Maximal subtotal extirpation of the horizontal rectus extraocular muscles for the treatment of nystagmus with no null point. A report of four successful human cases

Purpose: To evaluate the visual and restoration of normal appearance results of maximal excision of the horizontal rectus muscles in nystagmus patients. Setting: Menelik II Hospital, Addis Ababa, Ethiopia and the Sinskey Eye Institute, Santa Monica, California. Methods: The medial and lateral rectus muscles were extirpated as far back as possible with an enucleation snare in four patients with horizontal nystagmus. A complete eye examination was performed pre- and postoperatively. Using a camcorder, ocular movements were recorded before surgery, and at postop; days 1 and 40, and months 1, 3 and 10. Results: All four patients had a marked reduction in both abnormal and normal horizontal eye movement, and improvement in objective visual acuity. Postoperative residual intermittent fine horizontal movement was recorded in the left eye in a 6 year old and in both eyes of a 41 year old patient. A residual rotary component was recorded in a 15 year old patient. The 6 and 9 year old patients each developed a moderate exotropia. The 15 and 41 year old patients maintained binocular fusion with some residual ability to converge. Vision increased subjectively in all cases. Conclusion: Subtotal myectomy of the horizontal muscles in horizontal nystagmus with no null point was very effective in improving and/or eliminating horizontal eye movement. Restoration of normal or near normal appearance and improvement in visual acuity occurred in all cases. None of the patients complained of their loss of horizontal gaze and eye movement. More complete myectomy of the muscles should produce total elimination of both normal and abnormal horizontal eye movement including nystagmus.