Horizontal Rectus Tenotomy in the Treatment of Congenital Nystagmus

This is a prospective open-label pilot study of a new surgical approach never before performed on humans. Subjects of this study are patients with congenital nystagmus and no other treatment options. Using standard surgical techniques we will determine if simple tenotomy with reattachment will reduce their nystagmus. An oculographic reduction of the nystagmus is measured by the Nystagmus Acuity Function (NAF), considered a primary outcome. Phase II of the study includes binocular visual acuity as a second primary outcome. A 20% improvement in NAF will be considered a clinically significant reduction in nystagmus and a 10 letter or greater improvement in binocular vision will be considered a clinically significant improvement in visual acuity. Secondary oculographic outcomes include breadth or creation of null zones, slow phase velocity during foveation, and nystagmus intensity. Other secondary outcomes will include visual functions, assessed pre- and post-operatively using standard measures of binocular visual acuity (Phase I) and the National Eye Institute-Visual Function Questionnaire (NEI-VFQ) in patients 18 years or older. Extraocular muscle proprioception and afferent innervation in control of ocular motor behavior will also be examined as secondary outcomes. The study will initially be limited to 5 adults 18 years of age and older (Phase I). However, recognizing that there are many visual differences between younger and older patients, the study will then be expanded to include children after the initial pilot study (Phase II). The NEI DSMC, ICRRC, and IRB will assess adverse events after Phase I, and if in their judgment there are no serious safety concerns surrounding the procedure, Phase II will be initiated. The initiation of Phase II begins with enrollment of 5 adults and after review of 1 week post-surgical safety data, 5 patients under the age of 18 will be enrolled. Patients who have a clinical and oculographic diagnosis of congenital nystagmus as determined by a screening exam at NEI and have not had previous extraocular muscle surgery and have no other nystagmus treatment options (a gaze null or convergence damping) are eligible. They must be able to undergo a complete ophthalmic and ocular-motor evaluation and be cooperative for standard eye movement recordings. After informed consent and assent, eligible patients will undergo a complete ophthalmic and ocular motor examination. They will have their eye movements recorded using a standard oculographic recording technique and protocol. In Phase II these recordings will take place three preoperative visits at least 2 weeks apart and no more than 4 months prior to surgery. Using routine operative techniques for extraocular muscle surgery, the patient will have all four horizontal recti tenotomized and reattached at their original insertions. In addition to routine post-operative care, complete ocular examinations and eye movement recordings will be repeated at 1 week, 6 weeks, 6 months, and12 months after surgery. The patient's subjective visual responses (e.g., visual acuity and binocular function) will be compared before and after surgery. Objective changes in the eye movement recordings and binocular visual acuity post-operatively will be quantified and compared to preoperative values.