Effect of Four Horizontal Rectus Muscle Tenotomy and Replacement (TAR) Alone and in Combination with Recessions for Strabismus, on Visual Function and Eye Movements in Patients with Infantile Nystagmus Syndrome (INS) Without Abnormal Head Posture (AHP).

PURPOSE: To evaluate and compare the effect of four horizontal rectus muscle Tenotomy And Replacement (TAR) alone and in combination with recessions for strabismus, on visual function and eye movement records in patients with INS without AHP, and to compare these results.

METHODS: This was a prospective interventional case series of 14 patients with INS with no AHP or eccentric null point. Patients underwent 4 horizontal eye muscle tenotomy and replacement (TAR) alone or 2 muscle TAR in combination with conventional bilateral horizontal muscle recession according to the presence and type of strabismus. Outcome measures included best corrected visual acuity and nystagmus intensity from eye movement recordings pre and post operatively. Data were compared between patients with strabismus and those without.

RESULTS: Overall nystagmus amplitude and velocity was decreased 28.7% and 21.9% respectively for 4 muscle TAR and 2 muscle TAR with paired strabismus recessions. Visual outcome of combined procedure in patients with INS and strabismus was less comparing with 4 muscle tenotomy. All binocular deviations were surgically corrected and there was no undercorrection or complication. Visual acuity showed improvement in patients who had more impaired pre-operation vision. Most patients were satisfied with cosmetic outcomes.

CONCLUSIONS: Tenotomy alone and combined with recession improves both visual function and eye movement records in INS. The procedures show better results in more visually impaired patients. We should consider patients preop VA and their visual potential as prognostic factors for their visual gain. Although visual outcomes are not advanced in all patients, nystagmus dampening effect and cosmetic outcome of these procedures can make them reconstructive options for patients with INS who will not achieve better vision.