Magnitude Of Corneal Astigmatism Research Articles

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.

Spherical Aberration of Astigmatic Corneas in a Cataract Population.

To study the distribution of spherical aberration (SA) in astigmatic corneas in a cataract population and the relationship between magnitude of corneal astigmatism and fourth-order corneal SA. Data routinely collected using a Scheimpflug camera (Pentacam; Oculus Optikgeräte GmbH) were retrospectively analyzed. Patients with a minimum age of 60 years were included. Total corneal SA (from anterior and posterior corneal surface) was obtained for a 6-mm cor-neal area aligned with the pupil center. Exclusion criteria were insufficient measurement quality, total deviation index (Belin/Ambrósio Deviation) greater than 1.60, and corneal thickness at the thinnest point of less than 490 μm. One eye per patient was chosen randomly. Eyes were divided into low (≤ 1.00 diopters [D]), moderate (> 1.00 to ≤ 2.00 D), and high (> 2.00 D) astigmatism groups according to the Scheimpflug measurements. A total of 528 eyes were included in this analysis. Low astigmatism was found in 129 patients, moderate astigmatism in 265 patients, and high astigmatism in 134 patients. Mean astigmatism was 0.68 ± 0.24, 1.45 ± 0.28, and 2.91 ± 0.95 D in the low, moderate, and high astigmatism groups, respectively. Mean corneal SA in patients with moderate and high astigmatism was higher than in the low astigmatism group. The difference reached the significance level for the comparison of low and high astigmatism groups (P = .023). The fourth-order SA increased gradually with the magnitude of astigmatism with a slope of 0.015. SA was significantly larger in the cataract population with high corneal astigmatism. The increase of positive sign SA with the magnitude of astigmatism suggests that patients with moderate to high astigmatism may benefit more from intraocular lenses with negative sign SA correction. [J Refract Surg. 2023;39(8):532-538.].

Clinical Outcomes of Toric Intraocular Lenses in Patients with Fuchs Endothelial Corneal Dystrophy.

Implantation of toric intraocular lenses (IOLs) in patients with Fuchs endothelial corneal dystrophy (FECD) is still considered relatively contraindicated, without sufficient clinical evidence. Therefore, this study was designed to evaluate the results of toric IOL implantation in patients with FECD. A retrospective case-control study of 28 eyes of FECD patients and 84 eyes of healthy control patients who received toric IOLs during routine cataract surgery was performed. The outcome measures were uncorrected and corrected distance visual acuity, spherical equivalent, and refractive residual astigmatism. The mean postoperative uncorrected and corrected distance visual acuity in the FECD eyes compared to the control eyes were 0.15 ± 0.14 vs. 0.13 ± 0.17, respectively (P = 0.32), and 0.05 ± 0.08 vs. 0.06 ± 0.10, respectively (P = 0.95). The spherical equivalent in the FECD eyes compared to the control eyes was -0.29 ± 0.43 vs. -0.21 ± 0.50, respectively (P = 0.19). The preoperative corneal centroid astigmatism in the FECD eyes compared to the control eyes was 0.85D@93° ± 2.42° vs. 0.23D@68° ± 2.50°, respectively (P = 0.43), and the mean preoperative corneal astigmatism magnitude was 2.26 ± 1.1D vs. 2.28 ± 1.03D, respectively (P = 0.82). A trend toward higher postoperative refractive centroid astigmatism was found in the FECD eyes compared with the control eyes: 0.24D@28° ± 0.57° vs. 0.03D@127° ± 0.53°, respectively (P = 0.09). However, the mean refractive astigmatism magnitude was similar in FECD eyes and the healthy control eyes: 0.52 ± 0.31D vs. 0.42 ± 0.31D, respectively (P = 0.44) (D diopters). The postoperative refractive astigmatism (both centroid astigmatism and mean magnitude astigmatism) was no higher than 0.52D in both groups. Therefore, FECD patients without corneal edema can be considered for toric IOLs.

Ptosis effects on intraocular lens power calculation.

