Astigmatic Components Research Articles

Corneal Stromal Lenticule Rotation for High Astigmatism Correction.

To evaluate the clinical outcome of laser-assisted surgical correction of high hyperopic or mixed astigmatism using small incision intrastromal lenticule rotation (SMILERO) alone or combined with photorefractive keratectomy (PRK). This retrospective case series enrolled 25 eyes with high astigmatism that underwent SMILERO surgery. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), uncorrected near visual acuity (UNVA), manifest refraction, central corneal thickness, and corneal higher order aberrations were analyzed before surgery and after 3, 6, and 12 months of follow-up. The postoperative residual refractive errors were fine-tuned using PRK. The median absolute preoperative cylinder of 4.50 diopters (D) decreased to 1.25 D at 3 months postoperatively. The lenticule rotation improved UDVA (0.80 vs 0.45 logMAR) due to a noticeable myopic shift. Regarding UNVA, 14 of 24 eyes were capable of reading Jaeger number 1 chart postoperatively in comparison to one eye preoperatively. The lenticule rotation led to successful correction of both astigmatic and spherical components in 13 of 25 eyes. The residual refractive errors in 12 of 25 eyes were fine-tuned postoperatively by PRK. The SMILERO and PRK combination led to a satisfactory refractive outcome with median absolute cylinder of 0.75 D, median spherical equivalent of -0.25 D, and median UDVA of 20/40 Snellen equivalent at 12 months postoperatively. This study demonstrates that SMILERO is capable of correcting both corneal and refractive astigmatism with mid-term corneal stability. The residual refractive errors were further minimized with subsequent PRK fine-tuning. [J Refract Surg. 2025;41(1):e5-e13.].

Refractive Astigmatism Consistency Pre- and Post-Cycloplegia in Pediatric Population

Background: Cycloplegic refraction is crucial in pediatric eye assessments. While spherical refraction changes due to cycloplegia are well-documented, astigmatic alterations remain unclear. This study assessed the agreement between spherical and astigmatic refraction pre- and post-cycloplegia. Methods: We enrolled 96 patients (mean age: 12.5 ± 2.4 years), including 35 myopes, 30 emmetropes, and 31 hyperopes. Pre- and post-cycloplegia autorefraction and keratometry (Myopia Master) were conducted using 1% cyclopentolate. Ocular residual astigmatism (ORA) was calculated as the difference between refractive and keratometric astigmatism. Astigmatism was analyzed using Fourier analysis (J0 and J45). Results: Cycloplegia resulted in a more positive spherical equivalent (SE) (+0.80 D), with myopes showing the smallest (+0.38 D) and hyperopes showing the highest variation (+1.47 D) in SE. With-the-rule (WTR) astigmatism predominated in the refractive and keratometric measurements, while ORA was against-the-rule (ATR). Cycloplegia shifted the refractive J0 (+0.06 D) towards more WTR and decreased ORA J0 (+0.05 D). No effect was observed in the J45 component. About 25% of patients exhibited astigmatism changes above 0.25 D, with refractive J0 variation being positively correlated with accommodation relaxation (0.044 D per D of relaxation). Conclusion: Cycloplegia induces clinically significant changes in the spherical component, but minimal variations in astigmatic components, predominantly in hyperopic eyes, likely reflecting alterations in crystalline lens anatomy.

Outcomes of manual arcuate keratotomy with compression sutures for high regular postkeratoplasty astigmatism.

