Astigmatic Power Research Articles

Epidemiological Characteristics Associated with Astigmatism in a Population of 3- to 5-Year-Old Children in Los Angeles, CA

ABSTRACT Purpose To characterize the prevalence of astigmatism among the heretofore largest published sample of preschool children and to do so among different age, gender, and racial and ethnic subgroups. Methods This study included data from 79,330 preschoolers (49.0% female, 79.4% Latino, mean age 4.29 ± 0.66 years) who were screened using a Retinomax autorefractor between 2012 and 2017. Cylindrical power and astigmatism defined as 1.50 D or more of cylinder were the dependent variables. Children were stratified by age, race/ethnicity, and gender. T-test and chi-square analyses were performed. Results The average cylinder of the sample was found to be 0.65 ± 0.78 D and 11% of the children were astigmatic. Among all children, these values remain stable from age 3 (0.66 ± 0.76 D, 11.2%) to age 4 (0.66 ± 0.79 D, 11.4%, p = .53), but they decrease significantly from age 4 to age 5 (0.61 ± 0.80 D, 10.%, p < .01). Latinos have the highest average cylinder power and prevalence of astigmatism at 0.68 ± 0.82 D and 12.3%, and unlike most other race/ethnic subgroups, they do not experience an age-dependent decrease in astigmatism. While female and male students have equivalent cylindrical refractions broadly, Asian and African American females have higher levels of astigmatism than their male counterparts. Conclusion The data further demonstrate that Latino children in Los Angeles have significantly higher rates of astigmatism, which does not decrease during preschool years. These results emphasize the need for comprehensive school-based screening, especially among Latino enclaves in Los Angeles.

Estimating the astigmatic power of the crystalline lens and eye from ocular biometry.

To estimate the astigmatic power of the crystalline lens and the whole eye without phakometry using a set of linear equations and to provide estimates for the astigmatic powers of the crystalline lens surfaces. Linear optics expresses astigmatic powers in the form of matrices and uses paraxial optics and a 4 × 4 ray transfer matrix to generalise Bennett's method comprehensively to include astigmatic elements. Once this is established, the method is expanded to estimate the contributions of the front and back lens surfaces. The method is illustrated using two examples. The first example is of an astigmatic model eye and compares the calculated results to the original powers. In the second example, the method is applied to the biometry of a real eye with large lenticular astigmatism. When the calculated powers for the astigmatic model eye were compared to the actual powers, the difference in the power of the eye was (where T represents the matrix transpose) and for the crystalline lens, the difference was (power vector format). A second example applies the method to a real eye, obtaining lenticular astigmatism of -5.84 × 175. The method provides an easy-to-code way of estimating the astigmatic powers of the crystalline lens and the eye.

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.

Measurement of invivo lens shapes using IOLMaster 700 B-scan images: Comparison with phakometry.

This study compared invivo crystalline lens shape measurements using B-scan images from the IOLMaster 700 with phakometry. Twenty-four young adult participants underwent IOLMaster 700 and phakometry measurements under cycloplegia (1% cyclopentolate). The IOLMaster 700 generated B-scan images along six meridians in 30° increments, which were analysed using custom MATLAB software to determine lens surface radii of curvature. Phakometry measurements were obtained using Purkinje images reflected from the lens surfaces. The IOLMaster 700 image analysis method yielded a lower mean anterior lens surface spherical equivalent power (+6.20 D) than phakometry (+7.55 D); however, the two measurements were strongly correlated (R(21) = 0.97, p < 0.0001). The astigmatic power vectors (J0 and J45) for the anterior lens surface were significantly higher for the IOLMaster 700 measurements, with only J0 showing a significant moderate positive correlation (R(21) = 0.57, p = 0.005). For the posterior lens surface, the IOLMaster 700 measurements had a higher mean spherical power (+14.28 D) compared to phakometry (+13.70 D); however, a strong positive correlation (R(21) = 0.90, p < 0.0001) was observed. No significant correlations were noted for posterior lens surface astigmatic vectors (J0 and J45). The IOLMaster 700 estimates for the equivalent lens mean spherical power were slightly lower than those for phakometry, with a mean difference of -0.72 D, and both methods were positively correlated (R(21) = 0.94, p < 0.0001). The findings demonstrate that IOLMaster 700 B-scan image analysis technique provides similar estimates of lens surface powers to phakometry. These results highlight the potential of the IOLMaster 700 to provide measurements of lens shape, informing future research and clinical use.

