Correlation of Front Surface Indices (Topometric Indices) Obtained With Placido-Disk-Based Topography and Rotating Scheimpflug Tomography

Lopes, Bernardo

Correlation of Front Surface Indices (Topometric Indices) Obtained With Placido-Disk-Based Topography and Rotating Scheimpflug Tomography

Friday, April 25, 2014

KIOSKS (Boston Convention and Exhibition Center)

Bernardo T. Lopes, MD, Rio de Janeiro Corneal Tomography and Biomechanical Study Group, Rio de Janeiro, Brazil

Isaac C. Ramos, MD, Hospital de Olhos Santa Luzia, Maceió-AL, Brazil

Sergio Colosio, MD, Instituto de olhos Renato Ambrosio, Rio de Janeiro, Rio de Janeiro, Brazil

Allan Luz, MD, Hospital de Olhos de Sergipe, Aracaju, Brazil

Bruno F. Valbon, MD, University of São Paulo, Niterói, Brazil

Marcella Salomão, MD, Barra Vision Center, Rio de Janeiro, Brazil

Renato Ambrósio Jr., MD, PhD, Inst. Olhos R. Ambrósio, Rio de Janeiro, Brazil

Narrative Responses:

Purpose
To correlate front surface curvature derived indices (topometric indices) obtained with Placido disk based topography and rotating scheimpflug tomography. And to check the agreement of topometric classification obtained with both devices.

Methods
Retrospective observational study. All patients were, at the same day, consecutively submitted to Placido disk based topography (keratograph, oculus) and to rotating Scheimpflug tomography (pentacam, oculus). Indices of central keratometry (K1, K2 and delta K [central corneal astigmatism]), ISV (Index of surface variance), IVA (Index of vertical asymmetry), KI (Keratoconus index), CKI (Center keratoconus index), IHA(Index of highest asymmetry) e IHD (Index of highest decentration) along with oculus topographic keratoconus classification (TKC) were evaluated. Kolmogrov-Smirnov test was used to check for Normality and Spearman’s correlation coefficients were used to identify the correlation between the two devices.

Results
There were included in the study 1068 exams from 534 patients. The correlation found between the two devices was strong in almost all indices. The highest correlation coefficients obtained were the following: 0.89 for K1, 0.89 for K2, 0.94 for Kmax, 0.89 for ISV, 0.84 for IVA. There was an agreement of 87,3% in TKC between the two devices.

Conclusion
There is a strong correlation on front surface curvature derived indices obtained with Placido disk topography and rotating Scheimpflug tomography. Also high agreement was found in TKC between the two devices.