Making a Decision About Surgery

What are the Options in Strabismus Treatment?

As with any non-life threatening condition, the options range from no treatment—through optical, prismatic, certain medical, and occasional exercise therapies—to surgery. In leading up to a recommendation for surgery, you and your doctor have either tried or excluded for lack of benefit, non-surgical options. Hence, the choice will likely narrow to continuing with the condition and its current therapy (if any) or eye muscle surgery. Unfortunately, the only party that can make this decision is the person who bears the condition or that person’s family, particularly parents and caregivers. 

Your doctor will give you his or her best recommendation, and you should feel comfortable that you understand the risks, potential benefits, limitations and alternatives to surgery. If you do not have this comfort, you should discuss the matter with your doctor or seek a second (or more) opinion(s) from additional specialists. Your doctor should be willing and able to help you seek additional opinions about you or your child’s care. 

The Preoperative Consultation

Prior to recommending and performing surgery, all appropriate evaluations should be completed. First and foremost, the measurement of the deviation of the eyes must be reliable and consistent with a known or working diagnosis. Sometimes these measurements may require more than one evaluation to assure consistency of the presence and degree of the strabismus. Second, the sensory status—how the eyes see and work together—of the eye should be evaluated as possible, and any problems with vision addressed. In particular, refractive errors requiring eyeglasses and patching for decreased vision (amblyopia) should be initiated or complete. Third, the general medical status should be known and stable, to assure that there will be little to no risk to anesthesia. Finally, your doctor will discuss with you the potential risks, the benefits to be derived, the limitations of surgical correction of strabismus and the alternatives to surgery and its timing. Importantly, you should have a clear picture of the problem, how it currently affects (and may change in the future) your or your child’s life, what is being proposed, what the experience is likely to be, and what the most likely outcomes will be.

Choosing Your Surgeon

To the extent possible, you should feel comfortable about the surgeon you have selected. There are some ways in which your choices may be limited, and over which you have little to no control. Your health plan may restrict whom you may see with your current coverage. You may be isolated geographically, which limits your practical choices. Or you may have limited other resources that place limits on seeking additional opinions or options. Only you can determine the correct course of action for yourself and your child. The following may help you in this effort.

There is general agreement in medicine that a good surgeon is more than steady hands, as important as that is. Good surgeons also have: intelligent minds, honed with continuing study and inquiry; good hearts, taking the best interests of their patients as their habit of practice; courage and coolness under fire, to do what needs to be done particularly in difficult or unexpected circumstances; and experience, which leads to good judgment and the ability to avoid complications whenever possible. Good surgeons tend to operate expeditiously, not because they hurry, but because they do what needs to be done and nothing else (meaning no unnecessary or “complicating” moves). Strabismus surgery is technically demanding, and preoperative testing and surgical plan creation is challenging. Nonetheless, in the hands of skilled and experienced surgeons, it can (and for most cases should) be routine.

If you need advice about a surgeon to entrust you or your child’s care, the most informed sources include the people with whom they work professionally. These include referring physicians, operating room nurses, anesthesiologists and other strabismus surgeons. The latter will likely be somewhat cautious in their appraisals, not for lack of knowledge but for concerns about the propriety of commenting.   Health plans, despite their “credentialing” process, are not likely to have included physicians on their plans based primarily on their clinical skills. Patients who have had care or surgery provided can be a valuable source of information about how they were treated and give important information about what they have learned from their experiences, broadly speaking. General information about a surgeon’s credentials can be gleaned from reference sources, and can be of some benefit. The Internet has a wealth of information, yet it may be difficult to interpret it in light of the specific context of an individual’s care.  An experienced strabismus surgeon in whom you have confidence is your best source of perspective as to what should be done and when. Remember: if in doubt, it is reasonable to seek a second opinion.

Risks, Benefits, Limitations and Alternatives to Surgery

The most common risk to strabismus surgery is partial or complete failure to correct the condition and/or its effects, including associated symptoms such as double vision. In general, the more complicated the strabismus and its associated conditions, the more difficult it is to completely control the deviation and its effects. Because the visual system is complex, involving much of the brain, repositioning the extraocular muscles cannot be expected to resolve all problems associated with strabismus. In particular, the potential for binocular teaming of the eyes is known to have a significant effect; that is, if binocular vision can be achieved or recaptured, the likelihood of additional surgery diminishes. Decisions as to what and how much to do are based on experience—that experience is on a large number of patients, the effects and benefits of which cannot be known looking forward. How a given patient will respond to the experience of those before is unknowable; and there is a statistical bell shaped curve of effects for the population. In essence, therefore, some patients will be overcorrected, and some under corrected. The net effect is that additional surgery is required in a significant number of cases; the likelihood of more than one surgery, depending on a number of factors, can range from as low as 10% to 50% or more, with an average of between 20 and 25 percent. Most other complications, including anesthetic problems, infection and potential loss of vision are very rare. Working together, the patient, family, doctors and nurses can, and will take steps to assure that these potential complications are minimized. For example, post-operative antibiotics taken by mouth are often used to prevent infection, and careful attention to preoperative instructions, meticulous operating room procedures and prompt notification of any problems will be likely to prevent adverse consequences to these rare events. 

