Eye Muscle Surgery

Definition
Purpose
Demographics
Description
Diagnosis/Preparation
Aftercare
Risks
Normal results
Morbidity and mortality rates
Alternatives

Definition

Eye muscle surgery is performed to weaken, strengthen, or reposition any of the extraocular muscles (small muscles) located on the surface of the eye that move the eyeball in all directions.

Purpose

The extraocular muscles attach via tendons to the sclera (the white, opaque, outer protective covering of the eyeball) at different places just behind an imaginary equator circling the top, bottom, left, and right of the eye. The other end of each of these muscles attaches to a part of the orbit (the eye socket in the skull). These muscles enable the eyes to move up, down, to one side or the other, or any angle in between.

Normally, both eyes move together, receiving the same image on corresponding locations on both retinas. The brain fuses these matching images into one three-dimensional image. The exception is in strabismus, which is a disorder where one or both eyes deviate out of alignment, most often outwardly (exotropia) or toward the nose (esotropia). In this case, the brain receives two different images, and either suppresses one or allows the person to see double (diplopia). By weakening or strengthening the appropriate muscles to center the eyes, a person can correct this deviation. For example, if an eye turns upward, the muscle at the bottom of the eye could be strengthened.

The main purpose of eye muscle surgery is thus to restore straight eye alignment. The surgery is performed to align both eyes so that they gaze in the same direction and move together as a team; to improve appearance; and to promote the development of binocular vision in a young child. To achieve binocular vision, the eyes must align so that the location of the image on the retina of one eye corresponds to the location of the image on the retina of the other eye.

In addition to being used to correct strabismus, eye muscle surgery is also performed to treat other eye disorders such as nystagmus or special types of congenital strabismus such as Duane syndrome. Nystagmus is a condition in which one or both eyes move rapidly or oscillate; this condition can be improved by moving the eyes to the position of least oscillation. Duane syndrome is a disorder in which there is limited horizontal eye movement; it can sometimes be relieved by surgery that weakens an eye muscle.

Demographics

According to doctors at the Wills Eye Hospital, Philadelphia, the most common divergent strabismus in childhood has a variable onset, often between six months and four years. The disorder occurs in 1.2% of children by seven years of age and occurs equally in males and females.

Duane syndrome commonly affects girls more often than boys, and the left eye more often than the right eye.

KEY TERMS

Conjunctiva— The mucous membrane that covers the eyes and lines the eyelids.

Duane syndrome— A hereditary congenital syndrome in which the affected eye shows a limited capacity to move, and is deficient in convergence with the other eye.

Extraocular muscles— The muscles (lateral rectus, medial rectus, inferior rectus, superior rectus, superior oblique, and inferior oblique) that move the eyeball.

Nystagmus— An involuntary, rapid, rhythmic movement of the eyeball, which may be horizontal, vertical, rotatory, or mixed.

Orbit— The cavity in the skull containing the eyeball; formed from seven bones: frontal, maxillary, sphenoid, lacrimal, zygomatic, ethmoid, and palatine.

Retina— The inner, light-sensitive layer of the eye containing rods and cones. The retina transforms the image it receives into electrical messages sent to the brain via the optic nerve.

Sclera— The tough, fibrous, white outer protective covering of the eyeball.

Strabismus— A disorder in which two eyes cannot be directed at the same object at the same time.

Congenital nystagmus is thought to be present at birth, but is usually not apparent until the child is a few months old. Acquired nystagmus occurs later than six months of age, and can be caused by stroke, diseases such as multiple sclerosis, or even a heavy blow to the head. It is not known how many people suffer from nystagmus, but it is thought to be one in 1,000 adults, and one in 640 children in the United States, according to the Nystagmus Network.

Description

The procedure used by the surgeon depends on the condition that needs correcting. During surgery, eye muscles can be:

• Weakened. This usually involves recessing the eye muscle or moving it posteriorly on the eye to elongate the muscle and allow the muscle tissue to relax.
• Tightened. Muscles are tightened by resection, which involves removing a piece of the muscle near its point of insertion and then reinserting the muscle into its original location. By removing a piece of muscle, the muscle is shortened and therefore strengthened.
• Repositioned. For some forms of strabismus, the eye muscles are neither weakened nor strengthened, but repositioned: i.e., the muscle’s point of insertion is moved to a different location.

