Effect of the posterior corneal surface on total corneal astigmatism in patients with age-related cataract

Jin, Yingying; Zhou, Z.H.; Yuan, Xiaoyong; Song, Hui; Tang, Xin

doi:10.18240/ijo.2018.06.10

“…Previous studies showed that ignoring posterior corneal astigmatism may yield significant estimation errors for total corneal astigmatism in age-related cataract patients preparing for cataract surgery. To be more specific, error in magnitude was significantly increased when the magnitude of posterior corneal astigmatism was larger than 0.4 D. Additionally, when WTR anterior corneal astigmatism was more than 2.6 D or an ATR astigmatism was more than 1.6 D, the anterior measurement can cause errors influencing on the toric IOL decision [ 15 , 22 ]. In the present study, the posterior corneal astigmatism (PCA) of larger than 0.4 D, WTR anterior corneal astigmatism of larger than 2.6 D and ATR astigmatism of larger than 1.6 D accounted for 49.8, 32.2 and 23.5%, respectively.…”

Section: Discussionmentioning

confidence: 99%

Analysis of corneal astigmatism and aberration in chinese congenital cataract and developmental cataract patients before cataract surgery

Han

¹

,

Fan

²

,

Hua

³

et al. 2021

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Background To investigate the distribution of corneal astigmatism, aberration, and biometric parameters in Chinese congenital cataract (CC) /developmental cataract patients before cataract surgery. Methods We evaluated eyes of CC /developmental cataract patients scheduled for cataract surgery from January 2016 to September 2019. Astigmatism, aberrations, and biometric parameters were measured with the Pentacam Scheimpflug imaging device (Pentacam HR, Oculus). Cataract was diagnosed and classified by slit-lamp examination after full mydriasis. Results We evaluated 538 eyes in 356 patients. The mean values of anterior corneal astigmatism (ACA), posterior corneal astigmatism (PCA), and total corneal astigmatism (TCA) were determined as 1.98 ± 1.06 D (range 0.0‒4.8 D), 0.49 ± 0.26 D (range 0.0‒1.9 D), and 2.09 ± 1.19 D (range 0.2‒8.8 D), respectively. ACA and TCA ≥ 1.25 D was present in 379 eyes (70.3%) and 392 eyes (72.8%), respectively. PCA between 0.25 D and 0.75 D was found in 380 eyes (70.6%). There was a statistically significant positive linear correlation between lower-order aberrations root mean square values (LOA RMS) and corneal astigmatism (CA). Furthermore, in terms of distribution of central cornea thickness, anterior chamber depth, ACA, PCA, and TCA in different types of cataracts, ACA was highest in patients with zonular cataracts. Finally, we found anterior corneal measurements may overestimate WTR astigmatism, underestimate ATR astigmatism, and underestimate oblique astigmatism, respectively. Conclusions Most CC /developmental cataract patients had moderate to high astigmatism and ACA accounted for the largest proportion in the zonular group. This can provide a basis for planning of CC/developmental cataract surgery by ophthalmologists in clinical practice.

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“…Some have reported that astigmatism at the corneal posterior surface was generally less than 0.50DC. [ 18 19 20 21 22 23 24 25 26 ] It has been claimed that Orbscan II tends to overestimate characteristics of the posterior corneal surface compared with other systems. [ 5 27 ] Alternatively, it could equally be argued that other systems underestimated changes at the posterior surface of the cornea.…”

Section: Discussionmentioning

confidence: 99%

The influence of routine uncomplicated phacoemulsification on the orthogonality of the cornea

