Axis Of Astigmatism Research Articles

Wavefront aberrations in aging measured with Hartmann-Shack at 3- and 5-mm pupil sizes.

Visual acuity (VA) depends on many factors. When the goal is to assess retinal health rather than performance, then using a 3-mm pupil reduces unwanted wavefront aberrations. The axis of astigmatism can still potentially change with age. When VA measurements are intended to quantify the status of the retina, extraneous optical aberrations can make the measured VA worse and introduce variability, particularly in aging eyes. Our study quantifies wavefront aberrations for a 3-mm pupil, which is similar to the theoretical optical size for best VA, versus a 5-mm pupil. The wavefront aberrations of normally sighted adults (N = 39; age, 41.9 ± 16.3 years) were measured for a 3- and 5-mm pupil setting without pupil dilation, using a commercially available and semiautomatic instrument (Pentacam AXL WAV; Oculus Optikgeraete GmbH, Wetzlar, Germany). The mean wavefront errors from the average of three measurements with three samples each were computed for each Zernike term orders 1 to 6 and correlated with age. The difference of measurement 1 and measurement 2 provided the test-retest values. Each 3-mm pupil measurements had a reduced average aberration for all 26 aberrations Zernike values, and 21 of 26 were statistically significant (p<0.05). The variability of the Zernike values was less for the 3-mm pupil than for the 5-mm pupil for all 26 measured aberrations pooled (Zernike orders 1 to 6), which was statistically significant (F = 54.625, p<0.001). Most mean aberrations did not vary significantly with age for a 3-mm pupil, except for vertical astigmatism, horizontal coma, spherical aberration, and vertical quadrafoil. Against-the-rule astigmatism was more common in subjects >60 than <40 years old (p=0.05). The findings of this study indicate that measurements of VA to assess retinal health could be made less dependent on unrelated and unwanted anterior segment factors by using a 3-mm pupil, because the wavefront aberrations for a 3-mm pupil were less than those for a 5-mm pupil. The change with age in vertical astigmatism more than oblique is consistent with the expected increase in proportion of against-the-rule astigmatism.

Repeatability of Pentacam HR in Keratoconus According to Two Different Scan Protocols: 25-3D Scan and 50-Cornea Fine.

Background: This study aims to evaluate the repeatability of the Pentacam HR, comparing two different measurement modes (50-cornea fine and 25-3D scan) in patients affected by keratoconus. Methods: Multicenter retrospective study, conducted at Eye Clinic of the ASST-Spedali Civili-University of Brescia, Italy, and St. Paul's Eye Unit, Royal Liverpool University Hospital, United Kingdom. A total of 72 eyes from 72 patients with keratoconus underwent six consecutive measurements, three using the 25-3D scan mode and three with the 50-Cornea fine mode. Measurements were made by one single observer, using the Scheimpflug corneal tomographer camera (Pentacam HR, Oculus, Wetzlar, Germany). Repeatability was assessed using the within-subject SD (Sw) statistic from a two-way analysis of variance. Results: Both measurement modes had excellent repeatability. The interclass coefficient correlation (ICC) was excellent (>0.9) in all the parameters evaluated, apart from anterior and posterior astigmatic axes and posterior astigmatism (ICC > 0.8) and index of height asymmetry (IHA) (ICC < 0.6). However, in 18 of 29 parameters, the ICC was higher in case of 25-3D scan. Repeatability limit for Kmax was 1.00D in 25-3D scan mode and 1.02D in case of 50-cornea fine. Conclusions: 25-3D scan may be preferable to 50-Cornea fine, in view of having slightly higher ICC in case of patients with keratoconus. Repeatability limits reported may be helpful in clinical practice for assessing the progression of keratoconus.

