2 groups. There was no statistical correlation between preoperative posterior corneal astigmatism and postoperative 2 months total corneal astigmatism. After vector analysis, surgically induced astigmatism (SIA) of the anterior and total astigmatism in Group 1 were 0.03 D @ 30° and 0.07 D @ 74°, respectively, and in Group 2 were 0.27 D @ 100° and 0.36 D @ 86°, respectively. Conclusions: In patients with preoperative total corneal astigmatism less than 1.0 D, posterior corneal astigmatism had a small effect on postoperative total corneal astigmatism. J Korean Ophthalmol Soc 2015;56(11):1712-1719

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.

Relationship between the distance from thinnest point to pupil center and unevenness of corneal thickness and the influence of the unevenness on correction of astigmatism by LASEK

Objective To observe relationship between the distance from thinnest point to pupil center (DTP) and unevenness of distribution of corneal thickness using Pentacam,and to investigate influence of unevenness of distribution on the correction of astigmatism by LASEK.Methods One hundred and six myopic astigmatism eyes treated with LASEK were divided into two groups,low-midrange astigmatism (-0.25D～-2.00D) group and high astigmatism (-2.25D～-4.00D) group.The following-up period was for 6 months.The DTP,and the unevenness of distribution of corneal thickness of 3.0mm (D3.0mm) and 6.5ram (D6.5mm) area were calculated.The correction of myopic astigmatism by LASEK based on standard vector analysis was evaluated.Results The DTP was (0.64±0.23) mm,D6.5mm was (55.61±18.57) tm and D3.0mm was (16.71±4.45) μm in 106 eyes.The D6.5mm of low-midrange astigmatism group was significant lower than that of high astigmatism group (P ＜0.05).In 106 eyes,the DTP was positively correlated with D6.5mm and D3.0mm respectively (r =0.43,0.49,P ＜0.01).The D6.5mm was positively correlated with D3.0mm (r =0.42,P ＜0.01).The | EV | (absolute error vector) of low-midrange astigmatism group was significant lower than that of high astigmatism group (P ＜0.05).The | EV | of high astigmatism group was positively correlated with D6.5mm (r =0.47,P ＜0.05).Conclusions The distance from thinnest point to pupil center is correlated with the unevenness of distribution of corneal thickness.The unevenness of distribution of corneal thickness may influence the outcome of correction of myopia with high astigmatism by LASEK. Key words: Corneal thickness ; Pupil ; Vector analysis ; Astigmatism ; Excimer laser ;

