Against-the-rule Research Articles

Astigmatism in underserved rural areas: a population based study.

Studying the prevalence of astigmatism and its related factors in underprivileged rural areas in Iran. Using random cluster sampling, two rural areas in the north and southwest of Iran were randomly selected, and 3851 persons over 1year of age were invited to the study. In addition to recording demographics, retinoscopic refraction was conducted using baseline auto-refraction results. The prevalence of astigmatism was determined based on cylinder error cut-off points of 0.50dioptre (D), 1.00, 2.00 and 3.00D. Multiple logistic regression was used to assess variables' relationship with astigmatism. The prevalence of astigmatism as a cylinder error greater than 0.50D was 35.6% (95% CI: 33.7-37.6); this was 34.0% (95% CI: 31.4-36.6) in women and 36.9% (95% CI: 33.9-39.9) in men. The lowest prevalence was seen in the 6-20year old age group (13.6%) and the highest prevalence was found in individuals older than 70years (82.5%). In the multiple logistic regression model, age and education level were significantly related to astigmatism. The prevalence rates of with-the-rule (WTR), against-the-rule (ATR), and oblique astigmatism were respectively 15.0%, 17.2%, and 3.5%. The prevalence of WTR astigmatism decreased with age, while the prevalence of ATR (and oblique astigmatism to a lesser extent) increased. The prevalence of astigmatism was similar to previous studies; however, there were considerable age-related changes. In particular, the prevalence of astigmatism in elderly people was substantial and of concern, particularly given that virtually none of this age group were wearing distance spectacles.

The effect of astigmatism axis on visual acuity.

To evaluate the effect of astigmatism axis on uncorrected distance visual acuity (UDVA) in emmetropic eyes that underwent laser refractive surgery. This retrospective study included patients who underwent laser in situ keratomileusis or photorefractive keratectomy between January 2000 and December 2015 at the Care-Vision Laser Centers, Tel Aviv, Israel. Eyes with a 3-month postoperative spherical equivalent between -0.5 D and 0.5 D were included in this study. Eyes with ocular comorbidities and planned ametropia were excluded. Study eyes were divided into 3 groups according to the steep astigmatic axis: with the rule (WTR) (60-120), oblique (31-59 or 121-149), and against the rule (ATR) (0-30 or 150-180). The UDVA of these 3 groups was compared. The oblique group was divided into oblique ATR and oblique WTR, which were compared with each other. A total of 17,416 consecutive eyes of 8,708 patients were studied. The WTR eyes (n = 10,651) had significantly better UDVA (logMAR 0.01 ± 0.08) than the oblique (n = 3,141, logMAR 0.02 ± 0.09) and ATR eyes (n = 3,624, logMAR 0.02 ± 0.10) (p<0.001). The oblique WTR group had significantly better UDVA than the oblique ATR group (p<0.001). The UDVA of the oblique and ATR groups was similar. Stepwise multiple regression analysis showed that the group accounted for 15% of the UDVA variance (p = 0.04). The astigmatic axis has a small but significant effect on UDVA in emmetropic eyes; WTR was better than oblique and ATR astigmatism. Therefore, when correcting astigmatism, it may be preferable to err towards WTR astigmatism.

Influence of Posterior Corneal Astigmatism on Total Corneal Astigmatism in Eyes With Keratoconus.

To measure posterior corneal astigmatism (PCA) and investigate its influence on total corneal astigmatism (TCA) in eyes with keratoconus. Keratometric astigmatism (KA), PCA, and TCA were investigated by means of a dual Scheimpflug analyzer in patients with keratoconus. Vector analysis was carried out with the Næser polar value method. We enrolled 119 eyes. PCA magnitude averaged 0.77 ± 0.43 diopters (D) and exceeded 0.50, 1.00, and 2.00 D in 73.9%, 21.8%, and 16.8% of eyes, respectively. PCA averaged 0.95 ± 0.48, 0.55 ± 0.28, and 0.70 ± 0.35 D in eyes with with-the-rule (WTR), against-the-rule (ATR), and oblique astigmatism. The steepest posterior meridian was oriented vertically (between 61 and 119 degrees) in 55.5% of eyes, thus generating ATR astigmatism. The difference between the location of the steepest meridian of KA and that of TCA was >10 degrees in 8.4% of eyes. On average, KA overestimated TCA in eyes with WTR astigmatism by 0.16 D and underestimated TCA in eyes with ATR astigmatism by 0.22 D. The PCA power oriented along the steeper anterior corneal meridian averaged -0.83 ± 0.40, -0.40 ± 0.37, and -0.53 ± 0.43 D for WTR, ATR, and obliquely astigmatic eyes, respectively. Linear regression disclosed a statistically significant correlation (P < 0.0001, r = 0.16) between the meridional powers of TCA and PCA. In eyes with keratoconus, PCA displays large, variable values and is correlated to TCA. The influence of PCA on TCA cannot be disregarded when planning astigmatism correction by toric intraocular lenses.