Corneal topographic and aberrometric changes in patients with acquired blepharoptosis after levator resection surgery

Objective: To evaluate changes in corneal topography and aberrometry in patients with acquired blepharoptosis after levator resection surgery. Methods: This prospective, interventional study evaluated 30 eyelids of 19 patients who underwent levator resection surgery for acquired blepharoptosis with fair and good levator function (LF). Patients underwent corneal topography before and 3 months after surgery. Results: Eleven patients had bilateral, and 8 patients had unilateral surgery. There were significant decreases in steep keratometry (K2) (preoperative: 46.21±5.02, postoperative: 44.58±2.11, P=0.046) and corneal astigmatism (preoperative: 2.98±0.61, postoperative: 1.59±1.50, P=0.034). There were no statistically significant differences between the preoperative and postoperative values of flat keratometry (K1) (P=0.585), mean keratometry (Kmean) (P=0.122), axis of corneal astigmatism (P=0.548), central corneal thickness (P=0.350), anterior chamber depth (P=0.747) and anterior chamber volume (P=0.679). The root mean square (RMS)-higher order aberrations (HOA) (P&amp;lt;0.001), RMS-Coma (Z₃¹) (P&amp;lt;0.001), and RMS-Trefoil (Z₃³) (P=0.005) decreased significantly. Preoperative and postoperative values of the seconder astigmatism (P=0.345), RMS-spherical aberration (Z₄⁰) (P=0.255), and RMS-Quadrafoil (Z₄⁴) values were found similar. Conclusions: Levator resection for acquired blepharoptosis can improve the topography and aberrometry measurements of the cornea 3 months after surgery.

Correction of low to moderate corneal astigmatism by steep-axis incision in image-guided cataract surgery

Objective: To explore the corrective effect of cataract extraction surgery combined with a 2.8 mm steep-axis corneal incision under ophthalmic surgical navigation on low-to-moderate corneal astigmatism and different types of corneal astigmatism. Methods: A prospective cohort study was conducted. Patients with age-related cataract who underwent cataract extraction combined with single-focus intraocular lens implantation in the Department of Ophthalmology at the Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine from June to October 2023 and had a total corneal regular astigmatism degree of ≥0.50 D and <1.50 D were continuously collected. Patients were divided into a low-degree group (<1.00 D) and a moderate-degree group (≥1.00 D) according to corneal astigmatism degree. Simultaneously, they were classified into with-the-rule (WTR), against-the-rule (ATR), and oblique astigmatism based on preoperative corneal astigmatism axis position. Subjective refraction and anterior segment biometer examination were performed before and 3 months after surgery, respectively. Vector analysis of corneal astigmatism was conducted using the Alpins vector analysis method. The main observational indicators included target induced astigmatism, surgically induced astigmatism, and the correction index. Results: A total of 95 patients (110 eyes) were collected in this study. Thirteen patients (18 eyes) were lost to follow-up, and finally 82 patients (92 eyes) were included. In the low-degree group, there were 14 males (16 eyes) and 26 females (23 eyes), with an age of (69.62±12.22) years. In the moderate-degree group, there were 13 males (15 eyes) and 33 females (35 eyes), with an age of (72.98±8.28) years. The target astigmatism correction amount, surgically induced astigmatism, and deviation vector in the low-degree group were all smaller than those in the moderate-degree group (all P<0.05). Postoperative corneal astigmatism in both groups was undercorrected. The correction index in the low-degree group (0.88±0.44) was greater than that in the moderate-degree group (0.59±0.34) (P=0.001), and the undercorrection proportion in the moderate-degree group (90.00%, 45/50) was much higher than that in the low-degree group (57.14%, 24/42). In the low-degree group, the correction index from high to low was WTR (1.07±0.41), oblique (0.90±0.58), and ATR astigmatism eyes (0.69±0.37). After multiple comparison analysis, the correction index of WTR astigmatism eyes was significantly higher than that of ATR astigmatism eyes (P<0.05). The success index from high to low was oblique (0.82±0.57), ATR (0.74±0.39), and WTR astigmatism eyes (0.68±0.43). In the moderate-degree group, the order of the correction index from high to low was the same as that in the low-degree group, also WTR (0.79±0.33), oblique (0.71±0.50), and ATR astigmatism eyes (0.53±0.30), but there was no statistical significance among the three (P>0.05). In the low-degree group, there were 6 WTR astigmatism eyes undercorrected, fewer than 12 overcorrected eyes; there were 16 ATR astigmatism eyes undercorrected, more than 3 overcorrected eyes. In the moderate-degree group, there were 6 WTR astigmatism eyes undercorrected, more than 2 overcorrected eyes, but there were 2 ATR astigmatism eyes overcorrected, fewer than 34 undercorrected eyes. Conclusions: Cataract extraction surgery combined with a steep-axis corneal incision can achieve a certain astigmatism correction effect in patients with preoperative low-to-moderate corneal astigmatism. Patients with a preoperative corneal astigmatism degree of mild can achieve a better astigmatism correction effect than those with moderate, especially in the WTR astigmatism population. However, for cataract patients with preoperative corneal astigmatism of moderate and WTR astigmatism, a steep-axis corneal incision can also be combined to correct astigmatism as it can achieve the expected postoperative "with-the-rule undercorrection".