To report functional and refractive outcomes of manual arcuate keratotomy (AK) with compression sutures for high regular postkeratoplasty astigmatism. Department of Ophthalmology, Saarland University Medical Center, Homburg/Saar, Germany. Retrospective analysis. This study included 90 eyes with high regular postkeratoplasty astigmatism (>4 diopters [D]) who received AK with compression sutures between 2010 and 2022. Functional and refractive outcomes were assessed by evaluating topographic indices and by performing vector astigmatism and Fourier analysis. At last follow-up (mean 13.7 ± 16.6 months), corrected distance visual acuity improved from 0.59 ± 0.28 to 0.34 ± 0.25 logMAR. Cylinder magnitude decreased from 9.91 ± 2.88 to 5.42 ± 3.35 D. Surface asymmetry index, irregular astigmatism index, and corneal eccentricity index were equal to preoperative values, whereas surface regularity index approached normal values at last follow-up. Fourier analysis indicated a decrease in the regular astigmatic component, whereas nonregular components (asymmetry and higher-order irregularity) remained stable. In vector astigmatism analysis, target-induced astigmatism magnitude was 9.92 ± 2.86 D and surgically induced astigmatism magnitude was 10.16 ± 4.86 D (correction index of 0.91 ± 0.48) with a difference vector of 5.42 ± 3.35 D at last follow-up. Correction of astigmatism magnitude was adequate in 40% of the eyes, undercorrected in 30%, and overcorrected in 30%. Angle of error was <|22.5 degrees| in 88% resulting in a low risk of off-axis treatment. AK with compression sutures is a simple, relatively effective, and safe surgical procedure for astigmatism reduction after keratoplasty. In case of regular astigmatism, the procedure does not increase corneal irregularities. The remaining refractive error might be further corrected by spectacles, contact lenses, or toric intraocular lens implantation (in-the-bag/add-on), thus reducing the need for repeat keratoplasty.

The effect of cycloplegia in the accuracy of autorefraction, keratometry and axial length using the Myopia Master

BackgroundAssessing refractive errors under cycloplegia is recommended for paediatric patients; however, this may not always be feasible. In these situations, refraction has to rely on measurements made under active accommodation which may increase measurements variability and error. Therefore, evaluating the accuracy and precision of non-cycloplegic refraction and biometric measurements is clinically relevant. The Myopia Master, a novel instrument combining autorefraction and biometry, is designed for monitoring refractive error and ocular biometry in myopia management. This study assessed its repeatability and agreement for autorefraction and biometric measurements pre- and post-cycloplegia.MethodsA prospective cross-sectional study evaluated a cohort of 96 paediatric patients that underwent ophthalmologic examination. An optometrist performed two repeated measurements of autorefraction and biometry pre- and post-cycloplegia. Test-retest repeatability (TRT) was assessed as differences between consecutive measurements and agreement as differences between post- and pre-cycloplegia measurements, for spherical equivalent (SE), refractive and keratometric J0/J45 astigmatic components, mean keratometry (Km) and axial length (AL).ResultsCycloplegia significantly improved the SE repeatability (TRT, pre-cyclo: 0.65 D, post-cyclo: 0.31 D). SE measurements were more repeatable in myopes and emmetropes compared to hyperopes. Keratometry (Km) repeatability did not change with cycloplegia (TRT, pre-cyclo: 0.25 D, post-cyclo:0.27 D) and AL repeatability improved marginally (TRT, pre-cyclo: 0.14 mm, post-cyclo: 0.09 mm). Regarding pre- and post-cycloplegia agreement, SE became more positive by + 0.79 D, varying with refractive error. Myopic eyes showed a mean difference of + 0.31 D, while hyperopes differed by + 1.57 D. Mean keratometry, refractive and keratometric J0/J45 and AL showed no clinically significant differences.ConclusionsRefractive error measurements, using the Myopia Master were 2.5x less precise pre-cycloplegia than post-cycloplegia. Accuracy of pre-cycloplegic refractive error measurements was often larger than the clinically significant threshold (0.25 D) and was refractive error dependent. The higher precision compared to autorefraction measurements, pre- and post-cycloplegia agreement and refractive error independence of AL measurements emphasize the superiority of AL in refractive error monitoring.

The Homburg-Adelaide toric IOL nomogram: How to predict corneal power vectors from preoperative IOLMaster 700 keratometry and total corneal power in toric IOL implantation.

