Topometric and Tomographic Parameters for Diagnosis of Early Ectatic Disease
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.