There are two methods to alter extraocular muscles. Traditional surgery can be used to strengthen, weaken, or reposition an extraocular muscle. The surgeon first makes an incision in the conjunctiva (the clear membrane covering the sclera), then puts a suture into the muscle to hold it in place, and loosens the muscle from the eyeball with a surgical hook. During a resection, the muscle is detached from the sclera, a piece of muscle is removed so that the muscle is now shorter, and the muscle is reattached to the same place. This strengthens the muscle. In a recession, the muscle is made weaker by repositioning it. More than one extraocular eye muscle might be operated on at the same time.

Eye muscle surgery is performed with the eye in its normal position and usually takes an hour and a half. At no time during the operation is the eye removed from the socket. The surgeon determines where to reattach the muscles based on eye measurements taken before surgery. Most of the time, it can hardly be seen except with magnification.

Diagnosis/Preparation

Depth perception (stereopsis) in humans develops around the age of three months. For successful development of binocular vision and the ability to perceive three-dimensionally, eye muscle surgery should not be postponed past the age of four years. The earlier the surgery, the better the outcome, so an early diagnosis is important. Surgery may even be performed before the child is two years old.

Patients (or their caregivers) should make sure their doctors are aware of any medications that they are taking, even over-the-counter medications. Patients should not take aspirin, or any other blood-thinning medications for 10 days prior to surgery, and should not eat or drink after midnight the night before.

Aftercare

After surgery, the eyes feel scratchy, but not very painful. Patients must be kept from rubbing their eyes. The eyes are also a little red and watery. There may be some hemorrhage under the conjunctival membrane over the white of the eye that usually settles over a period of two to three weeks. It usually takes on a yellowish discoloration similar to a bruise as it clears. Sometimes there is some thickening of the membranes over the eye, which can take several more weeks to clear. Very fine dissolving sutures are used to reposition the conjunctival membrane at the end of surgery and, until these sutures dissolve, there may be some scratchiness in the eyes. This feeling usually disappears after two or three weeks.

There will also be some swelling and discharge after the surgery. The swelling is usually minor, and patients should be able to open their eyes within the next two days, as the swelling should gradually disappear.

Patients will need someone to drive them home after the operation. They should continue to avoid aspirin and other nonsteroidal anti-inflammatory agents for an additional three days, but they can take acetaminophen (e.g., Tylenol). Patients should discuss what medications they can or cannot take with the surgeon. Pain will subside after two or three days, and patients can resume most normal activities within a few days. Again, the period of recovery may vary with the patient, and the patient can discuss with the surgeon when to return to normal activities. Patients should not get their eyes wet for three to four days and should refrain from swimming for 10 days. Eyes receiving surgery will be red for about two weeks.

Adults and children over the age of six often experience double vision for a limited period of time after surgery. Children younger than six sometimes will have double vision for a short period of time. Double vision is rarely permanent.

Patients generally do not have to wear patches after surgery, although occasionally a temporary patch may be recommended. They are usually required to use eye drops for a week until the follow-up examination. If the eye is healing on schedule, then the eye drops are usually discontinued at that stage. A further postoperative appointment is usually made for six to eight weeks later, by which time the eye will have stabilized.

After surgery for strabismus, the patient usually needs corrective lenses and eye exercises (vision therapy) if binocular vision is to develop.

Risks

As with any surgery, there are risks involved. Eye muscle surgery is relatively safe, but very rarely a cut muscle cannot be retrieved. This, and other serious reactions, including those caused by anesthetics, can result in vision loss in the affected eye. Occasionally, retinal or nerve damage occurs. Permanent double vision is also a risk of eye muscle surgery. The success rate of this surgery varies from person to person and depends on each person’s particular condition.

Some infrequent complications include, but are not limited to, allergy to the sutures, bleeding, and change in pupil size.

WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?

Eye muscle surgery is performed by surgeons with specialized training in eye surgery. These physicians are usually board-certified ophthalmologists and fellowship-trained pediatric and/or adult strabismus specialists.

The surgery is almost always performed as outpatient surgery; that is, the patient comes into the hospital or day surgery facility the morning of the surgery and goes home the same day.

The major risk of eye muscle surgery is failure to achieve a satisfactory alignment of the eyes. This may be an under-correction or an over-correction, with the eyes turning the other way after the operation. Surgeons aim to achieve perfect alignment, but this is not always possible. If the alignment is still unsatisfactory at the final postoperative visit, then a second operation may be required.

Infection is an unusual postoperative complication and can be treated with antibiotic drops.

Because an incision is made through the conjunctiva and muscle, there is always some residual scarring. Usually, this is detectable only under a microscope, although it may be possible to see it on close examination.

As with any eye surgery, there is a potential risk of visual loss from strabismus operations, but this is a very rare complication.

Normal results

Normal results of eye muscle surgery are an improved alignment of the eyes and improved cosmetic appearance without complications. The surgery usually has a very good outcome.

Morbidity and mortality rates

Cosmetic improvement is likely with success rate estimates varying from about 65-85%. According to the latest statistics from 1998, binocular vision is improved in young children about 35% of the time following eye muscle surgery. Between 15% and 35% of patients have either no improvement or a worsening of their condition. A second operation may rectify less-than-perfect outcomes.

QUESTIONS TO ASK THE DOCTOR

• What is the chance of needing a second oeration?
• What are the possible risks and complications?
• Will I need eyeglasses?
• How much eye muscle surgery do you perform each year?
• Are there alternatives to surgery?
• Is a patch worn after surgery?
• Are there any scars after surgery?

Alternatives

Surgery is not the only treatment to correct eye muscle disorders. Options and outcomes vary considerably based on several factors such as the presence of double vision. Nonsurgical treatment is also available, such as orthoptics and vision therapy.

Orthoptics

Orthoptics is a medical term for the eye muscle training programs provided by orthoptists and optometrists. Vision therapy programs include orthoptics, but there are broad differences between vision therapy and orthoptics. Orthoptics dates back to the 1850s and is limited in scope to eye muscle training and the cosmetic straightening of eyes. Orthoptics treat muscle problems by considering only strength; it does not focus on neurological and visual-motor factors as vision therapy does. Treatment is home based.

Vision therapy

Vision therapy is an individualized, supervised, non-surgical treatment program designed to correct eye movements and visual-motor deficiencies. Vision therapy sessions include procedures designed to enhance the brain’s ability to control:

• eye alignment
• eye teaming
• eye focusing abilities
• eye movements
• visual processing

Visual-motor skills and endurance may be developed through the use of specialized computer and optical devices, including therapeutic lenses, prisms, and filters. During the final stages of therapy, the patient’s newly acquired visual skills are reinforced and made automatic through repetition and by integration with motor and cognitive skills.

Resources

BOOKS

Dyer, J. A., and D. A. Lee. Atlas of Extraocular Muscle Surgery. Westport, CT: Praeger Publishers, 1984.

Good, William V., and Craig S. Hoyt. Strabismus Management. Boston: Butterworth-Hienemann, 1996.

Roth, A., and C. Speeg-Schatz, eds. Eye Muscle Surgery. Lisse, The Netherlands: Swets & Zeitlinger, 2001.

Salmans, Sandra. Your Eyes: Questions You Have…. Answers You Need. Allentown, PA: People’s Medical Society, 1996.

von Noorden, Gunter K. Binocular Vision and Ocular Motility: Theory and Management of Strabismus, 5th edition. St. Louis: Mosby-Year Book, 1996.

PERIODICALS

Bosman, J., M. P. ten Tusscher, I. de Jong, J. S. Vles, and H. Kingma. “The Influence of Eye Muscle Surgery on Shape and Relative Orientation of Displacement Planes: Indirect Evidence for Neural Control of 3D Eye Movements.” Strabismus 10 (September 2002): 199–209.