The purpose of this study is to compare the reconstructed corneal power (RCP) by working backwards from the post-implantation spectacle refraction and toric intraocular lens power and to develop the models for mapping preoperative keratometry and total corneal power to RCP. Retrospective single-centre study involving 442 eyes treated with a monofocal and trifocal toric IOL (Zeiss TORBI and LISA). Keratometry and total corneal power were measured preoperatively and postoperatively using IOLMaster 700. Feedforward neural network and multilinear regression models were derived to map keratometry and total corneal power vector components (equivalent power EQ and astigmatism components C0 and C45) to the respective RCP components. Mean preoperative/postoperative C0 for keratometry and total corneal power was -0.14/-0.08 dioptres and -0.30/-0.24 dioptres. All mean C45 components ranged between -0.11 and -0.20 dioptres. With crossvalidation, the neural network and regression models showed comparable results on the test data with a mean squared prediction error of 0.20/0.18 and 0.22/0.22 dioptres2 and on the training data the neural network models outperformed the regression models with 0.11/0.12 and 0.22/0.22 dioptres2 for predicting RCP from preoperative keratometry/total corneal power. Based on our dataset, both the feedforward neural network and multilinear regression models showed good precision in predicting the power vector components of RCP from preoperative keratometry or total corneal power. With a similar performance in crossvalidation and a simple implementation in consumer software, we recommend implementation of regression models in clinical practice.

Repeatability and Agreement of 4 Biometers Measuring Corneal Astigmatism in Eyes With Irregular Corneal Astigmatism Component

To investigate the repeatability and agreement of corneal astigmatism measurements in eyes with irregular corneal astigmatism component (ICAC) using four devices: IOLMaster 700 biometer, Lenstar 900 biometer, iTrace, and Pentacam. Prospective cross-sectional reliability analysis. Sixty-four eyes (52 patients) with ICAC were examined three times using the four devices. The eye with ICAC in this study is defined as the cornea has a certain degree of irregular astigmatism (asymmetric and/or skewed bowtie pattern of corneal topography according to corneal topography classification), accompanied with total corneal higher-order aberrations in the 4 mm zone of 0.3 µm or greater. Corneal astigmatism was evaluated using three categories: anterior corneal astigmatism (ACA), posterior corneal astigmatism, and total corneal astigmatism (TCA). The repeatability was determined using the ∆Ast (arithmetic mean of vector differences among three repeated corneal astigmatism measurements). Bland-Altman plots and astigmatism vector analyses were employed to assess agreement. The IOLMaster 700 (∆Ast = 0.27 ± 0.20 D) showcased higher repeatability in ACA measurements compared to iTrace (∆Ast = 0.37 ± 0.38 D, P = .040) and Pentacam (∆Ast = 0.50 ± 0.22 D, P < .001), and paralleled the performance of Lenstar 900 (∆Ast = 0.31 ± 0.26 D, P = .338). The Pentacam (∆Ast = 0.09 ± 0.07 D, P < .001) demonstrated superior repeatability in posterior corneal astigmatism, whereas the IOLMaster 700 (∆Ast = 0.33 ± 0.23 D, P < .001) excelled in TCA. The IOLMaster 700 exhibited good agreement with either Lenstar 900 or iTrace, characterized by narrow 95% limits of agreement and clinically acceptable vector differences. Conversely, vector differences between Pentacam and the other three devices in ACA and TCA measurements were clinically significant, exceeding 0.50 D (all P < .05). In terms of repeatability of corneal astigmatism measurements in eyes with ICAC, the IOLMaster 700 and Lenstar 900 outperformed iTrace and Pentacam. While the IOLMaster 700 can be used interchangeably with either Lenstar 900 or iTrace, the Pentacam is not interchangeable with the other three devices.

Predicting the onset of myopia in children by age, sex, and ethnicity: Results from the CLEERE Study.