굴절이상 교정상태에 따른 동적시력 변화

목적: 남녀 대학생의 동공크기, 손의 반응력, 굴절이상, 교정시력, 우위안, 정지시각(static visual angle, SVA), 동적시력(kinetic visual acuity, KVA)등을 비교 분석하고, 굴절이상이 완전교정 된 상태에서 남녀 대학생의 KVA를 측정하고, 완전교정상태에 구면굴절력 <TEX>${\pm}0.50 $</TEX>D를 각각 변화시켜 KVA을 측정하여 변화를 알아보고자 하였다. 방법: 안경광학과 남학생 40명, 여학생 40명을 대상으로 KVA 측정장치(KOWA AS-4A)와 손의 반응력 측정 프로그램, 자 타각적 굴절검사기기 등을 이용하여 KVA, SVA, 동공크기, 손의 반응력, 굴절이상, 교정시력, 우위안 등을 측정하였고, 양안 구면굴절력을 <TEX>${\pm}0.50$</TEX> D 변화시켜 KVA를 측정하였다. 결과: 전체 대상자의 양안 KVA는 <TEX>$0.45{\pm}0.22$</TEX>이고, 단안은 우안 <TEX>$0.36{\pm}0.19$</TEX>, 좌안 <TEX>$0.34{\pm}$</TEX>0.19로 양안이 단안보다 유의하게 높게 나타났다. SVA가 좋을수록 KVA가 유의하게 좋은 것으로 나타났으며, 굴절이상은 근시량이 작을수록 KVA가 좋았으나 통계적으로 유의하지 않았다. 난시에서는 -1.00 D 이하와 초과로 나눌 때 난시가 작을수록 KVA가 유의하게 좋았다. 굴절이상 교정상태에 따른 KVA는 완전교정일 때 <TEX>$0.45{\pm}0.22$</TEX>, 완전교정에 +0.50 D 추가할 때 <TEX>$0.26{\pm}0.15$</TEX>, 완전교정에 -0.50 D 추가할 때 <TEX>$0.48{\pm}0.22$</TEX>로 근시 교정을 강하게 할 때가 유의수준에서 KVA가 가장 높게 나타났으며, 다음으로 완전교정, 근시 저교정의 순으로 낮게 나타났다. 또한 남녀로 구별하여 비교해 볼 때도 유사한 결과를 나타냈으며 남자가 여자보다 KVA가 좋은 것으로 나타났다. KVA와 우위안 비우위안 차이는 없었다. 결론: 따라서, KVA는 원거리 SVA, 난시량, 굴절이상량과 관계가 있는 것을 알 수 있었으며, 우위안과는 관계가 없었다. KVA를 높이는 굴절이상 처방은 완전교정 또는 근시방향에서 약간 과교정 하는 것이 효과적인 것을 알 수 있었다. Purpose: This study are to analyze and to compare between pupillary size, reaction time, refractive error, corrected vision, dominant eye, static visual angle (SVA) and kinetic visual acuity (KVA) of male and female college students, to measure KVA of them in full correction and to identify changes of KVA by +0.50 D and -0.50 D spherical power addition respectively in full correction condition. Methods: KVA, SVA, pupillary size, reaction time, refractive error, corrected vision and dominant eye of 40 male and 40 female optical science students were measured by utilizing KOWA AS-4A, reaction time measurement program, subjective refractometer, and objective refractometer, and KVAs were measured when +0.50 D/-0.50 D were added in both eyes respectively. Results: Binocular KVA of whole subjects was <TEX>$0.45{\pm}0.22$</TEX>, and in monocular KVAs were <TEX>$0.36{\pm}0.19$</TEX> for right eye and <TEX>$0.34{\pm}0.19$</TEX> for left eye, and binocular KVA was significantly higher than monocular KVA. It appeared that the better SVA was, the better KVA was in significant way, and in terms of refractive error the less myopia amount was, the better KVA was, but it was not significant statistically. The lower astigmatism was, the slightly and significantly higher KVA was when dividing between equal or less than -1.00 D astigmatism group and over -1.00 D astigmatism group. In resulting from correction condition of refractive error KVAs were <TEX>$0.45{\pm}0.22$</TEX> for full correction, <TEX>$0.26{\pm}0.15$</TEX> for +0.50 D addition, <TEX>$0.48{\pm}0.22$</TEX> for -0.50 D addition which indicates that KVA in over myopia correction was significantly the highest and followed by full correction and under correction. Similar findings were revealed in both male and female, and KVA of male was better than female in comparing between male and female. There was no significantly different KVA between dominant eye and non-dominant eye. Conclusions: Accordingly, it is concluded that KVA is related with far distance SVA, astigmatism amount, and refractive error amount except a dominant eye. Through this research, it was found that prescription for enhancing KVA is to make full correction or to overcorrect slightly myopia.

Standardized vector analysis of correction of astigmatism after Epi-LASIK

Objective To evaluate the correction of astigmatism after Epi-LASIK (epipolis laser in situ keratomileusis) by standardized vector analysis,and to investigate the factors that affect the outcome of correction.Methods Sixty-eight myopic astigmatism eyes treated with Epi-LASIK were divided into two groups,low-midrange astigmatism (0.00D ～-2.00D) group and high astigmatism (-2.25D ～-4.00D) group.The following-up period was for 6 months.The astigmatism status wasevaluated based on the standardized vector analysis which was recommended by the American National Standards Institute.Results The CR (correction ratio) was positively correlated with IRC (absolute intended refractive correction) (r =0.82,P ＜0.05).The ER (error ratio) was negatively correlated with IRC (r =-0.61,P ＜0.05).The EA (absolute error of angle) was negatively correlated with IRC (r =-0.74,P ＜0.05).The EV (absolute error vector) of low-midrange astigmatism group was significant lower than that of high astigmatism group (P ＜0.05).The EM (error of magnitude) of low-midrange astigmatism group was-0.12±0.15 and EM of high astigmatism group was-0.14±0.42.Conclusions The effectiveness of the correction of astigmatism after Epi-LASIK is closely correlated with that of axis alignment of astigmatism,and the diopter of astigmatism which is set as surgery parameter shall be transferred from spectacle to corneal plane according to the vertex distance of manifest refraction. Key words: Vector analysis; Astigmatism; Epi-LASIK

