Topometric and Tomographic Parameters for Diagnosis of Early Ectatic Disease

Friday, April 17, 2015
KIOSKS (San Diego Convention Center)
Marcella Salomão, MD
Bernardo T. Lopes, MD
Isaac C. Ramos, MD
Frederico P. Guerra, MD
Allan Luz, MD
Renato Ambrósio Jr, MD, PhD

Purpose
To investigate topometric (front surface

curvature) and tomographic (3D elevation and

thickness distribution) parameters for detecting

ectatic corneal disease.

Methods
Topometric and tomographic indices were

obtained using the  Pentacam HR

 from 266 normals (N), from

282 keratoconus (KC) cases, and from 211

cases of forme fruste keratoconus (FFKC) were

retrospectively reviewed.  The N

group comprised from the preoperative data of

cases that had LASIK with no ectasia

development after one year. The KC group

comprised from one eye randomly selected

from patients with bilateral keratoconus. FFKC

criteria was the eye with no clinical or

topographic evidence of keratoconus, from

patients with keratoconus diagnosed in the

fellow eye.

Wallis with post-hoc Dunn’s test were used for

assessing differences among the groups,

accordingly to the distribution of the variables

(Kolmogorov-Smirnov). The ability of the

parameters to distinguish KC and FFKC from N

was assessed by receiver operating

characteristic (ROC) curve analysis.

Results
All variables had significantly different

distributions among the groups with the ROC curve higher than 0.81 for N

and KC. Only tomographic parameters had

AUC higher than 0.81 for detecting FFKC from

N. The best parameter was Ambrósio Relational

Thickness (ART-Max) with AUC of 0.992 for

detecting KC  and

0.877 for detecting FFKC . IHD (index of height decentration) was

the best topometric parameter with AUC of

0.992 for detecting KC and 0.781 for detecting FFKC. BAD-D

version 3),  had AUC of 0.995 for

detecting KC (95% CI: 0.982 to 0.998) and

0.892 for detecting FFKC (95% CI: 0.861 to

0.919). A new function enhanced

the AUC to 0.998 for detecting KC (95% CI:

0.99 to 1.00) and 0.951 for detecting FFKC

(95% CI: 0.923 to 0.97).

Conclusion
Topometric and tomographic indices

successfully detect keratoconus, but the

integration parameters from curvature and 3-

D analysis is necessary to enhance accuracy

in identifying milder forms of ectasia. The

integration of age, a surrogate of biomechanical

properties of the cornea significantly improved

the ability to identify ectatic diseases.