Distribution of Posterior Corneal Astigmatism According to Axis Orientation of Anterior Corneal Astigmatism

Purpose.To assess the amount and the axis orientation of anterior and posterior corneal astigmatism after refractive lenticule extraction (ReLEx) for myopic astigmatism.Methods.We retrospectively examined 53 eyes of 53 consecutive patients (mean age ± standard deviation, 33.2 ± 6.5 years) undergoing ReLEx to correct myopic astigmatism (manifest cylinder = 0.5 diopters (D)). Power vector analysis was performed with anterior and posterior corneal astigmatism measured with a rotating Scheimpflug system (Pentacam HR, Oculus) and refractive astigmatism preoperatively and 3 months postoperatively.Results.Anterior corneal astigmatism was significantly decreased, measuring 1.42 ± 0.73 diopters (D) preoperatively and 1.11 ± 0.53 D postoperatively (p<0.001, Wilcoxon signed-rank test). Posterior corneal astigmatism showed no significant change, falling from 0.44 ± 0.12 D preoperatively to 0.42 ± 0.13 D postoperatively (p=0.18). Refractive astigmatism decreased significantly, from 0.92 ± 0.51 D preoperatively to 0.27 ± 0.44 D postoperatively (p<0.001). The anterior surface showed with-the-rule astigmatism in 51 eyes (96%) preoperatively and 48 eyes (91%) postoperatively. By contrast, the posterior surface showed against-the-rule astigmatism in all eyes preoperatively and postoperatively.Conclusions.The surgical effects were largely attributed to the astigmatic correction of the anterior corneal surface. Posterior corneal astigmatism remained unchanged even after ReLEx for myopic astigmatism.

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Does pterygium morphology affect corneal astigmatism?

Therapeutic Advances in Ophthalmology ◽

10.1177/25158414211030423 ◽

2021 ◽

Vol 13 ◽

pp. 251584142110304

Author(s):

Emine Doğan ◽

Burçin Çakır ◽

Nilgün Aksoy ◽

Elif Köse ◽

Gürsoy Alagöz

Keyword(s):

Anterior Segment ◽

Clinical Information ◽

Corneal Astigmatism ◽

Continuous Group ◽

Optic Coherence Tomography ◽

Morphological Pattern ◽

Horizontal Length ◽

The Mean ◽

Anterior Corneal Astigmatism ◽

Posterior Corneal Astigmatism

Purpose: The purpose of this study was to evaluate the correlation between corneal astigmatism and the morphology of pterygium with anterior segment optic coherence tomography (AS-OCT). Material and Methods: The size of pterygium (horizontal length, vertical width) was measured manually; pterygium area and percentage extension of the pterygium onto the cornea were calculated. Anterior and posterior corneal astigmatism, Sim K, K1, K2 were measured using a dual Scheimpflug analyzer. Morphological patterns of the pterygium analyzed with AS-OCT were determined according to the extension of the pterygium apex below the corneal epithelium. Two tomographic patterns were identified: continuous and nodular. Correlation between anterior corneal astigmatism and pterygium size, percentage extension of the pterygium, and morphological pattern of the pterygium was analyzed. Results: The mean ages of the 47 patients were 49.4 ± 16.6 (22–80) years. Mean horizontal pterygium length, vertical width, pterygium area, and percentage extension of the pterygium were 2.8 ± 1.2 mm, 4.8 ± 1.6 mm, 7.42 ± 5.6 mm2 and 24.5 ± 10.4%, respectively. Mean anterior corneal astigmatism was 2.3 ± 2.3 D and simulated keratometry was 43.4 ± 2.02 D. In terms of the morphological pattern of the pterygium, 24 eyes had continuous, 23 eyes had a nodular pattern and the median (interquartile range) anterior corneal astigmatism was 1.87 (1.01–3.80) and 1.22 D (0.58–2.35), respectively ( p = 0.102). Other topographic and pterygium size parameters were similar between groups. Analyzing the correlations in groups separately, a positive moderate statistically significant correlation was present between vertical width, percentage extension, pterygium area, and anterior corneal astigmatism in both continuous and nodular groups. Conclusions: Although not statistically significant, anterior corneal astigmatism was higher in continuous group. Using AS-OCT to standardize the morphology of pterygium could provide additional clinical information.

