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Novel keratoconus classification based on the evaluation of keratometry, corneal topometric Scheimpflug indices, and corrected distance visual acuity in 212 cases

Session Details

Session Title: Cornea Medical

Session Date/Time: Monday 07/10/2013 | 08:00-10:00

Paper Time: 09:28

Venue: Elicium 1 (First Floor)

First Author: : A.Kanellopoulos GREECE

Co Author(s): :    G. Asimellis              

Abstract Details

Purpose:

To comprehensively investigate the keratoconus grading (Amsler & Krumeich stages) scale with topometric and tomographic anterior corneal surface indices, the repeatability of their measurement, and the correlation with best spectacle corrected distance visual acuity in a large pool of keratoconic patients, as measured by a rotating Scheimpflug camera- system.

Setting:

Laservision.gr Eye Institute, Athens, Greece

Methods:

Two hundred twelve (212) keratoconic cases were evaluated for the keratoconic grading and anterior surface indexing by Scheimpflug imaging (Oculyzer , WaveLight AG, Erlagen, Germany), as well as for subjective refraction and best-spectacle corrected distance visual acuity (CDVA). The correlations between CDVA and the Scheimpflug keratoconic grading and the seven anterior – surface keratometric and topometric indices were assessed using paired two-tailed t-tests, coefficient of determination (r2), and trend line linearity.

Results:

Average CDVA (expressed decimally) was, for all eyes: (average ± standard deviation) 0.626 ± 0.244, range (max-min) 1.00 to 0.10). Average keratometry on the anterior surface flat axis (K1) of 46.7 ± 5.89 keratometric diopters (D), and for the steep axis (K2) of 51.05 ± 6.59 D. Average keratometry on the posterior corneal surface was for the flat axis, -6.67 ± 1.00 D, and for the steep axis, -7.68 ± 1.23 D. A significant positive correlation was found between the seven anterior-segment topographic indices and CDVA, with the Rmin (Pearson correlation r2 = 0.516, P < 0.001) and IHV (r2 = 0.55, P < 0.001) being the strongest-correlated indices with CDVA compared to the other indices. The correlations between CDVA, the seven Scheimpflug anterior – surface keratometric and topometric indices with the Amsler & Krumeich keratoconus grading were investigated. The correlations can be better described with the ISV (with the exception of the highest stage KC4, all other P-values were < 0.001), followed by the IHD (with the exception of the lowest stage KC1, all other P-values were < 0.001).

Conclusions:

Anterior segment topographic parameters may provide more reliable criteria to visual acuity for early diagnosis, proper follow-up (to monitor possible ectasia evolution) in keratoconus patients and keratoconus screening. Our data suggests that they may serve as a benchmark of comparison to be employed in future studies, to aid in the development of new keratoconus diagnostic and follow-up criteria. ?

Financial Interest:

... travel has been funded, fully or partially, by a company producing, developing or supplying the product or procedure presented