Clinicians and researchers would benefit from being able to predict the onset of myopia for an individual child. This report provides a model for calculating the probability of myopia onset, year-by-year and cumulatively, based on results from the largest, most ethnically diverse study of myopia onset in the United States. This study aimed to model the probability of the onset of myopia in previously nonmyopic school-aged children. Children aged 6 years to less than 14 years of age at baseline participating in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study who were nonmyopic and less hyperopic than +3.00 D (spherical equivalent) were followed up for 1 to 7 years through eighth grade. Annual measurements included cycloplegic autorefraction, keratometry, ultrasound axial dimensions, and parental report of children's near work and time spent in outdoor and/or sports activities. The onset of myopia was defined as the first visit with at least -0.75 D of myopia in each principal meridian. The predictive model was built using discrete time survival analysis and evaluated with C statistics. The model of the probability of the onset of myopia included cycloplegic spherical equivalent refractive error, the horizontal/vertical component of astigmatism (J0), age, sex, and race/ethnicity. Onset of myopia was more likely with lower amounts of hyperopia and less positive/more negative values of J0. Younger Asian American females had the highest eventual probability of onset, whereas older White males had the lowest. Model performance increased with older baseline age, with C statistics ranging from 0.83 at 6 years of age to 0.92 at 13 years. The probability of the onset of myopia can be estimated for children in the major racial/ethnic groups within the United States on a year-by-year and cumulative basis up to age 14 years based on a simple set of refractive error and demographic variables.

Higher order aberrations according to spherical, and astigmatic refractive errors in children

ABSTRACT Clinical relevance The results of this study present novel insights into the impact of spherical and astigmatic refractive errors on overall, corneal and internal aberrations and may provide a clear understanding of the emmetropisation process and the development of visual function. Background This study aimed to assess the association between overall, corneal and internal higher-order aberrations and the spherical and astigmatic components (magnitude and angle) of refractive error in a large sample of children. Methods A total of 311 children aged 7 – 8 years old were classified based on spherical equivalent refraction (myopic, emmetropic and hyperopic); magnitude of astigmatism (none, low and moderate); and angle of astigmatism (with-the-rule, against-the-rule and oblique). Refractive error and overall, corneal and internal higher-order aberrations were measured using the OPD-Scan III workstation. Results Regarding spherical equivalent refraction, myopic eyes had greater root mean square (RMS) overall higher-order values, total spherical, tetrafoil and secondary astigmatism aberrations, and internal higher-order, total spherical and tetrafoil aberrations in comparison to emmetropic eyes. The magnitude of astigmatism was positively associated with all overall RMS aberrations and with internal higher order, coma, total coma, total spherical and tetrafoil aberrations. Eyes with with-the-rule astigmatism showed higher RMS values of coma and total coma compared to eyes with against-the-rule and oblique astigmatism. Conclusions Higher-order aberrations are dependent on the spherical as well as astigmatic components of refractive error. These findings enhance the current understanding of the emmetropisation process and visual function development.

Method comparison and overview of refractive measurements in children: implications for myopia management

ObjectiveThis study investigated the agreement between objective wavefront-based refraction and subjective refraction in myopic children. It also assessed the impact of cyclopentolate and refraction levels on the agreement.MethodsA total of...

Evaluation of a new portable corneal topography system for self-measurement using smartphones: a pilot study.

Herein, we propose the use of the "KeraVio Ring", which is a portable, selfie-based, smartphone-attached corneal topography system that is based on the Placido ring videokeratoscope. The goal of this study was to evaluate and compare corneal parameters between KeraVio Ring and conventional corneal tomography images. We designed the KeraVio Ring as a device comprising 3D-printed LED rings for generating Placido rings that can be attached to a smartphone. Two LED rings are attached to a cone-shaped device, and both corneas are illuminated. Selfies were taken using the KeraVio Ring attached to the smartphone without assistance from any of the examiners. Captured Placido rings on the cornea were analysed by intelligent software to calculate corneal parameters. Patients with normal, keratoconus, or LASIK-treated eyes were included. Anterior segment optical coherence tomography (AS-OCT) was also performed for each subject. We found highly significant correlations between the steepest and flattest keratometry, corneal astigmatism, and vector components obtained with the KeraVio Ring and AS-OCT. In subjects with normal, keratoconus, and LASIK-treated eyes, the mean difference in corneal astigmatism between the two devices was -0.8 ± 1.4 diopters (D) (95% limits of agreement (LoA), -3.6 to 2.0), -1.8 ± 3.7 D (95% LoA, -9.1 to 5.5), and -1.5 ± 1.3 D (95% LoA, -4.0 to 1.1), respectively. The experimental results showed that the corneal parameters obtained by the KeraVio Ring were correlated with those obtained with AS-OCT. The KeraVio Ring has the potential to address an unmet need by providing a tool for portable selfie-based corneal topography.