To evaluate quantitatively ocular biometric parameters and intraocular lens (IOL) power measurements post-ptosis surgery. This study comprised involutional ptosis patients divided into droopy eyelid severity groups: Group 1:>4 mm, Group 2:3-4 mm, and Group 3:1-2 mm. The patients underwent anterior levator resection (ALR), and preoperative and postoperative biometry measurements 3 months postoperatively were obtained. The Group 1 sample size was 19, Group 2 was 22, and Group 3 was 16. The mean K1, K2, and Km values significantly decreased 3 months postoperatively in Group 1 (P<0.001 for all). The mean K1, K2, and Km values non-significantly decreased 3 months postoperatively in Groups 2 and 3 (P>0.05 for all). The mean corneal astigmatism magnitude decreased 3 months postoperatively in Group 1 (P<0.01), Group 2 (P=0.186), and Group 3 (P=0.952). The mean recommended IOL powers targeting emmetropia increased postoperatively in Group 1 and were similar pre- and postoperatively in Groups 2 and 3. In Group 1, the mean changes after ptosis surgery by formula were 0.47 D for SRK/T, 0.52 D for Hoffer Q, 0.55 D for Haigis, 0.50 D for Barrett Universal II and 0.55 D for Holladay 2. Ptosis > 4 mm significantly impacts corneal curvature values and IOL power calculations when cataract surgery is planned. Surgeons might consider altering their lens power choice accordingly if cataract surgery is to be sequentially followed by ptosis repair.

Changes in Vector Astigmatism After Superotemporal Versus Temporal Clear Corneal Incision Cataract Surgery.

To investigate vector and refractive astigmatism changes after superotemporal versus temporal clear corneal incision cataract surgery. Patients were diagnosed with age-related cataract with corneal astigmatism < 1.5 diopters (D) and were divided into two groups: superotemporal incision (R group) and temporal incision (L group). Uncorrected visual acuity, manifest refraction, corneal topography, anterior segment optical coherence tomography was performed pre- and six months postoperatively. Total ocular astigmatism, corneal astigmatism, vector of surgically induced corneal astigmatism (SICA), non-corneal ocular residual astigmatism (N-CORA), postoperative intraocular lens decentration and tilt were analyzed. Results: Thirty-eight subjects were included: 21, R group; 17, L group. After surgery, the N-CORA decreased significantly from 1.17±0.72 D to 0.73±0.47 D in all patients (P=0.001), 1.03±0.52 D to 0.70±0.40 D in the R group (P=0.005) and 1.35±0.90 D to 0.78±0.55 D in the L group (P=0.033). Significant differences between t:he R and L groups were found in the postoperative meridian of anterior corneal astigmatism (75.95±52.50 vs 116.79±47.29; P=0.017), total corneal astigmatism (51.65±42.75 vs 95.20±57.32; P=0.011), J45 change vector of SICA in the anterior cornea (-0.10±0.18 vs 0.00±0.11; P=0.048) and total cornea surface (-0.14±0.17 vs 0.03±0.12; P=0.001). Conclusion: The N-CORA decreased significantly after cataract surgery. Superotemporal and temporal incisions caused differences in the meridian components of oblique astigmatism in some patients but did not have a significant effect on the magnitude of corneal astigmatism.

Outcome of astigmatism correction using femtosecond laser combined with cataract surgery: penetrating vs intrastromal incisions.

To compare the effectiveness of penetrating vs intrastromal femtosecond laser corneal relaxing incisions (CRIs) in reducing corneal astigmatism during cataract surgery. Baylor College of Medicine and Mercy Clinic Eye Specialists. Prospective randomized study. 248 eyes from 248 patients were included. Patients were randomly assigned to undergo paired penetrating (8 mm optical zone [OZ] at 1 center and 9 mm OZ at the other) or intrastromal CRIs (8 mm OZ at both centers). The lengths of the CRIs were based on published nomograms but modified to take into account posterior corneal astigmatism. Vector analysis was performed, and net corneal changes along the CRI meridian were calculated. Multiple regression analysis was performed to assess factors contributing to net corneal changes. Preoperatively, 9% to 18% of eyes had corneal astigmatism of ≤0.5 diopters (D), and 76% to 93% of eyes had postoperative refractive astigmatism of ≤0.5 D ( P < .05). Both penetrating and intrastromal CRIs produced significant mean net corneal changes along the CRI meridian (-0.49 to -1.21 D), and 71% to 84% of eyes had postoperative astigmatism vector prediction errors of ≤0.50 D. The 8 mm penetrating CRIs induced greater net corneal changes but more eyes with overcorrection than did the intrastromal and 9 mm penetrating CRIs (all P < .05). Greater net corneal changes occurred with longer CRI length, higher preoperative corneal astigmatism magnitude, and preoperative against-the-rule corneal astigmatism. Nomograms based on anterior and total corneal astigmatism are proposed. Both penetrating and intrastromal CRIs were effective in reducing corneal astigmatism during cataract surgery.

