Examples

Some examples are given to make the use of the program easier for beginners. The description is more elaborated in the first examples and becomes shorter later in the text. All program buttons are written in sans serife.

Spherical Aberration

Start the program and adjust the screen resolution in the first window to full resolution (e.g. 1024 × 768), then: ok. This is neccessary only the first time the program is used. After that click to Retinal Image. The right and left subimage shows the same Landolt’s ring superimposed to the retinal receptor grid. Instead of a Landolt’s ring also the so-called "point-spreadfunction" can be displayed by activating the corresponding button. In this case the size of the retinal field is used instead of the visual acuity. The size of the Landolt’s ring corresponds to visual acuity of 1.0 (20/20, "Vis" in the upper part of the image), pupil width ("Pup") is 2.5mm. Even if the starting parameters describe a paraxially exactly emmetropic eye that corresponds to a Gullstrand’s eye (beside pseudophakia) the image is not really sharp. The blurring is caused by spherical aberration. It is responsible for the difference of paraxial emmetropia and best focus even for a pupil width of only 2.5mm. This difference can be compensated by a prescription glass. After licking to Image Param. (upper left) a window opens in which such prescrition glasses can be defined. For the sphere now a value of -0.25 ¹ has to be entered, then: ok. The left image is shifted to the right, and on the left a new Landolt’s ring is generated with the spherical ("Sph") prescription glass of -0.25 (red underlined). The image is significantly clearer.

All values have to be entered without unit (e.g. dpt or mm), otherwise an error message is produced. Therefore, the units are also omitted in the text of the examples.