Posters

Biomechanical analysis of the astigmatism induced by pterygium

Poster Details

First Author: M.del Buey SPAIN

Co Author(s): E. Lanchares   S. Briz                 

Abstract Details

Purpose:

To establish a relationship between the morphological characteristics of pterygium (length and width) and the astigmatism induced by this pathology.

Setting:

Department of Ophthalmology, University Clinic Hospital “Lozano Blesa”, Zaragoza, Spain and Department of Mechanical Engineering, University of Zaragoza, Zaragoza, Spain

Methods:

A biomechanical model of the eye composed of cornea and sclera was developed with a Finite Element (FE) software. An advanced case of pterygium with an astigmatism of -4.43D@7° was modelled and simulated to estimate the inward and tangential forces that the tissue applies on the cornea to achieve the astigmatism of the patient. Once the model was validated, a batch of cases with different morphologies of pterygium were simulated, ranging length from 2.9 to 4.2 mm and width from 1.9 to 6.6 mm. After the simulations, the astigmatism induced was estimated from the change of the corneal curvature.

Results:

The effect of pterygium on the cornea can be simulated with a FE-model and gives the astigmatism caused by this pathology. Pterygia with a length of 4.5 mm and widths of 6.6, 3.8 and 1.9 mm induce 1.9, 3.5 and 1.8 D of astigmatism, respectively. Pterygia with a width of 5.5 mm and lengths of 4.2, 3.8 and 2.9 mm induce 3.9, 3.5 and 2.6 D. For pterygia with the same area of invaded cornea, the length has a greater influence on the astigmatism than the width. Pterygia with length or width smaller than 2.5 mm induce astigmatism under 1D.

Conclusions:

Pterygium induces astigmatism since this abnormal tissue distorts the corneal curvature. The clinical experience indicates that the surgical resection of the pterygium is capable of reverting the astigmatism of the eye. Nevertheless, the astigmatism of the eye with pterygium may not only be due to this pathology. In this study we present a clinical tool to predict the amount of astigmatism that would be reverted with the pterygium removal, according to its dimensions (length and width).

Financial Disclosure:

None