Effect of Trabeculectomy on Mean and Centroid Surgically Induced Astigmatism.

This study aimed to investigate the arithmetic mean of surgically induced astigmatism (M-SIA) and the centroid of surgically induced astigmatism (C-SIA) after standard trabeculectomy. We comprised 185 eyes of 143 consecutive patients (mean age ± standard deviation, 67.7 ± 11.6 years) who underwent trabeculectomy and completed at least a 3-month routine follow-up. In all cases, the scleral flap was made at the nasal-superior location. Corneal astigmatism was measured with an automated keratometer. We calculated the M-SIA and the C-SIA using vector analysis and applied the astigmatism double angle plot. The magnitude of corneal astigmatism increased significantly, from 1.17 ± 0.92 D preoperatively to 1.77 ± 1.05 D postoperatively (paired t-test, p < 0.001). The M-SIA was 1.12 ± 0.55 D, and the C-SIA was 0.73 D @64° ± 1.02 D in the right eye group, and the M-SIA was 1.08 ± 0.48 D and the C-SIA was 0.60 D @117° ± 1.03 D in the left eye group. The C-SIA showed an astigmatic shift toward the nasal-superior location of the scleral flap creation. Our results revealed that trabeculectomy induced the SIA in the direction of the scleral flap location and that the C-SIA was much lower than the M-SIA in eyes undergoing trabeculectomy.

Effect of depth of the sclerocorneal incision on postoperative corneal astigmatism in manual small-incision cataract surgery.

Purpose:To determine the effect of depth of scleral tunnel incision measured by anterior segment OCT on postoperative corneal astigmatism by comparing the change of magnitude of corneal astigmatism between superficial and deep sclerocorneal tunnel incision in manual small-incision cataract surgery (SICS).Methods:Depths of sclerocorneal incision of 72 eyes of patients undergoing uncomplicated manual SICS and attending regular follow-up schedule were assessed with anterior segment OCT at 6-week post-op follow-up.Results:The overall mean ± standard deviation (SD) change of astigmatism for superficial incision, that is, ≤399 mm, was 0.44 ± 0.30 and that for deeper, that is, ≥400 mm, was 0.13 ± 0.48 and the change was significantly higher in ≤399 mm group than in ≥400 mm group (P = 0.003). In both superior and temporal incision locations, the mean ± SD change of astigmatism for ≤399 mm incision was 0.48 ± 0.29 and 0.40 ± 0.30, respectively, and that for ≥400 mm was 0.03 ± 0.34 and 0.23 ± 0.57, respectively. The change of astigmatism was significantly higher in ≤399 mm incision group overall (P = 0.003) and also higher in both superior and temporal incision location groups (P = 0.001 and P = 0.479, respectively).Conclusion:The depth of sclerocorneal incision had a statistically significant effect on the change of astigmatism following manual SICS, with superficial incision (≤399 μm) causing a higher change than deeper incision (≥ 400 μm).

Comparison of magnitude and summated vector mean of surgically induced astigmatism vector according to incision site after phakic intraocular lens implantation

BackgroundTo compare the arithmetic mean (M-SIA) and the summated vector mean of surgically induced astigmatism (SVM-SIA) according to the incision site after phakic intraocular lens (Visian implantable collamer lens (ICL), STAAR Surgical) implantation.MethodsThis study comprised 121 eyes of 121 consecutive patients undergoing ICL surgery through a 3.0-mm temporal or superior clear corneal incision. The magnitude and the axis of corneal astigmatism preoperatively and 3 months postoperatively were measured using an automated keratometer. The M-SIA and the SVM-SIA were determined according to the incision site.ResultsThe magnitude of corneal astigmatism significantly increased from 1.23 ± 0.59 D preoperatively to 1.46 ± 0.72 D postoperatively in the temporal incision group (Wilcoxon signed-rank test, P < 0.001), but it significantly decreased from 1.09 ± 0.36 D preoperatively to 0.86 ± 0.41 D postoperatively in the superior incision group (P < 0.001). The M-SIA was 0.48 ± 0.30 D, and the SVM-SIA was 0.23 ± 0.52 D at a meridian of 82° in the temporal incision group. The M-SIA was 0.57 ± 0.30 D, and the SVM-SIA was 0.47 ± 0.45 D at a meridian of 1° in the superior incision group.ConclusionsICL implantation induces the M-SIA by approximately 0.5 D, but the SVM-SIA decreased to 50% and 80% of the M-SIA in magnitude through temporal and superior incisions, respectively. The direction of the SVM-SIA showed a tendency toward corneal flattening to the incisional site. It should be noted that the M-SIA is somewhat different from the SVM-SIA according to the incision site.Trial registration University Hospital Medical Information Network Clinical Trial Registry (000044269)