Engineering Orbital Angular Momentum in Structured Beams in General Astigmatic Systems via Symplectic Matrix Approach

We studied theoretically and experimentally the propagation of structured Laguerre–Gaussian (sLG) beams through an optical system with general astigmatism based on symplectic ABCD transforms involving geometry of the second-order intensity moments symplectic matrices. The evolution of the coordinate submatrix ellipses accompanying the transformation of intensity patterns at different orientations of the cylindrical lens was studied. It was found that the coordinate submatrix W and the twistedness submatrix M of the symplectic matrix P degenerate in the astigmatic sLG beam with simple astigmatism, which sharply reduces the number of degrees of freedom, while general astigmatism removes the degeneracy. Nevertheless, degeneracy entails a simple relationship between the coordinate element Wxy and the twistedness elements Mxy and Myx of the submatrix M, which greatly simplifies the measurement of the total orbital angular momentum (OAM), reducing the full cycle of measurements of the Hermite–Gaussian (HG) mode spectrum (amplitudes and phases) of the structured beam to the only measurement of the intensity moment. Moreover, we have shown that Fourier transform by a spherical lens enables us to suppress the astigmatic OAM component and restore the original free-astigmatic sLG beam structure. However, with further propagation, the sLG beam restores its astigmatic structure while maintaining the maximum OAM.

Relationship between dynamic visual acuity and static visual acuity, refractive error, and binocular vision in elite soccer players

ABSTRACT Clinical relevance In many sports, dynamic visual acuity is used. In order to improve dynamic visual acuity, it is important to understand the aspects of the visual system that can cause compromise. Background To investigate the parameters of the visual system that may influence dynamic visual acuity in professional soccer players. Methods In 2022, 40 professional players were analysed. Screening consisted of a survey, the measurement refractive error, and static and dynamic visual acuity and the binocular vision parameters. All athletes were men with a mean age of 24.9 ± 4.8 years. Results The mean refractive error was −0.29 ± 0.61D, and 22.5% of athletes are myopic only and 7.5% hyperopic. Static visual acuity was R: −0.037 ± 0.094 LogMAR , L: −0.036 ± 0.098 LogMAR. Dynamic visual acuity was 0.154 ± 0.118 LogMAR . There is a positive and moderate correlation between monocular static visual acuity and dynamic visual acuity, with r = 0.524 (r2 = 0.275 , p < 0.001) for the right eye and r = 0.553 (r2 = 0.306, p < 0.001) for the left eye. For the component of astigmatism (J = 0) and for stereopsis in distance vision, the correlation was, r = –0.472 (r2 = 0.223, p = 0.002) and r = –0.467 (r2 = 0.218, p = 0.002), respectively. Conclusion Athletes with lower static visual acuity in distance vision, or with worse stereopsis in distance vision or more myopic astigmatism, have lower dynamic visual acuity than other athletes.

Absolute tests of three flats for interferometer with 800 mm aperture.

In this study, absolute tests of three flats were performed by using an 800 mm Fizeau interferometer. The flats were installed by employing double-wedge rubber, and the deformation of the flats, primarily involving power and spherical aberrations, was analyzed by conducting finite element analysis. The measurement results revealed an astigmatism component that did not follow the rotation. The astigmatism was separated from the measurement result, and the remaining aberration was consistent with the simulation results, confirming that the astigmatism deformation did not originate from the rubber installation. Subsequently, an absolute test of an 800 mm flat was completed, and the results were compared with those of the traditional three-flat absolute test and Zygo interferometer. The directions of the vertical diameter lines were consistent. The peak-to-valley difference in the full-surface shape was less than 4 nm, and the root mean square was less than 1 nm. The surface errors of flats A and C were consistent with the result of replacing the reference flat, B, with the fourth flat, D, to perform an absolute test. The difference between flats A and C was similar to Zygo's results, thus eliminating the influence of the transmission flat. These results verified the accuracy of the results.

