Anderson procedure
Principle: Weakening of the yoke muscle in the direction of the null point (recession only)
Correction: 10–15 degrees per 6 mm
Advantages: Less surgical trauma, room for additional surgery
Kestenbaum-Anderson procedure
Key Points at a Glance
Section titled “Key Points at a Glance”1. What is Kestenbaum-Anderson surgery?
Section titled “1. What is Kestenbaum-Anderson surgery?”Kestenbaum-Anderson surgery is a general term for strabismus surgery performed on patients with nystagmus. Many patients with nystagmus have a “null point,” a gaze direction where the amplitude of nystagmus is minimized. Patients adopt an anomalous head position (AHP) to fixate at this null point. The purpose of surgery is to mechanically shift the null point to the primary position (straight ahead) and eliminate the AHP.
In 1953, Anderson and Kestenbaum independently proposed this procedure. Anderson proposed recession of the yoke muscles toward the null point, while Kestenbaum proposed advancement and recession of all four horizontal rectus muscles. Kestenbaum’s original method involved 5 mm of surgery on each muscle, but it was considered insufficient for correcting typical AHP. In 1973, Parks modified it to the “5, 6, 7, 8” method (straight flush method), which is now the most widely used basic procedure.
Nystagmus surgery is based on two principles 1).
- Immobilisation: reduces muscle efficiency and attenuates nystagmus.
- Relocalisation: Move the null point to the primary position
The incidence of AHP varies from 19% to 94% depending on the report. The most common symptom is horizontal face turn, but some cases present with vertical chin-up/chin-down or head tilt.
Q
What is the difference between Kestenbaum surgery and Anderson surgery?
A
The Anderson method only performs recession (weakening) of the two yoke muscles in the direction of the null point. The Kestenbaum method performs recession and resection (advancement) on all four horizontal rectus muscles. Anderson’s original method has a smaller surgical amount and limited corrective effect, while Kestenbaum’s original method (and Parks modification) can achieve greater correction. In Japan, a stepwise approach is recommended: first perform Anderson surgery, and if the effect is insufficient, add Kestenbaum surgery.
2. Main symptoms and clinical findings
Section titled “2. Main symptoms and clinical findings”Subjective symptoms
Section titled “Subjective symptoms”The main forms of AHP exhibited by patients with nystagmus are as follows.
- Face turn: The most common. The face is turned left or right to align the horizontal null point with the front. Accounts for 47.5% of all AHP 2)
- Chin elevation: Seen when the null point is in downward gaze
- Chin depression: Seen when the null point is in upward gaze
- Head tilt: The head is tilted when there is rotary nystagmus
- Decreased visual acuity: In eye positions other than the null point, nystagmus worsens and fixation becomes unstable, leading to reduced visual function
Clinical Findings (Findings Confirmed by Physician Examination)
Section titled “Clinical Findings (Findings Confirmed by Physician Examination)”Nystagmus can be classified into pendular nystagmus and jerk nystagmus based on its movement characteristics. Sensory nystagmus is often pendular, while other types are mostly jerk.
- Null point: The gaze direction where the amplitude of nystagmus is minimal. In congenital motor nystagmus, the intensity of nystagmus often varies with eye position (positional nystagmus).
- Relationship between AHP direction and eye position: If nystagmus becomes stronger when the eyes are turned to the right, the patient prefers the left gaze position and turns the face to the right.
- Angle of AHP: Measured with a goniometer (articulated protractor). Surgical intervention is considered for AHP exceeding 20 degrees.
- Potential for visual improvement: Surgery may improve best-corrected visual acuity in up to 43% of patients and reduce recognition time by 60%.
3. Causes and Risk Factors
Section titled “3. Causes and Risk Factors”Nystagmus with AHP is broadly classified into the following causes 2).
- Congenital/infantile nystagmus syndrome: The most common indication for Kestenbaum-Anderson surgery. Onset within 6 months of birth.
- Acquired nystagmus: Associated with neurological diseases (brainstem/cerebellar lesions), ocular diseases, and other afferent pathway disorders. Additional workup (e.g., head MRI) is necessary.
- Periodic alternating nystagmus (PAN): The direction of nystagmus changes periodically, and the AHP direction also changes. Since the premise of null point shift surgery does not hold, Kestenbaum and Parks methods are not indicated.
Risk factors for consecutive strabismus include severe bilateral amblyopia, history of botulinum toxin treatment, and large recession of the four horizontal rectus muscles, with an incidence rate of 11%.
Q
Why is surgery avoided in periodic alternating nystagmus (PAN)?
A
In PAN, the direction of nystagmus changes periodically, and the null point shifts over time. Kestenbaum and Parks methods assume a fixed null point for surgical planning, so they are not suitable for PAN. For PAN, large horizontal rectus muscle recession is considered effective.
4. Diagnosis and Examination Methods
Section titled “4. Diagnosis and Examination Methods”Preoperative evaluation includes the following items.