Repeatability and comparability of the Galilei-G4 and Cassini in measuring corneal power and astigmatism in normal and post-refractive surgery eyes

To assess the repeatability and comparability of the Galilei G4 versus the Cassini topographer in post-refractive eyes and in normal eyes, including older patients representative of an initial cataract evaluation. Simulated keratometric (simK), total corneal and posterior corneal power and astigmatism were evaluated in both post-refractive and normal eyes. Repeatability was measured by calculating within-subject standard deviation (Sw), coefficient of variation (CoV), and intraclass correlation coefficient (ICC). Vector analyses and Bland–Altman plots were employed to assess agreement between devices. We studied 32 subjects with a history of refractive surgery and 32 subjects without a history of refractive surgery undergoing cataract surgery. The mean age was 55 ± 18.5 years and the age range was 21.5–91.5 years. In non-refractive and post-refractive eyes, the ICC was > 0.9 (P < 0.001) for all corneal powers and for simK and total corneal astigmatism for both analyzers. The ICC for posterior corneal astigmatism magnitude using the Galilei was 0.62 and 0.67 and for the Cassini 0.55 and 0.38 in normal and post-refractive eyes, respectively. In both post-refractive and normal eyes, the Galilei G4 and Cassini analyzers have high repeatability in simK, total, and posterior corneal power and low repeatability for posterior corneal astigmatism.

Comparison of corneal astigmatism characteristics and prevalence of corneal astigmatism between Turkish individuals and Syrian refugees

To compare the prevalence, magnitude and type of corneal astigmatism between Turkish individuals and Syrian refugees. Data of patients scheduled for cataract surgery between January 2019 and 2020 were reviewed. The patients were randomly stratified according to their ethnicity (Turkish individuals or Syrian refugees). Keratometry was performed with the keratometer of IOLMaster 500. Quantitative analysis was performed using the power vector method (J0 and J45). The association between age and astigmatism in the two groups was explored. The study included 4085 eyes of 2049 patients (3962 eyes of Turkish individuals and 123 eyes of Syrian refugees). The mean magnitude of corneal astigmatism, J0, J45 and prevalence of against the rule (ATR) astigmatism and with the rule (WTR) astigmatism were 1.01 D, 0.06, 0.01 D, 37.6% and 43.7% in Turkish individuals and 1.13 D, -0.02, 0.07 D, 46.3% and 37.4% in Syrian refugees, respectively. There were no significant differences according to age, sex, right/left eyes, corneal astigmatism magnitude, keratometric values, J0 and J45 (p > 0.05) between the two groups. Below 40 years of age, the mean corneal astigmatism magnitude in Syrian refugees was significantly higher than that in Turkish individuals (p = 0.037). At all ages, ATR astigmatism prevalence was higher in Syrian refugees than in Turkish individuals. ATR astigmatic shift began at a younger age in Syrian refugees (p = 0.037). Age- and sex-adjusted analysis showed that J0 was significantly lower in Syrian refugees than in Turkish individuals (p = 0.013). The prevalence and magnitude of ATR astigmatism were higher and onset earlier in Syrian refugees than in Turkish individuals.

Comparison of Mean and Centroid of Surgically Induced Astigmatism After Standard Cataract Surgery.

Purpose: To compare the arithmetic mean of surgically induced astigmatism (M-SIA) and the centroid of surgically induced astigmatism (C-SIA) after standard cataract surgery.Methods: We retrospectively examined 200 eyes of 100 consecutive patients undergoing bilateral cataract surgery through a 2.8 mm temporal clear corneal incision. We quantitatively measured the magnitude and axis of corneal astigmatism preoperatively and 3 months postoperatively using an automated keratometer (TONOREFF-II, Nidek). We assessed the M-SIA, the C-SIA, and the double angle plots for the display of the individual SIA distributions.Results: For bilateral data analysis, the magnitude of corneal astigmatism significantly increased from 0.66 ± 0.39 D preoperatively to 0.74 ± 0.46 D postoperatively (paired t-test, p = 0.012). The M-SIA was 0.50 ± 0.36 D. On the other hand, the C-SIA was 0.18 ± 0.60 D at an axis of 97°. For unilateral analysis, we obtained similar outcomes between the right and left eye groups.Conclusions: According to our experience, standard cataract surgery induces the M-SIA by approximately 0.5 D. The magnitude of the C-SIA largely decreased to approximately 40% of the M-SIA, and the direction of the C-SIA showed a tendency toward with-the-rule astigmatism. It should be noted that the M-SIA was considerably different from the C-SIA, especially when selecting the appropriate toric IOL model and power.