Ametropia detection using a novel, compact wavefront autorefractor.

Despite the well-known reproducibility issues of subjective refraction, most studies evaluating autorefractors compared differences between the device and subjective refraction. This work evaluated the performance of a novel handheld Hartmann-Shack-based autorefractor using an alternative protocol, which considered the inherent variability of subjective refraction. Participants underwent an initial measurement with a desktop autorefractor, two subjective refractions (SR1 and SR2) and a final measurement with the QuickSee Free (QSFree) portable autorefractor. Autorefractor performance was evaluated by comparing the differences between the QSFree and each of the subjective refractions with the difference between the subjective refractions (SR1 vs. SR2) using Bland-Altman analysis and percentage of agreement. A total of 75 subjects (53 ± 14 years) were enrolled in the study. The average difference in the absolute spherical equivalent (M) between the QSFree and the SR1 and SR2 was ±0.24 and ±0.02 D, respectively, that is, very similar or smaller than the SR1 versus SR2 difference (±0.26 D). Average differences in astigmatic components were found to be negligible. The results demonstrate that differences between QSFree and both subjective refractions in J0 and J45 were within ±0.50 D for at least 96% of the measurements. The limits of agreement (LOAs) of the differences between QSFree and SR1, as well as QSFree and SR2, were higher than those observed between SR1 and SR2 for M, J0 and J45 . A protocol was designed and validated for the evaluation of a refractive device to account for the variability of subjective refraction. This protocol was used to evaluate a novel portable autorefractor and observed a smaller difference between the device and subjective refractions than the difference between the two subjective refraction measurements in terms of mean bias error, although the standard deviation was higher.

Differences Between Keratometry and Total Keratometry Measurements in a Large Dataset Obtained With a Modern Swept Source Optical Coherence Tomography Biometer

This study aimed to explore the concept of total keratometry (TK) by analyzing extensive international datasets representing diverse ethnic backgrounds. The primary objective was to quantify the disparities between traditional keratometry (K) and TK values in normal eyes and assess their impact on intraocular lens (IOL) power calculations using various formulas. Retrospective multicenter intra-instrument reliability analysis. The study involved the analysis of biometry data collected from ten international centers across Europe, the United States, and Asia. Corneal power was expressed as equivalent power and astigmatic vector components for both K and TK values. The study assessed the influence of these differences on IOL power calculations using different formulas. The results were analyzed and plotted using Bland-Altman and double angle plots. The study encompassed a total of 116,982 measurements from 57,862 right eyes and 59,120 left eyes. The analysis revealed a high level of agreement between K and TK values, with 93.98% of eyes exhibiting an absolute difference of 0.25 D or less. Astigmatism vector differences exceeding 0.25 D and 0.50 D were observed in 39.43% and 1.08% of eyes, respectively. This large-scale study underscores the similarity between mean K and TK values in healthy eyes, with rare clinical implications for IOL power calculation. Noteworthy differences were observed in astigmatism values between K and TK. Future investigations should delve into the practicality of TK values for astigmatism correction and their implications for surgical outcomes.

Age-Related Changes in Total Corneal Astigmatism in Eyes With High Myopia.

The purpose of this study was to compare age-related changes in corneal astigmatism in eyes with and without high myopia. Eight-hundred eyes with high myopia (axial length ≥26.0 mm) and 800 eyes without high myopia (200 eyes each from patients in their 40s, 50s, 60s, and ≥70s) underwent videokeratographic examination. The amounts of vertical/horizontal (Rx) and oblique astigmatism (Ry) components, irregular astigmatism, and corneal shape were compared between eyes with and without high myopia and among age categories. In both groups, the mean Rx significantly changed to more positive with age ( P < 0.001), whereas the Ry did not change significantly. The Rx was significantly more negative in the high myopia group than in the control group in all age categories ( P ≤ 0.003), whereas the Ry did not differ significantly. The mean changes in the Rx and Ry during each 2 consecutive decades did not differ significantly between groups. The asymmetry and higher-order irregularity components increased with age ( P ≤ 0.001) but did not differ significantly between groups, except for the higher-order irregularity in patients in their 60s ( P = 0.018). In the averaged map, the corneal shape changed from with-the-rule to against-the-rule astigmatism with age in both groups, but the changes occurred later in the high myopia group. Age-related changes from with-the-rule to against-the-rule astigmatism occurred later in eyes with high myopia compared with eyes without high myopia in middle or older aged patients, but this change in each age decade was comparable between eyes with and without high myopia.