Tutchenko

¹

,

Patel

²

,

Voytsekhivskyy

³

et al. 2021

Indian Journal of Ophthalmology

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Purpose: The aim of this study was to determine the effect of routine uncomplicated phacoemulsification on the orthogonal distribution of mass within the central optical zone of the cornea. Methods: Astigmatism at both corneal surfaces was evaluated using Orbscan II (Bausch &and Lomb) before and up to 3 months after routine phacoemulsification (one eye/patient). The data were subjected to vector analysis to estimate the pre-and postoperative total astigmatism of the cornea (TCA). Results: Reporting the chief findings in minus cylinder (diopters, DC) over the central 3 mm (A) and 5 mm (B) optical zones. Mean TCA powers (±sd) at pre- and 3-months postop were A) –4.45DC (±2.00) and –5.69DC (±2.69), B) –2.91DC (±2.22) and –2.71DC (±1.60). Change in mean power was significant over 3 mm ( P < 0.01, n = 49) but not over 5 mm. Inter-zonal differences were significant ( P < 0.01). There was a significant linear relationship between the change in TCA power ( y = preoperative-postoperative) and TCA at preoperative stage (x) where, A) y = 0.45x + 3.12 ( r = 0.336, n = 49, P = 0.018), B) y = x + 2.65 ( r = 0.753, n = 49, P = <0.01). Over the central 3 mm zone only, change (preoperative-postoperative) in axis (°) of TCA (y 1 ) was significantly associated with TCA axis at preoperative stage (x 1 ) where y 1 = 1.391x 1 -0.008x 1 2 -0.701 ( r = 0.635, n = 49, P < 0.01). Conclusion: Changes in TCA power and axis at 3 months postop, determined using Orbscan II, are indicative of orthogonal alterations in the distribution of corneal tissue. Over the central 3 mm zone, the association between y 1 and x 1 shows that a change in TCA axis is more profound when preoperative axis is near 90° i.e., against-the-rule.

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“…This might make some compensation for the binocular refractive imbalance in aniso-axial length patients. Though the contribution of the posterior corneal curvature is small [ 32 ], its effects on total corneal refractive status should not be neglected casually, especially in aniso-axial length patients.…”

Section: Discussionmentioning

confidence: 99%

Eyes of Aniso-Axial Length Individuals Share Generally Similar Corneal Biometrics with Normal Eyes in Cataract Population

Zhang

¹

,

Chen

²

,

Deng

³

et al. 2020

Journal of Ophthalmology

0

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Aims. To determine the characteristics of corneal biometrics in eyes from aniso-axial length cataract patients compared with eyes from non-aniso-axial length individuals. Methods. This is a retrospective case series. Cataract patients with preoperative binocular measurements were recruited. A binocular axial difference of ≥1 mm was considered to indicate aniso-axial length. The anterior segmental biometrics were measured using Pentacam HR (Oculus, Wetzlar, Germany) and IOLMaster 500 (Carl Zeiss Meditec, Jena, Germany). Comparisons of biometrics were made among 4 eye conditions: the longer eyes from aniso-axial length patients, the shorter eyes from aniso-axial length patients, the longer eyes from non-aniso-axial length patients, and the shorter eyes from non-aniso-axial length patients. The aniso-axial length eyes were also stratified into 8 subgroups with axial length (AL) increments of 1 mm, and the biometrics of the subgroups were compared. Results. There was smaller anterior corneal astigmatism in the shorter aniso-axial length group than those in the longer aniso-axial length group (1.01 ± 0.70 D vs 1.12 ± 0.76 D, P = 0.031 ). The longer aniso-axial length eyes had greater anterior corneal steep curvature (44.13 ± 1.69 D vs 43.87 ± 1.69 D, P = 0.009 ) and anterior corneal astigmatism (1.12 ± 0.76 D vs 1.02 ± 0.69 D, P = 0.023 ) compared with longer non-aniso-axial length subjects. Other corneal biometrics were similar between the aniso-axial length eyes and the non-aniso-axial length eyes. In the longer aniso-axial length group, the posterior corneal aberrations of eyes in the ≥5 mm subgroups were greater than those in the <5 mm subgroups (0.879 ± 0.183 μm vs 0.768 ± 0.178 μm for total aberrations, P < 0.001 ; 0.228 ± 0.086 μm vs 0.196 ± 0.043 μm for high-order aberrations, P = 0.036 ; 0.847 ± 0.173 μm vs 0.741 ± 0.179 μm for low-order aberrations, P = 0.001 ). Conclusion. Eyes of aniso-axial length individuals share generally similar corneal biometrics with normal eyes in cataract population. Anterior corneal astigmatism of the longer eyes from the aniso-axial length cataract patients was higher than that of the longer eyes from the non-aniso-axial length individuals. Total posterior corneal aberrations of the longer aniso-axial length eyes increased when the binocular axial difference was over 5 mm.

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Effect of the posterior corneal surface on total corneal astigmatism in patients with age-related cataract

Cited by 7 publications

References 25 publications

Analysis of corneal astigmatism and aberration in chinese congenital cataract and developmental cataract patients before cataract surgery

Analysis of corneal astigmatism and aberration in chinese congenital cataract and developmental cataract patients before cataract surgery

The influence of routine uncomplicated phacoemulsification on the orthogonality of the cornea

Eyes of Aniso-Axial Length Individuals Share Generally Similar Corneal Biometrics with Normal Eyes in Cataract Population

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