- Cycloplegic refraction: Since astigmatism or anisometropia is common, this test should always be performed.
- Assessment of null point: Confirm that there is a single null point and that it remains stable over time through multiple examinations.
- Measurement of AHP angle: Use a goniometer, aligning one arm with the visual axis and the other with the head axis to measure the degree of face turn. It can also be measured with a smartphone app (e.g., EyeTilt)2).
- Prism evaluation: Record the prism power that improves head posture when worn.
- Nystagmus recording: Record electronystagmography (ENG) or video images to evaluate amplitude, frequency, and waveform.
The following are important for differential diagnosis.
| Differential diagnosis | Key points for differentiation |
|---|---|
| Periodic alternating nystagmus (PAN) | Nystagmus direction changes with observation for 1 minute or more |
| Nystagmus blockage syndrome | Nystagmus reduces with convergence; need to distinguish from esotropia |
| Congenital muscular torticollis | Non-ocular AHP, shortening of sternocleidomastoid muscle |
There is no established standard for the timing of surgery. For congenital nystagmus, it is considered appropriate to perform surgery before school age; for acquired nystagmus, after at least one year of follow-up and confirmation of a reproducible AHP angle on multiple examinations.
5. Standard treatment
Section titled “5. Standard treatment”Conservative treatment
Section titled “Conservative treatment”- Prism therapy: There is a composite prism method that combines the nystagmus suppression effect of convergence with face turn correction.
- Pharmacotherapy: Intravenous amobarbital (off-label) has been reported to improve nystagmus. Baclofen (off-label) has been shown to be effective for acquired pendular nystagmus.
Surgical treatment: When the main purpose is correction of abnormal head posture
Section titled “Surgical treatment: When the main purpose is correction of abnormal head posture”The following stepwise approach is recommended.
First step: Anderson procedure
Recession (weakening) of the yoke muscles in the direction of the null point is performed. Each 6 mm recession provides a correction effect of 10 to 15 degrees. When the null point is on the right side, equal recession of the right lateral rectus and left medial rectus is performed.
If the face turn does not improve after the Anderson procedure, observation is recommended. If visual acuity or vision improves, conservative observation with prism therapy may be considered. In some cases, the face turn gradually decreases over time as the null point expands and fixation stabilizes.
Second stage: Addition of the Goto procedure
If the Anderson procedure is insufficient, shortening (strengthening) of the yoke muscle in the direction opposite to the static position is added. Each shortening of 4 mm provides a correction effect of 10 to 15 degrees.
Kestenbaum procedure / Parks procedure
For cases with severe face turn, a static angle exceeding 20 degrees, and relatively good visual acuity, it may be considered as a first choice.
| Procedure | Surgical dose (medial rectus recession - lateral rectus recession - medial rectus resection - lateral rectus resection) |
|---|---|
| Parks method (5-6-7-8) | 5mm - 6mm - 7mm - 8mm |
| Plus one method (6-7-8-9) | Increase each muscle by 1mm |
The Parks method (straight flush method) is quantified considering that medial rectus surgery has a greater effect than lateral rectus surgery, and recession has a greater effect than resection. When the resting position is on the right side, the procedure is: left medial rectus recession 5mm, right lateral rectus recession 6mm, right medial rectus resection 7mm, and left lateral rectus resection 8mm.
Since it involves resection, it is desirable to perform this procedure after school age when PAN is sufficiently ruled out.
Kestenbaum/Parks procedure
Principle: Recession and resection of the four horizontal rectus muscles (weakening + strengthening)
Correction force: Approximately 20–25 degrees for 5-6-7-8 mm
Advantages: Sufficient correction effect for large head turns
Surgical treatment: When the main purpose is to reduce nystagmus
Section titled “Surgical treatment: When the main purpose is to reduce nystagmus”For cases without a clear null zone or with a null zone in the primary position, surgery aimed at reducing nystagmus itself is considered.
- Large recession of four horizontal rectus muscles: The medial and lateral rectus muscles of both eyes are moved posterior to the equator. Since equal recession of the medial and lateral rectus muscles tends to cause exotropia, the recession amount of the medial rectus is reduced by 1–2 mm. Each muscle is recessed by 8–12 mm. Reports indicate improvement in visual acuity by 1–3 lines. This procedure reduces nystagmus amplitude but does not affect frequency.
- Faden procedure (posterior fixation suture): Mainly used for nystagmus blockage syndrome. Often combined with recession surgery.
Surgery for Vertical AHP
Section titled “Surgery for Vertical AHP”For chin-up correction, both inferior rectus muscles are recessed 7–8 mm each, and both superior rectus muscles are resected 7–8 mm each. For chin-down, a combination of anterior transposition of the inferior oblique muscle and recession of the superior rectus muscle has been reported. For head tilt, oblique muscle surgery or vertical rectus muscle transposition is performed.
Cases with Strabismus
Section titled “Cases with Strabismus”When nystagmus and strabismus coexist, alignment of the fixing eye is prioritized, and the amount of surgery on the non-fixing eye is adjusted based on the strabismus angle.