Mayr, H. “Virtual Eye Muscle Surgery Based upon Biome-chanical Models.” Studies in Health and Technology Information 81(2001): 305–311.

Murray, T. “Eye Muscle Surgery.” Current Opinion in Ophthalmology 11 (October 2000): 336–341.

Rubsam, B., W. D. Schafer, B. Schulte, and N. Roewer. “Preliminary Report: Analgesia with Remifentanil for Complicated Eye Muscle Surgery.” Strabismus 8 (December 2000): 287–289.

Watts, J. C. “Total Intravenous Anesthesia Without Muscle Relaxant for Eye Surgery in a Patient with Kugelberg-Welander Syndrome.”Anaesthesia 58 (January 2003): 96.

ORGANIZATIONS

American Academy of Ophthalmology. 655 Beach Street, P.O. Box 7424, San Francisco, CA 94120-7424. http://www.eyenet.org.

American Academy of Pediatric Ophthalmology and Strabismus (AAPOS). <http://med-aapos.bu.edu>.

OTHER

Olitsky, Scott E., and Leonard B. Nelson. Strabismus Web Book.www.members.aol.com/scottolitsky/webbook.htm.

Kellogg Eye Center: Eye Muscle Surgery.www.kellogg.umich.edu/patient/surg/eyemuscle.html.

Pediatric Ophthalmic Consultants Webpage: Strabismus Surgery.www.pedseye.com/StrabSurg.htm.

Lorraine Lica, PhD

Monique Laberge, PhD

Eye surgery seeOphthalmologic surgery

Eyeball removal seeEnucleation, eye

Eyelid plastic surgery seeBlepharoplasty

Eyelid surgery seeTarsorrhaphy

Eye muscle surgery

Definition

Eye muscle surgery is performed to weaken, strengthen, or reposition any of the extraocular muscles (small muscles) located on the surface of the eye that move the eyeball in all directions.

Purpose

The extraocular muscles attach via tendons to the sclera (the white, opaque, outer protective covering of the eyeball) at different places just behind an imaginary equator circling the top, bottom, left, and right of the eye. The other end of each of these muscles attaches to a part of the orbit (the eye socket in the skull). These muscles enable the eyes to move up, down, to one side or the other, or any angle in between.

Normally, both eyes move together, receiving the same image on corresponding locations on both retinas. The brain fuses these matching images into one three-dimensional image. The exception is in strabismus, which is a disorder where one or both eyes deviate out of alignment, most often outwardly (exotropia) or toward the nose (esotropia). In this case, the brain receives two different images, and either suppresses one or allows the person to see double (diplopia). By weakening or strengthening the appropriate muscles to center the eyes, a person can correct this deviation. For example, if an eye turns upward, the muscle at the bottom of the eye could be strengthened.

The main purpose of eye muscle surgery is thus to restore straight eye alignment. The surgery is performed to align both eyes so that they gaze in the same direction and move together as a team; to improve appearance; and to promote the development of binocular vision in a young child. To achieve binocular vision, the eyes must align so that the location of the image on the retina of one eye corresponds to the location of the image on the retina of the other eye.

In addition to being used to correct strabismus, eye muscle surgery is also performed to treat such other eye disorders as nystagmus or such special types of congenital strabismus as Duane syndrome. Nystagmus is a condition in which one or both eyes move rapidly or oscillate; this condition can be improved by moving the eyes to the position of least oscillation. Duane syndrome is a disorder in which there is limited horizontal eye movement; it can sometimes be relieved by surgery that weakens an eye muscle.

Demographics

According to doctors at Wills Eye Hospital, Philadelphia, the most common divergent strabismus in childhood has a variable onset, often between six months and four years. The disorder occurs in 1.2% of children by seven years of age and occurs equally in males and females.

Duane syndrome commonly affects girls more often than boys, and the left eye more often than the right eye.

