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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 scatter diagram & regression line of Ranterior and Rposterior, Ratio and keratometric index (N) in the three group.A: The scatter diagram & regression line of Ranterior and Rposterior in untreated controls. The regression equation was Rposterior = 0.01021 + 0.8499×Ranterior (r = 0.884, r2 = 0.782, P<0.05). B: The scatter diagram & regression line of Ratio and keratometric index (N) in untreated controls. The regression equation was N = 1.3752–0.03852×Ratio (r = -0.997, r2 = 0.995, P<0.05). C: The scatter diagram & regression line of Ranterior and Rposterior in post-LASIK/PRK group. The regression equation was Rposterior = 4.3054 + 0.2596×Ranterior (r = 0.492, r2 = 0.242, P<0.05). D: The scatter diagram & regression line of Ratio and keratometric index (N) in post-LASIK/PRK group. The regression equation was N = 1.3775–0.04054×Ratio (r = -0.999, r2 = 0.999, P<0.05). E: The scatter diagram & regression line of Ranterior and Rposterior in keratoconus group. The regression equation was Rposterior = -2.8393 + 1.218×Ranterior (r = 0.854, r2 = 0.728, P<0.05). F: The scatter diagram & regression line of Ratio and keratometric index (N) in keratoconus group. The regression equation was N = 1.3759–0.03917×Ratio (r = -0.999, r2 = 0.999, P<0.05).
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pone.0122441.g003: The scatter diagram & regression line of Ranterior and Rposterior, Ratio and keratometric index (N) in the three group.A: The scatter diagram & regression line of Ranterior and Rposterior in untreated controls. The regression equation was Rposterior = 0.01021 + 0.8499×Ranterior (r = 0.884, r2 = 0.782, P<0.05). B: The scatter diagram & regression line of Ratio and keratometric index (N) in untreated controls. The regression equation was N = 1.3752–0.03852×Ratio (r = -0.997, r2 = 0.995, P<0.05). C: The scatter diagram & regression line of Ranterior and Rposterior in post-LASIK/PRK group. The regression equation was Rposterior = 4.3054 + 0.2596×Ranterior (r = 0.492, r2 = 0.242, P<0.05). D: The scatter diagram & regression line of Ratio and keratometric index (N) in post-LASIK/PRK group. The regression equation was N = 1.3775–0.04054×Ratio (r = -0.999, r2 = 0.999, P<0.05). E: The scatter diagram & regression line of Ranterior and Rposterior in keratoconus group. The regression equation was Rposterior = -2.8393 + 1.218×Ranterior (r = 0.854, r2 = 0.728, P<0.05). F: The scatter diagram & regression line of Ratio and keratometric index (N) in keratoconus group. The regression equation was N = 1.3759–0.03917×Ratio (r = -0.999, r2 = 0.999, P<0.05).

Mentions: In untreated controls, linear regression revealed that there were good correlations between Ranterior and Rposterior, Ratio and N. The regression equations were Rposterior = 0.01021 + 0.8499×Ranterior (r = 0.884, r2 = 0.782, P<0.05) and N = 1.3752–0.03852×Ratio (r = -0.997, r2 = 0.995, P<0.05) in Fig 3A and 3B. In post-LASIK/PRK group, linear regression revealed that there were good correlation between Ratio and N. The regression equations was N = 1.3775–0.04054×Ratio (r = -0.999, r2 = 0.999, P<0.05) in Fig 3D. In keratoconus group, the regression equations were Rposterior = -2.8393 + 1.218×Ranterior (r = 0.854, r2 = 0.728, P<0.05) and N = 1.3759–0.03917×Ratio (r = -0.999, r2 = 0.999, P<0.05) in Fig 3E and 3F.


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 scatter diagram & regression line of Ranterior and Rposterior, Ratio and keratometric index (N) in the three group.A: The scatter diagram & regression line of Ranterior and Rposterior in untreated controls. The regression equation was Rposterior = 0.01021 + 0.8499×Ranterior (r = 0.884, r2 = 0.782, P<0.05). B: The scatter diagram & regression line of Ratio and keratometric index (N) in untreated controls. The regression equation was N = 1.3752–0.03852×Ratio (r = -0.997, r2 = 0.995, P<0.05). C: The scatter diagram & regression line of Ranterior and Rposterior in post-LASIK/PRK group. The regression equation was Rposterior = 4.3054 + 0.2596×Ranterior (r = 0.492, r2 = 0.242, P<0.05). D: The scatter diagram & regression line of Ratio and keratometric index (N) in post-LASIK/PRK group. The regression equation was N = 1.3775–0.04054×Ratio (r = -0.999, r2 = 0.999, P<0.05). E: The scatter diagram & regression line of Ranterior and Rposterior in keratoconus group. The regression equation was Rposterior = -2.8393 + 1.218×Ranterior (r = 0.854, r2 = 0.728, P<0.05). F: The scatter diagram & regression line of Ratio and keratometric index (N) in keratoconus group. The regression equation was N = 1.3759–0.03917×Ratio (r = -0.999, r2 = 0.999, P<0.05).
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pone.0122441.g003: The scatter diagram & regression line of Ranterior and Rposterior, Ratio and keratometric index (N) in the three group.A: The scatter diagram & regression line of Ranterior and Rposterior in untreated controls. The regression equation was Rposterior = 0.01021 + 0.8499×Ranterior (r = 0.884, r2 = 0.782, P<0.05). B: The scatter diagram & regression line of Ratio and keratometric index (N) in untreated controls. The regression equation was N = 1.3752–0.03852×Ratio (r = -0.997, r2 = 0.995, P<0.05). C: The scatter diagram & regression line of Ranterior and Rposterior in post-LASIK/PRK group. The regression equation was Rposterior = 4.3054 + 0.2596×Ranterior (r = 0.492, r2 = 0.242, P<0.05). D: The scatter diagram & regression line of Ratio and keratometric index (N) in post-LASIK/PRK group. The regression equation was N = 1.3775–0.04054×Ratio (r = -0.999, r2 = 0.999, P<0.05). E: The scatter diagram & regression line of Ranterior and Rposterior in keratoconus group. The regression equation was Rposterior = -2.8393 + 1.218×Ranterior (r = 0.854, r2 = 0.728, P<0.05). F: The scatter diagram & regression line of Ratio and keratometric index (N) in keratoconus group. The regression equation was N = 1.3759–0.03917×Ratio (r = -0.999, r2 = 0.999, P<0.05).
Mentions: In untreated controls, linear regression revealed that there were good correlations between Ranterior and Rposterior, Ratio and N. The regression equations were Rposterior = 0.01021 + 0.8499×Ranterior (r = 0.884, r2 = 0.782, P<0.05) and N = 1.3752–0.03852×Ratio (r = -0.997, r2 = 0.995, P<0.05) in Fig 3A and 3B. In post-LASIK/PRK group, linear regression revealed that there were good correlation between Ratio and N. The regression equations was N = 1.3775–0.04054×Ratio (r = -0.999, r2 = 0.999, P<0.05) in Fig 3D. In keratoconus group, the regression equations were Rposterior = -2.8393 + 1.218×Ranterior (r = 0.854, r2 = 0.728, P<0.05) and N = 1.3759–0.03917×Ratio (r = -0.999, r2 = 0.999, P<0.05) in Fig 3E and 3F.

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