Distribution of the anterior corneal astigmatism in over 140 000 patients with age-related cataract

Objective: To analyze the distribution characteristics of the anterior corneal astigmatism in 140 000 cataract patients from 18 hospitals in China. Methods: Retrospective study. A total of 143 889 patients (143 889 right eyes) over the age of 40 years with age-related catarac were admitted to 18 Aier eye hospitals in China from July 2015 to October 2018. The average values of the three measurements of the magnitude of anterior corneal astigmatism, the meridian of corneal astigmatism, anterior chamber depth, corneal refractive power, and axial length measured by IOLMaster 500 were obtained. The data acquisition method of each sub-center was to collect and analyze the electronic case data in accordance with the inclusion and exclusion criteria, and to provide them for the sponsor Wuhan Aier Eye Hospital. Non-normal distribution data are presented as M (P25, P75). Mann-Whitney test, Kruskal-Wallis test, Chi-square test were used to analyze the distribution differences of the magnitude of corneal astigmatism and the meridian of corneal astigmatism in gender, age, anterior chamber depth, corneal refractive power and axial length. Results: Among the 143 889 patients, 84 319 were females and 59 570 were males, the median age was 72 (65, 78) years old, the median corneal astigmatism was 0.84 (0.51, 1.33) D; the corneal astigmatism was ≥0.75 D in 80 895 patients (56.22%) and was ≥1.00 D in 57 304 patients (39.83%). The median corneal astigmatism was 0.87 (0.53, 1.37) D in women and 0.82 (0.50, 1.29) D in men; with statistical difference (U=-14.891; P<0.05). The proportion of with-the-rule (WTR) astigmatism was 33.26% (28 046/84 319) for women and 34.26% (20 408/59 570) for men; The proportion of against-the-rule (ATR) astigmatism was 49.08% (41 385/84 319) for women and 46.91% (27 945/59 570) for men, with statistical difference (χ²=70.913; P<0.05). With the increase of age, the magnitude of corneal astigmatism first decreased from 0.94 (0.57, 1.48) D to 0.75 (0.46, 1.18) D, and then increased to 1.19 (0.74, 1.79) D, with statistical difference (H=1 263.438; P<0.05), and the change was at 61 to 70 years old. With the increase of age, the proportion of WTR astigmatism decreased from 77.50% (396/511) to 12.50% (3/24), the proportion of ATR astigmatism increased from 11.15% (57/511) to 79.07% (34/43), and the proportion of oblique astigmatism changed little from 17.02% (16/94) to 19.92% (245/1 230), the distribution difference was significant (χ²=10 174.496; P<0.05). As the anterior chamber became shallow, the magnitude of corneal astigmatism significantly increased from 0.82 (0.51, 1.31) D to 1.05 (0.61, 1.56) D, and the proportion of ATR astigmatism increased from 47.32% (60 207/127 227) to 51.69% (184/356) (H=409.961, χ²=120.995, both P<0.05). With the corneal refractive power rising, the magnitude of corneal astigmatism increased from 0.80 (0.49, 1.33) D to 0.95 (0.58, 1.53) D, the proportion of ATR astigmatism decreased from 52.84% (4 963/9 392) to 39.97% (9 023/22 577); the difference was significant (H=808.562, χ²=752.147, both P<0.05). When the axial length was>25.00 mm, the magnitude of corneal astigmatism was highest [1.04 (0.62, 1.65) D], and the proportion of ATR astigmatism was also highest [49.00% (10 964/22 376)]; the difference was significant (H=2 071.198, χ²=131.130, all P<0.05). Conclusions: The meridian of corneal astigmatism in middle-aged and elderly cataract patients is mainly ATR astigmatism. With the increasing of age, the magnitude of corneal astigmatism decreases first and then increases. The turning point from the proportion of WTR astigmatism to the proportion of ATR astigmatism is 65 years old. The shallower the anterior chamber is, the more the magnitude of corneal astigmatism and the proportion of ATR astigmatism increase. When the axial length is>25.00 mm, both the magnitude of corneal astigmatism and the proportion of ATR astigmatism reach the peak. (Chin J Ophthalmol, 2021, 57: 56-62).

