Non-surgical treatment alternatives to strabismus surgery - the risk of a single childhood exposure to anesthesia

The risks of strabismus surgery and exposure to anesthesia during surgery

We previously wrote about the new scientific evidence that repeat exposure to anesthesia at a young age is associated with the development of learning disabilities and ADHD later on in life.  As eye doctors, we care about this because strabismus (cross eyes, eye turn, esotropia, exotropia) is often treated in very young children with surgery using general anesthesia.  The safety of exposing children to anesthesia has been questioned in light of the recent research.  And with strabismus surgery there is a very high risk of repeat surgeries being performed on the same patient (click here to learn about all the risks of strabismus surgery) which means more potentially harmful anesthesia exposure.

The risks of surgery pose a problem because vision therapy is a safe and effective non-surgical treatment for most types of strabismus, which makes most people think twice about surgery as a first choice treatment.

A famous case of vision therapy treatment for strabismus was the subject of the book Fixing My Gaze, an inspirational book by neuroscientist, Susan Barry, who was born with strabismus and had lived all her life without stereo vision, meaning that she could not see in three dimensions.

Even a single exposure to anesthesia during surgery is associated with developmental problems in children: new study

There is now new evidence that even a single exposure to anesthesia can be dangerous for a child.  A study published in December 2012 in the journal Evidence Based Medicine  found that children exposed to anaesthesia for surgery under 3 years of age were found to be at significantly increased risk for developing disabilities in receptive language, expressive language, total language and abstract reasoning at age 10.

The study authors commented that:

This study was the first to report the effects of anaesthetic exposure early in life on neuropsychological outcome using individually administered neurocognitive tests. Perhaps due to the greater sensitivity of these tests, Ing and colleagues observed disability even following a single exposure in early childhood, while several previous reports, utilising group-administered tests, had only detected learning abnormalities following multiple exposures.

This is the latest of 250 studies that have linked anesthesia exposure at a young age to brain development disorders.  The previous studies found a link between anesthesia and learning disabilities in children who had two more more exposures to anesthesia, while the new study found a link in children with just one exposure.  In the study's own words:

Thus far, more than 250 studies in immature animals have demonstrated that exposure to commonly used anaesthetics produces neuronal cell death, alters brain development and may lead to neurocognitive impairment. Similarly, in humans, an association between learning disabilities and two or more anaesthetic exposures has been observed in some studies, as most recently reported in children under 2 years of age.

According to Cyber-Sight, a program of ORBIS International, a non-profit organization that prevents and treats blindness by providing quality eye care, "most immature patients (younger than mid-teens) require general anesthesia for extraocular muscle surgery." Click here to read more about anesthesia use in strabismus surgery.

Repeat strabismus surgeries are common

Children who have strabismus surgery are risk of repeat surgeries, all of which carry the same risk. Eye surgeons often lament the need for repeat eye surgeries for strabismus patients. Surgeon, John W. Simon, notes that "patients must regularly contend with the unfortunate reality that even the most accurately planned and carefully executed surgery may not totally eliminate the deviation [i.e. the misalignment of the eyes] or completely normalize rotations. In addition, strabismus tends to recur over time." This limitation of surgery often results in the the patient being subjected to repeated surgeries - all of which may be unsuccessful. It is not uncommon for a patient to have had two or three or more surgeries and still have a noticeable misalignment or poor binocular vision together with depth perception problems or all three. For this reason, the surgeon's view is that "strabismus is less a problem to be cured than a problem to be controlled, with the minimum number of surgeries": Simon, John W. Complications of Strabismus Surgery. Current Opinion in Ophthalmology. 2010. 21: 361-366.

One study found that only 45% of children had successful alignment of the eyes at an eight-year follow up to their strabismus surgery. And while the low percentage was disappointing enough, 20% of the children had to undergo repeat strabismus surgeries which were ultimately unsuccessful: Awadein A, Sharma M, Bazemore MG, et al. Adjustable suture strabismus surgery in infants and children. J AAPOS 2008; 12:585–590.

Parents need to get the right information and ask the right questions

Parents of children with strabismus need to carefully evaluate the available treatment options.  They should see a developmental optometrist like Dr. M.K. Randhawa  to talk about whether vision therapy is effective for the type of strabismus that the child has.   Parents contemplating surgery need to ask their surgeons about the risk of anesthesia exposure during surgery as well as all the other risks of strabismus surgery (ranging from death - a mortality rate of 1.1 per 10,000 cases is reported - scars, repeat surgeries, infections, lost muscles, vision loss, lack of depth perception). 

Parents should consider vision therapy if their developmental optometrist thinks that vision therapy is appropriate for the type of strabismus that the child has. At our clinic, we have successfully treated dozens of strabismus patients, achieving straight eyes as well as functional binocular vision and depth perception and other developmental optometrists likely have similar results. 

Here is a TED talk on vision therapy by neuroscientist, Dr. Susan Barry, author of Fixing my Gaze:

Vision therapy or surgery for strabismus (esotropia, exotropia)?

Strabismus surgery.  Image: wikipedia.

We here at Vision Source Vancouver think that it makes good sense to use effective non-surgical vision therapy to treat strabismus (sometimes called cross eyes, eye turn, esotropia, exotropia).  The reason is that strabismus or eye muscle surgery has many risks of bad or harmful outcomes.   