Impact of Astigmatism on Axial Elongation in School-Age Children: A Five-Year Population-Based Study in Tianjin, China.

To investigate the progression rates of axial length (AXL) among school-age children with baseline astigmatism and spherical ametropia. Annual vision screenings were conducted at seven schools in Tianjin, China, from 2018 to 2022. Ocular biometry and non-cycloplegic autorefraction were collected. Children 5 to 16years old without any myopia interventions were included and categorized by their baseline astigmatism magnitude (control, low, or high) and axis orientation (with the rule [WTR], against the rule [ATR], or oblique). Additionally, children were classified by baseline spherical ametropia (compound hyperopic, compound myopic, or other). Annual AXL progression rates of right eyes were calculated using regression models and compared across different types of astigmatism and spherical ametropia. A total of 10,732 Chinese children (baseline age, 9.26 ± 2.42years; follow-up duration, 2.63 ± 1.01years) were included and divided into a younger cohort (age<11years; n=7880) and an older cohort (age≥11years; n=2852). Across both age groups and all astigmatism magnitudes, ATR astigmatism exhibited the most rapid AXL progression, followed by oblique and WTR astigmatism. Two-way ANCOVA of the combined cohort revealed that both high-magnitude and ATR astigmatism were significantly associated with AXL progression (P≤0.018). However, the impact of astigmatism on AXL progression varied depending on baseline spherical ametropia, as high-magnitude and ATR astigmatism increased AXL progression in compound myopic eyes but decreased progression in compound hyperopic eyes. Both baseline magnitude and axis orientation of astigmatism are significantly associated with axial elongation in children. However, these associations may vary with spherical ametropia, with differential patterns being observed between compound hyperopic and myopic eyes.

Scleral sutured toric intraocular lens with pars plana vitrectomy for the correction of corneal astigmatism without capsular support.

To describe the repair of a patient with bilateral subluxed cataract and corneal astigmatism in the setting of a coloboma of the iris, zonules, lens, and retina. Pre-operatively his best corrected acuity was 20/500 OD and 20/200 OS. His pre-operative refraction was -7.25 +1.00 at 080 OD and -7.75 +3.00 at 040 OS. On corneal topography, he had 1.95D and 1.45D of regular astigmatism in the right and left eye respectively. This technique involves pars plana vitrectomy in combination with the placement of a MX60 toric intraocular lens fixated to the sclera using 8-0 Gore-Tex in line with the axis of steep corneal astigmatism. The lens is affixed through two pair of nasal and temporal sclerotomies, with each pair located 3 mm posterior to the limbus and 5 mm apart, centered along the axis of steep astigmatism. Post-operatively the patient was 20/25 uncorrected OD and 20/20 uncorrected OS with a refraction of -0.75 +0.50 at 180 in the OD and -0.75 +1.00 at 180 in the OS. Scleral sutured toric intraocular lens placement and pars plana vitrectomy is a viable solution for patients with regular corneal astigmatism and cataract repair in the absence of zonular support.

Incision-related astigmatism on the anterior and total cornea after implantable collamer lens implantation.