Effect of Long-Acting Diquafosol Sodium on Astigmatism Measurement Repeatability in Preoperative Cataract Cases with Dry Eyes: A Multicenter Prospective Study.

Dry eye can compromise corneal astigmatism measurement repeatability during preoperative cataract surgery examination. No previous studies have analyzed the effectiveness of long-acting 3% diquafosol sodium (LA-DQS) on astigmatism measurement repeatability. This research assessed the effect of LA-DQS on astigmatism measurement repeatability in preoperative patients with cataract and short tear break-up time (TBUT) type dry eyes in both eyes of the same patient. Correlations between repeatability and TBUT, corneal high-order aberrations (HOAs), and corneal astigmatism magnitude were also analyzed. In total, 122 eyes (61 patients) with short TBUT-type dry eye were enrolled. Preoperatively, only one eye of all patients was treated with LA-DQS for 4 weeks. TBUT and corneal HOAs were checked using CASIA 2 before and 4 weeks post-treatment. The cylindrical power and meridian of astigmatism were measured at 3- and 4-week post-treatment using IOLMaster 700. Power vectors J0 and J45 were used for astigmatism calculations. Repeatability of astigmatism measurements was assessed as the within-subject standard deviation (Sw). The relative effects of TBUT and HOAs on J0 Sw and J45 Sw were also analyzed. Comparative changes in these variables were evaluated between treated and non-treated eyes, with additional analysis of their correlations. Treated eyes exhibited significant improvements in TBUT, HOAs, and post-treatment measurements of J0 Sw and J45 Sw at 3 and 4 weeks. In non-treated eyes, J0 Sw and J45 Sw showed significant correlation with TBUT and corneal HOAs. HOAs showed stronger relative associations with J0 Sw and J45 Sw than TBUT. In non-treated eyes, no significant correlation was found between cylindrical power and astigmatism measurement repeatability. In short TBUT-type dry eye, preoperative treatment with LA-DQS significantly improved astigmatism measurement repeatability. This may improve the precision of intraocular lens (IOL) power calculations regardless of the magnitude of corneal astigmatism, especially when toric IOLs are used.

Symptomatic Presbyopia may Develop Earlier in Patients With Glaucoma-A Cross-Sectional Retrospective Cohort Study.

The purpose of this study was to explore risk factors for symptomatic presbyopia, defined as near add power ≥1.50 diopters, in patients with glaucoma. Treated glaucoma (n = 56), untreated glaucoma (n = 21), and control individuals (n = 376), aged 40 to 55 years at first visit, were enrolled in the study, and near add power, retinal thickness, and visual field were examined. The association between near add power and ocular parameters and the odds ratios (ORs) for symptomatic presbyopia were investigated. Survival analysis for symptomatic presbyopia was conducted. Age, astigmatic power, mean deviation, and ganglion cell complex thickness were associated with near add power. The OR for symptomatic presbyopia was significant for age (OR = 1.51), astigmatism (OR = 1.01), mean deviation (OR = 0.72), ganglion cell complex thickness (OR = 0.98), treated and untreated glaucoma (OR = 2.09), and use of glaucoma eye drops (OR = 3.33). Survival analysis showed that the treated glaucoma group reached the near add power endpoint of ≥1.50 D (symptomatic presbyopia) significantly earlier than the other two groups, and there was no difference between the control and untreated glaucoma groups. Glaucoma patients treated with eye drops may start near correction earlier. Symptomatic presbyopia may develop earlier in patients with glaucoma, and our findings could further contribute to better management and understanding of presbyopia with glaucoma.