Corneal astigmatism in patients with various ophthalmic pathologies

To analyze the prevalence, magnitude of corneal astigmatism, anatomical parameters of the eye and age of patients with the condition, as well as to assess the prospects of its correction with intraocular lenses (IOLs). The study involved a retrospective analysis of initial biometric data of 128 379 patients (256 630 eyes) referred to the S.N. Fedorov NMRC «MNTK «EYE MICROSURGERY» research center in the years 2013 to 2018. The patients previously operated for cataract were examined 6 months after surgery. In 5 years, corneal astigmatism of over 1.0 D was diagnosed in 66 610 (25.96%) eyes. Among them, low astigmatism was observed in 86.30% of cases, with-the-rule - in 56.10%, compound - in 78.72%, and astigmatism combined with myopic refraction - in 61.48%. More severe astigmatism is characterized by thinner cornea and lens (p<0.05). Cataract surgery with implantation of toric IOLs was performed only on 2.56% of eyes. The average age of the operated patients was 68.42±13.3. Patients with implanted toric IOLs had 23% better uncorrected visual acuity (UCVA), and 15% better corrected visual acuity compared with outcomes of spherical IOL implantation. Corneal astigmatism of more than 1.0 D was observed in 25.96% of examined subjects. Patients with corneal astigmatism apply for cataract surgery 10 years earlier, when they are still in the working age, due to inability to engage in professional activities; in most cases, those patients are female. Astigmatism of up to 0.75 D is more common on the right dominant eye, of 2.0 D and higher - on the left. The correlation coefficients determined for study data indicate a barely noticeable relationship between biometric parameters and the degree of astigmatism. The use of toric intraocular lenses provides a 2-fold increase in uncorrected visual acuity compared to spherical IOLs.

Femtosecond laser-assisted arcuate keratotomy for correction of postkeratoplasty astigmatism

Purpose The aim of this study was to evaluate the effect of femtosecond laser-assisted arcuate keratotomy (FS-AK) for correction of postkeratoplasty astigmatism.Patients and methods This is an interventional prospective clinical study that included 15 patients with postkeratoplasty corneal astigmatism more than 4 D for whom FS-AK was performed between January 2016 and September 2019 for correction of astigmatism. Femtosecond laser was used to perform paired arcuate incisions 1.00 mm inside the graft. Patients’ uncorrected visual acuity and astigmatic change were recorded with follow-up of up to 6 months after surgery.Results The mean magnitude of corneal astigmatism improved from 8.18±2.11 D preoperatively to 3.31±1.18 and 4.00±1.29 D at 2 and 6 months after FS-AK, respectively (P=0.000), with a significant improvement in uncorrected visual acuity from 0.72 LogMAR preoperatively to 0.36 and 0.38 LogMAR at 2 and 6 months, postoperatively (P=0.000). However, surgically induced astigmatism was 5.05±1.31 and 4.43±1.26 D at 2 and 6 months, postoperatively.Conclusion FS-AK is an effective and safe technique in reducing astigmatism following keratoplasty and in improving the visual outcome. Although regression may occur, the visual outcome is still satisfactory.

Intracorneal Ring Segment Implantation for the Management of Keratoconus in Children.

The short-term safety and efficacy of intracorneal ring segment (ICRS) implantation in keratoconus eyes of children are investigated in this study. A retrospective interventional case series study including a total of 33 keratoconus eyes (age 8 to 17 years) that had undergone ICRS (Keraring segments, Mediphacos) implantation was conducted. Information about visual, refractive, pachymetric, corneal topographic and aberrometric, and corneal endothelial changes during a 3-month follow-up were extracted and analysed. A significant improvement was observed in logMAR corrected distance visual acuity (p = 0.005), combined with a statistically significant reduction in keratometric readings (p < 0.001). A reduction in the magnitude of corneal astigmatism of ≥1 D was observed in 52.8% of eyes. No significant changes were observed in corneal endothelial density (p = 0.317). Significant changes were found in the anterior vertical coma component (p = 0.002) as well as in the spherical aberration of the posterior corneal surface (p = 0.004). Only two relevant complications were described: one corneal microperforation with penetration of the ring segment into the anterior chamber (1 eye, 2.8%), and a case of ring extrusion (1 eye, 2.8%). ICRS implantation in children keratoconus eyes allows a reduction of corneal astigmatism, irregularity, and aberrations, leading to a significant visual improvement.

