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Keratometric index obtained by Fourier-domain optical coherence tomography.

Hua Y, Stojanovic A, Utheim TP, Chen X, Ræder S, Huang J, Wang Q - PLoS ONE (2015)

Bottom Line: The ratio of anterior corneal curvature to posterior corneal curvature (Ratio) and keratometric index (N) were calculated within central 3 mm zone with the RTVue FD-OCT (RTVue, Optovue, Inc.) in 186 untreated eyes, 60 post-LASIK/PRK eyes, and 39 keratoconus eyes.The total corneal powers were calculated using different keratometric indices: Kcal based on the mean calculated keratometric index, K1.3315 calculated by the keratometric index of 1.3315, and K1.3375 calculated by the keratometric index of 1.3375.All the parameters were normally distributed.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, China.

ABSTRACT

Purpose: To determine the keratometric indices calculated based on parameters obtained by Fourier-domain optical coherence tomography (FD-OCT).

Methods: The ratio of anterior corneal curvature to posterior corneal curvature (Ratio) and keratometric index (N) were calculated within central 3 mm zone with the RTVue FD-OCT (RTVue, Optovue, Inc.) in 186 untreated eyes, 60 post-LASIK/PRK eyes, and 39 keratoconus eyes. The total corneal powers were calculated using different keratometric indices: Kcal based on the mean calculated keratometric index, K1.3315 calculated by the keratometric index of 1.3315, and K1.3375 calculated by the keratometric index of 1.3375. In addition, the total corneal powers based on Gaussian optics formula (Kactual) were calculated.

Results: The means for Ratio in untreated controls, post-LASIK/PRK group and keratoconus group were 1.176 ± 0.022 (95% confidence interval (CI), 1.172-1.179), 1.314 ± 0.042 (95%CI, 1.303-1.325) and 1.229 ± 0.118 (95%CI, 1.191-1.267), respectively. And the mean calculated keratometric index in untreated controls, post-LASIK/PRK group and keratoconus group were 1.3299 ± 0.00085 (95%CI, 1.3272-1.3308), 1.3242 ± 0.00171 (95%CI, 1.3238-1.3246) and 1.3277 ± 0.0046 (95%CI, 1.3263-1.3292), respectively. All the parameters were normally distributed. The differences between Kcal and Kactual, K1.3315 and Kactual, and K1.3375 and Kactual were 0.00 ± 0.11 D, 0.21 ± 0.11 D and 0.99 ± 0.12 D, respectively, in untreated controls; -0.01 ± 0.20 D, 0.85 ± 0.18 D and 1.56 ± 0.16 D, respectively, in post-LASIK/PRK group; and 0.03 ± 0.67 D, 0.56 ± 0.70 D and 1.40 ± 0.76 D, respectively, in keratoconus group.

Conclusion: The calculated keratometric index is negatively related to the ratio of anterior corneal curvature to posterior corneal curvature in untreated, post-LASIK/PRK, and keratoconus eyes, respectively. Using the calculated keratometric index may improve the prediction accuracies of total corneal powers in untreated controls, but not in post-LASIK/PRK and keratoconus eyes.

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The distribution of Ratio and keratometric index (N) in the three group.A: The distribution of Ratio (the ratio of the anterior corneal curvature to the posterior corneal curvature in central 3 mm zone) conforms to a normal distribution (P = 0.946, Kolmogorov-Smirnov test) in untreated controls. B: The distribution of calculated keratometric index (N) conforms to a normal distribution (P = 0.992, Kolmogorov-Smirnov test) in untreated controls. C: The distribution of Ratio conforms to a normal distribution (P = 0.945, Kolmogorov-Smirnov test) in post-LASIK/PRK group. D: The distribution of calculated keratometric index (N) conforms to a normal distribution (P = 0.972, Kolmogorov-Smirnov test) in post-LASIK/PRK group. E: The distribution of Ratio conforms to a normal distribution (P = 0.884, Kolmogorov-Smirnov test) in keratoconus group. F: The distribution of calculated keratometric index (N) conforms to a normal distribution (P = 0.888, Kolmogorov-Smirnov test) in keratoconus group.
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pone.0122441.g001: The distribution of Ratio and keratometric index (N) in the three group.A: The distribution of Ratio (the ratio of the anterior corneal curvature to the posterior corneal curvature in central 3 mm zone) conforms to a normal distribution (P = 0.946, Kolmogorov-Smirnov test) in untreated controls. B: The distribution of calculated keratometric index (N) conforms to a normal distribution (P = 0.992, Kolmogorov-Smirnov test) in untreated controls. C: The distribution of Ratio conforms to a normal distribution (P = 0.945, Kolmogorov-Smirnov test) in post-LASIK/PRK group. D: The distribution of calculated keratometric index (N) conforms to a normal distribution (P = 0.972, Kolmogorov-Smirnov test) in post-LASIK/PRK group. E: The distribution of Ratio conforms to a normal distribution (P = 0.884, Kolmogorov-Smirnov test) in keratoconus group. F: The distribution of calculated keratometric index (N) conforms to a normal distribution (P = 0.888, Kolmogorov-Smirnov test) in keratoconus group.

Mentions: Table 1 shows the corneal parameters obtained by RTVue FD-OCT in untreated controls, post-LASIK/PRK group and keratoconus group. All the values conformed to be normally distributed by Kolmogorov-Smirnov test (all P > 0.05). The distributions of Ratio and keratometric indices (N) in untreated controls, post-LASIK/PRK group and keratoconus group are shown in Fig 1A, 1B, 1C, 1D, 1E and 1F, respectively.