Congenital nystagmus is thought to be present at birth, but is usually not apparent until the child is a few months old. Acquired nystagmus occurs later than six months of age, and can be caused by stroke, such diseases as multiple sclerosis, or even a heavy blow to the head. It is not known how many people suffer from nystagmus, but it is thought to be one in 1,000 adults, and one in 640 children in the United States, according to the Nystagmus Network.

Description

The procedure used by the surgeon depends on the condition that needs correcting. During surgery, eye muscles can be:

• Weakened. This usually involves recessing the eye muscle or moving it posteriorly on the eye to elongate the muscle and allow the muscle tissue to relax.
• Tightened. Muscles are tightened by resection, which involves removing a piece of the muscle near its point of insertion and then reinserting the muscle into its original location. By removing a piece of muscle, the muscle is shortened and therefore strengthened.
• Repositioned. For some forms of strabismus, the eye muscles are neither weakened nor strengthened, but repositioned: i.e., the muscle's point of insertion is moved to a different location.

There are two methods to alter extraocular muscles. Traditional surgery can be used to strengthen, weaken, or reposition an extraocular muscle. The surgeon first makes an incision in the conjunctiva (the clear membrane covering the sclera), then puts a suture into the muscle to hold it in place, and loosens the muscle from the eyeball with a surgical hook. During a resection, the muscle is detached from the sclera, a piece of muscle is removed so that the muscle is now shorter, and the muscle is reattached to the same place. This strengthens the muscle. In a recession, the muscle is made weaker by repositioning it. More than one extraocular eye muscle might be operated on at the same time.

Eye muscle surgery is performed with the eye in its normal position and usually takes an hour and a half. At no time during the operation is the eye removed from the socket. The surgeon determines where to reattach the muscles based on eye measurements taken before surgery. Most of the time, it can hardly be seen except with magnification.

Diagnosis/Preparation

Depth perception (stereopsis) in humans develops around the age of three months. For successful development of binocular vision and the ability to perceive three-dimensionally, eye muscle surgery should not be postponed past the age of four years. The earlier the surgery, the better the outcome, so an early diagnosis is important. Surgery may even be performed before the child is two years old.

Patients (or their caregivers) should make sure their doctors are aware of any medications that they are taking, even over-the-counter medications. Patients should not take aspirin , or any other blood-thinning medications for 10 days prior to surgery, and should not eat or drink after midnight the night before.

Aftercare

After surgery, the eyes feel scratchy, but not very painful. Postoperatively, the eyes are also a little red and watery. There may be some hemorrhage under the conjunctival membrane over the white of the eye that usually settles over a period of two to three weeks. It usually takes on a yellowish discoloration similar to a bruise as it clears. Sometimes there is some thickening of the membranes over the eye, which can take several more weeks to clear. Very fine dissolving sutures are used to reposition the conjunctival membrane at the end of surgery and, until these sutures dissolve, there may be some scratchiness in the eyes. This feeling usually disappears after two or three weeks.

There will also be some swelling and discharge after the surgery. The swelling is usually minor, and patients should be able to open their eyes within the next two days, as the swelling should gradually disappear.

Patients will need someone to drive them home after the operation. They should continue to avoid aspirin and other nonsteroidal anti-inflammatory agents for an additional three days, but they can take acetaminophen (e.g., Tylenol). Patients should discuss what medications they can or cannot take with the surgeon. Pain will subside after two or three days, and patients can resume most normal activities within a few days. Again, the period of recovery may vary with the patient and the patient can discuss with the surgeon when to return to normal activities. Patient's should not get their eyes wet for three to four days and should refrain from swimming for 10 days. Operated eyes will be red for about two weeks.

Adults and children over the age of six often experience double vision for a limited period of time after surgery. Children younger than six sometimes will have double vision for a short period of time. Double vision is rarely permanent.

Patients generally do not have to wear patches after surgery, although occasionally a temporary patch may be recommended. They are usually required to use eye drops for a week until the follow-up examination. If the eye is healing on schedule, then the eye drops are usually discontinued at that stage. A further postoperative appointment is usually made for six to eight weeks later, by which time the eye will have stabilized.

After surgery for strabismus, the patient usually needs corrective lenses and eye exercises (vision therapy) if binocular vision is to develop.

