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Astigmatism and small aperture corneal inlays

Poster Details

First Author: J.Tabernero SPAIN

Co Author(s):    A. Vilupuru   J. Marín   P. Artal        

Abstract Details



Purpose:

Small aperture corneal inlays are successfully used to extend depth of focus in presbyopic patients. However, the visual outcomes in each patient depend on the residual refractive errors. While the impact of defocus has been already studied, the impact of uncorrected astigmatism in patients with inlay will be further explored.

Setting:

Laboratorio de Optica, Universidad de Murcia

Methods:

Personalized biometric data in the eyes of 20 healthy presbyopic subjects (mean age 59 years, standard deviation 7 years) were used to model the problem using ray-tracing. Corneal topography, ocular axial distances, angles and wavefront aberrations were available for each subject. A small aperture of 1.6 mm of diameter (simulating a KAMRA inlay, AcuFocus) was placed at the corneal plane. The pupil of the eye was set to 3 mm of diameter. Astigmatism was induced in steps of 0.25 D (axis 90ẃ) by placing a cylindrical lens at 15 mm from the corneal axis and then the eye’s modulation transfer function was obtained for every eye from 0 D up to 3 D of induced astigmatism. The spatial frequency that corresponded to a modulation value of 0.2 (along the orthogonal direction to the axis of the astigmatism) was used as an image quality metrics and calculated in every eye with and without the small aperture.

Results:

In average for the 20 eyes, 1 D of uncorrected astigmatism for a pupil diameter of 3 mm would have the same optical impact than 1.9 D with the small aperture inlay implanted (i.e. an increasing of 0.9 D of tolerance to astigmatism). However the inlay is actually an annulus with an external diameter of 3.8 mm. This implies that patients with natural pupil diameters significantly larger than 4 mm would exhibit a lower tolerance.

Conclusions:

The retinal image quality in eyes implanted with a small aperture corneal inlay to extend depth of focus is affected by the uncorrected astigmatism. Although there is an individual variability due to the particular eye’s aberrations, the presence of the small aperture approximately doubles the typical tolerance to astigmatism. As a rule of thumb, if visual symptoms appear at 0.75 D of astigmatism for a patient, with a small aperture inlay this would be equivalent to around 1.5-2D.

Financial Disclosure:

... is employed by a for-profit company with an interest in the subject of the presentation, ... travel has been funded, fully or partially, by a competing company, ... travel has been funded, fully or partially, by a company producing, developing or supplying the product or procedure presented, ... research is funded, fully or partially, by a company producing, developing or supplying the product or procedure presented, ... receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented

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