This website has featured articles outlining the risks associated with strabismus surgery and reported on studies that demonstrate the effectiveness of vision therapy in treating most kinds of strabismus -without any of the risks associated with surgery.

Professor Dominick Maino, a fellow of the College of Optometrists in Vision Development, recently had a discussion with an eye surgeon on his own blog, MainosMemos, on why surgery, because of the risks and results that are not satisfactory for many patients,  should only be used as a last resort. As only one example of undesirable outcomes, a study on surgery found that only 45% of children had successful alignment of the eyes at an eight-year follow up to their strabismus surgery. And while the low percentage was disappointing enough, 20% of the children had to undergo repeat strabismus surgeries which were ultimately unsuccessful: Awadein A, Sharma M, Bazemore MG, et al.Adjustable suture strabismus surgery in infants and children. J AAPOS 2008; 12:585–590. 

Other risks of strabismus surgery include death, infections, blindness, scars, mistakes like surgery on the wrong eye, etc.  You can read more about risks here. 

Repeat strabismus surgeries in children are causing concern because of new research that links anesthesia use in kids to learning disabilities and attention deficit hyperactivity disorder later in life.   In fact, the eye surgeon who commented on Professor Maino's blog had these same concerns, writing:

One can't ignore the studies regarding anesthesia and the potential for future cognitive impairment. This is a work in progress and the pediatric specialties are following closely.

However, the surgeon goes on to say:

Like anything in medicine (and you should be well-versed since you received an "Excellence in Medicine" award) you have to consider the risk-vs.-benefit ratio. If I have a young patient with a 40 PD decompensated exotropia who is in danger of developing irreversible amblyopia and loss of stereoacuity, 30-40 minutes of anesthesia for strabismus surgery is not going to prevent him or her from getting into Harvard. [NB vision therapy and patching will not touch a 40 XT]. People need to be properly educated, look at all of the facts, and not over-react.

If there are no studies that prove that anaesthesia during strabismus surgery is totally safe, our point is that it is not sensible to take the risk when you don't need to.  The basic ethical principle in medicine is "do no harm".  If there is a treatment option that has no risk of harm, it should be the first choice.  There are some types of strabismus that vision therapy cannot effectively treat, and for those surgery is probably a good idea given the cost-benefit analysis.  But for the most common kinds of strabismus, vision therapy is a safe and effective treatment. 

Dr. Maino referred to the following recent studies on strabismus surgery that highlight the reasons why it should not be first choice option for treating strabismus:

Haridas A, Sundaram V. Adjustable versus non-adjustable sutures for strabismus. Cochrane Database of Systematic Reviews 2005, Issue 1. Art. No.: CD004240. DOI: 10.1002/14651858.CD004240.pub2

"No reliable conclusions could be reached regarding which technique (adjustable or non-adjustable sutures) produces a more accurate long-term ocular alignment following strabismus surgery or in which specific situations one technique is of greater benefit than the other. High quality RCTs are needed to obtain clinically valid results and to clarify these issues. ......"

Rowe FJ, Noonan CP. Botulinum toxin for the treatment of strabismus. Cochrane Database of Systematic Reviews 2012, Issue 2. Art. No.: CD006499. DOI: 10.1002/14651858.CD006499.pub

The majority of published literature on the use of botulinum toxin in the treatment of strabismus consists of retrospective studies, cohort studies or case reviews. Although these provide useful descriptive information, clarification is required as to the effective use of botulinum toxin as an independent treatment modality. Four RCTs on the therapeutic use of botulinum toxin in strabismus have shown varying responses ranging from a lack of evidence for prophylactic effect of botulinum toxin in acute sixth nerve palsy, to poor response in patients with horizontal strabismus without binocular vision, to no difference in response in patients that required retreatment for acquired esotropia or infantile esotropia. It was not possible to establish dose effect information.Complication rates for use of Botox™ or Dysport™ ranged from 24% to 55.54%.

Elliott S, Shafiq A. Interventions for infantile esotropia. Cochrane Database of Systematic Reviews 2005, Issue 1. Art. No.: CD004917. DOI: 10.1002/14651858.CD004917.pub2

The main body of literature on interventions for IE are either retrospective studies or prospective cohort studies. It has not been possible through this review to resolve the controversies regarding type of surgery, non-surgical intervention and age of intervention. There is clearly a need for good quality trials to be conducted in these areas to improve the evidence base for the management of IE.

Br J Ophthalmol. 2012 Oct;96(10):1291-5. Epub 2012 Aug 11.Surgical intervention in childhood intermittent exotropia: current practice and clinical outcomes from an observational cohort study. Buck D, Powell CJ, Sloper JJ, Taylor R, Tiffin P, Clarke MP; Improving Outcomes in Intermittent Exotropia (IOXT) Study group. 

After surgery 65% had fair to poor outcomes and 20% of the subjects remained XT or the XT recurred

BMC Ophthalmol. 2012 Jan 18;12:1. doi: 10.1186/1471-2415-12-1.The improving outcomes in intermittent exotropia study: outcomes at 2 years after diagnosis in an observational cohort.
Buck D, Powell CJ, Rahi J, Cumberland P, Tiffin P, Taylor R, Sloper J, Davis H, Dawson E, Clarke MP.

....8% ...of those treated surgically required second procedures for overcorrection within 6 months of the initial procedure and at 6-month follow-up 21% ... were overcorrected ....