Risks

As with any surgery, there are risks involved. Eye muscle surgery is relatively safe, but very rarely a cut muscle cannot be retrieved. This, and other serious reactions, including those caused by anesthetics, can result in vision loss in the affected eye. Occasionally, retinal or nerve damage occurs. Permanent double vision is also a risk of eye muscle surgery. The success rate of this surgery varies from person to person and depends on each person's particular condition.

Some infrequent complications include, but are not limited to, allergy to the sutures, bleeding, and change in pupil size.

The major risk of eye muscle surgery is failure to achieve a satisfactory alignment of the eyes. This may be an undercorrection or an overcorrection, with the eyes turning the other way after the operation. Surgeons aim to achieve perfect alignment, but this is not always possible. If the alignment is still unsatisfactory at the final postoperative visit, then a second operation may be required.

Infection is an unusual postoperative complication and can be treated with antibiotic drops.

Because an incision is made through the conjunctiva and muscle, there is always some residual scarring. Usually, this is detectable only under a microscope, although it may be possible to see it on close examination.

As with any eye surgery, there is a potential risk of visual loss from strabismus operations, but this is a very rare complication.

Normal results

Normal results of eye muscle surgery are an improved alignment of the eyes and improved cosmetic appearance without complications. The surgery usually has a very good outcome.

Morbidity and mortality rates

Cosmetic improvement is likely with success rate estimates varying from about 65–85%. According to the latest statistics from 1998, binocular vision is improved in young children about 35% of the time, following eye muscle surgery. Between 15 and 35% of patients have either no improvement or a worsening of their condition. A second operation may rectify less than perfect outcomes.

Alternatives

Surgery is not the only treatment to correct eye muscle disorders. Options and outcomes vary considerably based on such factors as the presence of double vision. Nonsurgical treatment is also available, such as orthoptics and vision therapy.

Orthoptics

Orthoptics is a medical term for the eye muscle training programs provided by orthoptists and optometrists. Vision therapy programs include orthoptics, but there are broad differences between vision therapy and orthoptics. Orthoptics dates back to the 1850s and is limited in scope to eye muscle training and the cosmetic straightening of eyes. Orthoptics treats muscle problems by considering only strength; it does not focus on neurological and visual-motor factors as vision therapy does. Treatment is home-based.

Vision therapy

Vision therapy is an individualized, supervised, non-surgical treatment program designed to correct eye movements and visual-motor deficiencies. Vision therapy sessions include procedures designed to enhance the brain's ability to control:

• eye alignment
• eye teaming
• eye focusing abilities
• eye movements
• visual processing

Visual-motor skills and endurance may be developed through the use of specialized computer and optical devices, including therapeutic lenses, prisms, and filters. During the final stages of therapy, the patient's newly acquired visual skills are reinforced and made automatic through repetition and by integration with motor and cognitive skills.

Resources

books

Dyer, J. A., and D. A. Lee. Atlas of Extraocular Muscle Surgery. Westport, CT: Praeger Publishers, 1984.

Good, William V., and Craig S. Hoyt. Strabismus Management. Boston: Butterworth-Hienemann, 1996.

Roth, A., and C. Speeg-Schatz, eds. Eye Muscle Surgery. Lisse, The Netherlands: Swets & Zeitlinger, 2001.

Salmans, Sandra. Your Eyes: Questions You Have…Answers You Need. Allentown, PA: People's Medical Society, 1996.

von Noorden, Gunter K. Binocular Vision and Ocular Motility: Theory and Management of Strabismus, 5th edition. St. Louis: Mosby-Year Book, 1996.

periodicals

Bosman, J., M. P. ten Tusscher, I. de Jong, J. S. Vles, and H. Kingma. "The Influence of Eye Muscle Surgery on Shape and Relative Orientation of Displacement Planes: Indirect Evidence for Neural Control of 3D Eye Movements." Strabismus 10 (September 2002): 199–209.

Mayr, H. "Virtual Eye Muscle Surgery Based upon Biomechanical Models." Studies in Health and Technology Information 81 (2001): 305–311.

