Nystagmus Surgery
Eniolami O. Dosunmu, MD
PREOPERATIVE CONSIDERATIONS
Indications for surgical intervention:
Correct an abnormal head posture (AHP)—a consistent anomalous head turn, tilt, and/or chin position. The goal is to move the null point to primary position.
Improve visual function:
Studies have demonstrated improvement in visual acuity,1,2 which allows for better use of binocular function (without the interference of a head position).
Even in persons with no AHP, decreasing the frequency of the nystagmus may result in improved visual function.1,2
In infantile nystagmus, data consistently demonstrates that visual function is improved: recognition time, area of the null zone, and vision in the eccentric gaze.1
Even if visual acuity does not improve objectively with the AHP and under binocular conditions, many patients report subjective improvement following nystagmus surgery.
Dampen nystagmus.
Correct other associated strabismus.
Correct all refractive errors first! This can have a significant effect on vision.
Preoperative assessment:
Document observed nystagmus with any AHP (if present) and in all fields of gaze:
Direction: Horizontal, vertical, and/or torsional.
Description: Jerk or pendular, etc.
Frequency.
Amplitude.
Conjugacy.
Determine AHP: Measure the AHP in degrees of turn/chin position/tilt. A goniometer is a useful tool to perform these measurements. The AHP is often most
pronounced when the patient is asked to read the vision chart at the limits of their vision. It is important to observe the patient for more than 5 minutes, preferably longer, to ensure no periodicity.
Chin position (vertical).
Head tilt.
Head turn (horizontal).
Determine if the nystagmus worsens when the head is moved in the opposite direction of the observed AHP.
Document gaze preference at distance and near. Documenting both gaze and head position can help avoid confusion and errors in surgical planning, as you generally move the eyes toward the AHP.
Check visual acuity binocularly at distance and near with AHP and in forced fixed primary. Also check monocular visual acuity.
Determine if there is an associated strabismus that needs to be addressed (see below).
Remember to consider any previous eye muscle surgery in the surgical plan to avoid anterior segment ischemia (see Chapter 54).
If there has been previous eye muscle surgery, in children with no vascular disease, wait at least 6 months between surgeries.
In adults, screen for vascular systemic diseases and predispositions to anterior segment ischemia such as smoking, diabetes, and hypertension.
If your patient is able, check fusional amplitudes.
Be sure to monitor the nystagmus and AHP for a significant period of time (>5 minutes), as detecting periodic alternating nystagmus may require prolonged observation. Review home photographs and videos to ensure that the AHP is consistent and is not changing. Observe the head posture and eye position at various points during the examination including casual conversation, distance and near visual acuity testing, and stereopsis testing.
The eyeTilt app (see Vision, LLC) is an easy and efficient app that quantifies head tilt in real time.
Because an opaque occluder can worsen nystagmus, a Spielmann occluder or fogging with high plus lenses should be used to check monocular visual acuity.
Using video of the patient’s eye position and head posture, at distance and near, is also helpful in surgical planning.
SURGICAL PROCEDURES
Preoperative Assessment
Manage expectations of parents/caregivers prior to surgery. Emphasize the purpose of the surgery to reduce AHP. The AHP is often not completely resolved, or it may change to a different AHP after surgery. In order to resolve a horizontal or vertical head position, the surgeon will have to create a gaze palsy in the opposite direction (eg, for right head turn/eyes left preference, create a left gaze palsy).
Write out a surgical plan that includes the current position of eyes and head and post-surgical goals. It is very easy to make a mistake with head position surgery, and it is wise to check yourself at least twice on the surgical plan.
For horizontal and vertical head positions, think about moving the eyes TOWARD the anomalous head position.
For torsional surgery, think about taking the muscles off, moving the eye the direction you want it to go (intorted or extorted) and then suturing the muscles where they land with the eye in the new position.
Either fornix or conjunctival incisions can be used. If patient has aniridia or any disease process for which the limbal stem cells need to be spared, a fornix incision is preferred to preserve the limbal stem cells. Ensure excellent conjunctival closure for a good cosmetic outcome. Watch for postoperative dellen formation with large resections.
SURGERIES TO ADDRESS HEAD POSTURES
Determine the appropriate amount of surgery to perform (classic or augmented—see Table 53.1).
If the head turn is significant, only limitation of motility large enough to create a gaze palsy will correct the head turn.
Right head turn (eyes in left gaze)—move the eyes to the RIGHT.
Left head turn (eyes in right gaze)—move the eyes to the LEFT.