To evaluate incision-related astigmatism (IRA) on the anterior and total cornea after implantable collamer lens (ICL) implantation through superior and temporal corneal incisions. The retrospective study included 141 eyes of 80 consecutive patients who underwent ICL implantation. An ocular examination was performed preoperatively and at 1 and 6 months postoperatively. The magnitude and axis of corneal astigmatism were assessed with keratometry (AstigK) and total corneal refractive power (TCRP, AstigTCRP) using a Scheimpflug camera, while the IRA obtained from keratometry (IRAK) and TCRP (IRATCRP) were evaluated using vector analysis. At 6 months, AstigK significantly decreased from 1.45 ± 0.72 D to 1.15 ± 0.75 D in the superior incision group, whereas it increased from 1.70 ± 0.74 D to 1.88 ± 0.79 D in the temporal incision group (both P < 0.001). AstigTCRP significantly decreased from 1.32 ± 0.74 D to 1.09 ± 0.80 D in the superior incision group, while it increased from 1.61 ± 0.78 D to 1.83 ± 0.86 D in the temporal incision group (both P < 0.001). IRAK was 0.55 ± 0.30 D and 0.35 ± 0.25 D in the superior and temporal incision groups, respectively, while IRATCRP was 0.50 ± 0.28 D and 0.40 ± 0.26 D in the superior and temporal incision groups, respectively. IRAK was larger in the superior incision group than in the temporal incision group for both low- (P = 0.009) and high-astigmatism (P = 0.017). Incisions in ICL surgery cause corneal flattening in the meridian of the incision. The superior incision had a greater IRAK compared to the temporal incision.

Quantitative Evaluation of the Effects of Blepharoplasty on Visual Field, Corneal Changes, and Cosmetic Appearance.

Blepharoplasty is an important eyelid surgical procedure, involving aesthetic and functional changes to the eyelids. The aim of this study is to investigate the effects of upper eyelid blepharoplasty on changes in the visual field, corneal changes, and cosmetic appearance. This study was performed with preoperative and postoperative facial photographs of 32 patients who underwent bilateral blepharoplasty. Marginal reflex distance (MRD1), percentage of corneal exposure area (CEA), and brow height (BH) were obtained from photographs. intraocular pressure (IOP) and ocular biometric parameters were also obtained. The morphometric and ocular parameters obtained from preoperative, postoperative first-month, and postoperative third-month patients were compared using repeated measures ANOVA test. Significant differences in MRD1, CEA, and BH were observed between preoperative, postoperative first-month, and postoperative third-month patients. Improvements were observed in left axis and right corneal astigmatism axis measurements in the postoperative third month compared with preoperative measurements, and the positive change was statistically significant (P=0.020, P=0.036). Upper eyelid blepharoplasty could provide satisfactory functional and aesthetic outcomes by contributing to the improvement of pseudoptosis and reduction in eyebrow height postoperatively.

Change in Axial Length and Astigmatism after Scleral Buckling in Patients of Rhegmatogenous Retinal Detachment

Purpose: To determine changes in axial length and corneal astigmatism caused by scleral buckling in patients of uncomplicated retinal detachment undergoing scleral buckling procedure. Study Design: Quasi-experimental design. Place and Duration of Study: Peshawar Medical College and Allied hospitals, Pakistan from December, 2020 to May, 2021. Methods: This study included60 patients of uncomplicated rhegmatogenous retinal detachment, recruited through consecutive sampling technique and managed with primary scleral buckling. After a detailed history and complete examination including A-scan and Keratometric readings, patients underwent scleral buckling procedure. Changes in axial length and corneal curvatureswere measured at 6 months follow up. Quantitative analysis was done using paired T test. Results: Mean age of the sample was 41.95±13.67 years. The sample consisted of 42 males and 18 females. Encircling Band was used in 46 patients, segmental circumferential tire was used in 58 patients in one or more quadrants depending on the extent of the retinal detachment. Two patients underwent additional surgeries. The pre-operative mean axial length (AL) was 23.44±1.51 mm and post-operative AL at 6 months was 24.25±1.61mm (p &lt; 0.05). The pre-operative and post-operative astigmatism were 1.08±0.43 and 1.75 ± 0.33 diopter respectively (p &lt; 0.05). Conclusion: Scleral buckling led to a significant increase in axial length and astigmatism over a 6-month period. These changes suggest that scleral buckling can alter the optical properties of the eye, potentially affecting visual acuity and requiring careful consideration of these factors in post-operative management.

Objective Refraction Status before and after Cycloplegia: From Childhood to Young Adulthood.

