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Total corneal astigmatism in elder adults considering posterior corneal astigmatism by ray tracing

Session Details

Session Title: Imaging II

Session Date/Time: Monday 07/10/2013 | 16:30-18:00

Paper Time: 17:38

Venue: Main Lecture Hall (Ground Floor)

First Author: : A.Rodriguez-Raton SPAIN

Co Author(s): :    I. Romero   I. Basterra   H. Noguera   J. Orbegozo     

Abstract Details


To study the composition of corneal astigmatism in elder adults, evaluating the difference made by the inclusion of posterior corneal astigmatism in a ray tracing calculation of total corneal astigmatism


COI-BilbaoBerri. Bilbao. Spain


Right eyes of 100 consecutive patients between 60 and 80 years are studied in a prospective descriptive study. We measure the anterior corneal astigmatism (ACA) and the posterior corneal astigmatism (PCA), the total astigmatism based on anterior topographic data (SimK) and total corneal astigmatism (TCA) merging anterior and posterior astigmatism by ray tracing. We used for all the measurements and integrated Placido disk and rotating Scheimpflug camera topographer (CSO ™ Sirius).


Mean ACA is 1.51 diopters (D) and PCA 0.38 D. ACA is aligned 47% with the rule and PCA 87% against the rule. Cases with ACA against the rule showed low magnitude correlation between anterior and posterior faces. TCA has a mean deviation of 0.3 D @ 3 over SimK in vectorial calculation. 18% of cases differed 0.5D or more between SimK and TCA magnitude and 53% had 10 or more degrees of separation, the difference being higher at lower magnitude of astigmatism.


Anterior WTR astigmatism tends to be offset by the posterior ATR astigmatism in elder patients. Nevertheless, the spread of cases largely justifies the use of tomographic technology that takes into account the back corneal surface for managing individual total corneal astigmatism.

Financial Interest:


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