EVects of acupuncture on foveation characteristics in congenital nystagmus

Aims/background—To examine the eVects of acupuncture at the sternocleidomastoid muscles on foveation characteristics in congenital nystagmus. Methods—Six patients with congenital nystagmus (CN) received a series of treatments consisting of two needles inserted into each sternocleidomastoid, stimulated by tapping gently every 5 minutes, for 20 minutes per session. Their eye movements were recorded using scleral search coils and changes in their CN waveforms analysed at each point in the treatment. Changes in the stability and duration of foveation periods were examined. Results—Four of the six patients showed improved foveation at the commencement of treatment; three maintained this response throughout the treatment period and after the needles were removed. In two, the CN waveform itself was modified. Conclusion—This study and others involving aVerent stimulation to the neck and face suggest that projections from these areas to the reticular formation and vestibular nucleus may alter the behaviour of the pathophysiological mechanism underlying congenital nystagmus. (Br J Ophthalmol 1998;82:115–120) Congenital nystagmus (CN) is an ocular oscillation that usually appears in early infancy. It is most often, but not always, seen in association with visuosensory abnormalities. 2 Thus, while a sensory abnormality may often be a precipitating factor in the appearance of CN, it is not an obligate one. Although several models have been proposed, 4 the origins of CN remain uncertain. A variety of distinctive waveforms have been described in recordings of the eye movements of CN patients. 6 These may almost always be distinguished from the simpler waveforms seen in acquired nystagmus. One of the most common features of CN waveforms is the presence of segments of the slow phase wherein the eyes remain at or close to the point of regard with little or no movement. These foveation periods have been reported to enhance visual acuity. 7 Numerous treatments have been described for CN. These include drugs, contact lenses, 10 prisms, biofeedback, 13 acupuncture, and a variety of surgical procedures. Vibratory or electrical stimulation of the face and neck was found to improve foveation and acuity in some patients with CN. In that study, the best predictor of visual acuity was duration of foveation. Interestingly, the more beneficial site of stimulation in this study was the same as in a previous investigation on the eYcacy of acupuncture—the sternocleidomastoid muscles of the neck. The present study examines the eVects of acupuncture treatment on foveation duration and stability in the same muscles in six patients with CN. Methods After the procedures were explained and written informed consent was obtained, subjects were seated 1.0 metre from a screen onto which a red helium-neon laser spot 0.25 degree in diameter was rear projected. The subjects were asked to fix their eyes on the target as it stepped to plus or minus 10 degrees for calibration. Subjects were then presented with an illuminated Snellen chart in primary position and asked to focus on the large “E”. Frequent reminders to keep looking at the target were given during the recording sessions to maintain alertness and the brevity of each individual recording trial minimised fatigue. Horizontal eye movements of the dominant eye were recorded using the scleral coil technique, 21 displayed on a rectilinear chart recorder and digitised at 1000 Hz with 12 bit resolution for oV line analysis. Data were recorded at baseline before insertion of the needles, at 5 minute intervals thereafter for 20 minutes, and after the needles were removed. The length of each recording was about 30 seconds. Six patients with horizontal congenital nystagmus (all males, ages ranging from 16 to 46 years) were studied. Because the waveform variability seen in congenital periodic alternating nystagmus can make evaluation of the eYcacy of this or any other treatment diYcult to determine, such patients were not included in this study. The method of stimulation was the same as described by Ishikawa et al. The stainless steel needle used for acupuncture was 40 mm in length, with a diameter of 0.2 mm. During one session four needles were inserted within the muscle bellies of the sternocleidomastoid muscle about 10 mm through the skin at the distal and proximal points of the muscle insertion. The needles were inserted for a period of 20 minutes and then removed. Every 5 minutes the experimenter gently tapped the needles. These sessions were repeated several times at intervals of 2–3 weeks. While ideally any study of a proposed treatment would best be done in a double blind fashion with a control group, no study of congenital nystagmus therapies to date, whether evaluating surgery, biofeedback, conBritish Journal of Ophthalmology 1998;82:115–120 115 Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, USA