Drusen of the optic disc and occipital transient pattern reversal responses.

Compression of visual nerve fibres generally markedly increases the latency times of visually evoked occipital responses. If a visual fluid defect in optic disc drusen is caused by compression of nerve fibres, delayed responses would be expected in this condition too. Examination of 23 patients (43 eyes) with optic disc drusen revealed that even the cases with serious field defects showed no marked delay in the pattern responses. As a consequence, examination of pattern responses is of no value in predicting progressive visual damage in patients with drusen. As to an understanding of the cause of the field defects, the normal pattern responses excluded direct mechanical compression on the nerve fibres by drusen. More likely they are due to a circulatory disturbance in the small vessels, which in its turn may even be caused by gentle compression by the drusen.