Limits...
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.

Show MeSH

Related in: MedlinePlus

Band-Altman plots comparing the total corneal powers calculated with different indices (Kcal, K1.3315 and K1.3375) and the actual total corneal power calculated based on Gaussian optics formula (Kactual) in post-LASIK/PRK group.The solid lines represent mean differences, and the dotted lines represent 95%LoA. A: Comparison between Kcal and Kactual. B: Comparison between K1.3315 and Kactual. C: Comparison between K1.3375 and Kactual. Kcal was calculated with the mean keratometric index of 1.3242 obtained in this study. K1.3315 was calculated with the keratometric index of 1.3315 obtained from the Gullstrand schematic eye. K1.3375 was calculated with the conventional keratometric index of 1.3375.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4401696&req=5

pone.0122441.g005: Band-Altman plots comparing the total corneal powers calculated with different indices (Kcal, K1.3315 and K1.3375) and the actual total corneal power calculated based on Gaussian optics formula (Kactual) in post-LASIK/PRK group.The solid lines represent mean differences, and the dotted lines represent 95%LoA. A: Comparison between Kcal and Kactual. B: Comparison between K1.3315 and Kactual. C: Comparison between K1.3375 and Kactual. Kcal was calculated with the mean keratometric index of 1.3242 obtained in this study. K1.3315 was calculated with the keratometric index of 1.3315 obtained from the Gullstrand schematic eye. K1.3375 was calculated with the conventional keratometric index of 1.3375.

Mentions: Fig 5 shows the Bland-Altman plots of Kcal and Kactual, K1.3315 and Kactual, K1.3375 and Kactual in post-LASIK/PRK group, and the 95% CI for Kcal vs Kactual, K1.3315 vs Kactual, and K1.3375 vs Kactual were -0.40 to 0.38 D, 0.50 to 1.19 D and 1.23 to 1.86 D, respectively. In keratoconus group, K1.3315 and K1.3375 were 0.56 ± 0.70 D and 1.40 ± 0.76 D lager than Kactual, respectively (both P<0.05).


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)

Band-Altman plots comparing the total corneal powers calculated with different indices (Kcal, K1.3315 and K1.3375) and the actual total corneal power calculated based on Gaussian optics formula (Kactual) in post-LASIK/PRK group.The solid lines represent mean differences, and the dotted lines represent 95%LoA. A: Comparison between Kcal and Kactual. B: Comparison between K1.3315 and Kactual. C: Comparison between K1.3375 and Kactual. Kcal was calculated with the mean keratometric index of 1.3242 obtained in this study. K1.3315 was calculated with the keratometric index of 1.3315 obtained from the Gullstrand schematic eye. K1.3375 was calculated with the conventional keratometric index of 1.3375.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0122441.g005: Band-Altman plots comparing the total corneal powers calculated with different indices (Kcal, K1.3315 and K1.3375) and the actual total corneal power calculated based on Gaussian optics formula (Kactual) in post-LASIK/PRK group.The solid lines represent mean differences, and the dotted lines represent 95%LoA. A: Comparison between Kcal and Kactual. B: Comparison between K1.3315 and Kactual. C: Comparison between K1.3375 and Kactual. Kcal was calculated with the mean keratometric index of 1.3242 obtained in this study. K1.3315 was calculated with the keratometric index of 1.3315 obtained from the Gullstrand schematic eye. K1.3375 was calculated with the conventional keratometric index of 1.3375.
Mentions: Fig 5 shows the Bland-Altman plots of Kcal and Kactual, K1.3315 and Kactual, K1.3375 and Kactual in post-LASIK/PRK group, and the 95% CI for Kcal vs Kactual, K1.3315 vs Kactual, and K1.3375 vs Kactual were -0.40 to 0.38 D, 0.50 to 1.19 D and 1.23 to 1.86 D, respectively. In keratoconus group, K1.3315 and K1.3375 were 0.56 ± 0.70 D and 1.40 ± 0.76 D lager than Kactual, respectively (both P<0.05).

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.

Show MeSH
Related in: MedlinePlus