Long-Term Visual Quality and Pupil Changes after Small-Incision Lenticule Extraction for Eyes without Preoperative Cylinder Refraction.

To investigate the long-term changes in visual quality and pupil size after small incision lenticule extraction (SMILE) for eyes without preoperative cylinder refraction. Thirty-three myopic eyes (33 patients) without preoperative cylinder refraction were corrected using SMILE. Refractive outcomes, corneal curvature, aberrations, contrast sensitivity (CS), and pupil diameter were evaluated preoperatively, and 30 months postoperatively. The 30-month postoperative uncorrected and corrected distance visual acuity (UDVA and CDVA, LogMAR) were -0.10 ± 0.09 and -0.14 ± 0.06, respectively, whereas the preoperative CDVA (LogMAR) was -0.07 ± 0.05. Cylinder refraction of -0.11 ± 0.21 D (ranging from -0.50 to 0.00) was observed at 30 months postoperatively, increasing from the preoperative cylinder refraction of 0.00 ± 0.00 D (P=0.004). Moreover, the centroid coordinates x, y of corneal anterior astigmatic vectors were -0.19 ± 0.22, 0.81 ± 0.33 at 30 months postoperatively, and 0.02 ± 0.28, 0.76 ± 0.51 preoperatively (Px < 0.001 and Py=0.810, respectively). Furthermore, a 15° axis change in the mean anterior corneal astigmatic vector was observed at 30 months postoperatively from the preoperative state, as measured by Pentacam. At 30 months postoperatively, the photopic Log CS reduced significantly with glare at three and six cycles/degrees (P < 0.001 and P=0.015, respectively), a decreased photopic pupil diameter (3.27 ± 0.55 mm vs. 3.10 ± 0.66 mm, P=0.030), and an increased Coma (Z31) and Trefoil (Z3-3) at 4 mm diameter area analysis. However, a significant linear regression relationship was only observed between changes in photopic pupil diameter and changes in photopic Log CS with glare at 12 cycles/degree (P=0.038 and β = 0.282). Slight cylinder regression was observed with thicker corneal lenticular extraction after SMILE correction of nonastigmatic eyes 30 months postoperatively. This regression was mainly because of the axis changes in anterior corneal astigmatism power. Therefore, a cylinder nomogram modification of 0.25 to 0.50 D is considerable for correcting nonastigmatic myopic eyes with a predicted spherical lenticular thickness over 100 µm.

Repeatability and Interobserver Reproducibility of a Swept-Source Optical Coherence Tomography for Measurements of Anterior, Posterior, and Total Corneal Power.

The aim of this work is to evaluate the intraobserver repeatability and interobserver reproducibility of corneal power measurements obtained with a swept-source optical coherence tomographer (CASIA 2, Tomey, Japan) in healthy subjects. A total of 67 right eyes from 67 healthy subjects were enrolled. Two experienced observers measured each eye three times consecutively with the CASIA 2. Corneal power values were recorded as simulated keratometry, anterior, posterior, and total corneal power. Parameters were flattest keratometry (Kf), steepest keratometry (Ks), mean keratometry (Km), astigmatism magnitude, astigmatism power vectors J0 and J45. Intraobserver repeatability and interobserver reproducibility of the CASIA 2 were assessed by the within-subject standard deviation (Sw), test-retest repeatability (TRT), coefficients of variation (CoV), and intraclass correlation coefficients (ICCs). Double-angle plots were used for astigmatism vector analysis. The CASIA 2 had high repeatability for all corneal power values, with Sw values ≤ 0.17 diopters (D), TRT ≤ 0.46 D, and ICCs ranging from 0.866 to 0.998. Interobserver reproducibility was also high, showing all Sw values ≤ 0.10 D, TRT ≤ 0.27 D, and ICCs ≥ 0.944. The reproducibility of the average of three consecutive measurements (Sw 0.01-0.10 D, TRT 0.03-0.27 D, ICC 0.944-0.998) was higher than the reproducibility of single measurements (Sw 0.01-0.17 D, TRT 0.03-0.47 D, ICC 0.867-0.996). The CASIA 2 showed high intraobserver repeatability and interobserver reproducibility for anterior, posterior, and total corneal power measurementsin 6.0-mm diameter area. In addition, we suggest that using the average of three consecutive measurements can improve reproducibility between observers, compared to single measurements only.