Murray, T. "Eye Muscle Surgery." Current Opinion in Ophthalmology 11 (October 2000): 336–341.

Rubsam, B., W. D. Schafer, B. Schulte, and N. Roewer. "Preliminary Report: Analgesia with Remifentanil for Complicated Eye Muscle Surgery." Strabismus 8 (December 2000): 287–289.

Watts, J. C. "Total Intravenous Anesthesia Without Muscle Relaxant for Eye Surgery in a Patient with Kugelberg-Welander Syndrome." Anaesthesia 58 (January 2003): 96.

organizations

American Academy of Ophthalmology. 655 Beach Street, P.O. Box 7424, San Francisco, CA 94120-7424. <http://www.eyenet.org>.

American Academy of Pediatric Ophthalmology and Strabismus (AAPOS). <http://med-aapos.bu.edu>.

other

Olitsky, Scott E., and Leonard B. Nelson. Strabismus Web Book. <www.members.aol.com/scottolitsky/webbook.htm>.

Kellogg Eye Center: Eye Muscle Surgery. <www.kellogg.umich.edu/patient/surg/eyemuscle.html>.

Pediatric Ophthalmic Consultants Webpage: Strabismus Surgery. <www.pedseye.com/StrabSurg.htm>.

Lorraine Lica, PhD Monique Laberge, PhD

WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?

Eye muscle surgery is performed by surgeons with specialized training in eye surgery. These physicians are usually board-certified ophthalmologists and fellowship-trained pediatric and/or adult strabismus specialists.

The surgery is almost always performed as outpatient surgery ; that is, the patient comes into the hospital or day surgery facility the morning of the surgery and goes home the same day.

QUESTIONS TO ASK THE DOCTOR

• What is the chance of needing a second operation?
• What are the possible risks and complications?
• Will I need eyeglasses?
• How much eye muscle surgery do you perform each year?
• Are there alternatives to surgery?
• Is a patch worn after surgery?
• Are there any scars after surgery?

Eye Muscle Surgery

Definition

Eye muscle surgery is surgery to weaken, strengthen, or reposition any of the muscles that move the eyeball (the extraocular muscles).

Purpose

The purpose of eye muscle surgery is generally to align the pair of eyes so that they gaze in the same direction and move together as a team, either to improve appearance or to aid in the development of binocular vision in a young child. To achieve binocular vision, the goal is to align the eyes so that the location of the image on the retina of one eye corresponds to the location of the image on the retina of the other eye.

In addition, sometimes eye muscle surgery can help people with other eye disorders (nystagmus and Duane syndrome, for example).

Precautions

Depth perception (stereopsis) develops around the age of three months old. For successful development of binocular vision and the ability to perceive three-dimensionally, the surgery should not be postponed past the age of four. The earlier the surgery the better the outcome, so an early diagnosis is important. Surgery may even be performed before two years old. After surgery, if binocular vision is to develop, corrective lenses and eye exercises (vision therapy) will probably be necessary.

Description

The extraocular muscles attach via tendons to the sclera (the white, opaque, outer protective covering of the eyeball) at different places just behind an imaginary equator circling the top, bottom, left, and right of the eye. The other end of each of these muscles attaches to a part of the orbit (the eye socket in the skull). These muscles enable the eyes to move up, down, to one side or the other, or any angle in between.

Normally both eyes move together, receive the same image on corresponding locations on both retinas, and the brain fuses these images into one three-dimensional image. The exception is in strabismus which is a disorder where one or both eyes deviate out of alignment, most often outwardly (exotropia) or toward the nose (esotropia). The brain now receives two different images, and either suppresses one or the person sees double (diplopia). This deviation can be adjusted by weakening or strengthening the appropriate muscles to move the eyes toward the center. For example, if an eye turns upward, the muscle at the bottom of the eye could be strengthened.

Rarely, eye muscle surgery is performed on people with nystagmus or Duane syndrome. Nystagmus is a condition where one or both eyes move rapidly or oscillate; it can sometimes be helped by moving the eyes to the position of least oscillation. Duane syndrome is a disorder where there is limited horizontal eye movement; it can sometimes be relieved by surgery to weaken an eye muscle.

