Analysis of images of the Placido rings reflected from the cornea of the eye

Paper concerns acquisition of Placido rings images reflected from the cornea by use of videokeratometer and their numerical processing. In presented calculations image of every subsequent Placido ring has been approximated by an ellipse. Parameters of every ellipse, as: center of the ellipse, angle of slope of the ellipse and eccentricity have been taken under consideration.For some corneas centers of ellipses were distributed randomly but for some others relatively high correlation between position of centre of the ellipses and their number has been observed. Variability of the ellipses eccentricity and the angle of slope of the consecutive Placido discs show complex geometry and asymmetry of the corneal topography. Obtained results enable some interesting conclusions. Vertical orientation of centers of successive Placido rings may indicate the early stage of keratoconus, while the horizontal orientation can be related to the horizontal strabismus. Such application of videokeratometry can be used in new approach of early diagnosis of some eye pathologies.