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.

Distribution of Anterior and Posterior Corneal Astigmatism in Eyes With Keratoconus

To investigate the magnitude, with-the-rule (WTR) or against-the-rule (ATR) orientation, and vector components (Jackson astigmatic vectors [J0 and J45] and blurring strength) of the anterior and posterior corneal astigmatism (ACA and PCA) in patients with keratoconus (KC) in a retrospective study, and to try to find suitable cutoff points for ACA and PCA in an attempt to discriminate KC from normal corneas. Retrospective age- and sex-matched case-control study. Using the Pentacam images, the aforementioned parameters were compared between 1273 patients with KC and 1035 normal participants. The mean magnitude of the ACA and PCA was 4.49 ± 2.16 diopter (D) and 0.90 ± 0.43 D, respectively. The dominant astigmatism orientation of the ACA was ATR in KC patients and WTR in normal participants (P < .001), while for the PCA it was WTR in KC patients and ATR in normal participants (P < .001). There was a significant agreement between the axis orientations of ACA and PCA in KC patients (ĸ= 0.077, P< .001), but not in the normal group (P= .626). ACA and PCA magnitude, M, J0, J45, and blur significantly increased by increasing KC severity. There was a trend for increasing anterior ATR and posterior WTR, and decreasing oblique astigmatism on both corneal surfaces by increasing the KC severity according to the Amsler-Krumeich classification. A cutoff value of 1.8 D for ACA had 90.2% sensitivity and specificity, and that of 0.4 D for PCA had 89.5% sensitivity and 85.0% specificity for discriminating KC from normal corneas. Our findings can help clinicians in the diagnosis of KC and lens manufacturers in designing suitable contact or intraocular lenses.

Effect of astigmatism on refraction in children with high hyperopia.

The aim of this study was to evaluate primitively whether the extent and component of astigmatism influences regression in degree of spherical (DS) and the best corrected visual acuity (BCVA) of children with hyperopia of +5.00 diopters (D) or greater. Children were screened from the outpatient refraction database in the Wenling No. 1 People's Hospital in Zhejiang province and in Eye & ENT Hospital of Fudan University between June 2005 and December 2015. Eligible eyes were divided into three groups according to the extent of astigmatism: group of astigmatism ≤ -2 D of cylinder, group without astigmatism or with astigmatism ≥ -0.5 D of cylinder, and the group with astigmatism ≥ -0.75 D and ≤ -1.75 D of cylinder. For the component of astigmatism, eyes with astigmatism as ≤ -0.75 D of cylinder were divided into 3 groups: with the rule (WTR), against the rule (ATR) and the group with the oblique. Differences in the changes of BCVA and refractive error (RE) during follow-up terms were compared within and among groups. Differences in the mean DS or BCVA were not statistically significant between groups according to the extent of the astigmatism at the last visit (p = 0.2396 and p = 0.2131, respectively). As for the component of astigmatism, the group with oblique astigmatism had more severe hyperopia than the group of WTR (p < 0.0001) and mean BCVA in the group of ATR were better than that of the other two groups (p < 0.0001) at the first visit. However, the among-group changes were not significant at the end of the observation (p > 0.1). The regression of DS and improvement of the BCVA in children with hyperopia of +5.00D or greater may be irrespective of the component and the extent of astigmatism.

Postoperative Corneal and Surgically Induced Astigmatism following Superior Approach Manual Small Incision Cataract Surgery in Patients with Preoperative Against-the-Rule Astigmatism.

