Evaluation of augmented lateral rectus recession by hang back and Z-tenotomy for correction of large-angle exotropia

Abstract

Purpose: To evaluate the techniques of augmented lateral rectus (LR) muscle recession with hang-back and Z-tenotomy in correcting large-angle exotropia.

Design: This is a prospective, interventional, randomized clinical trial.

Methods: This institutional study included 62 patients with large-angle exotropia (40 Δ or greater). The patients were divided into two groups: Group A included 34 patients who underwent LR recession (7 mm) with hang-back, and Group B included 28 patients who underwent LR recession (7 mm) with Z-tenotomy. Ocular alignment, binocular vision, ocular motility, and satisfaction were evaluated as primary outcome measures.

Results: The angle ranged from -45 to -140 Δ for Group A and from -40 to -140 Δ for Group B. In Group A, 22 (64.7%) patients acquired orthophoria, while 12 (35.3%) remained exotropic at the 6-month visit. In Group B, 11 (39.3%) patients acquired orthophoria at the primary gaze position, while 17 (60.7%) remained exotropic after 6 months. None of the patients experienced abduction deficiency at the end of 6-month follow-up period. In Group A, the percentage of central fusion increased from 41.4% preoperatively to 68.9% at 6 months postoperatively, while stereopsis improved from 31.03% to 65.5%. In Group B, central fusion increased from 25% to 46.4% at 6 months postoperatively, while good stereopsis increased from 21.4% to 35.7%.

Conclusions: Augmented LR recession with hang-back is an effective and safe procedure for the treatment of large-angle exotropia up to 90 PD, whereas Z- tenotomy is another augmentation technique for exodeviation angles less than 45 PD.

Keywords: Augmented hangback; Z-Tenotomy; hangback; large-angle exotropia.

Figure 1

Diagramatic representation of the difference between (a) normal insertion of LR muscle, (b) traditional recession of 7 mm, and (c) LR augmented hang-back recession using Ethibond.*: The first line represents the normal insertion of the LR muscle.**The second line represents recession the traditional 7 mm recession behind the insertion site

Figure 2

Diagramatic representation of the difference between (a) normal insertion of the LR muscle, (b) traditional recession of 7 mm, (c) pale lines represent the two limbs of the Z- tenotomy, which involve approximately 2/3 of the LR tendon that will be crushed and cut, and (d) final augmented recession with Z-tenotomy.*: The first line represents the normal insertion of the LR muscle.**The second line represents traditional 7 mm recession behind the insertion site

Figure 3

Drawing and designation of different grades of abduction deficit, scaled from − 4 to 0; with No abduction deficit (0): Complete movement from the primary position toward the lateral canthus; Abduction deficit (−1): Completed 3/4 of the distance toward the lateral canthus; Abduction deficit (−2): Completed 2/4 of the distance toward the lateral canthus; Abduction deficit (−3): Completed 1/4 of the distance toward the lateral canthus; Abduction deficit (-4): No movement from the primary position toward the lateral canthus[9]