[Congenital nystagmus in the ophthalmologic automobile driving fitness verdict].

BACKGROUND

A driver with congenital nystagmus (CN) is supposed to have a certain minimum visual acuity and a minimum velocity of reading, with the head directed straight ahead or 10 degrees laterally. The ability to perform different oculomotor tasks depends, however, on individual properties of nystagmus and compensatory mechanisms, as is demonstrated in 4 cases.

METHODS

Detailed electrooculographic (EOG) recordings were performed in 4 CN patients, in addition to the examination of visual functions.

RESULTS

The visual acuity of patient 1 is sufficient (0.6 on both eyes), yet his retinal image is intermittently destabilized by a periodic alternating nystagmus. Case 2 with high myopic astigmatism and severely reduced visual acuity (right eye: finger counting; left eye: 0.2) compensates for his vertical pendular nystagmus by head nodding and for his manifest-latent horizontal nystagmus by a head turn. The optimal visual acuity of patient 3 (horizontal pendular nystagmus) is 0.3, with an oblique head position and convergence. In other head and gaze positions he has a coarse jerk nystagmus beating in the direction of gaze. Patient 4, with a high myopic astigmatism, microstrabism and manifest-latent fixational nystagmus, has a visual acuity between 0.2 and 0.3 in both eyes. He had been a licensed professional car driver, in spite of contradicting national and international criteria: but his license was refused later.

CONCLUSIONS

In patients with CN, the influence of head and gaze position, monocular fixation, convergence and self or object motion on nystagmus intensity and wave forms could be important for driving, because it might influence visual acuity and motion perception. The latter hypothesis still has to be proven in further studies, performed under conditions relevant for traffic.