The aim of the study was to report postoperative corneal and surgically induced astigmatism (SIA) in patients with preoperative against-the-rule (ATR) astigmatism who underwent superior approach manual small incision cataract surgery (MSICS). 58 eyes of 58 cataract patients with preoperative ATR astigmatism were involved in this study. All patients had operable cataracts and underwent superior approach MSICS. Keratometric (K) readings were taken prior to surgery and at 12 weeks after surgery. Centroid values of SIA, preoperative astigmatism, and postoperative astigmatism were calculated using Cartesian coordinates based analysis. Wilcoxon signed rank test was used to compute statistical significance between mean preoperative and postoperative corneal astigmatism. Cohen's d was used as effect size measure. Centroid values of 1.42 D × 179, 2.48 D × 0, and 1.07 D × 1 were recorded, respectively, for preoperative astigmatism, postoperative astigmatism, and SIA. Wilcoxon signed rank test indicated that mean ± SD postoperative corneal astigmatism (2.80 ± 1.40 D) was statistically significantly greater than preoperative corneal astigmatism (1.49 ± 1.34 D), Z = −6.263, p < 0.0001. A high Cohen's d of 1.32 was found. Our results suggest statistical and clinically significant greater postoperative corneal astigmatism than preoperative corneal astigmatism for ATR astigmatism cataract patients who underwent superior approach MSICS.

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...

Assessment of Anterior, Posterior, and Total Central Corneal Astigmatism in Eyes With Keratoconus

To investigate the magnitudes and the axis orientations of anterior, posterior, and total central corneal astigmatism in eyes with keratoconus. Retrospective case series. This study comprised 137 eyes of 137 keratoconic patients (97 men and 40 women; mean age ± standard deviation, 36.9 ± 12.2 years). The magnitude and the axis orientation of each corneal astigmatism were determined with a rotating Scheimpflug system. The mean magnitudes of anterior, posterior, and total central corneal astigmatism were 3.93 ± 2.74 diopters (D), 0.93 ± 0.64 D, and 3.90 ± 2.75 D, respectively. With-the-rule (WTR), against-the-rule (ATR), and oblique astigmatism of the anterior corneal surface was found in 90 eyes (65.7%), 33 eyes (24.1%), and 14 eyes (10.2%), respectively, whereas the corresponding astigmatism of the posterior corneal surface was found in 14 eyes (10.2%), 15 eyes (10.9%), and 108 eyes (78.8%), respectively. We found a significant correlation between the magnitudes of anterior and posterior corneal astigmatism (Pearson correlation coefficient r= 0.769, P< .001). The mean magnitudes of anterior and posterior corneal astigmatism were approximately 4 D and 1 D, respectively, in eyes with keratoconus. Approximately 65% and 80% of eyes showed that WTR anterior astigmatism and ATR posterior astigmatism, respectively. The presence of posterior corneal astigmatism is not necessarily negligible for the accurate astigmatic correction of toric intraocular lens implantation or rigid gas-permeable contact lens wear for keratoconus.

Prevalence of refractive errors among junior high school students in the Ejisu Juaben municipality of Ghana

Among school children, uncorrected refractive errors have a considerable impact on their participation and learning in class. The aim of this study was to assess the prevalence of refractive error among students in the Ejisu-Juabeng Municipality of Ghana. A survey with multi-stage sampling was undertaken. We interviewed 504 students aged 12-17 years and examined them for refractive errors. The prevalence of refractive errors among those with and without refractive error was compared by means of the chi-square test. Logistic regression analysis using refractive error as the dependent variable and adjusting for risk factors were performed. The overall prevalence rate of refractive errors was 7.5%. Out of the number of children with refractive errors, 39.5% had astigmatism, 31.6% had hyperopia and 28.9% had myopia. The prevalence rate was significantly higher among urban compared with rural students. Astigmatic refractive errors consists of with–the–rule (WTR) astigmatism 66.7%, against–the–rule (ATR) astigmatism 26.7% and oblique astigmatism (OBL) 6.6%. WTR and ATR astigmatism were more common in females than males. Multivariate logistic regression models showed no substantial confounding effects between near work, sex, and residence, suggesting that each covariate has an independent association with refractive error. In conclusion, near work, sex and high parental education level are factors contributing to refractive errors. Children in urban areas are at higher risk compared with their rural counterparts. We suggest that an efficient pre-school vision examination must be made part of the admission policy of all schools in Ghana.Keywords: Prevalence, refractive error, students, visual impairment, Ejisu-Juaben Municipality

