[Measuring device for determining monochromatic aberration of the human eye]

After refractive or cataract surgery, ocular optical errors can occur that are not correctable with spherical or astigmatic lenses and are probably responsible for the fact that in many cases the best possible (retinal) acuity is not achieved in spite of an optimum refraction. Assessment of these aberrations in the clinical routine is an important first step towards documentation and correction of these errors with modern photorefractive methods. PRINCIPLE OF MEASURING: Ocular optical errors are assessed from the viewpoint of the wave property of light as an aberration of the real wavefront of a central retinal image point from the ideal spherical from (wavefront aberration). The measurement is based on the principle of the Tscherning aberroscope.

A test setup is presented consisting of a laser system, a CCD fundus camera and a PC. A bundle of parallel equidistant rays is refracted by means of a lens in front of the eye producing an equivalent pattern of light spots on the retina. This pattern is more or less distorted according to the ocular aberrations. The deviations of all spots from their ideal (equidistant) positions are measured by means of the PC and from these values the wavefront aberration is computed in the form of Zernike and Taylor polynomials. The first results of emmetropic eyes are presented.

The method allows sufficiently accurate assessment of the ocular wavefront aberration and might be on principle suitable for clinical use, provided that some technical improvements are installed.