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Distribution and internal correlations of corneal astigmatism in cataract patients

Scientific Reports ◽

10.1038/s41598-021-91028-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Yuanfeng Jiang ◽

Ying Qin ◽

Shaochong Bu ◽

Hong Zhang ◽

Xiaomin Zhang ◽

...

Keyword(s):

Distribution Patterns ◽

Corneal Astigmatism ◽

Morphological Parameters ◽

Summation Effect ◽

Age Related ◽

Cataract Patients ◽

Age Related Changes ◽

Anterior Corneal Astigmatism ◽

Posterior Corneal Astigmatism ◽

Total Corneal Astigmatism

AbstractThe aim of the study is to explore the distribution patterns and internal correlations of the morphological parameters of the cornea in patients with age-related cataract. The Pentacam HR was used to measure anterior corneal astigmatism (ACA), posterior corneal astigmatism (PCA), total corneal astigmatism (TCA) and keratometric corneal astigmatism (KCA). With age, the proportion of with-the-rule (WTR) ACA decreased from 65.31% to 23.63%, while the against-the-rule (ATR) ACA increased from 26.53% to 56.20%. PCA exceeded 0.50 D in 9.14% of eyes, while 76.35% of them were ATR. The magnitude of ACA was positively correlated with PCA in the whole sample, with a more significant correlation in WTR eyes (sr = 0.349, P < 0.001). The vector summation effect of PCA to ACA changed from compensation to augmentation with aging. In 57.53% of WTR eyes, KCA was overestimated by an average of 0.21 ± 0.17 D, while it was underestimated by 0.38 ± 0.27 D in 87.62% of ATR eyes. In conclusion, among age-related cataract patients, ACA and TCA gradually shifted from WTR to ATR with aging, while most PCA remained as ATR. Ignoring the age-related changes and real PCA might cause overestimation of WTR astigmatism and underestimation of ATR astigmatism.

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A multicenter study of the distribution pattern of posterior corneal astigmatism in Chinese myopic patients having corneal refractive surgery

Scientific Reports ◽

10.1038/s41598-020-73195-w ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Yijun Hu ◽

Shanqing Zhu ◽

Lu Xiong ◽

Xuejun Fang ◽

Jia Liu ◽

...

Keyword(s):

Image Quality ◽

Distribution Pattern ◽

Multicenter Study ◽

Refractive Surgery ◽

Corneal Astigmatism ◽

Astigmatism Correction ◽

Corneal Refractive Surgery ◽

The Impact ◽

Anterior Corneal Astigmatism ◽

Posterior Corneal Astigmatism

Abstract Including posterior corneal astigmatism (PCA) into consideration may increase the accuracy of astigmatism correction after corneal refractive surgery. In the present study we aim to investigate the distribution pattern of PCA in a large number of myopic patients from multiple ophthalmic centers. There were 7829 eyes retrospectively included in the study. Pentacam data of the eyes were retrieved from the machine and only results with image quality labelled with ‘OK’ were included. Distribution of PCA was slightly positively skewed (Skewness = 0.419, Kurtosis = 0.435, KS P < 0.0001). Mean PCA was 0.34 ± 0.14 D (range: 0.00 D-0.99 D). PCA was ≥ 0.25 D in 74.91% of the eyes and was ≥ 0.50 D in 11.61% of the eyes. In 97.55% of the eyes the steep meridian of PCA was vertical (SMV). PCA magnitude was significantly higher in eyes with SMV PCA (P < 0.0001) or high manifest astigmatism (MA, P < 0.0001). There was a significant correlation between anterior corneal astigmatism (ACA) magnitude and PCA magnitude in all of the eyes (r = 0.704, P < 0.0001). There was also a trend of decreasing frequency and magnitude of SMV PCA with aging (both P < 0.0001). In conclusion, PCA is present in myopic patients having corneal refractive surgery and PCA magnitude is increased with higher MA or ACA. Consideration of the impact of PCA on laser astigmatism correction may be necessary.