This study aimed to evaluate the clinical information revealed after cycloplegia and assess how age and non-cycloplegic refractive status influence the classification of types of refractive error, as well as the relationship between age and cycloplegia-induced changes in the power of refractive errors. We analysed the records of 472 non-population-based ophthalmology practice patients aged 3-28 years (mean ± SD: 9.1 ± 4.6). Cycloplegia was induced with one drop of cyclopentolate 1% in each eye, and eye refraction was measured 30 ± 5 min later using an objective autorefractometer. Cycloplegia induced a clinically significant (≥0.50 D) hyperopic shift in the spherical equivalent of 60.2% of participants and a myopic shift in 1%, resulting in a 34.1% increase in the frequency of participants with hyperopia, while the frequency of those with myopia and emmetropia decreased by 5.5% and 23.3%, respectively. The average spherical equivalent difference (mean ± SD) induced by cycloplegia was 0.72 ± 0.73 D, with the highest difference observed in the 3-5 years age group (1.18 ± 0.85 D). The differences in astigmatism power (p = 0.84) and astigmatism axis (p = 0.97) between non-cycloplegic and cycloplegic conditions were not statistically significant.

Investigating the topographic effect of epithelium in myopic eyes with subtle topographic preoperative abnormalities.

To explore the topographic effect of the epithelium in keratoconus suspected (KCS) and in normal Placido classified corneas. Rothschild Foundation, Paris, France. Prospective interventional case series. Anterior corneal specular Placido topography using OPD-Scan II was performed in 97 eyes of 67 patients undergoing photorefractive keratectomy for myopia, before and after epithelium removal. The differences in axial keratometry, asphericity, and astigmatism were computed. After epithelial peeling, some Placido-normal classified corneas became KCS. Therefore, we have subdivided this group into 2 groups: one of normal classified corneas which stayed normal after epithelium removal (Group NN) and another of corneas that became KCS classified (Group NK). The mean difference in axial mean keratometry in the third central millimeter rings was +0.50 ± 0.24 diopters (D), 0.69 ± 0.31 D, and 0.49 ± 0.35 D and the mean difference in the magnitude of epithelial-induced astigmatism in the first central millimeter ring was 0.37 D × 89 degrees (positive cylinder), 0.54 D 86 degrees, and 0.52 D 86 degrees, respectively, in Group NN, NK, and KK (KCS corneas that stayed KCS). These differences were significant ( P < .0001). Preoperative keratometry was the only predictive factor differentiating Group NN from NK ( P < .001). The epithelial layer tended to reduce the magnitude of the Bowman layer's astigmatism, prolateness, and keratometry, more importantly in Group NK. In the KK group, we found a similar trend as in normal eyes (Group NN). The epithelium would be able to mask Bowman layer's irregularities until a certain degree of severity.

Clinical examples of correct orientation of a toric intraocular lens in patients with postkeratotomic corneal ectasia

BACKGROUND: Surgical treatment of cataract in patients with postkeratotomic corneal ectasia has various features. First, difficulties arise when calculating the optical strength of an intraocular lens and its cylindrical component and determining the location of the main axes of astigmatism for toric intraocular lens implantation. Additionally, not all modern keratotopography installations are able to accurately determine the refractive power of the cornea in such patients owing to pronounced irregular astigmatism and a large difference in keratometric parameters in the main meridians. CLINICAL CASES DESCRIPTION: Two clinical cases of surgical treatment of cataract in combination with postkeratotomic keratectasia are presented. Patients underwent a standard preoperative ophthalmological examination. TMS-4 Tomey keratotopograph was used to accurately determine the refractive power of the cornea. The optical power of toric intraocular lens were calculated using the Holladay 2 formula with amendments for radial keratotomy and the Johnson Johnson VISIC online calculator. SN6AT9 intraocular lens (Alcon) and a Tecnis ZCT800 toric intraocular lens (Johnson Johnson) were implanted in patients. The orientation of the position of the cylinder axis of toric intraocular lens was performed perpendicular to the most flattened meridian, corresponding to the position of the keratectasia zone, determined by the most expanded keratotomy scar. Before surgery, the best corrected visual acuity of patient M was OD=0.2, OS=0.4 and that of patient K was OD=0.4, OS=0.2. After surgery, the best corrected visual acuity of patient M was OD=0.8, OS=0.8 and that of patient K was OD=0.8, OS=0.7. CONCLUSION: This study aimed to familiarize practicing ophthalmologists, clinical residents, and postgraduates with a possible treatment option for cataracts by phacoemulsification with implantation of a toric intraocular lens in patients with postkeratotomic keratectasia. The resulting high visual acuity and subjective satisfaction of patients indicate the accuracy of chosen treatment tactics. A reliable visual guide for choosing the cylinder axis is the meridian of the greatest degree of keratectasia (cornea flattening), which is determined by the maximally expanded keratotomy scar position. The intraocular lens cylinder axis is oriented perpendicular to the keratectasia meridian. Ultrasound phacoemulsification of cataract with implantation of a toric intraocular lens is an effective method for correcting induced ametropia after radial keratotomy against the background of postkeratotomy keratectasia with high astigmatism.

