With-the-rule Research Articles

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.

Ocular Biometric Changes after Trabeculectomy.

This review article aimed to evaluate ocular biometric changes after trabeculectomy. The PubMed database was searched using the keywords “axial length” (AL), “anterior chamber depth” (ACD), “corneal astigmatism,” “corneal topography” and “trabeculectomy.” The extracted studies were categorized based on the evaluated parameters and the biometry method (contact and non-contact). Comparable studies with respect to their sample size were combined for statistical analysis. Twenty-five studies including 690 individuals which met the inclusion criteria were selected. After trabeculectomy, a significant and persistent AL reduction, with a range of 0.1-0.19 and 0.1-0.9 mm measured with contact and non-contact methods, respectively, was observed. With respect to topographic changes, 0.38-1.4 diopters (D) with-the-rule (WTR) astigmatism was induced postoperatively. All studies revealed ACD reduction immediately after surgery, which gradually deepened and approximated its preoperative levels on day 14. ACD reduction was not significant after that period in the majority of cases. In conclusion, changes in ACD is of small amount and of short period, thus it can be ignored; however, reported changes in AL and keratometry are of sufficient magnitude and can affect the refractive prediction of combined cataract surgery and trabeculectomy.

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.

The Prevalence of Ptosis and Its Association with Amblyopia and Strabismus in 7-Year-Old Schoolchildren in Iran

Purpose: To determine the prevalence of ptosis (congenital/acquired) in Iranian children aged 7 years and its relationship with amblyopia and strabismus.Methods: Eight Iranian cities were selected for this cross-sectional study using multistage randomized cluster sampling. A number of primary schools were randomly selected in each city. All grade 1 students in each selected primary school underwent optometric examinations including the measurement of uncorrected and corrected visual acuity, cover test, and cycloplegic and non-cycloplegic refraction.Results: Of 4614 selected students, 4106 students participated in the study (response rate = 89%). The prevalence of ptosis (congenital/acquired) was 1.41% (95% CI 1–1.83); 0.49% (95% CI 0.26–0.72) and 0.93% (95% CI 0.59–1.26) had unilateral and bilateral ptosis, respectively. The prevalence of ptosis had no significant correlation with sex (p = 0.810, OR = 1.07, 95% CI 0.59–1.97). The prevalence of amblyopia was 48.28% and 0.89% in students with and without ptosis, respectively. The prevalence of tropia was significantly higher in cases with bilateral ptosis (p < 0.001). The mean cylinder error was 1.63 ± 1.72 and 0.44 ± 0.60 in ptotic and non-ptotic eyes, respectively (p < 0.001). With-the-rule (WTR) astigmatism was significantly more prevalent in students with ptosis.Conclusion: We report the prevalence of ptosis (congenital/acquired) in children in Iran and the Middle East region for the first time. Amblyopia was considerably more prevalent in ptotic patients. We found a significant correlation between ptosis and tropia. Astigmatism, especially WTR stigmatism, was more prevalent in children with ptosis.

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

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.

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.

Refractive errors in a Brazilian population: age and sex distribution.

To determine the prevalence of refractive errors and their distribution according to age and sex in a Brazilian population. This population-based cross-sectional study involved 7654 Brazilian inhabitants of nine municipalities of Sao Paulo State, Brazil, between March 2004 and July 2005. Participants aged >1year were selected using a random, stratified, household cluster sampling technique, excluding individuals with previous refractive or cataract surgery. Myopia was defined as spherical equivalent (SE) ≤-0.5D, high myopia as SE ≤-3.0D, hyperopia as SE ≥+0.5D, high hyperopia as SE ≥+3D, astigmatism as ≤-0.5DC and anisometropia as ≥1.0D difference between eyes. Age, sex, complaints and a comprehensive eye examination including cycloplegic refraction test were collected and analysed using descriptive analysis, univariate and multivariate methods. The prevalence of astigmatism was 59.7%, hyperopia 33.8% and myopia was 25.3%. Astigmatism had a progressive increase with age. With-the-rule (WTR) axes of astigmatism were more frequently observed in the young participants and the against-the-rule (ATR) axes were more frequent in the older subjects. The onset of myopia occurred more frequently between the 2nd and 3rd decades of life. Anisometropia showed a prevalence of 13.2% (95% CI 12.4-13.9; p<0.001). There was an association between age and all types of refractive error and hyperopia was also associated with sex. Hyperopia was associated with WTR axes (odds ratio 0.73; 95% CI: 0.6-0.8; p<0.001) and myopia with ATR axes (odds ratio 0.66; 95% CI: 0.6-0.8; p<0.001). Astigmatism was the most prevalent refractive error in a Brazilian population. There was a strong relationship between age and all refractive errors and between hyperopia and sex. WTR astigmatism was more frequently associated with hyperopia and ATR astigmatism with myopia. The vast majority of participants had low-grade refractive error, which favours planning aimed at correction of refractive error in the population.

