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Mengchan Sun, Aixa Alarcon, Carmen Canovas, Mihai State, Henk A Weeber, Joy Domingo, Patricia Piers; The effect of angle kappa in visual performance in diffractive intraocular lenses. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2966.
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© ARVO (1962-2015); The Authors (2016-present)
The purpose of this study is to evaluate the effect of the angle kappa on the visual performance provided by diffractive intraocular lenses (IOL) using a realistic eye model.
The through focus modulation transfer function (MTF) was calculated by ray tracing for 0, 5 and 10 degrees of angle kappa using a computer eye model with average ocular dimensions and corneal aberrations (Liou and Brennan 1997). Induced astigmatism was calculated as the relative defocus between best foci MTF positions for the two main meridians. The area under the MTF from 0 to 50 cycles per mm (MTFa) and the simulated VA (sVA) were calculated from the MTF data for the average pupil size of the pseudophakic eye (Alarcon, Canovas et al. 2016).
Calculations in the eye model showed that angle kappa was mostly related to IOL tilt rather than IOL decentration. For example, 10 degrees of angle kappa induced 10 degrees of IOL tilt and 0.13 mm of decentration respect to the center of the pupil. An average angle kappa of 5 degrees induced 5 degrees of IOL tilt and 0.07 mm of decentration. Induced astigmatism increased with the angle kappa due to the oblique incidence of the rays on the cornea. The induced astigmatism was 0.1D for 5 degrees and 0.4D for 10 degrees angle kappa. The increase of the astigmatism was correlated with the reduction in MTF at distance (R2=0.98). For the multifocal IOL, relative to 0 degrees, the MTF was reduced by 5 and 30% for 5 and 10 degrees of angle kappa respectively. Simulated VA did not change for 5 degrees angle kappa and was reduced by 0.02 logMAR for 10 degrees.
Simulations in computer eye models showed that a large angle kappa may induce low amounts of astigmatism (up to 0.5D for 10 degrees) determining an MTF reduction. Simulated VA was not affected even for large amounts of angle kappa.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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