Ординатура / Офтальмология / Английские материалы / Strabismus Surgery and Its Complications_Coats, Olitsky_2007

symptomatic latent deviation can provide great comfort to the patient. If there is a question as to whether or not a strabismic deviation is responsible for a patient’s visual complaints, a trial of prism correction or monocular occlusion is often of great diagnostic value. Resolution or marked reduction of symptoms with either of these diagnostic trials is good evidence that the latent strabismus is contributing to the problem.

if even rudimentary fusion is restored. Other ophthalmologists believe that surgery should be performed if the deviation is significant as determined by the patient and/or family. These ophthalmologists feel that there is no functional deficit that can be demonstrated in real world situations in patients who do not have peripheral fusion.

3.5 Asymptomatic Patients

Treatment of strabismus in patients who are not experiencing diplopia or other symptoms, but who have an angle of deviation too large for the development of binocular vision, may still be justified, though not all ophthalmologists agree. Some ophthalmologists believe that any deviation greater than 8 prism diopters warrants surgical correction in order to reduce the deviation and provide a chance for the patient to develop some degree of fusion. This goal can be achieved often, even in older patients with long-standing uncorrected deviations [8]. Morris and co-workers [8] operated on 24 adult patients with longstanding strabismus, 7 of whom had congenital esotropia or exotropia. All patients developed some degree of fusion after surgery and 50% achieved stereopsis. Eight of these were in the congenital group. These ophthalmologists believe that even peripheral fusion is beneficial to patients and that the prognosis for maintaining ocular alignment long term will be enhanced

3.6 Compensatory Head Posture

Some patients are able to achieve single vision only in eccentric gaze. Such patients have an incomitant deviation and will typically develop a compensatory head posture to take advantage of the fusion that they can achieve in the eccentric gaze position (>Fig. 3.1). Paralytic, restrictive and A-pattern and V-pattern strabismus are frequent causes of incomitant deviations that are often associated with a compensatory head posture. Thy- roid-related orbitopathy, for example, often leads to the development of a restrictive strabismus that necessitates the patient to maintain an awkward and uncomfortable head position to avoid diplopia. Traditionally, it has been taught that strabismus surgery on patients with thyroid-related ophthalmopathy should be delayed until the ocular deviation has been stable and unchanging for at least 3–6 months. This is our general treatment philosophy, though we have treated several patients who were so severely disabled by their abnormal head posture that we felt earlier surgical intervention prior to stabilization of

Fig. 3.1a,b. a A patient who presented with a long-standing face turn and complaints of diplopia in other gaze positions. b The same patient as seen in a childhood photograph demonstrating the same head tilt.

(Reprinted with permission from Nelson and Olitsky, Harley’s pediatric ophthalmology, 5th edn. Lippincott, Williams & Wilkins, 2005, Fig. 9.26, page 170 [28])

the strabismus measurements was justified [9]. The need for reoperation is probably greater when surgery is performed prior to documented stabilization of the deviation, but patients we have treated early have been able to return to work and other activities and have felt that the tradeoff was reasonable

3.7 Miscellaneous Surgical Indications

In patients with a congenital or early-onset superior

palsy, earlier surgical intervention may prevent development of the facial asymmetry that has been reported with this disorder [10, 11] (Chap. 1). Patients with Duane syndrome who have pronounced upshoots, downshoots, or globe retraction due to co-contraction may benefit from strabismus surgery to blunt these conditions, with a reasonable risk to benefit profile (>Fig. 3.2a, b).

3.8 Nystagmus

Extraocular muscle surgery may also be of value in some patients with nystagmus, including patients with and without a compensatory head posture. Kestenbaum [12], Anderson [13], and Goto [14] each independently reported different surgical procedures to move the null zone closer to the primary position in patients with nystagmus and a compensatory head posture (>Fig. 3.3). Each of these procedures accomplished the same goal of moving the eyes in the direction of the compensatory head posture, thus moving the null zone closer to the primary position. While the procedure described by Goto, which involved isolated resection of a rectus muscle, has largely been abandoned as a primary treatment of nystagmus, both the Kestenbaum and Anderson procedures are frequently utilized, though both have been modified significantly from their original descriptions. The Anderson technique involves recession of a rectus muscle in each eye, while the Kestenbaum procedure involves recession of a rectus muscle in each eye as well as resection of a rectus muscle in each eye.