Evaluation of posterior and total corneal astigmatism with colour-LED topography.

To characterise the posterior and total corneal astigmatism using colour point-source light-emitting diodes (LED) topography. In a prospective case series 400 eyes from 400 patients were evaluated by colour-LED topography. Only eyes with normal topographies were considered. The following parameters were studied: magnitude and distribution of SimK and posterior corneal astigmatism, correlation between SimK and posterior corneal astigmatism, and differences in magnitude and axis between total and anterior corneal astigmatism. The mean SimK corneal astigmatism was 1.21 ± 0.94 D. The mean posterior corneal astigmatism was 0.37 ± 0.24 D. Posterior astigmatism was vertically oriented in 68% of eyes. Twenty-two percent of eyes showed a posterior corneal astigmatism ≥ 0.50 D. The correlation coefficients between SimK and posterior corneal astigmatism were: r2 = 0.066; p = 0.371 in WTR eyes, r2 = 0.112; p = 0.173 in ATR eyes and r2 = -0.019; p = 0.879 in oblique eyes. A difference between SimK and total corneal astigmatism ≥ 0.50 D was found in 7% of eyes. A difference in axis between SimK and total corneal astigmatism ≥ 10° was found in 24% of eyes. The percentage of eyes with posterior corneal astigmatism ≥ 0.50 D and the differences between anterior and total corneal astigmatism were higher than those previously reported in the literature. Therefore, this study supports the consideration of total corneal astigmatism magnitude and axis is mandatory for a precise surgical correction of astigmatism.

Posterior and total corneal astigmatism measured with optical coherence tomography-based biometer and dual Scheimpflug analyzer.

To compare corneal astigmatism obtained from an optical coherence tomography-based biometer (OCT) and dual Scheimpflug analyzer (DSA). Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. Retrospective case series. Consecutive cases with both OCT and DSA measurements were reviewed. Three parameters were analyzed with OCT and DSA: (1) standard keratometric astigmatism (K vs simulated keratometry [SimK]), (2) posterior corneal astigmatism, and (3) total corneal astigmatism (total keratometry [TK] vs total corneal power [TCP]). The magnitudes of corneal astigmatism obtained from the 2 devices were compared. Vector analysis was used to assess differences in corneal astigmatism between devices. In this study 530 corneas in 530 patients were measured. Compared with the DSA, the OCT produced a lower mean magnitude of posterior corneal astigmatism (-0.19 vs -0.29 diopter [D]) and a higher percentage of eyes with magnitude ≤0.25 D (75.5% vs 41.9%) (P < .05). Comparing TK and TCP, (1) TK was greater in magnitudes (1.03 vs 0.98 D); (2) 84.3% of eyes had differences in magnitude of ≤0.50 D; (3) in eyes with TK astigmatism ≥0.5 D, 34.5% and 60.1% of eyes had differences in steep meridian of ≤5 degrees and ≤10 degrees, respectively, and (4) 59.2% of eyes had vector differences of ≤0.50 D. In with-the-rule and against-the-rule eyes, respectively, the vector differences between TK and TCP were 0.16 D @ 83 degrees and 0.17 D @ 12 degrees, and in posterior corneal astigmatism, 0.06 D @ 173 degrees; and 0.15 D @ 175 degrees. There were clinically significant differences in total corneal astigmatism obtained from OCT and DSA devices. Compared with DSA, OCT produced lower values for posterior corneal astigmatism.

Characteristics and analysis of corneal astigmatism in age-related cataract patients over 50 years old