Q
Can head turn recur after surgery?
A
Recurrence is possible. Success rates vary from 50% to 100% depending on reports. In case of recurrence, reoperation with further shortening of previously shortened muscles or addition of posterior fixation suture (Faden procedure) to recessed muscles is considered safe and effective. Postoperative follow-up over a certain period is important.
Q
Is there surgery to stop nystagmus itself?
A
Currently, there is no treatment that completely stops nystagmus. Large recession of all four horizontal rectus muscles can reduce nystagmus amplitude and improve visual acuity, but it does not affect frequency. See “Surgical treatment: When the main purpose is to reduce nystagmus” section for details.
6. Pathophysiology and detailed mechanism
Section titled “6. Pathophysiology and detailed mechanism”Nystagmus surgery is based on the following two principles1).
Immobilisation
Decreased muscle efficiency: Recession of the extraocular muscles reduces their working efficiency.
Nystagmus attenuation: The amplitude of eye oscillations decreases, stabilizing fixation.
Expansion of the null zone: The range where nystagmus is minimal widens after surgery, improving visual function.
Relocalisation
Shift of the null point: Combining recession and resection of extraocular muscles moves the null point to the primary position.
Resolution of AHP: Since nystagmus is minimized in primary gaze, the abnormal head posture is no longer necessary.
The Anderson method primarily uses the principle of immobilization. By recessing the yoke muscle in the direction of the null point, eye movement is restricted and the null point is shifted.
The Kestenbaum and Parks methods utilize both immobilization and relocalization. By combining recession and resection of the four horizontal rectus muscles, the eye is moved away from the null point and repositioned toward primary gaze1).
In determining surgical dosage, medial rectus surgery has a greater effect than lateral rectus surgery, and recession has a greater effect than resection. The surgical amounts in the Parks method (5-6-7-8 mm) are designed considering this difference in muscle effect.
In large horizontal rectus recessions, the tension of the extraocular muscles in both eyes is reduced as much as possible to decrease nystagmus amplitude. However, it is thought not to affect frequency.
7. Latest Research and Future Prospects (Investigational Reports)
Section titled “7. Latest Research and Future Prospects (Investigational Reports)”Optimization of Surgical Techniques and Dosage
Section titled “Optimization of Surgical Techniques and Dosage”In a surgical technique combining the Kestenbaum procedure with muscle shortening and tucking, 42 cases (ages 4–57) underwent symmetric recession and tucking of the horizontal rectus muscles by 5.5–10 mm. The median preoperative head turn of 30 degrees was corrected to 0 degrees immediately postoperatively, and was 10 degrees at long-term follow-up 2).
Two protocols of modified Kestenbaum surgery were compared in 92 cases of infantile nystagmus. With a mean follow-up of 33 months, 88.2% of the Parks modification group and 87.8% of the other protocol group achieved a face turn of less than 10 degrees 2).
The augmented Kestenbaum procedure was performed in 50 patients with congenital nystagmus. Postoperatively, AHP resolved in 80% of patients. However, some patients developed exodeviation or exotropia after surgery 2).
Evaluation of the augmented Anderson procedure
Section titled “Evaluation of the augmented Anderson procedure”The augmented Anderson procedure for idiopathic infantile nystagmus was prospectively evaluated. In cases with a mean preoperative head turn of 32.5±5.8 degrees, nystagmus amplitude and frequency significantly decreased postoperatively, and ocular stability improved 2).
High-dose Anderson surgery was performed in 29 patients with orthotropic infantile nystagmus (median age at surgery 7 years, range 4–44 years). Preoperative head turn averaged 35 degrees at 5 m and 20 degrees at 0.3 m, and the yoke muscles were recessed by 9–16 mm 1).
Other surgical approaches
Section titled “Other surgical approaches”Surgical outcomes in 32 patients with congenital nystagmus were reported. Overall, 72% had head turn reduced to ≤15 degrees, and 35% improved to ≤5 degrees. However, overcorrection of ≥10 degrees occurred in 9% 2).
Rectus muscle plication was performed in 4 cases of nystagmus-related AHP. At 6–18 months of follow-up, AHP decreased from an average of 22.5 degrees to 2.5 degrees 2).
Tenotomy and reattachment has been reported to expand the null zone, but it has the disadvantage of disrupting the feedback signal from extraocular muscle proprioceptors, and results are mixed 1). Retrobulbar injection of botulinum toxin weakens the extraocular muscles and reduces nystagmus, but the effect is temporary and has side effects such as loss of physiological eye movements, diplopia, and ptosis 1).
8. References
Section titled “8. References”- Gurnani B, et al. Nystagmus: a comprehensive review. Clinical Ophthalmology. 2025;19:1617-1647.
- Al-Dabet S, et al. Anomalous head posture (AHP): a comprehensive review. Survey of Ophthalmology. 2025;70:771-816.