Corneal Higher Order Aberrations and Epithelial Remodeling With Femtosecond Laser-Assisted LASIK Topography-guided and Customized Asphericity Ablation in the Contralateral Eye: A Randomized, Double-Blind, Prospective Study.

To evaluate refractive results, corneal higher order aberrations (HOAs), and epithelial remodeling in the preoperative and postoperative period of regular corneas that had topography-guided femtosecond laser-assisted laser in situ keratomileusis (LASIK) (Contoura WaveLight; Alcon Laboratories, Inc) and compare them with the contralateral eye that underwent ablation customized by asphericity (Custom-Q WaveLight; Alcon Laboratories, Inc) in myopic eyes with or without astigmatism. A prospective, randomized, and double-blind study was conducted. Patients underwent preoperative and postoperative epithelial mapping and corneal tomography to assess the epithelial thickness map, HOAs of the corneal anterior surface, visual acuity, and refractive evaluation. This study enrolled 96 normal eyes of 48 patients. Uncorrected distance visual acuity of 20/20 or better was achieved in 97% of patients and gains in corrected distance visual acuity and effectiveness in correcting refractive astigmatism were similar in both techniques. Seventeen sectors of the corneal epithelium map were assessed by spectral-domain optical coherence tomography and no significant differences were found between techniques preoperatively and postoperatively (P > .05). HOA root mean square, coma Z3±1, trefoil Z3-3, and tissue consumption exhibited statistically significant between-technique differences (P < .05). The Contoura and Custom-Q techniques were similar with respect to refractive and visual outcomes after 3 months, as well as in epithelial remodeling. The Contoura provides lower postoperative HOA root mean square, coma Z3±1, and trefoil Z3-3 values, but the techniques showed no differences in the correction of the corneal astigmatic wavefront component and in the spherical aberration after 3 months. [J Refract Surg. 2023;39(11):751-758.].

Auto-refraction versus subjective refraction in different phakic and pseudophakic conditions: the Tehran Geriatric Eye Study (TGES).

To compare the subjective refraction data with non-cycloplegic auto-refraction findings in the geriatric population above 60 years of age according to the different crystalline lens conditions. This report is a part of the Tehran Geriatric Eye Study (TGES) that was conducted from January 2019 to January 2020 on elderly population 60 years of age and above in Tehran. The samples were selected by multi-stage stratified random cluster sampling. Of 3791 individual invitees, 3310 (response rate: 87.3%) participated in this study. All study participants underwent non-cycloplegic auto-refraction (auto-refractometer/keratometer Nidek ARK-510) and subjective refraction. Regarding the sphere, eyes with mixed cataract had the worst limits of agreement (LoA: -1.24 to 0.87) and the best agreement was related to the pseudophakic eyes (LoA: -0.83 to 0.54). The highest (0.27±0.31 D) and lowest (0.21±0.27 D) differences between the two methods regarding the cylinder power were observed in eyes with cortical cataract and normal eyes, respectively. The worst LoA between the two methods in measuring the cylinder power was related to the eyes with mixed cataract (LoA: -0.44 to 0.96). Regarding the J0 (horizontal/vertical components of astigmatism), the mean values of J0 obtained by auto-refraction were tended more toward against the rule direction in all crystalline lens conditions, and the two methods had the greatest difference in cortical cataract cases (0.05±0.17 D). Regarding the J45 (oblique components of astigmatism), the lowest (0±0.11 D) and highest (-0.01±0.12 D) differences were observed in normal eyes and eyes with cortical cataract, respectively. The auto-refractometer/keratometer Nidek ARK-510 results in the elderly with different phakic and pseudophakic conditions do not correspond well with subjective refraction findings. This discrepancy in spherical findings is more pronounced in individuals with mixed cataract than in other cases.