Objective: To investigate the relationship between corneal astigmatism and age, axial length (AL) in age-related cataract patients over 50 years old. Methods: In this retrospective study, 1 906 eyes of 953 patients with age-related cataract were diagnosed from February 2016 to August 2016 atPeking University People's Hospital, and their demographics, preoperative AL, magnitude and meridian of the corneal astigmatism measured by IOL Master were collected. Restricted cubic splines and Spearman rank correlation coefficients were used to investigate the relationship of the magnitude of cornea astigmatism to age. Chi-square test was used to assess the relationship of the meridian of astigmatism to age, AL and the magnitude of cornea astigmatism. Results: The patients were 410 men and 543 women. The corneal astigmatism was with-the-rule (WTR) in 570 eyes (29.91%), against-the-rule (ATR) in 1 005 eyes (52.73%) and oblique in 331 eyes (17.37%). The mean age was (72±9) years old. The medians (min, max) of AL and corneal astigmatism magnitude were 23.49 mm (19.83 mm to 33.89 mm) and 0.97 D (0.06 D to 4.65 D) in right eyes and 23.41 mm (17.54 mm to 32.09 mm) and 0.92 D (0.11 D to 4.88 D) in left eyes, respectively. The corneal astigmatism was ≥0.75 D in 64.95% (619/953) of the right eyes and 61.59% (587/953) of the left eyes. Among the elderly patients over 65 years old, when the AL was between 22.00-25.99 mm (r=0.186-0.279), the value of corneal astigmatism was positively correlated with age (all P<0.01) in both eyes. The value of ATR corneal astigmatism was positively correlated with age (right eyes, r=0.278, P<0.01; left eyes, r=0.225, P<0.01), while the value of WTR corneal astigmatism had no statistically significant correlation with age (right eyes, P=0.335; left eyes, P=0.633). The prevalence of WTR astigmatism decreased with age from 43.81% (46/105) to 20.73% (51/246) in right eyes and from 40.00% (42/105) to 24.80% (61/246) in left eyes, while the prevalence of ATR astigmatism increased with age from 38.10% (40/105) to 61.38% (151/246) in right eyes and from 33.33% (35/105) to 58.94% (145/246) in left eyes. The prevalence of oblique astigmatism was not significantly changed with age (right eyes, χ(2)=31.986, P<0.01; left eyes, χ(2)=27.686, P<0.01). There was no statistically significant difference in the distribution of corneal astigmatism meridians between different AL groups (right eyes, P=0.497; left eyes, P=0.897). With the increase of the magnitude of corneal astigmatism, the prevalence of oblique astigmatism significantly decreased from 25.45% (85/334) to 0 in right eyes and from 29.78% (109/366) to 1.35% (1/74) in left eyes, while the prevalence of ATR astigmatism significantly increased from 39.82% (133/334) to 79.27% (65/82) in right eyes and from 41.80% (153/366) to 59.46% (44/74) in left eyes (right eyes, χ(2)=72.229, P<0.01; left eyes, χ(2)=72.166, P<0.01). Conclusions: A majority of age-related cataract patients over 50 years old have astigmatism ≥0.75 D before cataract surgery. When the AL is between 22.00 mm and 25.99 mm, the magnitude of corneal astigmatism increases with age among people over 65 years old, especially the magnitude of ATR corneal astigmatism, while the magnitude of WTR corneal astigmatism has no obvious increase with age. The percentage of ATR astigmatism increases while the percentage of WTR astigmatism decreases with age. (Chin J Ophthalmol, 2020, 56: 349-355).

Outcome of toric intraocular lenses implanted in eyes with previous corneal refractive surgery.

To evaluate the outcome of toric intraocular lens (IOL) implantation in eyes with previous laser in situ keratomileusis/photorefractive keratectomy (LASIK/PRK). Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. Retrospective case series. Consecutive cases that had previous myopic or hyperopic LASIK/PRK and had undergone cataract surgery with toric IOL implantation were retrospectively reviewed. Included were eyes that had (1) preoperative ocular biometry measurements with the Lenstar, (2) no intraoperative or postoperative complications, and (3) available postoperative manifest refraction at ≥3 weeks with corrected distance visual acuity of 20/30 or better. Vector analysis was used to assess the preoperative corneal and postoperative refractive astigmatism. In 56 eyes with previous myopic LASIK/PRK and 19 eyes with previous hyperopic LASIK/PRK, respectively, the mean magnitudes of corneal astigmatism were 1.34 ± 0.62 diopters (D) and 1.66 ± 0.80 D, 5% and 0% of eyes had anterior corneal astigmatism ≤0.50 D, and the centroid values were 0.31 D at 19 degrees ± 1.45 D and 0.74 D at 92 degrees ± 1.72 D preoperatively. Postoperatively, the mean magnitudes of refractive astigmatism were 0.36 ± 0.31 D and 0.34 ± 0.34 D, 80% and 84% of eyes had refractive astigmatism of ≤0.50 D, and the centroid values were 0.12 D at 152 degrees ± 0.46 D and 0.05 D at 172 degrees ± 0.48 D (all P < .05). Toric IOLs were effective to correct preexisting corneal astigmatism in eyes with previous excimer laser corneal refractive surgery.