Influence of Posterior Corneal Astigmatism on Total Corneal Astigmatism in Eyes With Keratoconus

Savini, Giacomo; Næser, Kristian; Schiano-Lomoriello, Domenico; Mularoni, Alessandro

doi:10.1097/ico.0000000000000920

Cited by 20 publications

(28 citation statements)

References 26 publications

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“…The mean power values for posterior astigmatism as reported by Ho et al [11], Koch et al [12], and Zhang et al [25] are 0.30 D, 0.30 ± 0.15 D, and 0.33 ± 0.16 D, respectively. In eyes with keratoconus, the posterior corneal astigmatism displays large and variable values for total corneal astigmatism [26]. Anterior corneal astigmatism and posterior corneal astigmatism were 4.47 ± 2.05 diopters and 0.87 ± 0.44 diopters in the present study.…”

Section: Discussionsupporting

confidence: 39%

Analysis of total corneal astigmatism with a rotating Scheimpflug camera in keratoconus

2020

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Background To analyze mean corneal powers and astigmatisms on anterior, posterior, and total cornea in patients with keratoconus as calculated according to various keratometric measurements using a Scheimpflug camera. Methods We examined the left eyes of 64 patients (41 males and 23 females; mean age 29.94 ± 6.63 years) with keratoconus. We measured simulated K (Sim-K), posterior K, true net power (TNP) and four types of total corneal refractive powers (TCRP). We then used the obtained values to analyze mean K, and corneal astigmatism. TCRP were measured at 2.0 ~ 5.0 mm. Results Mean corneal powers from Sim K, posterior K, and TNP were 49.12 ± 3.99, − 7.39 ± 0.79, and 47.78 ± 4.09 diopters, respectively. For TCRP centered on the pupil, mean K tended to decrease with measurement area (all p < 0.01). While, both mean K and astigmatism measured using TCRP centered on the apex decreased with measurement area (all p < 0.001). TCRP centered on the apex were greater than those centered on the pupil for mean K values calculated using TCRP (all p < 0.001). The proportion of WTR was greatest on the anterior and total cornea. As the measurement area moved to the periphery, the proportion of WTR increased. Conclusions Mean corneal powers and astigmatisms on total cornea with keratoconus change depending on calculation methods and measurement areas.

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Section: Discussionsupporting

confidence: 39%

Analysis of total corneal astigmatism with a rotating Scheimpflug camera in keratoconus

2020

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“…As a result, in 90.9% of eyes with keratoconus, the flat meridian difference between the anterior corneal surface and the total cornea was less than or equal to 10 degrees. In line with this study, Savini et al [ 18 ] demonstrated that eyes with keratoconus showed a tendency for the steep meridians of the anterior and posterior corneal surfaces to be aligned regardless of the type of astigmatism (WTR, ATR, or oblique astigmatism). In that study, the steep meridian difference between the anterior corneal surface and the total cornea was greater than 10 degrees in only 8.4% of eyes with keratoconus [ 18 ].…”

Section: Discussionsupporting

confidence: 79%

Comparison of Anterior, Posterior, and Total Corneal Astigmatism Measured Using a Single Scheimpflug Camera in Healthy and Keratoconus Eyes

Choi

Eom

Song

et al. 2018

Korean J Ophthalmol

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PurposeTo compare the effect of posterior corneal astigmatism on the estimation of total corneal astigmatism using anterior corneal measurements (simulated keratometry [K]) between eyes with keratoconus and healthy eyes.MethodsThirty-three eyes of 33 patients with keratoconus of grade I or II and 33 eyes of 33 age- and sex-matched healthy control subjects were enrolled. Anterior, posterior, and total corneal cylinder powers and flat meridians measured by a single Scheimpflug camera were analyzed. The difference in corneal astigmatism between the simulated K and total cornea was evaluated.ResultsThe mean anterior, posterior, and total corneal cylinder powers of the keratoconus group (4.37 ± 1.73, 0.95 ± 0.39, and 4.36 ± 1.74 cylinder diopters [CD], respectively) were significantly greater than those of the control group (1.10 ± 0.68, 0.39 ± 0.18, and 0.97 ± 0.63 CD, respectively). The cylinder power difference between the simulated K and total cornea was positively correlated with the posterior corneal cylinder power and negatively correlated with the absolute flat meridian difference between the simulated K and total cornea in both groups. The mean magnitude of the vector difference between the astigmatism of the simulated K and total cornea of the keratoconus group (0.67 ± 0.67 CD) was significantly larger than that of the control group (0.28 ± 0.12 CD).ConclusionsEyes with keratoconus had greater estimation errors of total corneal astigmatism based on anterior corneal measurement than did healthy eyes. Posterior corneal surface measurement should be more emphasized to determine the total corneal astigmatism in eyes with keratoconus.

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“…[5][6][7] This may be due to the unsynchronized changes of the ACA and PCA during the development of keratoconus, and the tendency towards a better alignment of the PCA to the ACA in keratoconus eyes. [16][17][18] In the present study, there were weak correlations (R: 0.29 to 0.45) between the anterior and posterior corneal asphericity in all the quantile groups. These ndings were different from previous studies where poor anteriorposterior corneal asphericity correlations in normal eyes 1,5 and good correlations in keratoconus eyes were observed.…”

Section: Discussioncontrasting

confidence: 67%

A Multicenter Study of the Correlations of Anterior and Posterior Corneal Parameters in Chinese Myopic Patients

Hu¹,

Wang²,

Zhu³

et al. 2020

Preprint

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In this observational cross-sectional study consisting of 8365 Chinese myopic patients from five different ophthalmic centers, we investigated the correlations between anterior and posterior corneal parameters. Strongly negative anterior-posterior correlations of the mean corneal curvature were observed, with similar correlation coefficients in all myopic groups (R: -0.85 to -0.88). The anterior-posterior correlations of corneal astigmatism (R: 0.65 to 0.75), eccentricity (R: 0.27 to 0.38) and asphericity (R: 0.29 to 0.41) were all positive, with slightly different correlation coefficients between the myopic groups. The anterior-posterior correlations of mean corneal curvature were strongly negative with similar correlation coefficients in all quantile groups of six corneal and anterior chamber parameters (R: -0.84 to -0.91), except Sim Km (R: -0.36 to -0.64). The anterior-posterior correlations of corneal astigmatism were all positive with slightly different correlation coefficients between the quantile groups of SimKm (R: 0.66 to 0.74). The anterior-posterior correlations of corneal eccentricity (R: 0.30 to 0.44) and asphericity (R: 0.33 to 0.45) were positive and slightly different between the quantile groups of SimKm, pachy apex and corneal volume. In conclusion, anterior-posterior correlations of corneal curvature, astigmatism, eccentricity and asphericity can be affected by the severity of myopia and some other corneal parameters.

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Influence of Posterior Corneal Astigmatism on Total Corneal Astigmatism in Eyes With Keratoconus

Abstract: In eyes with keratoconus, PCA displays large, variable values and is correlated to TCA. The influence of PCA on TCA cannot be disregarded when planning astigmatism correction by toric intraocular lenses.

Cited by 20 publications

References 26 publications

Analysis of total corneal astigmatism with a rotating Scheimpflug camera in keratoconus

Analysis of total corneal astigmatism with a rotating Scheimpflug camera in keratoconus

Comparison of Anterior, Posterior, and Total Corneal Astigmatism Measured Using a Single Scheimpflug Camera in Healthy and Keratoconus Eyes

A Multicenter Study of the Correlations of Anterior and Posterior Corneal Parameters in Chinese Myopic Patients

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