Analysis of anterior corneal astigmatism before cataract surgery using power vector analysis in eyes of Korean patients

To analyze the pattern of anterior corneal astigmatism before cataract surgery in Korean patients using power vector analysis and to assess the effect of aging on astigmatism. Seoul St. Mary's Hospital, Catholic University of Korea, Seoul, South Korea. Cross-sectional retrospective study. The study evaluated eyes with cataract from May 1, 2009, to July 1, 2013. All eyes received a complete ophthalmologic examination and manual keratometer measurement (OM-4) preoperatively. Power vector J0 and linear regression analyses were used to assess the association between age and anterior corneal astigmatism. The study evaluated 2847 right eyes (2847 patients). The mean age of the patients was 66.64 years ± 12.06 (SD) (range 20 to 100 years); 64.2% of the patients were women. The corneal J0 vector values became progressively negative and trended toward against-the-rule (ATR) astigmatism with increasing age (for men, r = -0.388 and P < .001; for women, r = -0.348 and P < .001). The ATR shift occurred earlier in men than in women. The regression coefficient of J0 values analyzed by age was -0.014 in men and -0.015 in women (both P < .001). Anterior corneal astigmatism in Korean patients with cataract shifted with age from with-the-rule to ATR in both sexes. No author has a financial or proprietary interest in any material or method mentioned.

English

Abstract This cross-sectional study aimed to describe the variation in ocular biometry and investigate the relationship among the parameters of the adult cataract surgery candidates at the Zhongshan Hospital, Fudan University, Shanghai, China. The study included 1975 cataract patients (1975 eyes) aged from 18 to 95 years old. Axial length (AL), corneal curvature, anterior chamber depth (ACD) and horizontal corneal diameter (white-to-white [WTW] distance) were optically measured by partial coherence interferometry (IOL Master). Spearman rank correlation coefficients were used to evaluate bivariate correlations. The average AL and the mean corneal curvature were 24.86 ± 2.72 mm and 44.13 ± 1.58 D, respectively. The mean ACD and WTW were 3.11 ± 0.50 mm and 11.83 ± 0.42 mm, respectively. The mean corneal curvature was negatively correlated with AL, especially in the range of AL from 22 mm to 25 mm, while ACD and WTW were positively correlated with AL. However, the correlation coefficient between AL and WTW was relatively low. Slight corneal astigmatism, especially against-the-rule (ATR) astigmatism, was common in cataract patients. Corneal curvature seemed to be relatively flat to compensate for the long axial length achieving the emmetropic state in limited range. Corneal expansion was limited with the increasing of axial length.

Visual outcome and complications of manual small incision cataract Surgery (MSICS) in a peripheral CMH

Introduction: Manual small incision cataract surgery (MSICS) is a cost-effective alternative to phacoemulsification cataract surgery for developing countries. This prospective study was carried out in Combined Military Hospital (CMH), Chittagong from October 2009 to March 2011 on 75 cataract patients who were operated by MSICS technique. Objectives: Aim of this study was to assess the visual outcome and complications of MSICS in a peripheral CMH. Methods: Seventy five cataract patients were operated by MSICS technique. All surgical procedures were performed by the principal author. Major per-operative and postoperative complications were documented. Visual outcome was assessed by Snellen’s visual acuity test 06 weeks after operation. Results: Uncorrected visual acuity (UCVA) was 6/6 – 6/18 in 57 (76.0%) patients, &lt; 6/18 – 6/60 in 15 (20%) and &lt; 6/60 in 03 (4.0%) patients. Best corrected visual acuity (BCVA) was 6/6-6/18 in 65 (86.7%) patients, &lt; 6/18-6/60 in 07 (9.3%) and &lt; 6/60 in 03(4.0%) patients. Visual outcome was good in 86.7% of patients according to World Health Orgnization (WHO) criteria and was not far away from the WHO expected outcome. Posterior capsule rupture was the most significant per-operative complication which was found in 7(9.3%) cases and surgically induced astigmatism was main postoperative complication that affected visual outcome. Mean postoperative astigmatism (against-the rule) was - 1.25DC. 14 JAFMC Bangladesh. Vol 10, No 1 (June) 2014 Conclusion: MSICS is a safe and cost-effective technique of extra-capsular cataract extraction where surgical skill and experience of the surgeon plays a significant role in the result. DOI: http://dx.doi.org/10.3329/jafmc.v10i1.22895 Journal of Armed Forces Medical College Bangladesh Vol.10(1) 2014

Refractive errors, visual impairment, and the use of low-vision devices in albinism in Malawi.

