Purpose: To investigate the stereopsis functions in the cases of congenital nystagmus (CN) and determine the relations between nystagmus, visual acuity (VA) and stereoacuity (SA).Methods: The random-dot stereograms was used to examine the patients’ SA, crossed and uncrossed disparity. The oscillation types of the eyeballs were determined under the naked eyes cooperating with the electronystagmorgraphy ( ENG) examination. VA was measured at 5m and 30cm with distance and near International Standard Charts. The patient was permitted to see the target with his compensatary head posture.Results: Of the 57 patients tested, only 8 cases have normal stereopsis including normal SA,crossed and uncrossed disparity, which are all the jerk nystagmus. Forty-one have abnormal SA including 19 stereoblind, 18 abnormal stereopsis and 4 abnormal SA only. Serious damages of stereopsis exist in most of the pendular and more than half of the jerk nystagmus. The relations between stereopsis and VA are that (1)the better the V Purpose: To investigate the stereopsis functions in the cases of congenital nystagmus (CN) and determine the relationship between nystagmus, visual acuity (VA) and stereoacuity (SA). Methods: The random-dot stereograms was used to examine the patients’ SA, The oscillation types of the eyeballs were determined under the naked eyes cooperating with the electronystagmorgraphy (ENG) examination. VA was measured at 5m and 30cm with distance and near International Standard Charts. The patient was permitted to see the target with his compensatary head posture. Results: Of the 57 patients tested, only 8 cases have normal stereopsis including normal SA, crossed and uncrossed disparity, which are all the jerk nystagmus. Forty-one have abnormal SA including 19 stereoblind, 18 abnormal stereopsis and 4 Serious damages of stereopsis exist in most of the pendular and more than half of the jerk nystagmus. The relations between stereopsis and VA are that ( 1) the better the V