For an Anderson procedure to be effective, the rectus muscles must be recessed well posterior to the equator of the globe in each eye. Our typical approach is to perform an Andersontype procedure. If a residual face turn persists, the treatment is augmented by performing resection surgery of the unoperated

the development of postoperative strabismus [15], to treat larger face turns [16], as well as to improve a vertical compensatory head posture due to the presence of a null zone in vertical gaze [17] (>Table 3.3). More recently, four-muscle retro-equatorial recessions of the horizontal muscles has been advocated by several surgeons in an effort reduce the intensity of nystagmus (>Fig. 3.3d). Reports on this procedure have described minor objective, but often significant subjective improvement of visual function [18, 19], and this has been our experience with this procedure also. Recently, four-muscle tenotomy (two rectus muscles in each eye), which involves detachment and immediate reattachment to the original insertion, has been reported to reduce the intensity of nystagmus, resulting in improved visual function by altering foveation time [20, 21].

3.9Expansion of the Field of Vision in Patients with Esotropia

Although reestablishing binocular vision, eliminating diplopia, expanding the area of single binocular vision, and improving vision and/or a compensatory head posture in patients with nystagmus have been the most important historical roles for strabismus surgery, recent studies have demonstrated additional benefits that are unrelated to these traditional goals. Kushner described a series of patients who underwent surgery for the treatment of esotropia [22]. Each patient achieved a significant expansion of their binocular visual field consistent with the degree to which their eyes were surgically straight-

ened. This study demonstrated a benefit to strabismus surgery unrelated to the patient’s level of binocular vision [23].

3.10 Psychosocial and Vocational Indications

In addition to the improvements obtained in binocular function and the binocular visual field, strabismus surgeons and patients frequently relate anecdotal stories about the psychosocial and vocational benefits obtained after ocular alignment has been improved following strabismus surgery. After successful strabismus surgery, many patients relate improvement in self-

image, interpersonal relationships, and school and work performance. In addition, operated patients often feel that others view them more positively after their strabismus is rendered less obvious with surgery. Until recently, these anecdotal experiences have been the only evidence available to support the role of strabismus surgery in patients who are not anticipated to achieve a significant functional physiologic improvement in their visual system through surgery. Several studies have now been published in the medical literature providing scientific evidence that these improvements in psychosocial and vocational experiences are, in fact, common following strabismus surgery. Studies have demonstrated that strabismus creates a significant negative psychosocial impact on patients [24]. Stra-

bismus can create biases which have a detrimental impact on socialization and employability [25]. These socialization culties begin early in childhood and continue into adult Strabismus can adversely impact interpersonal relationships between children and between adults, and can adversely pact the relationships between teachers and affected children which could have a detrimental effect on educational performance [26]. These biases have been shown to begin

in childhood and continue through the adult years. The tive consequences of these biases affect not only individual tients, but also society as a whole.

Prior to the formal publication of data on the impact of bismus on these important aspects of life, the treatment of bismus in adults who did not experience diplopia or who did have binocular potential was often regarded as purely “cosmetic.” Use of the term cosmetic in the treatment of affected patients is inaccurate. Cosmetic surgery is performed to enhance or beautify. Strabismus is the result of an underlying disease process, abnormal binocular vision, which leads to an objective deviation from a normal appearance. Because of the pathophysiology involved in the development of strabismus, and the potentially negative psychosocial effects of this disorder, surgery should be referred to as “reconstructive.” We often utilize the terms socially significant strabismus and vocationally significant strabismus in this setting. Surgery is indicated to provide the only ocular alignment status that is normal for a human, straight.

The indications for strabismus surgery reviewed in this chapter (>Table 3.4) should be considered general in nature and are neither absolute nor all-inclusive. The risks, benefits, and alternatives to surgery should be individually considered with each patient. Some patients will benefit greatly from surgery even when the indications for surgery may initially appear to be small. Likewise, other patients may achieve little personal benefit even when the indications for surgical intervention appear obvious to the surgeon. In short, strabismus surgery should not be undertaken just because ocular misalignment is present, and should not be denied just because a deviation is small or the patient is not anticipated to achieve gains in binocular function.

