Abstract
Abstract: :
Purpose: to analyze higher–order optical aberrations (HO) distribution, looking for symmetry between both eyes (enantiomorphism), and compare these aberrations in function of associated ametropia. Methods: Wave–front measurement was performed by Hartmann–Shack aberrometer and analyzed with Zernike polynomials. Optical aberrations were quantitatively analyzed using RMS (root mean square) coefficient values. Symmetry between both eyes was assessed for each aberration according to 3 criteria : RMS coefficient value, magnitude, and axis. Differences in aberration magnitude were explored in emmetropic, myopic and hyperopic group. Results: 60 patients were included and divided into 3 groups: emmetropic, myopic and hyperopic. HO aberrations presenting the highest magnitude were coma (Z31; magnitude M=0,2285 µm), fourth order aberrations (Z40; M=0,2032), and trefoil (Z33; M=0,1870). Symmetry between both eyes were present for 12 polynomials of 15 when evaluated using RMS coefficient value. Considering magnitude, symmetry was present in 7 of 8 aberrations (all but coma). Considering axis, only 3 aberrations of 7 presented miror symmetry (primary coma Z31, secondary coma Z51, and secondary astigmatism Z42). Finaly, only 2 oriented aberrations of 7 showed simultaneous symmetry in the 3 parameters (RMS coefficient value, magnitude and axis). These aberrations were Z42 and Z51. Concerning Z40 (lack of axis), there was only a magnitude symmetry. Emmetropic patients presented less total–HO aberrations than myopic or hyperopic patients. There was no difference between myopic and hyperopic patients. No difference was founded between the 3 groups concerning each HO aberration, except for Z40, highest in hyperopic patients. Conclusions: Symmetry between right and left eye is a less commun caracteristic of HO aberrations when we consider axis than when we consider only magnitude. The term "enantiomorphism" may be attributed only for a symmetry based on the axis, and not on the magnitude.
Keywords: clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology • refractive surgery: optical quality • astigmatism