Keratometric index obtained by Fourier-domain optical coherence tomography.

Hua Y, Stojanovic A, Utheim TP, Chen X, Ræder S, Huang J, Wang Q - PLoS ONE (2015)

The distribution of Ratio and keratometric index (N) in the three group.A: The distribution of Ratio (the ratio of the anterior corneal curvature to the posterior corneal curvature in central 3 mm zone) conforms to a normal distribution (P = 0.946, Kolmogorov-Smirnov test) in untreated controls. B: The distribution of calculated keratometric index (N) conforms to a normal distribution (P = 0.992, Kolmogorov-Smirnov test) in untreated controls. C: The distribution of Ratio conforms to a normal distribution (P = 0.945, Kolmogorov-Smirnov test) in post-LASIK/PRK group. D: The distribution of calculated keratometric index (N) conforms to a normal distribution (P = 0.972, Kolmogorov-Smirnov test) in post-LASIK/PRK group. E: The distribution of Ratio conforms to a normal distribution (P = 0.884, Kolmogorov-Smirnov test) in keratoconus group. F: The distribution of calculated keratometric index (N) conforms to a normal distribution (P = 0.888, Kolmogorov-Smirnov test) in keratoconus group.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401696&req=5

pone.0122441.g001: The distribution of Ratio and keratometric index (N) in the three group.A: The distribution of Ratio (the ratio of the anterior corneal curvature to the posterior corneal curvature in central 3 mm zone) conforms to a normal distribution (P = 0.946, Kolmogorov-Smirnov test) in untreated controls. B: The distribution of calculated keratometric index (N) conforms to a normal distribution (P = 0.992, Kolmogorov-Smirnov test) in untreated controls. C: The distribution of Ratio conforms to a normal distribution (P = 0.945, Kolmogorov-Smirnov test) in post-LASIK/PRK group. D: The distribution of calculated keratometric index (N) conforms to a normal distribution (P = 0.972, Kolmogorov-Smirnov test) in post-LASIK/PRK group. E: The distribution of Ratio conforms to a normal distribution (P = 0.884, Kolmogorov-Smirnov test) in keratoconus group. F: The distribution of calculated keratometric index (N) conforms to a normal distribution (P = 0.888, Kolmogorov-Smirnov test) in keratoconus group.
Mentions: Table 1 shows the corneal parameters obtained by RTVue FD-OCT in untreated controls, post-LASIK/PRK group and keratoconus group. All the values conformed to be normally distributed by Kolmogorov-Smirnov test (all P > 0.05). The distributions of Ratio and keratometric indices (N) in untreated controls, post-LASIK/PRK group and keratoconus group are shown in Fig 1A, 1B, 1C, 1D, 1E and 1F, respectively.

Bottom Line: The ratio of anterior corneal curvature to posterior corneal curvature (Ratio) and keratometric index (N) were calculated within central 3 mm zone with the RTVue FD-OCT (RTVue, Optovue, Inc.) in 186 untreated eyes, 60 post-LASIK/PRK eyes, and 39 keratoconus eyes.The total corneal powers were calculated using different keratometric indices: Kcal based on the mean calculated keratometric index, K1.3315 calculated by the keratometric index of 1.3315, and K1.3375 calculated by the keratometric index of 1.3375.All the parameters were normally distributed.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, China.

ABSTRACT

Purpose: To determine the keratometric indices calculated based on parameters obtained by Fourier-domain optical coherence tomography (FD-OCT).

Methods: The ratio of anterior corneal curvature to posterior corneal curvature (Ratio) and keratometric index (N) were calculated within central 3 mm zone with the RTVue FD-OCT (RTVue, Optovue, Inc.) in 186 untreated eyes, 60 post-LASIK/PRK eyes, and 39 keratoconus eyes. The total corneal powers were calculated using different keratometric indices: Kcal based on the mean calculated keratometric index, K1.3315 calculated by the keratometric index of 1.3315, and K1.3375 calculated by the keratometric index of 1.3375. In addition, the total corneal powers based on Gaussian optics formula (Kactual) were calculated.

Results: The means for Ratio in untreated controls, post-LASIK/PRK group and keratoconus group were 1.176 ± 0.022 (95% confidence interval (CI), 1.172-1.179), 1.314 ± 0.042 (95%CI, 1.303-1.325) and 1.229 ± 0.118 (95%CI, 1.191-1.267), respectively. And the mean calculated keratometric index in untreated controls, post-LASIK/PRK group and keratoconus group were 1.3299 ± 0.00085 (95%CI, 1.3272-1.3308), 1.3242 ± 0.00171 (95%CI, 1.3238-1.3246) and 1.3277 ± 0.0046 (95%CI, 1.3263-1.3292), respectively. All the parameters were normally distributed. The differences between Kcal and Kactual, K1.3315 and Kactual, and K1.3375 and Kactual were 0.00 ± 0.11 D, 0.21 ± 0.11 D and 0.99 ± 0.12 D, respectively, in untreated controls; -0.01 ± 0.20 D, 0.85 ± 0.18 D and 1.56 ± 0.16 D, respectively, in post-LASIK/PRK group; and 0.03 ± 0.67 D, 0.56 ± 0.70 D and 1.40 ± 0.76 D, respectively, in keratoconus group.

Conclusion: The calculated keratometric index is negatively related to the ratio of anterior corneal curvature to posterior corneal curvature in untreated, post-LASIK/PRK, and keratoconus eyes, respectively. Using the calculated keratometric index may improve the prediction accuracies of total corneal powers in untreated controls, but not in post-LASIK/PRK and keratoconus eyes.

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Related in: MedlinePlus