References

1.Paysse EA (2001) Adult strabismus: goals of realignment surgery. Binocul Vis Strabismus Q 16:9–10

2.Worth C (1903) Squint, its causes and treatment. Bailliere, Tindall, and Cox, London

3.Chavasse F (1939) Worth’s squint on the binocular reflexes and the treatment of strabismus, 7th edn. Blakiston’s, Philadelphia, Pa.

4.Ing M, Costenbader FD, Parks MM, Albert DG (1966) Early surgery for congenital esotropia. Am J Ophthalmol 61:1419–1427

5.von Noorden GK (1988) A reassessment of infantile esotropia. XLIV Edward Jackson memorial lecture. Am J Ophthalmol 105:1–10

6.Parks MM (1969) The monofixation syndrome. Trans Am Ophthalmol Soc 67:609–657

Chapter 3

Develop, restore or maintain binocular vision Resolution or improvement of diplopia Resolution or improvement of asthenopia

Resolution or improvement of a compensatory head posture Improvement of anomalous eye movements

Improvement of vision in a patient with nystagmus Expansion of visual field in a patient with esotropia Improvement in psychosocial function Improvement in vocational prospects

7.Arthur BW, Smith JT, Scott WE (1989) Long-term stability of alignment in the monofixation syndrome. J Pediatr Ophthalmol Strabismus 26:224–231

8.Morris RJ, Scott WE, Dickey CF (1993) Fusion after surgical alignment of longstanding strabismus in adults. Ophthalmology 100:135–138

9.Coats DK, Paysse EA, Plager DA, Wallace DK (1999) Early strabismus surgery for thyroid ophthalmopathy. Ophthalmology 106:324–329

10.Wilson ME, Hoxie J (1993) Facial asymmetry in superior oblique muscle palsy. J Pediatr Ophthalmol Strabismus 30:315–318

11.Goodman CR, Chabner E, Guyton DL (1995) Should early strabismus surgery be performed for ocular torticollis to prevent facial asymmetry? J Pediatr Ophthalmol Strabismus 32:162–166

12.Kestenbaum A (1953) [New operation for nystagmus.] Bull Soc Ophtalmol Fr 6:599–602

13.Anderson JR (1953) Causes and treatment of congenital eccentric nystagmus. Br J Ophthalmol 37:267–281

14.Goto N (1954) A study of optic nystagmus by the electro-oculo- gram. Acta Soc Ophthalmol Jpn 58:851–854

15.Parks MM (1973) Symposium: nystagmus. Congenital nystagmus surgery. Am Orthopt J 23:35–39

16.Calhoun JH, Harley RD (1973) Surgery for abnormal head position in congenital nystagmus. Trans Am Ophthalmol Soc 71:70– 83; discussion 84–87

17.Yang MB, Pou-Vendrell CR, Archer SM, Martonyi EJ, Del Monte MA (2004) Vertical rectus muscle surgery for nystagmus patients with vertical abnormal head posture. J AAPOS 8:299–309

18.Helveston EM, Ellis FD, Plager DA (1991) Large recession of the horizontal recti for treatment of nystagmus. Ophthalmology 98:1302–1305

19.von Noorden GK, Sprunger DT (1991) Large rectus muscle recessions for the treatment of congenital nystagmus. Arch Ophthalmol 109:221–224

20.Hertle RW, Dell’Osso LF, FitzGibbon EJ, Yang D, Mellow SD (2004) Horizontal rectus muscle tenotomy in children with infantile nystagmus syndrome: a pilot study. J AAPOS 8:539–548

21.Hertle RW, Anninger W, Yang D, Shatnawi R, Hill VM (2004) Effects of extraocular muscle surgery on 15 patients with oculocutaneous albinism (OCA) and infantile nystagmus syndrome (INS). Am J Ophthalmol 138:978–987

22.Kushner BJ (1994) Binocular field expansion in adults after surgery for esotropia. Arch Ophthalmol 112:639–643

23.Wortham ET, Greenwald MJ (1989) Expanded binocular peripheral visual fields following surgery for esotropia. J Pediatr Ophthalmol Strabismus 26:109–112

24.Olitsky SE, Sudesh S, Graziano A, Hamblen J, Brooks SE, Shaha SH (1999) The negative psychosocial impact of strabismus in adults. J AAPOS 3:209–211

25.Coats DK, Paysse EA, Towler AJ, Dipboye RL (2000) Impact of large angle horizontal strabismus on ability to obtain employment. Ophthalmology 107:402–405