This study focuses on the refractive implications of albinism in Malawi, which is mostly associated with the burden of visual impairment. The main goal was to describe the refractive errors and to analyze whether patients with albinism in Malawi, Sub-Saharan Africa, benefit from refraction. Age, sex, refractive data, uncorrected and best-corrected visual acuity (UCVA, BCVA), colour vision, contrast sensitivity, and the prescription of sunglasses and low vision devices were collected for a group of 120 albino individuals with oculocutaneous albinism (OCA). Refractive errors were evaluated objectively and subjectively by retinoscopy, and followed by cycloplegic refraction to reconfirm the results. Best-corrected visual acuity (BCVA) was also assessed binocularly. One hundred and twenty albino subjects were examined, ranging in age from 4 to 25 years (median 12 years), 71 (59 %) boys and 49 (41 %) girls. All exhibited horizontal pendular nystagmus. Mean visual acuity improved from 0.98 (0.33) logMAR to 0.77 (0.15) logMAR after refraction (p < 0.001). The best improvement of VA was achieved in patients with mild to moderate myopia. Patients with albinism who were hyperopic more than +1.5 D hardly improved from refraction. With the rule (WTR) astigmatism was more present (37.5 %) than against the rule (ATR) astigmatism (3.8 %). Patients with astigmatism less than 1.5 D improved in 15/32 of cases (47 %) by 2 lines or more. Patients with astigmatism equal to or more than 1.5 D in any axis improved in 26/54 of cases (48 %) by 2 lines or more. Refraction improves visual acuity of children with oculocutaneous albinism in a Sub-Saharan African population in Malawi. The mean improvement was 2 logMAR units.

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.

An analysis of the factors influencing the residual refractive astigmatism after cataract surgery with toric intraocular lenses.

To investigate the influence of posterior corneal astigmatism, surgically-induced corneal astigmatism (SICA), intraocular lens (IOL) orientation, and effective lens position on the refractive outcome of toric IOLs. Five models were prospectively investigated. Keratometric astigmatism and an intended SICA of 0.2 diopters (D) were entered into model 1. Total corneal astigmatism, measured by a rotating Scheimpflug camera, was used instead of keratometric astigmatism in model 2. The mean postoperative SICA, the actual postoperative IOL orientation, and the influence of the effective lens position were added, respectively, into models 3, 4, and 5. Astigmatic data were vectorially described by meridional and torsional powers. A set of equations was developed to describe the error in refractive astigmatism (ERA) as the difference between the postoperative refractive astigmatism and the target refractive astigmatism. We enrolled 40 consecutive eyes. In model 1, ERA calculations revealed significant cylinder overcorrection in with-the-rule (WTR) eyes (meridional power = -0.59 ± 0.34 D, P < 0.0001) and undercorrection in against-the-rule (ATR) eyes (0.32 ± 0.42 D, P = 0.01). When total corneal astigmatism was used instead of keratometric astigmatism (model 2), the ERA meridional power decreased in WTR (-0.13 ± 0.42 D) and ATR (0.07 ± 0.59 D) eyes, both values being not statistically significant. Models 3 to 5 did not lead to significant improvement. Posterior corneal astigmatism exerts the highest influence on the ERA after toric IOL implantation. Basing calculations on total corneal astigmatism rather than keratometric astigmatism improves the prediction of the residual refractive astigmatism.

