Surgical dampening of nystagmus in patients with achromatopsia.

Lack of cone function is one and nystagmus is the other cause of low vision in patients with rod monochromatism. The nystagmus has been assumed to be a consequence of the increased light sensitivity due to the predominance of rods. However, symptoms of patients with cone dystrophy are not very different from those observed in patients with congenital nystagmus. For example, they occasionally have a dampening of the nystagmus on fixation at near. Therefore, like in congenital nystagmus, we can elicit convergence innervation during fixation at distance with prisms base-out or with a surgically induced divergence ('artificial divergence'). This approach only works in patients with binocular function, necessary to keep the eyes aligned. The authors report on three patients with complete rod monochromatism in whom they performed an artificial divergence operation (OAD) by recessing the medial rectus muscle and resecting the lateral muscle of one eye. After surgery, the measured visual acuity was the same but the nystagmus of these patients had been considerably reduced. The patients themselves considered the effect of surgery a great improvement.