Subjective refraction using power vectors by updating a conventional phoropter with a Stokes lens for continuous astigmatic power generation.

To implement a pure power vector method for monocular subjective refraction using a regular phoropter with the only modification being the inclusion of a Stokes lens. The proposed methodology was tested with three different Stokes lenses, and the results were compared with conventional clinical refraction procedures. Power vector subjective refraction was performed by attaching a Stokes lens to the Risley prism holder. Stokes lenses allow for pure astigmatic compensation in the form of the J0 , J45 components while the spherical lenses in the phoropter allow determination of the spherical component in the form of M (spherical equivalent). The proposed routine is presented step-by-step using three Stokes lenses having different astigmatic powers. Monocular subjective refraction was performed on 26 healthy subjects with a mean age of 44 ± 16 years, mean spherical equivalent of -0.56 D (range -5.50 to +2.38 D) and refractive astigmatism ≤1.50 D. No differences were found between the results obtained with the conventional technique versus the vector-based procedure for the spherical equivalent (p = 0.28) or astigmatic components (p = 0.34). In addition, visual acuity (VA) was equivalent through the refractions measured with the conventional and vector procedures (p = 0.12). Repeatability coefficients for J0 and J45 with the new vector methodology were <0.38 D. The proposed routine could be helpful for cases where it is difficult to get a valid starting point for conventional refraction (e.g., irregular corneas and media opacities), for testing facilities with limited resources/equipment and/or for motivated clinicians who wish to know about alternative methods of refractive error determination.

Toric intraocular lenses versus paired opposite corneal incisions in correction of low-grade astigmatism after phacoemulsification

Purpose To compare toric intraocular lens (IOL) implantation versus monofocal (Eyhance) IOL with paired corneal incisions for correction of low-grade astigmatism after phacoemulsification. Patients and methods A retrospective comparative study included 30 patients with low-grade astigmatism (−0.75 to −1.50 D) who underwent phacoemulsification: group 1 underwent toric IOL implantation (TECNIS toric) and group 2 underwent enhanced monofocal IOL (TECNIS Eyhance) with paired corneal incision along steep corneal meridian. Best-corrected visual acuity, astigmatism power, and axis were assessed preoperatively and 3 months postoperatively. Vector analysis of astigmatism was done using the Alpins method. Results The mean postoperative residual astigmatism was significantly lower in group 1 versus group 2 (−0.357±0.128 and −0.538±0.225 D, respectively; P=0.015). A significantly higher decrease in astigmatism was noted in group 1 (−0.93±0.18 and −0.38±0.69 D, respectively; P=0.006), with no significant difference in postoperative visual acuity. Paired comparison revealed significant decrease in astigmatism (P&lt;0.0001 in group 1 and 0.04 in group 2) and improvement in uncorrected visual acuity (P&lt;0.0001 for both groups). A significantly higher percentage of success was noted in group 1 (P=0.017), with a higher difference vector in group 2 (P=0.008). Conclusion Our results suggest that both toric IOL and paired corneal incision are efficient methods for postoperative astigmatism correction and achieving postoperative spectacle independence in patients with low-grade astigmatism. Toric IOL is superior in reducing postoperative astigmatism, reflecting more consistent results. The recommendation of IOL type and astigmatism correction should be tailored according to the patient's requirements, especially with the expanded need for good intermediate vision for everyday tasks that may benefit from enhanced IOLs.