The benefits of surgery are aligned with the goals of surgery, and may vary from person to person. Alignment of the eyes may make amblyopia therapy less intense. Proper alignment may eliminate a range of symptoms such as double vision, eye strain or fatigue, and restore the normal relationships between the eyes themselves and other facial structures. Only the patient and his family, with the advice of their doctor can determine if these benefits warrant undergoing strabismus surgery.

Because of the complexity of the system, strabismus surgery may solve only a portion of a complex problem. Some forms of strabismus respond better than others. And some problems are not amenable to surgery. Your doctor will be able to explain the application of these generalities to your condition.

Non-surgical options in the treatment of strabismus include patching (occlusion) prisms, botulinum toxin injection, monocular occlusion or fogging, and in some cases eye exercises. 

Occlusion of one eye (or patching) may be useful in selected circumstances. Its principal use is in the treatment of amblyopia, or decreased vision associated with strabismus or other conditions. It is also somewhat useful in children with intermittent outward deviation of the eyes in infancy (typically under two years of age), called intermittent exotropia. 

The use of prisms in adult strabismus is commonly applied. Indications for use are broad and flexible based on the individual patient’s circumstances. Small angle strabismus with diplopia is the most common condition where prisms are effective. For example, a patient with a vertical deviation of five to six diopters (the unit of measurement of angles of deviation; one diopter equals about ½ degree of angle), which is comitant (meaning the same in all directions of gaze), would certainly be a candidate for prisms. Prisms may be useful in those patients that show an early over correction following strabismus surgery, and may be effective in helping to maintain good binocularity. Prisms have also been used in helping the surgeon decide how much surgery to do. The Prism Adaptation Trial showed some effectiveness in the preoperative evaluation in esotropia. Those patients who responded to the prism (binocularly) and whose angle increased showed a greater surgical success. However, it should be mentioned that prisms are not without disadvantages. Primarily, prisms are limited by the fact that it is impractical to correct large deviations due to the thickness and weight of the prism. In addition, those patients whose deviation is incomitant or changes from one gaze position to another may continue to manifest diplopia. In addition, patients who normally do not wear glasses may find difficulty in adjusting to glasses with prisms. When using prisms, there are two options. Ground in (to eye glass lenses) prisms are useful when the patient will be wearing the prisms for an extended period of time. Fresnel or stick-on prisms are useful when the prisms will be temporary, although many note degradation in visual acuity with and the unusual appearance of Fresnel prisms.

Botulinum toxin has gained significant popular appeal particularly with its cosmetic indications such as removing unwanted wrinkles. Interestingly, botulinum toxin’s role in medical therapy was discovered by a strabismus surgeon 25 years ago in California. Botulinum toxin is one of the most deadly toxins known to man. However, in microscopic quantities it is effective in temporarily weakening specific muscles for six to twelve weeks. The potential advantages of this option, most commonly used in adults, are: 1) it can be injected in the office without requiring general anesthesia; 2) it can be employed as a temporary treatment, e.g., in patients with acute cranial nerve palsies, and this option may be highly effective in the short term while the surgeon waits to see if the palsy will resolve; and 3) this may be an effective treatment in patients who show early over corrections following strabismus surgery. The chief disadvantage of botulinum toxin is that its effect maybe variable and unpredictable. In addition, it is not useful as a permanent form of treatment as its effect wears off after one to two months. In addition, risks include ptosis which maybe very troubling for the patient.

In patients who manifest intractable diplopia or who are poor surgical candidates occlusion or fogging may be an alternative treatment to avoid diplopia. In some patients who suffer mid-brain injury or disease, motor fusion may be permanently impaired. These individuals may never be able to fuse normally. Patching one eye or fogging one lens with a filter may be the only treatment that relieves them of their diplopic symptoms.

The use of eye exercises in strabismus is only occasionally beneficial in the long term. The best example of their potential usefulness is convergence exercises in persons with convergence insufficiency—a form of exodeviation where there is a tendency of the eyes to drift outwardly apart for near visual tasks. However, exercises may be useful: 1) for selected individuals and mild conditions; 2) when signs and symptoms are mild; 3) when affected persons are motivated, and 4) when expected benefits may be sustained through time.