26.Uretmen O, Egrilmez S, Kose S, Pamukcu K, Akkin C, Palamar M (2003) Negative social bias against children with strabismus. Acta Ophthalmol Scand 81:138–142

27.Berens CEA (1927) Routine examination of the ocular muscles and non-operative treatment. Am J Ophthalmol 10:910

28Nelson LB, Olitsky SE (2005) Harley’s pediatric ophthalmology, 5th edn. Lippincott, Williams and Wilkins, Baltimore

Proper surgical technique is obviously a prerequisite when caring for the strabismus patient. Decisions regarding the type and amount of surgery to be performed as well as the planned surgical approach are equally important. This chapter will provide an overview of the decision-making process that is vital to maximizing the outcomes of strabismus surgery. It should be noted that these are general suggestions and ideas based upon our experience. There are many ways to properly treat most strabismus disorders. For most strabismus problems, there is no single approach that is absolutely correct, or necessarily clearly better than every other choice. However, there are often clear advantages of some choices over others when considering the range of possible treatment options for any given condition. Each surgeon ultimately develops a pattern of treatment based upon his or her training, experiences and consultations or discussions with other strabismus surgeons.

4.1 Preoperative Evaluation

4.1.1 Strabismus History

In order to make good decisions when planning a strabismus procedure, it is important to have the necessary data available that will make these decisions possible. In the examination room, this starts with a thorough history. Knowing a patient’s prior history of treatment for strabismus and/or amblyopia is important, but full details of treatments received as a child are often not available. A history of prior strabismus surgery may lead the surgeon to choose muscles on which to operate that would not otherwise be the first choice if no prior surgery had been performed. Old records and/or operative notes can be helpful in these cases. However, old records and clinical notes are often not available due to the age of the patient, their relocation, or an inability to obtain the records for other reasons. In these cases, the history obtained from the patient may help to determine the type of surgery previously performed. A patient who had surgery before 1 year of age most likely underwent surgery for congenital esotropia. Based upon that knowledge, it can often be extrapolated that both medial rectus muscles were operated or a recess/resect procedure was performed in one eye. This can be further supported by examination of the

conjunctiva for evidence of previous conjunctival incisions. Such information is helpful when developing a surgical plan for an older patient who may later present with esotropia; for example, where the surgical plan may call for resection of both lateral rectus muscles if previous medial rectus recessions have been performed, or a recess and resect operation in one eye if it can be determined that surgery was previously only performed on one eye.

4.1.2 Ocular Motor and Sensory Examination

Following the history, a thorough examination of the ocular motor system appropriate for the condition being treated is essential to providing the data necessary to complete the surgical plan. The motility evaluation may include measurements of alignment in primary position, at distance fixation and near fixation, in the diagnostic and cardinal positions of gaze, and in head tilt positions. Evaluation of ductions is also important in patients with limitations of globe excursion noted during testing of versions. Measurements of motor fusional amplitudes may be helpful in select patients. For example, knowing the convergence and divergence fusional amplitudes of a diplopic patient with an esotropia may allow the surgeon to council the patient on the risk of continued double vision should an overor under-correction occur following surgery.

Sensory evaluation may help the surgeon in many different ways. For example, it may help the surgeon to decide on optimal surgical timing in young children with intermittent exotropia, the ability to perform superior oblique tenotomy procedures in patients with A-pattern exotropia or to monitor the success of previous treatments. In the preceding examples, a decline in stereo vision may prompt surgical intervention for intermittent exotropia and a superior oblique tenotomy would probably be avoided in a patient with A-pattern exotropia who had high-grade stereopsis. Another approach to managing the A-pattern would likely be chosen instead to avoid the high risk that the patient will develop symptomatic diplopia and/or lose stereopsis following surgery on the superior oblique tendons in this setting.

Some ophthalmologists will repeat motility examinations following monocular occlusion in some patients, such as pat­ ients with intermittent exotropia [1, 2]. Monocular occlusion

for a period of 30 min or longer may uncover a larger deviation and could alter surgical planning.

