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Understanding the Correlation between Tomographic and Biomechanical Severity of Keratoconic Corneas.

Shetty R, Nuijts RM, Srivatsa P, Jayadev C, Pahuja N, Akkali MC, Sinha Roy A - Biomed Res Int (2015)

Bottom Line: Spearman correlation coefficient was significant between most variables (P < 0.05).Conclusions.There was lack of significant biomechanical difference between mild disease grades, despite progressive corneal thinning.

View Article: PubMed Central - PubMed

Affiliation: Cornea and Refractive Surgery, Narayana Nethralaya, Bangalore 560010, India.

ABSTRACT
Purpose. To evaluate correlation between tomographic gradation of keratoconus (KC) and its corresponding air-puff induced biomechanical response. Methods. Corneal tomography and biomechanics were measured with Scheimpflug imaging in 44 normal and 92 KC corneas. Deformation waveform was also analyzed with Fourier series. A custom KC severity scale was used from 1 to 3 with 3 as the most severe grade. Tomographic and biomechanical variables were assessed among the grades. Sensitivity and specificity of the variables were assessed using receiver operating characteristics (ROC). Results. Curvature variables were significantly different between normal and disease (P < 0.05) and among grades (P < 0.05). Biomechanical variables were significantly different between normal and disease (P<0.05) but similar among grades 1 and 2 (P > 0.05). All variables had an area under the ROC curve greater than 0.5. The root mean square of the Fourier cosine coefficients had the best ROC (0.92, cut-off: 0.027, sensitivity: 83%, specificity: 88.6%). Spearman correlation coefficient was significant between most variables (P < 0.05). However, tomographic segregation of keratoconus did not result in concomitant biomechanical segregation of the grades. Conclusions. There was lack of significant biomechanical difference between mild disease grades, despite progressive corneal thinning. Mathematical models that estimate corneal modulus from air-puff deformation may be more useful.

No MeSH data available.


Related in: MedlinePlus

(a) Median curvature in diopters (simulated keratometry (K1, K2), mean curvature (Kmean), and maximum curvature (Kmax) as a function of KC grade. Grade 0 implies unaffected eyes; (b) median central corneal thickness (CCT) and thickness of thinnest point as a function of grade.
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fig1: (a) Median curvature in diopters (simulated keratometry (K1, K2), mean curvature (Kmean), and maximum curvature (Kmax) as a function of KC grade. Grade 0 implies unaffected eyes; (b) median central corneal thickness (CCT) and thickness of thinnest point as a function of grade.

Mentions: Table 1 lists the median and 95% CI for all the variables. All variables increased in magnitude with increasing severity of keratoconus (Table 1). Figures 1(a) and 1(b) show the median curvature and thickness of the different grades. The severity scale graded the curvature and thickness of keratoconic corneas as a linear function of grade number (Figures 1(a) and 1(b)). Statistical analyses of curvature and thickness yielded a statistically significant difference between the grades. Kmax of grades 0, 1, 2, and 3 were significantly different from each other (P < 0.0001). Also, Kmean, K1, and K2 differed significantly among the grades (P < 0.0001). Both CCT and TPT differed significantly among the grades as well (P < 0.0001). The location of the cone was similar among all keratoconus grades (P = 0.25).


Understanding the Correlation between Tomographic and Biomechanical Severity of Keratoconic Corneas.

Shetty R, Nuijts RM, Srivatsa P, Jayadev C, Pahuja N, Akkali MC, Sinha Roy A - Biomed Res Int (2015)

(a) Median curvature in diopters (simulated keratometry (K1, K2), mean curvature (Kmean), and maximum curvature (Kmax) as a function of KC grade. Grade 0 implies unaffected eyes; (b) median central corneal thickness (CCT) and thickness of thinnest point as a function of grade.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4402575&req=5

fig1: (a) Median curvature in diopters (simulated keratometry (K1, K2), mean curvature (Kmean), and maximum curvature (Kmax) as a function of KC grade. Grade 0 implies unaffected eyes; (b) median central corneal thickness (CCT) and thickness of thinnest point as a function of grade.
Mentions: Table 1 lists the median and 95% CI for all the variables. All variables increased in magnitude with increasing severity of keratoconus (Table 1). Figures 1(a) and 1(b) show the median curvature and thickness of the different grades. The severity scale graded the curvature and thickness of keratoconic corneas as a linear function of grade number (Figures 1(a) and 1(b)). Statistical analyses of curvature and thickness yielded a statistically significant difference between the grades. Kmax of grades 0, 1, 2, and 3 were significantly different from each other (P < 0.0001). Also, Kmean, K1, and K2 differed significantly among the grades (P < 0.0001). Both CCT and TPT differed significantly among the grades as well (P < 0.0001). The location of the cone was similar among all keratoconus grades (P = 0.25).

Bottom Line: Spearman correlation coefficient was significant between most variables (P < 0.05).Conclusions.There was lack of significant biomechanical difference between mild disease grades, despite progressive corneal thinning.

View Article: PubMed Central - PubMed

Affiliation: Cornea and Refractive Surgery, Narayana Nethralaya, Bangalore 560010, India.

ABSTRACT
Purpose. To evaluate correlation between tomographic gradation of keratoconus (KC) and its corresponding air-puff induced biomechanical response. Methods. Corneal tomography and biomechanics were measured with Scheimpflug imaging in 44 normal and 92 KC corneas. Deformation waveform was also analyzed with Fourier series. A custom KC severity scale was used from 1 to 3 with 3 as the most severe grade. Tomographic and biomechanical variables were assessed among the grades. Sensitivity and specificity of the variables were assessed using receiver operating characteristics (ROC). Results. Curvature variables were significantly different between normal and disease (P < 0.05) and among grades (P < 0.05). Biomechanical variables were significantly different between normal and disease (P<0.05) but similar among grades 1 and 2 (P > 0.05). All variables had an area under the ROC curve greater than 0.5. The root mean square of the Fourier cosine coefficients had the best ROC (0.92, cut-off: 0.027, sensitivity: 83%, specificity: 88.6%). Spearman correlation coefficient was significant between most variables (P < 0.05). However, tomographic segregation of keratoconus did not result in concomitant biomechanical segregation of the grades. Conclusions. There was lack of significant biomechanical difference between mild disease grades, despite progressive corneal thinning. Mathematical models that estimate corneal modulus from air-puff deformation may be more useful.

No MeSH data available.


Related in: MedlinePlus