Placido-Based Indices of Corneal Irregularity

Abstract

All the primary indices proposed in this work exhibit very good performance in discriminating between normal and irregular corneas. The accuracy of the combined indices is optimal within the test group (perfect classification), allowing their use in clinical practice as corneal markers of a disease. All these indices are fast to compute and can be easily implemented in any corneal topography system.

Characterization of corneal structure in keratoconus

“…7,8,[59][60][61][62][63] The digital analysis of the image of the Placido disks projected on the cornea has also been shown to be a valid tool for keratoconus diagnosis, avoiding the use of estimated data or parameters obtained indirectly. 64 Specifically, the use of primary corneal indices characterizing the asymmetry of the mires seems to be especially useful for keratoconus detection. 64 …”

“…64 Specifically, the use of primary corneal indices characterizing the asymmetry of the mires seems to be especially useful for keratoconus detection. 64 …”

A Study for Parametric Morphogeometric Operators to Assist the Detection of Keratoconus

“…More specifically, in the field of ophthalmology, there are several studies that use CAD methods to develop the concept of a patient-specific model [16][17][18][19][20]. These patient-specific models are obtained from the so called "raw data" [21], which are generated by systems based on the projection of a slit of light onto the cornea and on the principle of the Scheimpflug photography [5]. These raw data are not interpolated and are used to generate a geometric model with the modal methods called Zernike polynomials.…”

“…These Zernike polynomials are defined for all discrete points of the anterior and posterior corneal surfaces for their reconstruction. However, in cases of pathological corneas as, for instance, very aberrated corneas, it has been demonstrated that it is very difficult to define the Zernike polynomial order required to get the most relevant information about the corneal surfaces [21,22]. An alternative to these geometric models are the zonal methods called B-Spline functions [23].…”

“…In the case of significant imperfections of the cornea, the data acquisition is difficult and a significant level of missing data could require the interpolation of important areas of the cornea resulting in a very ambiguous model. The development of methods to define in vivo customised geometric properties of the cornea based only on real raw data and without any kind of interpolation is extremely useful in clinical practice for the modelization of pathological corneas [21]. Therefore, a rational and objective keratoconus detection technique could be based on analysing the geometric morphometry of discrete landmarks in the region where the focused curvature was initially manifested on the posterior corneal surface.…”