First Author: F.Faria-Correia PORTUGAL
Co Author(s): L. Torr L. Figueira R. Moreira F. Falc
Purpose:
The keratoconus is a noninflammatory and progressive ectatic disease of the cornea, which leads to corneal thinning. Previous data reports that cone decentration determines an increase in the magnitude of higher order aberrations, particularly vertical coma. Thus, in the evaluation and staging of this disease is indispensable to study the corneal tomography and wavefront analysis. The purpose of this study is to examine and correlate corneal tomography and aberrometric data in keratoconus eyes using Scheimpflug imaging.
Setting:
Hospital Sćo Joćo / Faculdade de Medicina da Universidade do Porto
Methods:
Comparative retrospective study of 97 eyes with keratoconus. The eyes were classified into 5 groups: Suspect group and four other groups according to the Amsler-Krumeich classification of keratoconus. Wavefront (RMS Vertical coma; Zernicke analysis - Front Cornea, Back Cornea, Total Cornea) and tomography data (Belin-Ambrosio Display) were obtained using the software provided by the Oculus Pentacam system. The values of apex-distance thinnest point were divided in corneal rings centered at the apex (scale in mm): 1st) <0.70 2nd) 0.70 to 0.89 3rd) 0.90 to 1.09 4th) 1.10 to 1.29 5th) > 1.30. RESULTS There was a statistically significant difference in the RMS Vertical Coma (Front Surface, Back Surface, Total Cornea) between the rings. For Total Vertical Coma, the 2nd and 3rd rings had the highest mean values (-2.653 and -2.537, respectively), being the difference with the mean values of 4th ring (-1.258) statistically significant (p <0.05). The diference of anterior/posterior surface elevation and keratoconus degree between the rings was not statistically significant (p> 0.05).
Results:
There was a statistically significant difference in the RMS Vertical Coma (Front Surface, Back Surface, Total Cornea) between the rings. For Total Vertical Coma, the 2nd and 3rd rings had the highest mean values (-2.653 and -2.537, respectively), being the difference with the mean values of 4th ring (-1.258) statistically significant (p <0.05). The diference of anterior/posterior surface elevation and keratoconus degree between the rings was not statistically significant (p> 0.05).
Conclusions:
Keratoconus is associated with an increase in HOAs, being negative vertical coma aberration its main wavefront feature. When assessing cone decentration, we noted that RMS of Vertical Coma increased to a certain hypothetical limit, beyond which would decrease. Therefore, this aberration should not be regarded as simple measurement of decentration in ectatic disease, as decentration does not necessarily correlate with disease severity. FINANCIAL DISCLOSURE?: No
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