Developmental Changes in Anterior Corneal Astigmatism in Tohono O’odham Native American Infants and Children

ABSTRACTPurpose: To describe change in corneal astigmatism in infants and children of a Native American tribe with a high prevalence of astigmatism.Methods: Longitudinal measurements of corneal astigmatism were obtained in 960 Tohono O’odham children aged 6 months to <8 years. Change in corneal astigmatism (magnitude (clinical notation), J0, J45) across age in children with high astigmatism (≥2 diopter (D) corneal astigmatism) or low/no astigmatism (<2 D corneal astigmatism) at their baseline measurement was assessed.Results: Regression analyses indicated that early in development (6 months to <3 years), astigmatism magnitude decreased in the high astigmatism group (0.37 D/year) and remained stable in the low/no astigmatism group. In later development (3 to <8 years), astigmatism decreased in the high (0.11 D/year) and low/no astigmatism groups (0.03 D/year). In 52 children who had data at all three of the youngest ages (6 months to <1 year, 1 to <2 years, 2 to <3 years) astigmatism decreased after infancy in those with high astigmatism (p = 0.021), and then remained stable from age 1–2 years, whereas astigmatism was stable from infancy through age 1 year and increased from age 1–2 years in the low/no astigmatism group (p = 0.026). J0 results were similar, but results on J45 yielded no significant effects.Conclusions: The greatest change occurred in highly astigmatic infants and toddlers (0.37 D/year). By age 3 years, change was minimal and not clinically significant. Changes observed were due primarily to change in the J0 component of astigmatism.

Astigmatism correction with toric intraocular lenses: wavefront aberrometry and quality of life

Background/aimTo evaluate wavefront aberrations and subjective quality of life after toric intraocular lens (TIOL) implantation.MethodsThree groups of subjects who underwent unilateral cataract surgery with intraocular lens (IOL) implantation were compared:...

Ocular and systemic associations of against-the-rule astigmatism in children from tertiary ophthalmology clinic

Ocular and systemic associations of against-the-rule astigmatism in children from tertiary ophthalmology clinic

Anterior segment study with the pentacam scheimpflug camera in refractive surgery candidates

Purpose:The purpose of this study was to evaluate the anterior segment measurements according to refractive status in a sample of the Iranian population.Setting:Rassoul Akram Hospital, Tehran University of Medical Sciences.Material and Methods:In this study, refractive surgery candidates were assigned according to the refractive error to one of three groups : emmetropia, myopia, and hyperopia. Myopic eyes were further divided to four subgroups : simple myopic group, simple myopic astigmatism group, high myopic group, and high myopia with astigmatism group. Anterior segment measurements with the Pentacam Scheimpflug system were performed in the right eye of all subjects.Results:The study sample was comprised of 283 subjects with a mean age of 29.1 ± 7.5 (standard deviation) years. Mean keratometry reading, Anterior chamber depth (ACD) and volume measurements were significantly higher in the myopic group and mean keratometry reading and anterior chamber angle measurements were significantly lower in the hyperopic group (P < 0.05, all comparisons). Maximum anterior elevation (AEmax) and maximum posterior elevation (PEmax), Q value, progression index, minimum corneal thickness, and corneal volume measurements were similar for all groups (P > 0.05, all comparisons). In the myopic subgroups, AEmax and PEmax and maximum keratometry (Kmax) were significantly higher, and ACD was lower in the astigmatic groups (P < 0.05, all comparisons). The Q value was less negative in low myopia (P < 0.05).Conclusions:Myopic eyes had steeper corneas than hyperopic eyes and anterior chamber measurements were significantly higher in the myopic eyes. In myopic eyes, AEmax and PEmax and Kmax measurements were higher, and ACD measurements were lower in the astigmatic groups.