Completing the documentation of your informed consent for strabismus surgery is dual—medical information combined with certain legal requirements. You have both legal and moral rights to know what the diagnosis for your condition is, what treatment is being proposed (including surgery), and what are the most likely risks, benefits, limitations and alternatives to the treatment proposed. This booklet, along with your discussions with your doctor, can help with these elements. 

The documents that you will be required to sign, consenting to the surgery, are legal documents. They are constructed to fully inform you of the worst thing(s) that could happen, and sometimes the effect is to add to your anxiety about the procedure. While such added anxiety is unfortunate, there is no option to their required use. Please read them with this understanding in mind. Do not consent to the surgery if you have unanswered questions or concerns. Surgery is best deferred until you have the information you need to make an informed decision about your or your child’s care. 

Please also see Chapters 15 & 16, which describe what to expect and watch for after surgery. These matters should be considered in the context of the risks and consequences of surgery, as well as understanding what may be of concern.

How is Strabismus Surgery Performed?

What is done in strabismus surgery should make sense to you, and reasonably address the condition as you understand it. For example, if an eye is turned inward, one can logically conceive that the muscles that pull it inward are either overacting or too tight. Therefore one should do something to weaken the pulling power, or loosen, that muscle. There are a number of methods to weaken a muscle’s pulling power, including moving it (generally called a recession) or, in certain instances, severing all or a portion of it. Strengthening a muscle’s action may be performed by tightening it (generally called a resection) or by “borrowing” muscle power from and adjacent muscle. Transposing all or portions of muscles may be of benefit when there are certain patterns to strabismus, or when a muscle is absent or neurologically weakened. The following is a summary of commonly performed operations for some common conditions. Be aware that there is more than one method for effectively treating strabismus surgically; and your or your child’s condition may warrant something varying from these examples.

            Recession of the medial rectus muscle of each eye

            Recession of one medial rectus and resection of one lateral rectus

            For very large angles, combinations of the above

            For small angles of deviation, recession of one lateral rectus muscle

            Recession of the lateral rectus muscle of each eye

            Recession of one lateral rectus muscle and resection of one medial rectus muscle

            For very large angles, combinations of the above

            Recession of one or more vertical rectus (superior and inferior) muscle(s)

            Weakening of one or more oblique (superior and inferior) muscle(s)

            Transposition of a muscle and its insertion

            Detaching a muscle

            An assistant or co-surgeon

Exercises: Eye exercises, sometimes called orthoptics or vision training, have proven to be of some value in strabismus care. In some instances, exercises may be used as a temporizing or preparatory strategy prior to surgery. However, when the amount of the strabismus is substantial, the deviation is not likely to be overcome with exercises.

Botulinum toxin: Botulinum toxin may sometimes be used as part of or an adjunct to surgery. For additional perspectives, please see the section on alternatives to surgery.

Adjustable sutures: Some surgeons will use adjustable suture techniques in adults and older children routinely, some in selected circumstances, and others rarely if at all. Reasonable and experienced surgeons continue to debate the relative merits of these procedures. The potential merits seem intuitive, i.e., if the correction is not proper, it may be adjusted immediately after the surgery, hopefully to avoid additional procedures. 

There remain unanswered questions. The adjustment is generally accompanied by significant discomfort; there may be some imprecision in where the muscle actually reattaches to the globe, and some changes in eye position continue to occur during the healing process. Hence, it is not definitively known the degree to which (and in what ways) adjustments may be of benefit, or the necessary and sufficient criteria for their application. This dilemma would benefit from a prospective controlled trial of comparison in patients with similar conditions performed by the same surgeons. Your surgeon will share with you her or his recommended choice of technique.

Timing of Surgery

Strabismus surgery is rarely an emergency procedure. Accordingly, there is time, and the time should be taken to fully evaluate the condition. On the other hand, it should be remembered that strabismus rarely goes away spontaneously. If anything, there is a general tendency for strabismus to worsen with time—in degree and/or frequency of deviation of the eyes, as well as complications such as loss of vision and binocular capacity. Furthermore, in children, there is a general principle that the younger the child, the more flexible and adaptable is their neurology, including the entire visual system. This can work for both good and bad. The following general approach is therefore recommended. Once the condition has been fully evaluated, the indication for surgery is established and the choice to proceed made, there is no particular advantage to waiting. In certain circumstances, waiting (or delay) may decrease the likelihood of a positive outcome. A second advantage to proceeding with surgery when warranted in children is that older children often worry more and are more anxious about the surgical experience.