One approach is to attempt to obtain every piece of information on every strabismus patient. Using this approach, the surgeon will always have the ability to decide which data need to be analyzed at a later time. For most patients, this is not only unnecessary but time consuming, inefficient, and taxing for the patient. Rather we suggest a motility evaluation that is tailored to the individual patient and their specific problem. Some surgeons prefer to repeat the motility examination at least once prior to devising a surgical plan and recommending surgery. This has not been our typical practice pattern. For most patients, repeated visits to assess ocular motility appear to be unnecessary. Repeat examinations require the patient and/or parents to take additional time off from work and increase the cost of care by increasing the number of office visits required for treatment. We believe that the surgical decision can and should be made as soon as the ophthalmologist is comfortable with the diagnosis and feels comfortable making treatment recommendations. For many patients, this can occur during the initial examination. For patients in whom the clinical picture is unclear or is changing, follow-up examinations prior to making a surgical recommendation are obviously important.

4.2 Devising the Surgical Plan

Once a set of data and information that is sufficient to make a surgical recommendation has been obtained it is time to devise a surgical plan. For some problems, this process will be straightforward and routine and for others significantly more complex. We generally prefer to devise the proposed surgical plan when the patient is still in our presence. This allows for the ability to obtain repeat or additional information if needed and allows us to discuss our recommendations with the patient as they are being formulated. Other surgeons prefer to devise a surgical plan after the patient has left the office. Either approach is reasonable and has both advantages and disadvantages.

4.2.1 Which Eye to Operate?

A logical starting point when devising a surgical plan is determining which eye to operate. Factors that may influence this decision include visual acuity, ocular dominance, history of previous strabismus surgery or other surgeries, and the presence of nystagmus or strabismus with a compensatory head posture. Patient fears and patient preference sometimes overrule the surgical plan that the surgeon feels is optimal. For example, patients with a strabismus and diplopia due to a scleral buckle are often, if not usually, reluctant to have surgery performed on their contralateral eye, which they perceive as their “normal” eye, because they fear a complication of surgery. Though the surgeon may feel that surgery on the contralateral eye is the best treatment option, the practical reality is that surgery may need to be performed on the previously buckled eye

Chapter 4

because the patient overrules the initial treatment recommendation. Flexibility during surgical planning is important.

It is our general practice to operate on only the eye with the worst vision when there is a significant difference in visual acuity to avoid putting the sound eye at a real, albeit very low risk of a vision-threatening complication. This does not mean that we never operate on the eye with better vision. There are situations in which surgery on the better eye is required to correct the patient’s deviation. Some examples of this are discussed below. In general, because the requirement for obtaining a license to drive is 20/40 in many States, we generally limit surgery to only one eye when the visual acuity is worse than 20/40 in one eye. Some patients with a smaller difference in visual acuity or a strong ocular dominance will strongly consider themselves to have one “good” and one “bad” eye. In these cases, it may be reasonable to operate on both eyes. However, the patient may become anxious when surgery is suggested for their “better” eye. In cases where the outcome would not be altered, we tend to acquiesce to the patient’s wishes.

A history of previous strabismus surgery can also be an important factor when determining which eye to operate. If it is determined that the patient had strabismus surgery on only one eye, we will often suggest surgery be performed on the previously unoperated eye as long as the visual acuity is similar in both eyes. This might mean performing a monocular recess/resect procedure that would normally be our second option to a bilateral symmetric recession procedure for the same disorder, if there were not a history of previous history of surgery. The need to treat a compensatory face turn associated with nystagmus or an incomitant strabismus will also lead to the decision to operate one eye over another, as discussed below.

In some strabismus disorders, the need to operate on a specific eye is readily apparent to the surgeon but may not be apparent to the patient and/or parent. For example, the need to weaken the superior oblique tendon of patients with Brown syndrome is clear once the diagnosis has been made. However, parents and patients are often under the impression that it is the contralateral eye that moves “too much” and is therefore the eye that requires surgery. It is important to educate patients and parents as part of the decision-making, educational, and informed consent process when this confusion occurs. It is interesting to us that even with careful preoperative discussion of treatment recommendations with patients and after having had patients accurately repeat to us their basic understanding of the surgical recommendations in the office, that patients sometimes show up on the day of surgery unaware that surgery is going to be performed on the eye that they did not believe needed to be operated. We routinely review the proposed surgical plan with patients and/or parents on the day of surgery to mitigate this confusion.

