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N. Lopez-Gil, A. Pallikaris, H. Ginis, V. Fernández-Sánchez; Effect of the Spherical Aberration in the Subjective Spherical Refraction and Depth of Field. Invest. Ophthalmol. Vis. Sci. 2007;48(13):972.
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© ARVO (1962-2015); The Authors (2016-present)
We analyze the effect of spherical aberration on the estimation of the subjective spherical refraction and the depth of field.
Subjective spherical refraction and depth of field were measured for a 5 mm artificial pupil in 8 subjects with their accommodation paralyzed. The measures were obtained with white light in the presence of, at least, 5 different values of Seidel spherical aberration (K*r^4, with K=0, ±1.0225, ±0.5112, ±0.2556, ±0.1278, 10^-4mm^-3) generated by means of phase plates. Spherical refraction was obtained modifying the vergence of a grid (used as a target) by means of a Badal optometer to get the best image. Depth of field was measured by two methods: a) Computing the standard deviation of the 10 measurements performed to obtain the spherical refraction; b) as the diopter range measured in the object space, where the subjects could still see the grid.
Spherical refraction decreased in all the subjects with spherical aberration (mean slope: -3.01 D per microns of induced spherical aberration, R=0.91). This value lied between the slope expected if the defocus induced were corrected (-5.12 D/µm) and the slope that should minimized RMS (0 D/µm). In average, depth of field increased 0.26 and 0.17 D when inducing 0.30 and -0.39 microns of spherical aberration, respectively.
In the presence of induced spherical aberration the subjective best image does not correspond to the one that minimize the RMS. Depth of field increases slightly in the presence of spherical aberration (either positive or negative). The results could be applied in the design of contact and intraocular lenses for presbyopes.
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