Extraocular muscle surgery for nystagmus may correct a stable anomalous head position by shifting the null point closer to the primary position; this is achieved with medial rectus recession in one eye and lateral rectus recession in the other (Anderson procedure) or a recess-resect procedure in both eyes (Kestenbaum procedure). Surgery can similarly alleviate compensatory head positions in adults with acquired nystagmus. Bilateral medial rectus recession can treat esotropia resulting from nystagmus blockage syndrome (using larger-than-normal recessions for the amount of esotropia, sometimes in combination with posterior fixation sutures). Extraocular muscle surgery may also improve vision in nystagmus by increasing foveation time, as reported with recession or tenotomy of all 4 horizontal rectus muscles. See Chapter 14 for further discussion of surgical procedures mentioned in this chapter.
In a Kestenbaum or Anderson procedure, the eyes are rotated toward the direction of the head turn and away from the preferred gaze position, moving both eyes in the same direction. For patients with infantile nystagmus syndrome (congenital nystagmus), a left head turn, and null point in right gaze, the eyes are surgically rotated to the left by recessing the right lateral and left medial rectus muscles and resecting the right medial and left lateral rectus muscles. The right-gaze effort, which damps nystagmus, now brings the eyes from this leftward-rotated position to primary position, instead of from primary position into right gaze; in other words, the null point has been shifted toward the primary position (Fig 13-3).
Suggested amounts of recession and resection are listed in Table 13-3. The total amount of surgery for each eye (in millimeters) is equal in order to rotate each globe an equal amount. For head turns of 30°, 40% augmentation is recommended; for turns of 45°, 60% augmentation is used. Augmentation may restrict motility, but this is usually necessary to achieve a satisfactory result.
A, Infantile nystagmus syndrome with the null point in right gaze. B, Null point shifted by the Kestenbaum procedure, reducing the head turn.
(Courtesy of Edward L. Raab, MD.)
Table 13-3 Amount of Recession and Resection for Kestenbaum Procedure, With Modificationsa
Similarly, chin-up or chin-down positions may be ameliorated by use of a vertical prism (apex toward the null point) or surgery on vertical rectus or oblique muscles, rotating the eyes away from the preferred gaze position. For a chin-up, eyes-down position, the inferior rectus muscles are recessed and the superior rectus muscles are resected, usually by 8–10 mm in each eye. Alternatively, combined weakening of a vertical rectus muscle and an oblique muscle in each eye can be used. For a chin-up position, the inferior rectus and superior oblique muscles are weakened; for a chin-down position, the superior rectus and inferior oblique muscles are weakened. Improvement of head tilt in nystagmus has been reported with torsional surgery involving the oblique muscles or transposition of the vertical rectus muscles.
For nystagmus patients with strabismus, surgery to shift the null point is performed on the dominant eye; surgery on the nondominant eye is then adjusted to account for the strabismus. For example, a patient who is right-eye dominant with a right head turn and null point in left gaze would undergo right medial rectus recession and right lateral rectus resection, as shown in Table 13-3. This would contribute to reducing the angle of an esodeviation or increasing the angle of an exodeviation. Surgery would then be performed on the nonpreferred eye to correct the residual or resultant deviation.
Other types of nystagmus surgery are less widely practiced. The goal of recession of all 4 horizontal rectus muscles to a position posterior to the equator (8- to 10-mm recessions of medial rectus muscles and 10- to 12-mm recessions of lateral rectus muscles) is to improve vision. Simple 4-muscle tenotomy, which involves disinserting and reattaching the horizontal rectus muscles without recession or resection, has produced similar results, improving recognition time and foveation time on electronystagmography, with modest improvements in visual acuity (approximately 1 line on average).
Hertle RW, Dell’Osso LF, FitzGibbon EJ, Thompson D, Yang D, Mellow SD. Horizontal rectus tenotomy in patients with congenital nystagmus: results in 10 adults. Ophthalmology. 2003; 110(11):2097–2105.
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.