Comparative Analysis of Corneal Parameters Performed with GalileiG6 and OCT Casia 2.

To compare keratometry (Ks and Kf), astigmatism (Ast.), and the astigmatism axes (Ax.) of the posterior surface of the cornea; the total, central cornea thickness (CCT); and the thinnest corneal thickness (TCT) measured using two different measurement methods. Patients qualified for cataract surgery at the Chair and Clinical Department of Ophthalmology, Division of Medical Science in Zabrze, Medical University of Silesia, Katowice, Poland, were included in the study and monitored with the following two devices: OCT-CASIA2 and Dual Scheimpflug Analyzer GalileiG6. Our work was a randomized, prospective study in which compliance with the agreement of measurements between the devices was evaluated using the Bland-Altman method. A total of 110 patients (62 females and 48 males) were examined. Overall, 100 eyes of patients that qualified for cataract surgery were enrolled in the study. No statistically significant difference was observed for Total-Ks and Total-Kf. A significant difference was observable for the following parameters: total Ks-ax, total Kf-ax, the total power of astigmatism, and in all parameters of the part of the cornea and corneal thickness (CCT and TCT). The measurements obtained using Casia2 and the Dual Scheimpflug Analyzer GalileiG6 were significantly different and not interchangeable except for total Ks and Kf.

PENTACAM STUDY OF ANTERIOR AND POSTERIOR CORNEAL ASTIGMATISM IN PATIENTS WITH KERATOCONUS AND HEALTHY CONTROLS

Keratoconus is a chronic, noninflammatory, progressive, ectatic corneal disorderthat degrades vision due to myopia and irregular astigmatism. Recently, the priority of posteriorcorneal astigmatism has been identified when toric IOL is considered. The aim of the study wasto assess and correlate the power and axis orientation of anterior and posterior corneal astigmatism in keratoconus patients and healthy controls.

A Comparative Study of Refraction in Skiascopy and Autorefractometry before and after Application of Cycloplegics

Purpose: To evaluate the difference of refractive errors measured by skiascopy and autorefractometry before and after application of cycloplegics according to age, the degree of myopia and of astigmatism.Methods: School myopia (384 eyes of 227 persons) were measured by skiascopy and autorefractometry before and after instillation of cycloplegics, and each refractive error was compared. According to age, it was divided into elementary school group (236 eyes), middle and high school group (54 eyes), and university group (94 eyes). Myopic spherical power was classified into mild group with power -2.0 diopter (D) or less (119 eyes), moderate group with -2.0 D or more and -6.0 D or less (178 eyes), and high group with greater than -6.0 D (87 eyes). Astigmatism is divided into mild group with less than -2.0 D (296 eyes) and high group with greater than -2.0 D (88 eyes).Results: The post-cycloplegics spherical and spherical equivalent refractive values by the autorefractometry and the skiascopy were measured to be lower than manifest autorefractometry, and the astigmatic power after cycloplegic refraction was measured to be high, but there is no statistically significant difference (&lt;i&gt;p&lt;/i&gt; &gt; 0.05). In the case of elementary school, middle and high school, the value of spherical and astigmatism increased significantly compared to the university group, but there is no statistically significant difference (&lt;i&gt;p&lt;/i&gt; &gt; 0.05). The difference of refractive errors between the spherical and the spherical equivalent value increased significantly as the degree of myopia increased. The value of difference between mild and high group of astigmatism was significantly increased in high group compared to mild group.Conclusions: It should be necessary to accurately measure to wear glasses in school myopia with the younger, the more myopia is greater than -6.0 D, and high astigmatism with more than -2.0 D.

Accuracy of the Goggin Nomogram for 0.50 D Steps in Toric IOL Cylinder Power Calculation.

