Total Aberrations vs. High Order Aberrations in Operated Eyes

F. Viola, J.M. Dias, and A. Castanheira-Dinis (Portugal)


Optical aberrations, visual acuity, corneal refractive surgery.


Human eyes present natural amounts of optical aberra tions that can be studied by measuring the eye’s wave front. This measurement can be performed using com mercial devices called aberrometers. We developed a sim ulation tool using MATLAB that reconstructs the eye’s wavefront from Zernike’s polynomials and calculates dif ferent optical functions such as the Point Spread Function (PSF) and the Modulation Transfer Function (MTF). Us ing Fourier techniques we convoluted the PSF with test im ages in order to observe the image’s degradation induced by the measured aberration. We compared test images of both non operated eyes and operated ones and we evalu ated the contribution of high order and total aberrations to visual acuity. We verified that in contrast to the predicted, the simulated images computed from all Zernike’s coeffi cients terms (total aberrations) presented better visual acu ity than the ones computed from high order terms (high order aberrations). This was more noticeable for the op erated eyes, which presented bigger amounts of spherical aberration. Regarding the modus operandi of the commer cial aberrometers, we should not dissociate lower order and high order terms when evaluating the eye’s visual acuity since both can balance each other.

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