KTH Physics

Spherical aberration in the human eye - is it good or bad?

by Docent lecture (Biomedical and X-Ray Physics, KTH), Dr Peter Unsbo (Biomedical and X-Ray Physics, KTH)

FD5 (Svedberg Hall) ()

FD5 (Svedberg Hall)

Ever since the invention of the spectacle lens, which appeared in Europe about 1200 A.D., and the understanding of ocular astigmatism in the 19th century, the correction of refractive errors of the human eye has relied on spherical or toric lenses.

Nonetheless it has also been known for a long time that there are other, higher-order, aberrations in the eye that limit the visual performance, especially for larger pupil sizes. Until recently this qualitative knowledge has been more of an academic interest, since it was neither possible to measure nor to correct these aberrations. However, during the last ten to fifteen years the research on the optics of the eye has progressed extensively. Measuring techniques that can map the wave-front aberrations of the eye have been developed and new ways of correcting the optical errors are being explored.

Spherical aberration is the largest higher-order aberration in the human eye and it is the only aberration with a nonzero population average. Furthermore, in contrast to other aberrations such as, e. g., coma, spherical aberration can be corrected by rotationally symmetric optical surfaces. These facts form the basis for an increasing number of optical products on the vision care market which manipulate the spherical aberration in the eye.

This seminar will give a background on spherical aberration and state of the art aberration measurements in the human eye. Different aspects of ocular spherical aberration will be reviewed and the implications and possible visual benefits of correcting, or even inducing, spherical aberration will be discussed.