There are two methods to alter extraocular muscles. Traditional surgery can be used to strengthen, weaken, or reposition an extraocular muscle. The surgeon first makes an incision in the conjunctiva (the clear membrane covering the sclera), then puts a suture into the muscle to prevent it from getting lost and loosens the muscle from the eyeball with a surgical hook. During a resection, the muscle is detached from the sclera, a piece of muscle is removed so the muscle is now shorter, and the muscle is reattached to the same place. This strengths the muscle. In a recession, the muscle is made weaker by repositioning it. More than one extraocular eye muscle might be operated on at the same time.

Another way of weakening eye muscles, using botulinum toxin injected into the muscle, was introduced in the early 1980s. Although the botulinum toxin wears off, the realignment may be permanent, depending upon whether neurological connections for binocular vision were established during the time the toxin was active. This technique can also be used to adjust a muscle after traditional surgery.

The cost of eye muscle surgery is about $2,000-$4,000, and about 700,000 surgeries are performed annually in the United States.

Preparation

Patients should make sure their doctors are aware of any medications that they are taking, even over-the-counter medications. Patients should not take aspirin, or any other blood-thinning medications for ten days prior to surgery, and should not eat or drink after midnight the night before.

Aftercare

Patients will need someone to drive them home after their surgery. They should continue to avoid aspirin and other non-steroidal anti-inflammatory agents for an additional three days, but they can take acetaminophen (e.g., Tylenol). Patients should discuss this with the surgeon to be clear what medications they can or cannot take. Pain will subside after two to three days, and patients can resume most normal activities within a few days. Again, this may vary with the patient and the patient should discuss returning to normal activity with the surgeon. They should not get their eyes wet for three to four days and should refrain from swimming for 10 days. Operated eyes will be red for about two weeks.

Risks

As with any surgery, there are risks involved. Eye muscle surgery is relatively safe, but very rarely a cut muscle gets lost and can not be retrieved. This, and other serious reactions, including those caused by anesthetics, can result in vision loss in the affected eye. Occasionally, retinal or nerve damage occurs. Double vision is not uncommon after eye muscle surgery. As mentioned earlier, glasses or vision therapy may be necessary.

Normal results

Cosmetic improvement is likely with success rate estimates varying from about 65-85%. According to the best statistics as of 1998, binocular vision is improved in young children about 35% of the time. There is no improvement, or the condition worsens 15-35% of the time. A second operation may rectify less-than-perfect outcomes.

Resources

ORGANIZATIONS

American Academy of Ophthalmology. 655 Beach Street, PO Box 7424, San Francisco, CA 94120-7424. 〈http://www.eyenet.org〉.

American Academy of Pediatric Ophthalmology and Strabismus (AAPOS). 〈http://med-aapos.bu.edu〉.

OTHER

Olitsky, Scott E., and Leonard B. Nelson. Strabismus WebBook. May 4, 1998. 〈http://www.smbs.buffalo.edu/oph/ped/webbook.htm〉.

KEY TERMS

Botulinum toxin (botulin)— A neurotoxin made by Clostridium botulinum ; causes paralysis in high doses, but is used medically in small, localized doses to treat disorders associated with involuntary muscle contraction and spasms, in addition to strabismus.

Conjunctiva— The mucous membrane that covers the eyes and lines the eyelids.

Extraocular muscles— The muscles (lateral rectus, medial rectus, inferior rectus, superior rectus, superior oblique, and inferior oblique) that move the eyeball.

Orbit— The cavity in the skull containing the eye-ball; formed from seven bones: frontal, maxillary, sphenoid, lacrimal, zygomatic, ethmoid, and palatine.

Retina— The inner, light-sensitive layer of the eye containing rods and cones; transforms the image it receives into electrical messages sent to the brain via the optic nerve.

Sclera— The tough, fibrous, white outer protective covering of the eyeball.

Strabismus— A disorder where the two eyes do not point in the same direction.