Impact of Posterior Corneal Surface on Toric Intraocular Lens (IOL) Calculation

Purpose: To quantify the impact of posterior cornea on toric IOL calculation accuracy using Placido-topography of anterior corneal surface and Scheimpflug measurements of corneal thickness.Materials and Methods: Three-hundred seventy-nine non-selected eyes undergoing cataract surgery with non-toric intraocular lens (IOL) implantation were measured with TMS-5 (Tomey, Japan), IOLMaster (Zeiss, Germany) and Lenstar (Haag-Streit, Switzerland). Anterior, posterior and total measured corneal astigmatisms were compared with astigmatisms from postoperative refraction by calculating vector differences.Results: The average absolute vector difference between anterior astigmatism and total astigmatism combining the measurements of anterior and posterior cornea was only 0.3 ± 0.2 D, with a median of only 0.27 D, but a maximum of 1.5 D. Measurements of anterior cornea alone show a systematic difference from refractive cylinder of 0.3–6 D at 90, 0.38 D at 89° and 0.28 D at 91° (IOLMaster, Lenstar and anterior TMS5), whereas the total TMS5 cylinder differs on average by only 0.14D at 81° from the refractive cylinder. With-the-rule (WTR) corneal astigmatism is slightly reduced and against-the-rule (ATR) astigmatism slightly increased on average when posterior corneal surface is taken into account additionally. This could also be confirmed by the calculation of an average pachymetry of all eyes in which the thinnest central part shows an ellipsoidal shape with horizontally long axis.Conclusion: Measurements of posterior cornea have on average only a small but significant impact on the outcome of toric IOL calculation, however, they are nevertheless recommended to detect outliers in which corneal irregularities (e.g. beginning keratokonus) may be overlooked.

Influence of simple myopic against-the-rule and with-the-rule astigmatism on visual acuity in eyes with monofocal intraocular lenses.

To analyze the influence of simple myopic against-the-rule (ATR) and with-the-rule (WTR) astigmatism on uncorrected distance visual acuity (UDVA) in eyes after monofocal intraocular lens (IOL) implantation. Patients with a postoperative spherical refractive error within ±0.5 diopter (D) and a negative cylindrical refractive error ≥0.5D were enrolled and divided into two groups: ATR or WTR astigmatism. Age, pupil size, spherical equivalent refractive error, spherical refractive error, cylindrical refractive power, UDVA, corrected distance visual acuity (CDVA) and ocular wavefront aberrations were compared between groups. Correlations between UDVA and other parameters were also examined within groups. Twenty-five eyes (25 patients) with ATR astigmatism and 18 eyes (18 patients) with WTR astigmatism were evaluated. The logMAR UDVA was 0.30±0.22 (mean±SD) in the ATR group and 0.11±0.15 in the WTR group, showing a significant difference between groups (P<0.01). There were no significant differences in other parameters between groups. The UDVA was significantly correlated with spherical equivalent refractive error (r=-0.51, P<0.01) and cylindrical refractive power (r=-0.48, P=0.01) in the ATR group, but not in the WTR group. No other parameters were significantly correlated with UDVA in either group. After monofocal IOL implantation, UDVA in eyes with simple myopic ATR astigmatism was worse than in eyes with simple myopic WTR astigmatism. Additionally, UDVA was significantly influenced by cylindrical refractive power in eyes with ATR astigmatism, but not in eyes with WTR astigmatism.