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Polar Value Analysis of Low to Moderate Astigmatism with Wavefront-Guided Sub-Bowman Keratomileusis

Journal of Ophthalmology ◽

10.1155/2017/5647615 ◽

2017 ◽

Vol 2017 ◽

pp. 1-9

Author(s):

Pisong Yan ◽

Zhiyu Du ◽

Yu Zhang

Keyword(s):

Corneal Astigmatism ◽

Corneal Surface ◽

Value Analysis ◽

Surgically Induced Astigmatism ◽

Induced Astigmatism ◽

A Minor ◽

Surgically Induced ◽

Myopic Astigmatism ◽

Anterior Corneal Astigmatism ◽

Posterior Corneal Astigmatism

Purpose. To evaluate the astigmatic outcomes of wavefront-guided sub-Bowman keratomileusis (WFG-SBK) for low to moderate myopic astigmatism.Methods. This study enrolled 100 right eyes from 100 patients who underwent WFG-SBK for the correction of myopia and astigmatism. The polar value method was performed with anterior and posterior corneal astigmatism measured with Scheimpflug camera combined with Placido corneal topography (Sirius, CSO) and refractive astigmatism preoperatively and 1 month, 3 months, and 6 months postoperatively.Results. Similar results for surgically induced astigmatism (SIA) and error of the procedure in both anterior corneal astigmatism (ACA) and total ocular astigmatism (TOA). There was a minor undercorrection of the cylinder in both ACA and TOA. Posterior corneal astigmatism (PCA) showed no significant change.Conclusions. Wavefront-guided SBK could provide good astigmatic outcomes for the correction of low to moderate myopic astigmatism. The surgical effects were largely attributed to the astigmatic correction of the anterior corneal surface. Posterior corneal astigmatism remained unchanged even after WFG-SBK for myopic astigmatism. Polar value analysis can be used to guide adjustments to the treatment cylinder alongside a nomogram designed to optimize postoperative astigmatic outcomes in myopic WFG-SBK.

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Changes in Anterior, Posterior, and Total Corneal Astigmatism after Descemet Membrane Endothelial Keratoplasty

Journal of Ophthalmology ◽

10.1155/2017/4068963 ◽

2017 ◽

Vol 2017 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Maged Alnawaiseh ◽

Lars Zumhagen ◽

André Rosentreter ◽

Nicole Eter

Keyword(s):

Corneal Astigmatism ◽

Endothelial Keratoplasty ◽

Descemet Membrane Endothelial Keratoplasty ◽

Axis Orientation ◽

Descemet Membrane ◽

Before And After ◽

Vector Difference ◽

Anterior Posterior ◽

Posterior Corneal Astigmatism ◽

Total Corneal Astigmatism

Purpose. To evaluate changes in anterior, posterior, and total corneal astigmatism in patients after Descemet membrane endothelial keratoplasty (DMEK). Methods. We retrospectively included 29 eyes of 23 patients (age 67.6 ± 9.8 years, 13 female, 10 male) after DMEK surgery. The magnitude and axis orientation of anterior, posterior, and total corneal astigmatism before and after DMEK were determined using a rotating Scheimpflug system (Pentacam HR, Oculus). Results. The magnitude of anterior, posterior, and total corneal astigmatism in the central cornea did not change significantly after surgery. Before surgery, we found a significant correlation between the magnitudes of anterior and posterior corneal astigmatism (Spearman’s correlation coefficient rS=0.526, P=0.003), while after surgery this correlation was no longer significant (rS=0.038, P=0.843). There was a significant correlation between the vector difference between preoperative and postoperative posterior astigmatism and the change in corneal pachymetry (rP=0.47, P=0.010). Conclusions. Posterior corneal astigmatism (especially the orientation) and therefore the relationship between anterior and total corneal astigmatism may change after DMEK. This should be considered to improve the accuracy of toric IOL power calculations following phakic DMEK or in combined procedures.

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Effect of 1.8-mm steep-axis clear corneal incision on the posterior corneal astigmatism in candidates for toric IOL implantation

10.21203/rs.2.24131/v1 ◽

2020 ◽

Author(s):

Xi Li ◽

Xiang Chen ◽

Suhong He ◽

Wen Xu

Keyword(s):

