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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) Time of first applanation (A1), peak applanation (Time), and second applanation (A2) as a function of KC grade. Grade 0 implies unaffected eyes. All units are msec; (b) deformation amplitude in mm as a function of KC grade. All values are the medians ±95 CI.
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fig2: (a) Time of first applanation (A1), peak applanation (Time), and second applanation (A2) as a function of KC grade. Grade 0 implies unaffected eyes. All units are msec; (b) deformation amplitude in mm as a function of KC grade. All values are the medians ±95 CI.

Mentions: The biomechanical parameters were also evaluated. Figures 2(a) and 2(b) show the median values of A1, Time, A2, and deformation amplitude (DA) of the grades. While A1 decreased, A2 and Time increased with increasing severity of keratoconus (Table 1). A1 of grade 0 was significantly different from other grades (P < 0.0001). A1 of grade 1 was similar to grade 2 (P > 0.05) but not to grade 3 (P < 0.05). Time did not differ significantly among the grades (P = 0.83). A2 of grades 0 and 1 were similar (P > 0.05). A2 of grades 2 and 3 were similar (P > 0.05) but were different from grades 0 and 1 (P < 0.05). DA also differed among the groups. DA of grade 0 differed from all other grades (P < 0.001). While DA of grades 1 and 2 were similar (P > 0.05), DA of grade 4 differed significantly from other grades (P < 0.05). Figures 3(a) and 3(b) show the median values ±95% CI of AUDA and an RMS of all grades. AUDA of grades 0 and 4 differed significantly from other grades and from each other (P < 0.05). However, AUDA of grades 1 and 2 were similar to each other (P > 0.05) and differed from grades 0 and 4 (P < 0.05). Similar trends were observed with an RMS but bn RMS of all grades were similar to each other (P > 0.05). IOP of grade 0 was significantly greater than all keratoconus grades (P < 0.001). However, IOP of grades 1, 2, and 3 were similar (P > 0.05).


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) Time of first applanation (A1), peak applanation (Time), and second applanation (A2) as a function of KC grade. Grade 0 implies unaffected eyes. All units are msec; (b) deformation amplitude in mm as a function of KC grade. All values are the medians ±95 CI.
© Copyright Policy
Related In: Results  -  Collection

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

fig2: (a) Time of first applanation (A1), peak applanation (Time), and second applanation (A2) as a function of KC grade. Grade 0 implies unaffected eyes. All units are msec; (b) deformation amplitude in mm as a function of KC grade. All values are the medians ±95 CI.
Mentions: The biomechanical parameters were also evaluated. Figures 2(a) and 2(b) show the median values of A1, Time, A2, and deformation amplitude (DA) of the grades. While A1 decreased, A2 and Time increased with increasing severity of keratoconus (Table 1). A1 of grade 0 was significantly different from other grades (P < 0.0001). A1 of grade 1 was similar to grade 2 (P > 0.05) but not to grade 3 (P < 0.05). Time did not differ significantly among the grades (P = 0.83). A2 of grades 0 and 1 were similar (P > 0.05). A2 of grades 2 and 3 were similar (P > 0.05) but were different from grades 0 and 1 (P < 0.05). DA also differed among the groups. DA of grade 0 differed from all other grades (P < 0.001). While DA of grades 1 and 2 were similar (P > 0.05), DA of grade 4 differed significantly from other grades (P < 0.05). Figures 3(a) and 3(b) show the median values ±95% CI of AUDA and an RMS of all grades. AUDA of grades 0 and 4 differed significantly from other grades and from each other (P < 0.05). However, AUDA of grades 1 and 2 were similar to each other (P > 0.05) and differed from grades 0 and 4 (P < 0.05). Similar trends were observed with an RMS but bn RMS of all grades were similar to each other (P > 0.05). IOP of grade 0 was significantly greater than all keratoconus grades (P < 0.001). However, IOP of grades 1, 2, and 3 were similar (P > 0.05).

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