To examine the accuracy of the cylinder power choice for toric intraocular lenses (IOLs) using the Goggin Nomogram, which adjusts anterior keratometric astigmatic power values for the likely effect of posterior corneal and non-corneal, non-lenticular astigmatism. A consecutive, retrospective case series was based at the Queen Elizabeth Hospital and Ashford Advanced Eye Care in Adelaide, Australia. A total of 586 consecutive eyes of 586 patients underwent phacoemulsification surgery with implantation of a Zeiss AT TORBI 709MP or AT LISA Tri Toric 939 MP toric IOL, calculated using the Goggin Nomogram. The median absolute magnitude of error and geometric mean astigmatic correction index in consecutive eyes with toric IOL cylinder powers of 1.00 to 3.00 diopters (D) were analyzed. Overall, all eyes receiving IOL cylinder powers of 1.00 to 3.00 D inclusive had a median magnitude of error value of 0.19 D (IQR: 0.31) and astigmatic correction index value of 1.03 (IQR: 0.33). For eyes with with-the-rule, against-the-rule, and oblique astigmatism, the median magnitude of error was 0.18 D (interquartile range [IQR]: 0.29), 0.19 D (IQR: 0.31), and 0.17 D (IQR: 0.39), respectively, and the astigmatic correction index was 1.06 (IQR: 0.28), 1.01 (IQR: 0.35) and 1.08 (IQR: 0.32), respectively. Goggin Nomogram adjusted keratometry provided optimal refractive astigmatic outcome in IOL cylinder powers of 1.00 to 3.00 D in eyes with with-the-rule, against-the-rule, and oblique astigmatism. Goggin Nomogram adjusted keratometry compensates for both posterior corneal astigmatism and any other source of ocular astigmatism. [J Refract Surg. 2022;38(5):298-303.].

The Pentacam® AXL Wave provides a reliable wavefront-based objective refraction when compared to manifest subjective refraction: A prospective study.

Purpose:Accurate refraction is arguably the most important parameter for a successful laser vision correction surgery and is based on a combination of manifest and cycloplegic refraction. Wavefront-based objective refraction may be useful in the evaluation of patients. So far, the reliability of objective refraction as measured using the Pentacam® AXL Wave has not been published in the literature.Methods:This was a prospective study including a total of 168 eyes belonging to 84 young non-presbyopic patients evaluated for refractive surgery. Pentacam® AXL Wave full sequence was taken for all patients. Then, a clinician who was unaware of the objective refraction results performed a full physical examination, including manifest refraction starting from an autorefractometer value. All refraction values were transferred to astigmatic power vectors as per the Thibos method. Reliability of the different vectors and a unifying blur value were compared using Spearman correlation, Bland–Altman plot, and intraclass correlation coefficient.Results:The mean age was 28.8 ± 5.4 years, with a female preponderance (60.7%). The correlation between both eyes was high. The difference in M vector between subjective and objective refraction was 0.16 D, while the difference was 0.04 and 0.01 D for the J0 and J45 vectors, respectively. Paired samples Student t was non-significant for all comparisons. Spearman rho correlations were high (0.666–0.924, all P < 0.001). Intraclass correlation coefficients were also high (0.890–0.966). Bland–Altman plots did not demonstrate any systematic errors.Conclusion:Wavefront-based refractive refraction obtained using the Pentacam® AXL Wave is highly agreeable and correlated with measurements obtained by manifest subjective refraction.

Astigmatic Stokes lens revisited.