T Test ◽

Corneal Astigmatism ◽

Corneal Incision ◽

Toric Iol ◽

Iol Implantation ◽

Clear Corneal Incision ◽

Significant Difference ◽

Paired T Test ◽

Anterior Corneal Astigmatism ◽

Posterior Corneal Astigmatism

Abstract PURPOSE In the present study, we aimed to analyze the effects of cataract surgery using a 1.8-mm steep-axis clear corneal incision (CCI) on the posterior corneal surfaces based on the keratometry from the rotating Scheimpflug imaging device (Pentacam HR) in candidates for toric intraocular lens (IOL) implantation. METHODS Preoperative and at least 1-month postoperative data measured by Pentacam HR were collected in patients for toric IOL implantation. Surgically induced astigmatism on the posterior cornea (P-SIA) was calculated based on the preoperative and postoperative keratometric data, and the related factors of P-SIA were analyzed. RESULTS A total of 60 eyes from 56 patients were enrolled. The preoperative anterior and posterior corneal astigmatism was 1.58±0.61 D and 0.28±0.22 D, respectively. The postoperative anterior and posterior corneal astigmatism was 1.26±0.68 D and 0.41±0.26 D, respectively. The astigmatism was significantly decreased on anterior surface (P<0.001, paired t-test) and increased on posterior surface (P<0.001, paired t-test). The mean of P-SIA calculated by Holladay–Cravy–Koch method was 0.34±0.20 D, with 0.5 D or greater accounting for 26.7%. P-SIA showed no significant difference among with-the-rule (WTR) astigmatism, against-the-rule (ATR) astigmatism and oblique astigmatism (F=1.85, P=0.167). A statistically significant correlation was observed between the P-SIA and preoperative anterior corneal astigmatism (r = 0.29, P=0.024), as well as preoperative posterior corneal astigmatism (r=0.27, P=0.038). CONCLUSIONS In candidates for toric IOL implantation with a 1.8-mm steep-axis CCI, the incision caused a significant reduction of the anterior corneal astigmatism but an increase of the corneal posterior astigmatism. P-SIA could not be ignored, and it played a significant role in SIA, especially in cases with higher preoperative anterior or posterior corneal astigmatism.

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Effect of 1.8-mm steep-axis clear corneal incision on the posterior corneal astigmatism in candidates for toric IOL implantation

10.21203/rs.2.24131/v2 ◽

2020 ◽

Author(s):

Xi Li ◽

Xiang Chen ◽

Suhong He ◽

Wen Xu

Keyword(s):

Corneal Astigmatism ◽

Corneal Incision ◽

Toric Iol ◽

Iol Implantation ◽

Clear Corneal Incision ◽

Paired T Test ◽

Anterior Posterior ◽

Anterior Corneal Astigmatism ◽

Posterior Corneal Astigmatism ◽

Total Corneal Astigmatism

Abstract Background: In the present study, we aimed to analyze the effects of cataract surgery using a 1.8-mm steep-axis clear corneal incision (CCI) on the posterior corneal surfaces based on the keratometry from the rotating Scheimpflug imaging device (Pentacam HR) in candidates for toric intraocular lens (IOL) implantation. Methods: Preoperative and at least 1-month postoperative data measured by Pentacam HR were collected in patients for toric IOL implantation. Surgically induced astigmatism on the posterior cornea (P-SIA) was calculated based on the preoperative and postoperative keratometric data, and the related factors of P-SIA were analyzed. Results: A total of 60 eyes from 56 patients were enrolled. The preoperative anterior, posterior and total corneal astigmatism was 1.58±0.61 D ,0.28±0.22 D and 1.70 ± 0.52 D respectively. The postoperative anterior, posterior and total corneal astigmatism was 1.26±0.68 D, 0.41±0.26 D and 1.30 ± 0.51 D respectively. The astigmatism was significantly decreased on anterior surface (P＜0.001, paired t-test) and increased on posterior surface (P＜0.001, paired t-test). The mean of P-SIA calculated by Holladay–Cravy–Koch method was 0.34±0.20 D, with 0.5 D or greater accounting for 26.7%. A statistically significant correlation was observed between the P-SIA and preoperative anterior corneal astigmatism (r = 0.29, P=0.024), as well as preoperative posterior corneal astigmatism (r=0.27, P=0.038). Multivariate regression analysis showed the preoperative anterior and posterior corneal astigmatism had a significant effect on P-SIA (F=7.344, P=0.001). Conclusions: In candidates for toric IOL implantation with a 1.8-mm steep-axis CCI, the incision caused a significant reduction of the anterior corneal astigmatism but an increase of the posterior corneal astigmatism. P-SIA could not be ignored, and it played a significant role in SIA, especially in cases with higher preoperative anterior or posterior corneal astigmatism.

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