The amount of surgery is based on the size of the preoperative deviation. One commonly used surgical formula for medial rectus muscle recession or lateral rectus muscle resection for esodeviations is given in Table 14-1 (also see the section Rectus Muscle Tightening Procedures, later in this chapter). Surgical options for infants with large-angle esotropia (>60 prism diopters [Δ]) include combined recession-resection of 3 or 4 horizontal rectus muscles or bilateral medial rectus muscle recessions of 7.0 mm. Augmentation of the latter with botulinum toxin has been advocated.
A commonly used surgical formula for exodeviation is provided in Table 14-2. Some surgeons use bilateral lateral rectus muscle recessions of 9.0 mm or greater for deviations larger than 40Δ. Others prefer to limit lateral rectus recession to no more than 8.0 mm and add resection of 1 or both medial rectus muscles for larger-angle exotropias.
Lueder GT, Galli M, Tychsen L, Yildirim C, Pegado V. Long-term results of botulinum toxin–augmented medial rectus recessions for large-angle infantile esotropia. Am J Ophthalmol. 2012;153(3):560–563.
Table 14-1 Surgical Amounts for Esodeviation
Table 14-2 Surgical Amounts for Exodeviation
Monocular horizontal rectus recess-resect procedures
The values given in Tables 14-1 and 14-2 may also be used in unilateral recess-resect procedures, with the surgeon selecting the appropriate number of millimeters for each muscle. For example, for an esotropia measuring 30Δ, the surgeon would recess the medial rectus muscle by 4.5 mm and resect the lateral rectus muscle by 7.0 mm. For an exodeviation measuring 15Δ, the surgeon would recess the lateral rectus muscle by 4.0 mm and resect the antagonist medial rectus muscle by 3.0 mm. Unilateral surgery for exotropia beyond the given values (ie, >40Δ) is likely to result in a limited rotation; thus, a 3- or 4-muscle procedure is preferable if there is at least moderately good vision in each eye.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.