Effects of Zernike wavefront aberrations on visual acuity measured using electromagnetic adaptive optics technology

PURPOSE: This study measured the changed in visual acuity induced by individual Zernika ocular aberrations of various root-mean-square (RMS) magnitudes. METHODS: A crx1 Adaptive Optics Visual Simulator (Image Eyes) was used to modify the wavefront aberrations in nine eyes. After measuring ocular aberrations the device was programmed to compensate for the eyes wavefront error up to the 4th order and successively apply different individual Zernike aberrations using a 5mm pupil. The generated aberration included defocus astigmatism, coma, trefoil, and sperical aberration at a level of 0.1, 0.3 and 0.9 mu m. Monocular visual acuity was assessed using computer-generated Landolt-C optotypes. RESULTS: Correction of the patients' aberrations improved visual acuity by a mean of 1 line (-0.1 logMAR) compared to best sphero-cylinder correction. Aberrations of 0.1 mu m RMS resulted in a limited decrease in visual acuity (mean +0.05 logMAR), whereas aberrations of 0.3 mu m RMS induced significant visual acuity losses with a mean reduction of 1.5 lines (+0.15 logMAR). Larger aberrations of 0.9 mu m RMS resulted in greater visual acuity losses that were more pronounced with spherical aberration (+0.64 logMAR), whereas terfoil (+0.22 logMAR) was found to be better tolerated. CONCLUSIONS: The electromagnetic adaptive optics visual simulator effectively corrected and generated wavefront aberrations up to the 4th order.Custom wavefront correction significantly improved visual acuity compared to best-spectable correction. Symmetric aberrations (eg, defocus and spherical aberration) were more detrimental to visual performance.