Arne Ohlendorf studies features of contrast adaptation. Contrast adaptation occurs if people (or animal models) are exposed to defocus, for instance because they wear inappropriate or no spectacle corrections.
If myopic subjects take off their glasses, their visual acuity is initially very poor but improves over a period of a few minutes. This improvement cannot be based on optical changes but results from changes in the processing of spatial features in the visual system. Probably, the retina changes contrast sensitivity for those spatial frequencies that are lacking in the retinal image or have only low contrast (defocus affects the higher spatial frequencies).

Arne Ohlendorf studies how long this process of contrast adaptation takes, how long it lasts, whether it is similar for defocus in positive or negative direction, at which spatial frequencies it occurs and whether it is different in the fovea and the periphery.

Different from most studies on contrast sensitivity and contrast adaptation, Arne Ohlendorf uses an inter-ocular contrast matching task (Figure 1).

After 10 minutes, the supra-threshold contrast sensitivity was compared in both eyes, using the stimulus shown in Figure 2.

This study provided some interesting new results. Contrast adaptation lasted for about 3 minutes (Figure 3), and contrast adaptation could be induced by defocus only in the case of positive lenses.

The studies on contrast adaptation are important since contrast adaptation may be an error signal for emmetropization, causing the eye to grow differently. In addition, these studies may help to resolve the long-standing question as to how the retina can distinguish between positive and negative defocus (see Michaela Bitzer).

Arne Ohlendorf also studies how subject evaluate the angle of kappa from outside. An interesting problem is how people can judge so well in which direction other people look and whether they fixate their eyes or look a few degrees aside. Since the pupil axis (which can be estimated by looking at a subjects eye from outside) and the fixation axis (passing through the fovea but cannot be seen from outside) differ by a few degrees in most subjects, it is difficult to judge were people look at. A comparison of both eyes may the key to this problem and, in fact, most people rapidly switch fixation from one eye to the other when they look in other's people faces. Preliminary results suggest that this happens just to eliminate the effects of kappa, which displays mirror symmetry in both eyes.

Finally, Arne Ohlendorf studies the effects of peripheral defocus on accommodation, with and without foveal stimulation.