Analysis of Miscorrection after Implantation of the Toric Intraocular Lens

Purpose: To evaluate the efficacy and stability of AcrySof Toric intraocular lens (IOL) implants and to analyze the miscorrection that resulted after implantation. Methods: This retrospective study included 422 eyes of 348 patients who underwent cataract surgery with implantation of the AcrySof toric IOL between December 2011 and June 2013. We evaluated uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), keratometry and refraction preoperatively and 3 months postoperatively. The axis of implanted AcrySof Toric IOL was measured using the KR-1W aberrometer before mydriasis. At 3 months postoperatively, patients with a residual cylindrical power of 0.50 diopters (D) or more, and having an IOL rotation of 10 degrees (°) or more were considered having miscorrection. Results: UCVA (log MAR) improved from 0.58 ± 0.35 to 0.18 ± 0.26. Preoperative corneal astigmatism was 1.46 ± 0.72 D and postoperative refractive cylindrical power was 0.45 ± 0.30 D. The postoperative miscorrection was 50.5% in the T3 group, 35.7% in the T4 group, and 27.2% in the T5 group. The incidence of overcorrection was significantly higher in the T3 group than in the T4 and T5 group. In eyes with with-the-rule (WTR) astigmatism, overcorrection was found in 36.4% (32/88 eyes), while in eyes with against-the-rule (ATR) astigmatism, undercorrection was found in 37.6% of cases (44/117 eyes). There were five cases of IOL rotation at 3 months postoperatively. Conclusions: AcrySof Toric IOL was effective in correcting corneal astigmatism and had good rotational stability. However, the incidence of miscorrection, especially for overcorrection, was higher with lower power toric IOL. Patients with WTR astigmatism tend to have overcorrection, while those with ATR show a tendency toward undercorrection, suggesting that these changes considered at the time of cataract surgery. J Korean Ophthalmol Soc 2014;55(11):1636-1641

Prevalence of Pre-Existing Corneal Astigmatism in Age Related Cataract Patient

Cataract surgery is no more a blind rehabilitation surgery, it absolutely gives normal vision. In the era of modern cataract surgery patients expectations are also high about visual outcome. This prospective study was carried out to investigate the magnitude and pattern of pre-existing corneal astigmatism in age related cataract patient at Faridpur Medical College Hospital, Faridpur and Agha Yusuf Adhunik Hospital, Kustia, from July 2009 to June 2012. We examined 850 eyes of 730 patients who underwent cataract surgery. The mean age at the time of surgery was 61.9±8.1 (40 to 70) years. Corneal astigmatism was measured by Auto Refracto Keratometer at least two times for each patient. Astigmatism was calculated from diopteric difference of vertical reading from horizontal reading. With the rule (WTR) astigmatism was considered when steep meridian at 90°± 20°. Against the rule (ATR) astigmatism was considered when steep meridian at 180°±20°. Astigmatism is in other direction is defined as oblique. On keratometry, when vertical reading (k1) was found greater than horizontal (k2) was considered WTR astigmatism and the reverse reading for ATR astigmatism. The percentage of corneal astigmatism was 1D or less was 69.6%, more than 1D and less than 1.5D, 27.6% and more than 1.5D and less then 2D 2.8%. Prevalence of ATR astigmatism was more than WTR astigmatism and prevalence of ATR astigmatism increases significantly with age. Approximately two third of pre-operative patient had 1D or less astigmatism and one third had more than 1D corneal astigmatism. DOI: http://dx.doi.org/10.3329/fmcj.v8i1.16887 Faridpur Med. Coll. J. 2013;8(1): 02-04

Correcting astigmatism with toric intraocular lenses: Effect of posterior corneal astigmatism

To evaluate the impact of posterior corneal astigmatism on outcomes with toric intraocular lenses (IOLs). Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. Case series. Corneal astigmatism was measured using 5 devices before and 3 weeks after cataract surgery. Toric IOL alignment was recorded at surgery and at the slitlamp 3 weeks postoperatively. The actual corneal astigmatism was calculated based on refractive astigmatism 3 weeks postoperatively and the effective toric power calculated with the Holladay 2 formula. The prediction error was calculated as the difference between the astigmatism measured by each device and the actual corneal astigmatism. Vector analysis was used in all calculations. With the IOLMaster, Lenstar, Atlas, manual keratometer, and Galilei (combined Placido-dual Scheimpflug analyzer), the mean prediction errors (D) were, respectively, 0.59 @ 89.7, 0.48 @ 91.2, 0.51 @ 78.7, 0.62 @ 97.2, and 0.57 @ 93.9 for with-the-rule (WTR) astigmatism (60 to 120 degrees), and 0.17 @ 86.2, 0.23 @ 77.7, 0.23 @ 91.4, 0.41 @ 58.4, and 0.12 @ 7.3 for against-the-rule (ATR) astigmatism (0 to 30 degrees and 150 to 180 degrees). In the WTR eyes, there were significant WTR prediction errors (0.5 to 0.6 diopters [D]) by all devices. In ATR eyes, WTR prediction errors were 0.2 to 0.3 D by all devices except the Placido-dual Scheimpflug analyzer (all P<.05 with Bonferroni correction). Corneal astigmatism was overestimated in WTR by all devices and underestimated in ATR by all except the Placido-dual Scheimpflug analyzer. A new toric IOL nomogram is proposed.