Studying the contribution of posterior corneal astigmatism to total corneal astigmatism

Settings The Faculty of Medicine, Alexandria University, Egypt. Purpose The aim of this work was to study the contribution of posterior corneal astigmatism to total corneal astigmatism. Patients and methods A descriptive prospective observational study that included 100 eyes of 100 patients aged 18 years and above. Scheimpflug camera imaging was performed using a Pentacam. The following data were recorded: anterior corneal radii of curvature, posterior corneal radii of curvature and astigmatism, simulated keratometry (sim K) and astigmatism, the true net power and astigmatism, and central corneal pachymetry. All included participants signed a written informed consent. Results The mean age was 38.11 ± 12.69 years. The orientation of the steep axis of the anterior corneal surface was vertical in 70% of the cases, resulting in with-the-rule astigmatism. For the posterior corneal surface, the steep axis orientation was vertical in 94% of the cases, resulting in against-the-rule (ATR) astigmatism. The mean sim K astigmatism was higher than that of the true net K astigmatism by 0.12 ± 0.18 D (range -0.3-0.4 D) at 4 ± 5° (range 0-21°). Conclusion Anterior corneal with-the-rule astigmatism tends to change to ATR astigmatism with age. The posterior corneal surface showed ATR astigmatism regardless of the age. Using data from the anterior corneal surface only resulted in a higher astigmatism of 0.12 D compared with using data from both the anterior and the posterior surfaces. Also, data from the anterior corneal surface alone resulted in a difference in the axis of more than 10° in 11% of the cases.

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

Effect of posterior corneal astigmatism on refractive outcomes after toric intraocular lens implantation

To compare the prediction error after toric intraocular lens (IOL) (Acrysof IQ) implantation using corneal astigmatism measurements obtained with an IOLMaster automated keratometer and a Galilei dual rotating camera Scheimpflug-Placido tomographer. Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, USA. Retrospective case series. The predicted residual astigmatism after toric IOL implantation was calculated using preoperative astigmatism values from an automated keratometer and the total corneal power (TCP) determined by ray tracing through the measured anterior and posterior corneal surfaces using dual Scheimpflug-Placido tomography. The prediction error was calculated as the difference between the predicted astigmatism and the manifest astigmatism at least 1 month postoperatively. The calculations included vector analysis. The study evaluated 35 eyes (35 patients). The preoperative corneal posterior astigmatism mean magnitude was 0.33 diopter (D) ± 0.16 (SD) (vector mean 0.23 × 176). Twenty-six eyes (74.3%) had with-the-rule (WTR) posterior astigmatism. The postoperative manifest refractive astigmatism mean magnitude was 0.38 ± 0.18 D (vector mean 0.26 × 171). There was no statistically significant difference in the mean magnitude prediction error between the automated keratometer and TCP techniques. However, the automated keratometer method tended to overcorrect WTR astigmatism and undercorrect against-the-rule (ATR) astigmatism. The TCP technique lacked these biases. The automated keratometer and TCP methods for estimating the magnitude of corneal astigmatism gave similar results. However, the automated keratometer method tended to overcorrect WTR astigmatism and undercorrect ATR astigmatism. Dr. Hamilton has received honoraria for educational lectures from Ziemer Ophthalmic Systems. No other author has a financial or proprietary interest in any material or method mentioned.

Astigmatism among myopics and its changes from childhood to adult age: a 23-year follow-up study.

To study the prevalence of and changes in astigmatism from the onset of myopia at school age. Two hundred and forty myopic schoolchildren (mean age 10.9 years), with no previous spectacles, were recruited during 1983-1984 to a randomized 3-year clinical trial of bifocal treatment of myopia. Three annual examinations with subjective cycloplegic refraction were performed for 237-238 subjects. Subsequent examinations were performed at the mean ages of 23.2 and 33.9 years for 178 and 163 subjects, and the last examination, including data from prescriptions of different ophthalmologists, for 32 subjects. Corneal topography was studied at baseline, at the 3-year follow-up and at the two adulthood follow-ups. Prevalence and changes in refractive astigmatism (RA), in its polar values J0 and J45, and corneal astigmatism (CA) were studied. Mean RA of the right eye increased during follow-up from 0.26 D (SD) ± 0.30 to 0.79 D ± 0.74. Mean CA was 1.07 D ± 0.74 at study end. The prevalence of RA ≥0.25 or ≥1.00 D increased from 54.9 and 3.8% to 83.4 and 34.4%, respectively. The main direction of the axis of RA and its polar value J0 and CA changed mainly through sphericity, from against the rule (ATR) to with the rule during the follow-up. There was a negative correlation between RA and spherical refraction in the ATR group at end of follow-up. Changes in RA were associated with increase in myopia and with changes in CA. The prevalence and mean amount of RA associated with CA increased, and the axis of astigmatism changed among myopics during the 23-year follow-up.