Stokes lenses are variable power astigmatic lenses comprising of, in its standard version, two pure cylindrical lenses of equal but contrary power that rotate in opposite directions. Here, we present an optical device with variable and continuous astigmatic power which is based on a modified Stokes lens where two sphero-cylindrical lenses (in the form of pure astigmatic lenses) are combined in the classical way but merged with another fixed pure astigmatic lens for improving the capabilities of the resulting optical device concerning the expansion of the astigmatic range without worsening the dioptric power step resolution. The performance of this device is theoretically analyzed in virtue of the power vectors formalism including a three-dimensional (3-D) representation of the generated dioptric power as a function of both the meridian and the rotation angle between the cylinder's axes. In addition, we have assembled a lab-made prototype of the proposed modified Stokes lens and validated its theoretical behavior by dioptric power measurements with an automatic focimeter. As conventional Stokes lenses, the applications of this new optical device range from astigmatism compensation in optical instruments to measurement of refractive error in subjective routines with the previously commented improved capabilities.

Femtosecond laser-assisted corneoscleral lamellar keratoplasty for peripheral corneal disease

Objective: To evaluate the effect of femtosecond laser-assisted corneoscleral lamellar keratoplasty (FL-CSLK) on peripheral corneal disease (PCD). Methods: Retrospective cohort study. Six patients (6 eyes) with PCD who underwent FL-CSLK in Qingdao Eye Hospital from March 2014 to March 2017 were grouped as the FL-CSLK group, including 4 males and 2 females, aged (46.7±17.9) years. In addition, 8 patients (8 eyes) with PCD who underwent traditional corneoscleral lamellar keratoplasty in the same period were included in the control group. The items for analyses were as follows: visual function recovery, including visual acuity, equivalent spherical power, and astigmatism; the state of the cornea, including the healing time of the corneal epithelium, the transparency of the graft, the thickness of the corneal graft and implant bed, and the loss rate of corneal endothelial cells; intraoperative and postoperative complications, including high intraocular pressure, interlayer effusion, delayed corneal epithelial healing, immune rejection, and primary recurrence. Paired t-test was used to compare the best corrected visual acuity (BCVA), equivalent spherical power, and astigmatism before and after operation. The BCVA and corneal graft epithelial healing time between the two groups were compared by independent sample t-test. Results: The 6 patients in the FL-CSLK group included 2 cases of Mooren ulcer, 3 cases of Terrien marginal degeneration, and 1 case of pellucid marginal degeneration. The control group consisted of 4 eyes with Mooren ulcer and 4 eyes with Terrien marginal degeneration. The BCVA (logarithm of the minimum angle of resolution) in the FL-CSLK group was 0.35±0.09 at 6 months after operation, which was significantly higher than that before operation (1.17±0.15; t=9.01, P<0.001) and at 6 months after operation in the control group (0.78±0.29; t=-3.96, P=0.003). The equivalent spherical power was (4.8±2.7) D, lower than that before operation (t=-3.71, P=0.014), and the astigmatism power was (10.1±4.1) D, lower than that before operation (t=6.04, P=0.002) in the FL-CSLK group. The healing time of the graft epithelium in the FL-CSLK group and control group was (8.5±3.3) days and (12.8±6.1) days, respectively, with no significant difference (t=-1.54, P=0.149). The central thickness of the graft in the FL-CSLK group was (525±47) μm at 6 months after operation, the central thickness of the implant bed was (189±119) μm, and the loss rate of the corneal endothelium was 7.5%±2.1%. In the control group, 1 case had intraoperative perforation, 2 cases had intracorneal hemorrhage, and 1 case had intracorneal epithelial implantation cysts and graft ulcer. There were no intraoperative and postoperative complications in the FL-CSLK group. Conclusions: FL-CSLK can yield good clinical results in the treatment of PCD. The smooth optical interface made by femtosecond lasers can help the patient achieve a good visual prognosis. The procedure reduces the risk of corneal perforation and thus improves the surgery safety.

Effect of Pterygium Removal Combined with Conjunctival Autograft on Corneal Parameters in Swept-Source Imaging.

