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Probability of confounding sizing in the phakic IOL selection due to white-to-white bias

Poster Details

First Author: J.Fernández SPAIN

Co Author(s):    M. Rodriguez-Vallejo   J. Martinez   A. Tauste   E. Hueso   D. Pinero        

Abstract Details


To evaluate how critical could be the agreement and reproducibility of systems for measuring white-to-white (W2W) in the sizing selection of Implantable Collamer Lens (ICL).


Department of Ophthalmology (Qvision), Vithas Virgen del Mar Hospital, Almer�Ã�­a, Spain


The right eye of 192 subjects was measured with the Keratograph 5M (K5M) and the Orbscan IIz (OIIz). Two trained experimenters measured the horizontal W2W with the caliper option from the images obtained with each instrument. One of the experimenters repeated the process randomly in four different days, 2 weeks spaced. The inter-system agreement for the same experimenter, inter-experimenter agreement for the same system and the intra-experimenter reproducibility for each system were computed. ICL sizing was also calculated for each W2W confronted measure obtaining the probability of selecting two ICLs with different sizing or probability of confounding sizing (PCS).


The K5M overestimated the W2W measure a mean difference of 0.13 �Â�± 0.18 mm (p<0.001) in comparison to the OIIz. The comparison of one unique measure in two different days resulted in coefficients of reproducibility of 0.26 mm for the OIIz [PCS of 18.8%] and 0.26mm [10.9%] for the K5M. These coefficients improved to 0.19mm [11.7%] and 0.14mm [6.3%], respectively, considering a mean of two measures. The inter-rater reproducibility was 0.43mm [25.0%] for the OIIz and 0.29mm [13.2%] for the K5M. The W2Ws with higher PCS were from 11.1 to 11.2 mm, 11.6 to 11.7 and 12.3 to 12.4 mm.


The mean difference is not enough to apply conversions between devices and the limits of agreement and reproducibility should be considered. Special attention should be taken for WTWs with higher PCS.

Financial Disclosure:

receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented, travel has been funded, fully or partially, by a company producing, developing or supplying the product or procedure presented

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