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New approach for the correction of error associated with keratometric estimation of corneal power in keratoconus

Poster Details

First Author: V.Camps Sanchis SPAIN

Co Author(s):    D. Pinero   E. Caravaca-Arens   D. de Fez   R. Perez-Cambrodi   A. Artola        

Abstract Details


To obtain the exact value of the keratometric index (nkexact) as well as to validate clinically a variable keratometric index (nkadj).


University of Alicante, Spain


The nkexact value was performed by making differences (ΔPc) between keratometric corneal power (Pk) and Gaussian corneal power (PcGauss) equal to 0. The nkadj value was defined as the value associated to an equivalent difference in the magnitude of ΔPc for extreme values of posterior corneal radius (r2c) for each anterior corneal radius value (r1c). This nkadj was considered for the calculation of the adjusted corneal power (Pkadj). Values of r1c [4.2, 8.5] mm and r2c[3.1, 8.2] mm were considered. Differences of TNP with PcGauss, Pkadj, and Pk(1.3375) were calculated in a clinical sample of 44 keratoconic eyes.


The nkexact ranged from 1.3153 to 1.3396 and nkadj from 1.3190 to 1.3339 depending the eye model analyzed. All the nkadj values adjusted perfectly to 8 linear algorithms. Differences between Pkadj and PcGauss did not exceed the ±0.7 D. Clinically, nk=1.3375 was not valid in any case. Pkadj and True Net Power and Pk(1.3375) and Pkadj were statistically different (p<0.01), meanwhile no differences were found between PcGauss and Pkadj (p>0.01).


The use of a single value of nk for the calculation of the total corneal power in keratoconus has been shown to be imprecise, leading to inaccuracies in the detection and classification of this corneal condition. Furthermore, our study shows the relevance of corneal thickness in corneal power calculations in keratoconus.

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