4.2.2 How Many Muscles to Operate?

For many cases, the number of muscles on which to operate is the next logical step in the decision-making process. The number of muscles on which to operate is most commonly

dictated by the size of the preoperative deviation. Treatment recommendations vary for horizontal deviations depending on the surgeon. Some strabismus surgeons prefer surgery on two muscles for most cases, except those with very small deviations. Others prefer to operate on only a single muscle when the deviation is small to moderate in size. Single-muscle recession and resection has been shown to be a useful surgical technique for moderate angles of strabismus [3, 4]. The purported benefits of single-muscle surgery include shorter anesthesia time, reduced risk because surgery is restricted to only one eye and the sparing of other muscles for future possible surgery.

For very large angles of strabismus, some surgeons will operate on a third, or even fourth muscle. This issue has been extensively discussed in the literature with regard to the treatment of congenital esotropia when the deviation angle is large. The use of threeor four-muscle surgery was first advocated when the theoretical limit of recession of the medial rectus was thought to be 5 mm. Now that it is known that much larger recessions of the medial rectus muscles can be safely performed, the need to operate on more than two muscles has been questioned by some surgeons. The hang-back suture technique, which safely facilitates large recessions, can be helpful (Chap. 9). We rarely choose to perform surgery on more than two horizontal muscles to treat a horizontal deviation. This choice spares two of the horizontal rectus muscles for later operation should further surgery be needed.

The same issue has been discussed with regard to the treatment of large angle exotropia and we use a similar approach to this problem. A large exotropia may be present in patients with poor vision in one eye. Performing large amounts of surgery on only two muscles in one eye of a patient with a large sensory exotropia may indeed lead to the development of a duction deficit. We warn these patients of this possibility prior to surgery and it has been our experience that these patients are rarely bothered by the small duction deficit that may be produced. Given that this is the tradeoff that eliminates the need to operate on their better seeing eye, patients usually fully support this preoperative recommendation.

The need to operate on more than one muscle for the treatment of vertical strabismus follows a similar decision-making process. For a comitant deviation, a single muscle can be recessed or resected for smaller deviations. Vertical deviations larger than approximately 15 prism diopters generally require that a second muscle be operated. In cases of superior

palsy with a large deviation angle, multiple options are able. The surgeon may decide to operate on the ipsilateral perior oblique tendon and inferior oblique muscle, the eral inferior oblique and contralateral inferior rectus

or the ipsilateral inferior oblique and superior rectus When the inferior oblique and superior rectus muscles operated on simultaneously in the same eye, large

of the superior rectus muscle should be avoided. Significant weakening of both elevators of an eye can lead to limitation of elevation postoperatively. The decision

ing which two muscles to operate is primarily based upon pattern of incomitancy and the surgeon’s preference. A mendation is made after analysis of the measurements

diagnostic positions of gaze and analysis of the patient’s ductions and version.

Anterior transposition of the inferior oblique muscles is a useful procedure for the treatment of inferior oblique overaction, dissociated vertical deviation and, in some cases, superior oblique palsy. Anterior transposition leads to an elevation deficiency in many patients, but is usually well tolerated. When the procedure is performed unilaterally, this elevation deficiency may become obvious. It is less noticeable when both eyes are treated. For this reason, we rarely perform unilateral anterior transposition except in unusual circumstances. Severe bilateral inferior oblique overaction may be treated with this procedure; unilateral overaction is generally best treated with an inferior oblique weakening procedure alone. Likewise, bilateral dissociated vertical deviation is often treated with anterior transposition of the inferior oblique muscles, especially if concurrent inferior oblique overaction is present. However, in cases of unilateral dissociated vertical deviation, recession of the superior rectus may be a preferable approach.

4.2.3 Surgical “Dose”

The amount of recession or resection performed for a given deviation depends primarily on the size of the deviation. However, many other factors may be considered in a given case including the presence or absence of a duction limitation, level of fusion, associated central nervous system disease, results of forced traction testing, history of previous strabismus surgery, and findings at surgery that could alter the surgical plan such as abnormal anatomy. General guidelines for bilateral surgery to treat esotropia (>Table 4.1) and exotropia (>Table 4.2) are provided. These procedures represent the majority of strabismus operations. These general guidelines require modification depending on other factors as outlined and based on the experience of the individual surgeon. General guidelines

Esotropia (bilateral surgery)

Table 4.2. Suggested surgical guidelines for bilateral recession or resection surgery to treat exotropia. (LR Lateral rectus, MR medial rectus, OU both eyes, XT exotropia)

Exotropia (bilateral surgery)