Effect of Computer Tasks in Straight Gaze on Corneal Topographic Indices.

To investigate the effect of the near visual task of movie-watching in the straight gaze position on corneal topographic parameters. Thirty myopic young adults with an average age of 25.10 4.13 years were recruited for the study. The designed near visual task consisted of watching a movie in the straight gaze position at a distance of 40 cm for 30 minutes. Corneal topography was performed using Oculus Keratograph 4 (OCULUS, Wetzlar, Germany) before and immediately after watching the movie, as well as at 10, 20, and 30 minutes intervals after completing this near visual task. Zernike coefficients, asphericity indices, refractive parameters, and diagnostic indices of keratoconus were recorded for statistical analysis. Movie-watching at a close distance solely using the straight gaze position had no effect on Zernike coefficients (P 0.130). Also, watching the movie had no effect on other corneal topography parameters including irregularities (P = 0.208), spherical eccentricity (P = 0.270), maximum decentration (P = 0.553), axis of maximum decentration (P = 0.186), peripheral astigmatism (P = 0.179), and average asphericity of the quadrants at 10 to 30º (P 0.163). The results of the present study showed that watching movies in the straight gaze position had no effect on corneal topographic parameters and did not cause errors in corneal topographic measurements.

Accuracy of Toric Intraocular Lens Formulas With Measured Posterior Corneal Astigmatism of Different Orientations

PurposeTo assess whether the use of measured posterior corneal astigmatism (PCA) values improves the prediction accuracy of toric intraocular lens power formulas, compared to predicted PCA values, when the orientation of the steep axis of PCA is non-vertical. DesignRetrospective observational cohort study Methods418 eyes of 344 patients were included in the study. Prediction errors (PE) for postoperative refractive astigmatism at 4 weeks postoperatively were determined using vector analysis and compared for the following toric intraocular lens power formulas: Barrett Toric with predicted posterior corneal astigmatism (PPCA); Barrett Toric with measured posterior corneal astigmatism (MPCA); EVO Toric PPCA; EVO Toric MPCA; Holladay I with Abulafia-Koch regression. Subgroup analysis compared PEs for eyes with a vertically orientated steep axis of PCA (60-120o) to eyes with a non-vertically orientated steep axis of PCA. SettingCathedral Eye Clinic, Belfast, United Kingdom and Tan Tock Seng Hospital, Singapoore. ResultsStandard keratometry was with-the-rule in 48% of eyes, while the steep PCA axis was vertically orientated in 91% of eyes. For all eyes, EVO PPCA had a smaller mean absolute error than Barrett-MPCA, Barrett-PPCA and Abulafia-Koch (p < 0.01 for all). EVO-PPCA had the highest percentage of eyes within 0.50D of predicted postoperative astigmatism for eyes with vertical PCA (61%), while EVO-MPCA had the highest percentage for eyes with non-vertical PCA (54%). EVO-MPCA had the smallest centroid error for all eyes, and the subgroups (p < 0.01 for all). Eyes with non-vertical PCA had a lower percentage within 0.50D than eyes with vertical PCA when using PPCA (43% vs 61%, p = 0.034), but there was no significant difference between these groups when MPCA is used for eyes with non-vertical PCA (54% vs 61%, p = 0.40). ConclusionsWhen the steep axis of posterior corneal astigmatism is not vertically orientated, the use of measured posterior keratometry values improves prediction accuracy.

