[Visual image in high ametropia. Computer-assisted simulation with optic ray calculation].

PURPOSE: A computer program developed by the authors allows to calculate the path of light rays coming from an object through all the refractive surfaces of a Gullstrand model eye until it reaches the retina.

METHOD: The program calculates several hundred light rays for every point of a given object. A menue allows to modify optical and morphological parameters in an interactive way. For instance, the indices of refraction, the radii of the cornea and of the cristalline lens, as well as the length of the bulbus can be modified. Further, one can add seeing aids such as eye glasses or a contact lens, or implant an artificial intraocular lens. The seeing aids may be decentered and/or tilted.

RESULTS

The code calculates also the visual impression by projecting the image from the retina back to a screen at the distance of the object, where the human brain "sees" the object. For image interpretation we use a normal Gullstrand eye with a very small aperture stop. In this way we can simulate the visual mapping (visual impression) of a corrected or uncorrected ametropia.

CONCLUSIONS

In this paper we present two nontrivial examples: we calculate the regional polyopia ("Bildverdoppelung") and the annular scotoma which appear whenever a high myopia or aphakia are corrected by eye glasses.