SONOGRAPHY IN OPTIC DISK DRUSEN - IMAGING FINDINGS AND ROLE IN DIAGNOSIS WHEN FUNDUSCOPIC FINDINGS ARE NORMAL

OBJECTIVE. Optic disk drusen are relatively benign lesions of the eye but can cause visual symptoms and may occasionally mimic papilledema o n funduscopy. We studied the range of sonographic findings and determi ned if sonography can be used to diagnose this condition in the absenc e of typical funduscopic findings. SUBJECTS AND METHODS. Sonography of the eyes was performed in 12 patients with known or suspected optic d isk drusen by using a 10-MHz transducer. Optic disk drusen were diagno sed clinically in 16 of the 24 eyes. The funduscopic appearance was ty pical in 11 eyes and atypical in five eyes. In these five patients, th e diagnosis was made on the basis of an abnormal appearance of the dis k and either a strong family history of drusen (four patients) or fund uscopic findings that were typical of drusen in the opposite eye (one patient). RESULTS. The head of the optic nerve was abnormal in 19 of 2 4 eyes on sonography and in 16 on funduscopy. In all cases with abnorm al findings on sonograms, an ovoid echogenic lesion was evident at the junction of the retina and the optic nerve. The lesions varied in siz e from 1.5 to 4.0 mm in diameter and from 1 to 3 mm in thickness and p rojected posteriorly rather than into the vitreous body. Calcification was evident on sonograms in 16 cases. The degree of acoustic shadowin g was proportional to the size of the echogenic focus. In the three ca ses in which funduscopic findings were normal, sonography showed small drusen deposits. In the five eyes that showed disk abnormality but we re not typical of drusen on funduscopy, sonography showed lesions of v arying size; cases with typical funduscopic appearances tended to show large lesions on sonography. CONCLUSION. Optic disk drusen can be dia gnosed on the basis of their typical sonographic appearance even in th e absence of typical funduscopic findings. Optic disk drusen may be se en:incidentally when sonograms are made for other conditions, and the finding should not be confused with more serious lesions of the optic nerve.