Comparison of photorefraction by Plusoptix A12 and cycloplegic autorefraction in children

BackgroundPlusoptix photoscreeners are capable of measuring refractive errors of children from 1 meter distance, without cyloplegia. We aimed to compare refractive data obtained from the newest version of Plusoptix (model 12) with cycloplegic autorefraction.MethodsWe examined 111 consecutive children aged 3-7 years first by Plusoptix A12C under manifest condition and subsequently for cycloplegic refraction by Topcon KR-1 tabletop autorefractometer. Sphere, spherical equivalent, cylinder and axis of astigmatism measured by the two methods were analyzed to determine correlation, agreement and differences.ResultsBinocular examination of 111 children aged 4.86±1.27 years revealed good agreement between refractive data obtained by Plusoptix and cycloautorefraction, according to Bland-Altman plots. Significant (p < 0.001) and strong correlation was found between all refractive measurements (Pearson’s r value of 0.707 for sphere, 0.756 for pherical equivalent, and 0.863 for cylinder). Plusoptix mean sphere, spherical equivalent and cylinder were 1.22, 0.56, and -1.32 D, respectively. Corresponding values for cycloautorefraction were 1.63, 1.00, and -1.26 D. The difference between axis of cylinder measured by the two methods was < 10° in 144 eyes (64.9%).ConclusionsConsidering the significant agreement and correlation between Plusoptix photoscreener and cycloplegic autorefraction, the need for cycloplegic drops in refractive examination of children may be obviated. The mean difference between cylinder measurements are considerably trivial (0.06 D), but sphere is approximately 0.4 D underestimated by Plusoptix compared to cycloautorefraction, on average.

Refractive changes associated with oculoplastic surgeries: A scoping review.

To carry out a comprehensive critical review of the peer-reviewed literature on the refractive changes associated with oculoplastic surgeries. This review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) statement recommendations. Following specific inclusion and exclusion criteria, 20 articles were selected for the current scoping review. Each of them was analyzed carefully and their risk of bias was assessed with the Quality Assessment Tool for case Series Studies from the National Heart, Lung and Blood Institute. Data of 1428 eyes from 1051 patients were analyzed. All studies were case series. Regarding the oculoplastic pathologies, five articles focused on dermatochalasis, four on chalazion, five on ptosis and six on congenital ptosis. Most articles did not report changes in the spherical equivalent (SE), astigmatism changes of less than 0.5 diopters (D), changes in astigmatism axis of less than 11 degrees and changes in uncorrected distance visual acuity (UDVA) of less than 0.06 logMAR. Out of the 20 articles reviewed, 6 achieved a risk of bias score between 6 and 8, representing a low level of evidence and highlighting the limitations in the study design. Based on the findings of this study, there is no evidence to suggest clinically significant refractive changes following oculoplastic surgeries. The most notable changes may occur after surgery for severe ptosis; however, further research is needed to confirm this observation.

Changes in Corneal Epithelial Thickness in Different Areas After Femtosecond Laser-Assisted LASIK in Patients With High Astigmatism.

To explore changes in corneal epithelial thickness (CET) after femtosecond laser-assisted laser in situ keratomileusis in patients with high astigmatism. CET was measured at every intersection of the concentric circles and specific axes using AngioVue optical coherence tomography (Angio-OCT) preoperatively and 1 month postoperatively. The average thickness of corneal central, paracentral, and peripheral regions was the mean of the points within the central 2, 2 to 5, and 5 to 7 mm areas, respectively. Correlation analysis was performed to investigate the association between CET along different axes and other preoperative and postoperative parameters. Forty-two eyes of 28 patients were included. CET along the astigmatic (K1) and perpendicular (K2) axes in the central and paracentral areas increased (P < .001), whereas that along the K2 axis decreased in the peripheral area 1 month postoperatively (P = .001). The amount of CET change in the peripheral area between the K1 and K2 axes was significantly different (P < .001). In the central area, the change in CET along the K2 axis was positively correlated with ablation depth (r = 0.315, P = .042) and negatively with refractive power after surgery (r = -0.347, P = .024). In the peripheral area, the changes in CET along both K1 and K2 axes were negatively correlated with ablation depth (r = -0.431, P = .004; r = -0.387, P = .011, respectively). Epithelial modeling differed between the different astigmatism axes after refractive surgery. The compensatory response of the corneal epithelium is more pronounced along the steeper axis. [J Refract Surg. 2024;40(4):e239-e244.].