Table 4.4. Suggested surgical guidelines for bilateral recession and resection surgery to treat exotropia. (LR Lateral rectus, MR medial rectus, XT exotropia)

Exotropia (unilateral surgery)

Table 4.6. Suggested surgical guidelines for treatment of vertical deviations. There are two commonly used guidelines. (LR Lateral rectus, PD prism diopters, SR superior rectus)

Vertical deviations

Chapter 4

Table 4.3. Suggested surgical guidelines for unilateral recession and resection surgery to treat esotropia. (ET Esotropia, LR lateral rectus, MR medial rectus)

Esotropia (unilateral surgery)

Table 4.5. Suggested surgical guidelines for unilateral recession surgery to treat esotropia and exotropia. (ET Esotropia, LR lateral rectus, MR medial rectus, XT exotropia)

Unilateral recession

for unilateral surgery on two rectus muscles to treat esotropia and exotropia are provided in Tables 4.3 and 4.4, respectively. Recession surgery on a single rectus muscle to treat esotropia and exotropia is less commonly performed (>Table 4.5). Two general guidelines are often suggested for determining the surgical dose for vertical strabismus (>Table 4.6). Surgery can be based on the ratio of approximately 3 PD of correction for each millimeter of recession or resection performed. Alternatively, recession of the superior rectus may be performed according to guidelines for unilateral lateral rectus recession. Surgical guidelines for treatment of nystagmus are available in Table 3.3.

4.3 Special Considerations

4.3.1 Torsion

Some forms of strabismus require special attention because they are not routine and a surgical plan tailored to a unique situation is required. Patients with torsional diplopia require a surgical plan specifically designed to threat the torsional component of their strabismus, or the procedure is not likely to be successful. Often the most difficult part of this process is identifying the presence of torsion. Once identified, treatment of the torsion is usually best accomplished by surgical manipulation of an oblique muscle. Nasal or temporal offset of the rectus muscles may be of value in some cases (Chapter 15).

tion, if the antagonist of the paralytic muscle has contracted, release of this restriction may be necessary as well.

4.4 Adjustable Suture Surgery

Many strabismus surgeons utilize adjustable suture techniques for both complex and routine surgical cases. While some surgeons heavily rely on their use, others do not use them at all. Adjustable sutures may give a strabismus surgeon a “second chance” when the initial postoperative alignment appears to be undesirable. However, it is also possible that adjustment in the early postoperative period may alter other factors that exist that would have led to a good end result. Not infrequently, we have performed surgery on patients without the use of adjustable sutures and have been concerned about a large initial overcorrection in the early postoperative period only to discover that the patient obtained excellent alignment several weeks later. We question what the outcome would have been in such cases had the patient undergone early adjustment. It should be noted that no published study has shown that adjustable suture surgery provides superior results to conventional strabismus surgery. Considering the variable and complex nature of the patients often treated, it is unlikely that such a study will ever be performed to the satisfaction of both the surgeons that employ their use and those who do not. Given this reality, it is up to the individual strabismus surgeon to make a decision regarding the use of adjustable sutures based upon his/her own experience, preference, and patient population.

Restrictive strabismus is another form of strabismus that dictates surgery on specific muscles. In these cases, the restriction must usually be improved in order to achieve an optimal outcome. Identifying the nature of the restriction is imperative to the optimal treatment of these patients. Identifying other causes of incomitant strabismus during the evaluation process is also important. Proper identification of these problems allows the strabismus surgeon to devise a plan that not only aligns the eyes in primary position but increases the area of single binocular vision to the greatest extent possible. Patients with a complete or nearly complete paralysis of one or more eye muscles often require a transposition procedure. In addi-

1.Marlow FW (1920) Prolonged monocular occlusion as a test for the muscle balance. Trans Am Ophthalmol Soc 18:275–290

2.Kushner BJ, Morton GV (1998) Distance/near differences in intermittent exotropia. Arch Ophthalmol 116:478–486

3.Olitsky SE (1998) Early and late postoperative alignment following unilateral lateral rectus recession for intermittent exotropia. J Pediatr Ophthalmol Strabismus 35:146–148

4.Olitsky SE, Kelly C, Lee H, Nelson LB (2001) Unilateral rectus resection in the treatment of undercorrected or recurrent strabismus. J Pediatr Ophthalmol Strabismus 38:349–353