Distribution of Anterior and Posterior Corneal Astigmatism in Eyes With Keratoconus

Naderan, Mohammad; Rajabi, Mohammad Taher; Zarrinbakhsh, Parviz

doi:10.1016/j.ajo.2016.03.051

Cited by 26 publications

(27 citation statements)

References 15 publications

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“…In contrast, Kamiya et al[ 16 ] found that WTR astigmatism was more prevalent at the anterior corneal surface (65.7%) and oblique astigmatism was more prevalent at the posterior corneal surface (78.8%). Our findings are also different from those of Naderan et al,[ 17 ] who reported that ATR astigmatism was more prevalent at the anterior corneal surface (57.4%) and that WTR astigmatism was more common at the posterior corneal surface (63.2%) in their patients with KCN.…”

Section: Discussioncontrasting

confidence: 99%

“…We found a significant correlation between the magnitude of ACA and that of PCA, which is in accordance with the reports by Naderan et al[ 17 ] and Kamiya et al[ 16 ] We did not find any significant increase in ACA and PCA with the progressive stages of KCN, which again is consistent with the findings of Kamiya et al However, Naderan et al reported a gradually significant increase in the magnitude of ACA and PCA in eyes with stage 1, 2, and 3 KCN. Although the findings of our study are similar to those in the above two studies, we detected larger ACA and PCA values in eyes with stage 4 KCN than in those with less severe KCN (stages 1–3).…”

Section: Discussionsupporting

confidence: 94%

“…In the present study, we found that the mean magnitudes for ACA and PCA in our study population were 4.08 ± 2.21 D and 0.86 ± 0.45 D, respectively. Naderan et al[ 17 ] evaluated 1273 patients with KCN using Pentacam images and reported that the mean ACA and PCA magnitudes of 4.49 ± 2.16 D and 0.90 ± 0.43 D, respectively, which are very similar to our results. Our findings are also in line with those of Kamiya et al[ 16 ] who evaluated ACA and PCA in 137 patients with KCN using the Pentacam HR and reported mean respective magnitudes of 3.93 ± 2.73 D and 0.93 ± 0.64 D. Orucoglu et al[ 18 ] also evaluated ACA and PCA in patients with KCN using the Pentacam and reported mean magnitudes of 3.05 ± 1.97 D and 0.71 ± 0.44 D, respectively, which were lower than those in our study.…”

Section: Discussionsupporting

confidence: 90%

“…The notable difference between the findings of our study and those of the two previous studies cannot be attributed to ethnic differences between the study populations. Naderan et al[ 17 ] reported that a possible reason for the difference between their Pentacam results for ACA and PCA axis orientation and those of Kamiya et al[ 16 ] was that their subjects were of Iranian descent (mostly Caucasian ethnicity), whereas those in the study by Kamiya et al were exclusively Japanese (Asian ethnicity). The difference in axis orientation values obtained in our study and those obtained by Naderan et al[ 17 ] cannot be explained by ethnicity because both study populations were Iranian.…”

Section: Discussionmentioning

confidence: 99%

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Characteristics of posterior corneal astigmatism in different stages of keratoconus

Aslani

Khorrami-Nejad

Amiri

et al. 2018

J Ophthalmic Vis Res

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Purpose: To evaluate the magnitudes and axis orientation of anterior corneal astigmatism (ACA) and posterior corneal astigmatism (PCA), the ratio of ACA to PCA, and the correlation between ACA and PCA in the different stages of keratoconus (KCN). Methods: This retrospective case series comprised 161 eyes of 161 patients with KCN (104 men, 57 women; mean age, 22.35 ± 6.10 years). The participants were divided into four subgroups according to the Amsler-Krumeich classification. A Scheimpflug imaging system was used to measure the magnitude and axis orientation of ACA and PCA. The posterior-anterior corneal astigmatism ratio was also calculated. The results were compared among different subgroups. Results: The average amounts of anterior, posterior, and total corneal astigmatism were 4.08 ± 2.21 diopters (D), 0.86 ± 0.46 D, and 3.50 ± 1.94 D, respectively. With-the-rule, against-the-rule, and oblique astigmatisms of the posterior surface of the cornea were found in 61 eyes (37.9%), 67 eyes (41.6%), and 33 eyes (20.5%), respectively; corresponding figures in the anterior corneal surface were 55 eyes (32.4%), 56 eyes (34.8%), and 50 eyes (31.1%), respectively. A strong correlation (P ≤ 0.001, r = 0.839) was found between ACA and PCA in the different stages of KCN; the correlation was weaker in eyes with grade 3 (P ≤ 0.001, r = 0.711) and grade 4 (P ≤ 0.001, r = 0.717) KCN. The maximum posterior-anterior corneal astigmatism ratio (PCA/ACA, 0.246) was found in patients with stage 1 KCN. Conclusion: Corneal astigmatism in anterior surface was more affected than posterior surface by increasing in the KCN severity, although PCA was more affected than ACA in an early stage of KCN.

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionsupporting

confidence: 94%

Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Characteristics of posterior corneal astigmatism in different stages of keratoconus

Aslani

Khorrami-Nejad

Amiri

et al. 2018

J Ophthalmic Vis Res

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show abstract

“…A significant correlation was found between ACA and PCA, especially in eyes of anterior WTR astigmatism [6,12,24]. Our findings were consistent with the previous studies (r 2 = 0.089 and r 2 = 0.298, respectively, both P < 0.001).…”

Section: Discussionsupporting

confidence: 92%