Calculation of the total corneal astigmatism using the virtual cross cylinder method on the secondary principal plane of the cornea

This study aimed to establish a virtual cross cylinder method to calculate the total corneal astigmatism by combining the anterior and posterior corneal astigmatism on the secondary principal plane of the cornea based on Gaussian optics. The meridian with the least refractive power, namely, the flattest meridian of the virtual cross cylinder of a ± 0.5 × C diopter, is set as the reference meridian, and the power (F) at an angle of φ between an arbitrary meridian and the reference meridian is defined as F(φ) = − 0.5 × C × cos2φ. The magnitude and axis of the total corneal astigmatism were calculated by applying trigonometric functions and the atan2 function based on the combination of the virtual cross cylinders of the anterior corneal astigmatism and the posterior corneal astigmatism. To verify the performance of the virtual cross cylinder method, a verification experiment with two Jackson cross cylinders and a lensmeter was performed, and the measured and calculated values were compared. The limit of the natural domain of the arctangent function is circumvented by using the atan2 function. The magnitude and axis of the total corneal astigmatism are determined through generalized mathematical expressions. The verification experiment results showed good agreement between the measured and calculated values. Compared to the vector analysis method, the virtual cross cylinder method is mathematically sound and straightforward. A novel technique for calculating total corneal astigmatism, the virtual cross cylinder method, was developed and verified.

Subjective versus objective refraction in healthy young adults

PurposeTo evaluate objective and subjective refraction differences in healthy young adults.MethodsData concerning candidates for the Israeli Air Force Flight Academy, as well as active air force pilots in all stages of service who underwent a routine health checkup between the years 2018 and 2019 were retrospectively analyzed. Objective refraction measured using a single autorefractometer was compared with subjective refraction measured by an experienced military optometrist during the same visit. The results were converted to power vectors (spherical equivalent [SE], J0, and J45). To interpret astigmatism using power vector values, the cylinder power (Cp) was determined.ResultsThis study included 1,395 young adult participants. The average age was 22.17 years (range, 17–39, 84.8% males). The average SE was − 0.65 ± 1.19 diopter (D) compared with − 0.71 ± 0.91D in the auto- and subjective refraction, respectively (p = 0.001). Cp was 0.91 ± 0.52D and 0.67 ± 0.40D, respectively (p < 0.001). This difference was more common in older participants (p < 0.001). J0 and J45 value differences were not significant. The absolute SE value of subjective refraction was lower in the myopic (p < 0.001) and hyperopic (p < 0.001) patients.ConclusionsYoung hyperopic participants tended to prefer “less plus” in subjective refraction compared with autorefraction. Young myopic participants tended to prefer “less minus” in subjective refraction compared with autorefraction. All participants, but mainly older participants, preferred slightly “less Cp” than that measured using autorefraction; The astigmatic axis did not differ significantly between the methods.

Determination of the toric axis by using internal astigmatism axis in non-dilated eyes.

To determine the toric intraocular lens (IOL) axis by using internal astigmatism axis obtained from Optical Path Difference (OPD) Scan III (Nidek Co.) in non-dilate eyes. The eyes of patients who underwent toric IOL implantation for astigmatic correction were investigated. Patients who have ocular surface disorder, keratoconus, posterior capsule opacification were excluded. The IOL axis measured in non-dilated eyes in mesopic conditions by OPD scan III device and the IOL axis measured by using classical slit lamp biomicroscopy method in dilated eyes were detected at postoperative 1st and 6th months. Results were compared with correlation and linear regression analysis. Totally, 26 eyes of 18 patients were included. The difference between biomicroscopic IOL axis and OPD internal astigmatism axis was 4.96 ± 4.41 degrees at the 1st month and 3.62 ± 3.5 degrees at the 6th month. There was a significant and high correlation between biomicroscopic IOL axis and OPD internal astigmatism axis at both 1st month (r = 0.992 p < 0.001) and 6th month (r = 0.995 p < 0.001). According to regression analysis, the results of two measurement methods were significantly compatible with each other at 1st month (R Sq = 0.984 p < 0.001) and 6th month (R Sq = 0.990 p < 0.001) and there was a close to ideal linear (R Sq = 1) relationship between two methods. In eyes with toric IOL implantation, the IOL axis and IOL rotation according to target IOL axis can be detected easily and effectively in a short time by OPD scan internal astigmatism axis without the need to dilate the pupil.