A MEASURING DEVICE FOR THE ASSESSMENT OF MONOCHROMATIC ABERRATIONS INHUMAN EYES

Background: After refractive or cataract surgery, ocular optical error s can occur that are not correctable with spherical or astigmatic lens es and are probably responsible for the fact that in many cases the be st possible (retinal) acuity is not achieved in spite of an optimum re fraction. Assessment of these aberrations in the clinical routine is a n important first step towards documentation and correction of these e rrors with modern photorefractive methods. Principle of measuring: Ocu lar optical errors are assessed from the viewpoint of the wave properl y of light as an aberration of the real wavefront of a central retinal image point from the ideal spherical form (wavefront aberration). The measurement is based on the principle of the Tscherning aberroscope. Result: A test setup is presented consisting of a laser system, a CCD fundus camera and a PC. a bundle of parallel equidistant rays is refra cted by means of a lens in front of the eye producing an equivalent pa ttern of light spots on the retina. This pattern is more or less disto rted 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 f orm of Zernike and Taylor polynomials. The first results of emmetropic eyes are presented. Conclusions: The method allows sufficiently accur ate assessment of the ocular wavefront aberration and might be on prin ciple suitable for clinical use, provided that some technical improvem ents are installed.