Background: Both pterygium ingrowth and excision determine alterations in corneal topography. The aim of this study was to evaluate the influence of pterygium removal combined with conjunctival autografts in addition to the use of human fibrin tissue glue on changes in corneal parameters as measured by 3-D swept-source anterior segment optical coherence tomography (AS-OCT) imaging. Methods: Sixteen eyes (16 patients) with pterygium that qualified for surgical treatment were enrolled in this study. Eye examination, slit lamp, and 3-D AS-OCT (CASIA 2) assessment were performed before the surgery and 7 days, 1 month, and 6 months after pterygium excision. Topographic parameters of both anterior and posterior surfaces of the cornea were analysed at each follow-up visit. Results: The gradual decrease in total astigmatism power from preoperative median 2.75 (6.15) D to 1.2 (1.1) D at 6-month follow-up (p = 0.034) was noted from the day 7 visit. Values were strongly influenced by variations of anterior cornea astigmatism. In contrast, a gradual total HOA reduction at the 1-month (from median 0.79 (1.3) D to 0.44 (0.27) D; p = 0.038) and at 6-month visits (0.25 (0.09); p = 0.001) was observed. Similarly, values were strongly influenced by variations of the anterior. Additionally, total average keratometry values increased from preoperative 44.05 (2.25) D to 44.6 (1.9) (p = 0.043) 1 month after the surgery. Conclusions: Significant steepening of the anterior cornea and a reduction in both astigmatism and HOA were observed after pterygium excision. The anterior corneal surface was an essential component of the total postoperative corneal topography values. Three-dimensional swept-source AS-OCT imaging seems to be a valuable tool for monitoring both the progression of the disease and postoperative effects in pterygium eyes.

Novel Microsoft Excel spreadsheet calculator for vector analysis of mass astigmatism data and comparison between Alpins and Thibos methods

Background Vector analysis is mandatory for reporting astigmatism and for the evaluation of different refractive procedures.Aim The aim of this study was to describe and evaluate a new spreadsheet calculator for vector analysis of mass astigmatism data and to compare between Alpins and Thibos methods.Patients and methods Using Microsoft Office Excel 2016, a new astigmatic calculator was designed, based on Alpins and Thibos methods of vector analysis. Mass astigmatic data input involved power in diopters and axis direction in degrees. The calculator was investigated on 20 eyes for which photorefractive keratectomy was performed. Preoperative and postoperative manifest refractions were measured. Comparisons were done between the results of Alpins and Thibos methods of analysis.Results The mean surgically induced astigmatism (SIA) was 2.547±0.721 D and the change in astigmatism power vector (ΔAPV) calculated with the Thibos method was 1.27±0.36 D. A perfect positive correlation (r=1; P<0.000) was present between SIA and ΔAPV with SIA=2ΔAPV. A perfect positive correlation (r=1; P<0.000) was also present between the index of success and APV ratio.Conclusion Vector analysis of mass astigmatism data could be performed using the new Excel calculator. Alpins and Thibos methods showed interchangeability between their results.

Astigmatism in Infants: Study of Changing Visual Axis in Infants and Children

Background: Astigmatism is an abnormality within the curvature of the attention. It occurs when light rays strike a spherical lens obliquely, or the line of vision to its principal axis is not parallel. Refraction away from the axis occurs when light strikes a lens obliquely and distorts the image formed.&#x0D; Aim: This study aimed to look at the prevalence of against-the-rule, with the-rule, and oblique-axis astigmatism in children. The change in cylinder index of refraction power and alignment of astigmatism in babies and young children is studied.&#x0D; Methodology: To conduct the study and thoroughly search the literature separately, references and abstracts were reviewed. Books like Parson’s diseases of the Eye by Dr. Radhika Tandon and several articles, WHO website, etc., were referred.&#x0D; Results: The study relied upon many studies on refractions procured by the near-retinoscopy methodology that knowledgeable Refractionist accomplished.&#x0D; Conclusion: It can be concluded that young children have a high incidence of against (???) type of astigmatism and that after this age (which age?), most children are with the rule.