Revisiting Javal's rule: a fresh and improved power vector approach according to age.

The scientific community has established Javal's rule as a model linking refractive (RA) and keratometric (KA) astigmatism since its appearance more than 100 years ago. The aim was to improve the accuracy of this relationship according to subject's age by applying the power vector analysis. Posterior corneal curvature has also been studied. The IOLMaster 700 optical biometer was used to measure the corneal thickness and the radius of curvature of the anterior and posterior corneal surfaces. Refractive error was determined by a non-cycloplegic subjective refraction process with trial lenses. Linear regression analyses were applied using J0 and J45 power vector components. An evaluation was carried out according to the subject's age resulting into eight regression relationships for each astigmatic vector component for each relationship. A total of 2254 right eyes from 2254 healthy subjects were evaluated. A trend towards against-the-rule astigmatism (ATR) was found with aging, both for refractive astigmatism (RA) and keratometric astigmatism (KA), with 95.2% of subjects under 20 years old having with-the-rule (WTR) KA, and only 22.8% above 79 years old. The following regression equations were found between RA and KA: [Formula: see text] = 0.73 × [Formula: see text] - 0.18 (R = 0.78) and [Formula: see text] = 0.70 × [Formula: see text] + 0.04 (R = 0.69) and between RA and total corneal astigmatism (TCA): [Formula: see text] = 0.73 × [Formula: see text] + 0.13 (R=0.78) and [Formula: see text] = 0.70 × [Formula: see text] - 0.06 (R = 0.68) for the whole sample, but with sensible differences among age groups, both in the slope and in the intercept. Ignoring the age of the subject when using Javal's rule could lead to an error in the final cylinder calculation that would increase in high astigmatisms. Applying this new power vector approach based on subject's age could improve the accuracy of the astigmatism prediction.

Size of living space as a moderator for central and peripheral refractions in children

Undesirable living environment may impose risk on myopia development. Furthermore, peripheral refractive error was suggested to contribute to juvenile eye growth modulation. This study aimed to investigate the interaction between peripheral refractive error and living environment in relation to central refractive status in Hong Kong schoolchildren. Central and peripheral refractive errors, axial length (AL), and corneal radius of curvature (CR) were measured in 573 schoolchildren (age 9.5 ± 0.9 years). The AL/CR ratio was used to represent the central refractive status, accounting for non-cycloplegic refraction. The relative peripheral refractive errors (RPRE) up to ± 20° eccentricities were converted into power vectors: spherical-equivalent error (SER) and J0 astigmatic components and fitted with quadratic equations. The second-order coefficients of SER (aSER) and J0 astigmatism (aJ0) and home size reported by parental questionnaires were analyzed to indicate their relationships with AL/CR. Our results showed that children with higher AL/CR lived in smaller homes (p = 0.01) and had a more hyperopic (p < 0.001) but less astigmatic RPRE (p = 0.01). We further analyzed the relationship between AL/CR with RPRE for children living in small (< 300 ft2), moderate (300–600 ft2), and large home sizes (> 600 ft2). Regardless of the home size, a higher AL/CR remained moderately correlated with a more hyperopic aSER (all p < 0.001). However, a higher AL/CR was associated with a more positive aJ0 only in children living in large homes, and the relationships were not significant for small and moderate home sizes. Linear regression models further indicated that home size was a significant moderator contributing to the relationship between AL/CR and aJ0. In conclusion, our results were consistent with previous studies, showing that children with axial myopia usually lived in smaller homes and had more hyperopic defocus and more positive J0 astigmatism. However, the relationship between peripheral astigmatism and axial refraction was modulated by the home size of Hong Kong schoolchildren. While peripheral astigmatism is hypothesized as a visual cue for axial refractive development in children, extrinsic environmental factors, such as home size, might interfere with the relationship and dominate refractive development.