Accommodative Changes After Medial Rectus Resection Versus Plication in Primary Exotropia

Overview

Exotropia is a type of eye misalignment in which one eye turns outward. In some patients, surgery is needed to improve eye alignment and binocular function. Different surgical techniques can be used to strengthen or adjust the eye muscles responsible for eye position. This study compares two surgical approaches used in patients with primary exotropia. In one group, patients undergo medial rectus resection together with lateral rectus recession. In the other group, patients undergo medial rectus plication together with lateral rectus recession. Both procedures aim to improve ocular alignment, but they may differ in their effects on focusing ability, also called accommodation. Before surgery, patients undergo a detailed ophthalmologic and strabismus examination, including measurement of ocular deviation and assessment of accommodative function. After surgery, patients are followed and reassessed to evaluate changes in eye alignment, surgical success, and accommodative parameters. The purpose of this study is to evaluate and compare postoperative eye alignment, surgical success, and changes in accommodative function after these two surgical techniques. The study will help determine whether medial rectus plication and medial rectus resection have different effects on accommodation and surgical outcomes in patients treated for primary exotropia.

Primary exotropia is a common form of horizontal strabismus characterized by outward deviation of one eye. Surgical treatment is considered in patients with clinically significant deviation, stable ocular misalignment, symptoms, cosmetic concerns, or impaired binocular function. Horizontal strabismus surgery commonly includes weakening of the lateral rectus muscle, strengthening of the medial rectus muscle, or a combination of both procedures, depending on the measured deviation angle and clinical characteristics of the patient. Medial rectus resection and medial rectus plication are two medial rectus strengthening techniques used in the surgical management of exotropia. Medial rectus resection involves disinsertion of the medial rectus muscle, removal of a measured segment of the muscle, and reattachment of the shortened muscle to the sclera. Medial rectus plication strengthens the medial rectus muscle by folding and suturing the muscle without complete disinsertion from its original scleral insertion. Because plication avoids full muscle disinsertion and may better preserve the anterior ciliary vessels and adjacent neurovascular structures, it has been proposed as a vessel-sparing and tissue-sparing alternative to resection. The anterior ciliary arteries travel with the rectus muscles and contribute to the blood supply of the anterior segment, including structures related to accommodation such as the ciliary body and ciliary muscle. Accommodation is the focusing ability of the eye, especially important for near vision. Changes in extraocular muscle tension, ocular alignment, convergence, binocular interaction, and postoperative sensory adaptation may potentially influence accommodative parameters after strabismus surgery. Although the primary goal of exotropia surgery is improvement of ocular alignment, postoperative changes in accommodation may also affect visual comfort, near work, and binocular visual performance. Therefore, evaluation of accommodative changes may provide additional clinically meaningful information beyond motor alignment alone. This prospective, interventional, comparative clinical study evaluates postoperative surgical outcomes and accommodative changes in patients with primary exotropia who underwent unilateral horizontal strabismus surgery. Patients aged 5 to 40 years with basic primary exotropia were evaluated for eligibility. Eligible participants had literacy sufficient for accommodative testing, a stable deviation angle over three consecutive preoperative visits, and agreed to undergo unilateral surgery. Surgery was recommended for patients with a deviation angle of at least 20 prism diopters and a stable deviation angle over the last three visits. Patients were excluded if they had high refractive error, reduced best-corrected visual acuity, paralytic or restrictive strabismus, previous strabismus surgery, additional ocular disease, history of ocular trauma, long axial length, aphakia or pseudophakia, high accommodative convergence/accommodation ratio, systemic disease, or use of medications known to affect accommodation. Patients with incomplete examinations or loss to follow-up were excluded from the final analysis. Participants were assigned to one of two parallel surgical groups according to an alternating sequential allocation method based on enrollment order. The first participant who consented to participate was assigned to the lateral rectus recession plus medial rectus resection group, and the second participant was assigned to the lateral rectus recession plus medial rectus plication group. Subsequent participants were assigned alternately thereafter. No randomization procedure was used. Participants were assigned to one of two parallel surgical groups according to an alternating sequential allocation method based on enrollment order. The first participant who consented to participate was assigned to the lateral rectus recession plus medial rectus resection group, and the second participant was assigned to the lateral rectus recession plus medial rectus plication group. Subsequent participants were assigned alternately thereafter. No randomization procedure was used. The final analysis included 85 patients: 40 patients in the lateral rectus recession plus medial rectus resection group and 45 patients in the lateral rectus recession plus medial rectus plication group. The primary functional assessment was accommodative amplitude. Accommodative amplitude was measured separately in each eye using the minus lens method by a single investigator. The highest minus lens power at which clear near vision was maintained was recorded, and 3.00 diopters were added to account for the 33-cm testing distance. All surgeries were performed under general anesthesia by a single experienced strabismus surgeon. Participants underwent unilateral lateral rectus recession combined with either medial rectus resection or medial rectus plication according to group assignment. Follow-up examinations were performed at postoperative week 1, postoperative month 1, and postoperative month 3. At each postoperative visit, best-corrected visual acuity, ocular motility, primary position deviation angle, and accommodative amplitude measurements were recorded. Postoperative accommodative changes were evaluated in both the operated and fellow eyes. Changes in accommodative amplitude from baseline to postoperative visits and between postoperative time points were compared within and between the surgical groups. Surgical outcome was assessed using postoperative ocular alignment. Surgical success at postoperative month 3 was defined as a deviation in the primary position of 10 prism diopters or less of exotropia or 5 prism diopters or less of esotropia. Patients with residual exotropia of 12 prism diopters or more at postoperative month 3 were scheduled for additional surgery in the fellow eye after completion of the study follow-up period. The main objective of the study is to compare postoperative accommodative changes after lateral rectus recession combined with medial rectus resection versus lateral rectus recession combined with medial rectus plication in patients with primary exotropia. Secondary objectives include comparison of postoperative ocular alignment, surgical success, and time-dependent changes in accommodative amplitude between the two surgical techniques. By evaluating both motor alignment and accommodative outcomes, this study aims to clarify whether medial rectus plication and medial rectus resection provide comparable surgical correction and whether preservation of anterior segment vascular and neural structures during plication may be associated with different early postoperative accommodative changes.