Strabismus Surgery – A parent’s question.


Here is a parent’s question regarding her niece’s recent strabismus surgery. It seems obvious that the solution to a turned eye would be to ‘realign’ it surgically, but if you look a little deeper, this ‘leap before you look’ approach can often lead to unexpected and disastrous results:

“Dr. Boulet

My niece has a “lazy eye”.  She had surgery in the spring to tighten the eye muscle.  At that time, the doctor said that up to that point she had not been seeing in three dimensions.  Now, she has gained some three dimensional vision.

So, she is in grade one and having a bit of a difficult time with the printed words.   She can spell words verbally, can form letters and knows all the sounds and letters but is having a hard time reading the words from the page. So, my sister wonders how this can be since print is two dimensional.  I’m wondering if she is still catching up (her brain and vision) from missing the vision previously.


Dear RL:

3-D vision, otherwise known as stereopsis, is only possible when both eyes can acquire the same visual signal simultaneously and overlapping perfectly – what vision scientists, including optometrists, call third-degree fusion. We don’t need both eyes to compute depth, but it’s a lot easier if at one point in your life you learned to appreciate depth with both eyes.

If, for example, you had both eyes until you were three years old, they were free of significant health or refractive defect and you were free to use them both as you liked, you would have learned to see the full depth humans are capable of achieving naturally. Later, due to some tragic accident, let’s say, you lose your eye and grow to be an adult with only one eye – you would still be able to calculate depth by using other ‘monocular’ depth cues, such as relative size, parallax, interposition of objects (near objects appear in front of more distant objects), relative speed of movement (driving down the road, you notice objects in the distance seem to pass by more slowly than road signs which are much nearer), and others. You learn these when both eyes work together and can refer to them later to assist in determining depth, but they are not true stereopsis.

When we achieve third-degree fusion, our visual brain switches gears, it stops thinking so much about acquiring the signals and aligning them, and it ‘locks on’, going into a sort of autopilot mode. It is much easier for the visual guidance mechanism to keep up with small movements in a fused system, as compared the effort required to align the images in the first place. Like when you start your car, it takes relatively more effort and more energy to get it started, then once it’s running, the engine’s efforts can be put into more important things, like going fast.

So what does this have to do with 2D reading? Our ability to acquire an image in 2D comes from having learned to do this in 3D space, with both eyes working together. In fact, if you imagine the paper as invisible and only the letters visible, this starts to show how t the letters are still in a 3D realm. In other words, the idea that the page represents 2D vision is really only a convention that we use to suggest something that in reality isn’t happening. The same rules of visual engagement apply, and the same visual signal acquisition process occurs in three dimensions, it just so happens the next signal to be acquired is in the same plane (y-axis, distance away from your nose) as the last. This is different from acquiring the signals of road signs which appear in different distances along the y-axis (nearer to your car and more distant).

So, now we know that 2D reading is really 3D reading. My answer to your question regarding your niece depends on a few things, and I don’t generally like to provide this sort of commentary by email. Since I don’t know this girl, I will allow some hypothetical, theoretical comments. Let’s call this theoretical kid ‘Alice’.

1. Surgeons know little to nothing of the visual behavioural mechanisms that ‘glue’ vision together. They don’t know this because they don’t study it. They see turned eyes and realign them by cutting and reattaching muscles. There is generally little thought given to the effects this will have on future behaviour and perception, and they can be debilitating.

2.  Our internal spatial mapping (our sense of where things are in the world and how we must move our eyes to find a target) is hard-wired to a given neuromuscular arrangement – that is, our internal map knows where our eyes are positioned and can instruct muscles to direct our gaze accordingly based on that hard-wired frame of reference (each eye alone, as well as BOTH eyes together). If you change the connection points on the eyeballs, the mapping no longer applies in a predictable fashion. VSA now becomes laborious and can never just simply hand over control to VSP and leave things in autopilot. There is a constant need for re-calculating the actual position of the eye and the position the brain thinks it’s in – frequently it’s easier for kids to just suppress one eye, or read with one eye closed which brings all sorts of other problems with it.

3. Frequently, acceptable results can be achieved through application of visual rehabilitative techniques. Eye turns, or strabismus (a better term than ‘lazy eye’), arise for different reasons and most of the time they can be fixed without surgery, even in very small infants and toddlers. This should always be attempted first as it is generally much less traumatic and it respects that hard-wired mapping so that, later in life, the child can learn to use automated eye movements for little details like reading. If you can achieve this, the child will grow up able to concentrate on what is read, as opposed to struggling through the act of reading itself. For a capable child, they can work around it, but they will never read as fluidly as they would have otherwise (I suppose there are rare exceptions, but it’s almost impossible to prove one way or another – but logic dictates this must be true and I’m sure it’s easy to demonstrate. For example, a simple Visagraph reading will demonstrate the marked difference performance between a children with and without strabismus surgery.) Sadly, parents are never given the option for visual rehabilitation because there is an erroneous and grotesque belief that, even though physiotherapy and occupational therapy somehow can impact outcomes, similar attention paid to the most complex sensory in our bodies will have no impact at all. This is a shameful display of ignorance regarding visual function and behaviour, and it’s made worse by the fact that ophthalmologists actively ignore and deny the benefits that are proven daily in rehabiltation clinics around the world, mine included. It’s really disappointing when you see the results of surgery after the fact and know that it’s too late to do any real good – you can never fix a broken system.

4. If Alice was having her trouble before surgery, then I would approach it one way, as a combined vsa/vsp concern and would recommend intensive activities along those lines. Generally healthy capable kids respond very readily.

5. If Alice started having this trouble following surgery, this is more complicated and the prognosis is not so good. If she engaged in monocular reading before surgery, now she’s struggling to read with two ‘nearly-aligned’ images – not stereopsis/third-dgree fusion, but something more like second-degree (two overlapping but not fused images), or even first-degree fusion (two overlapped images, but no common borders). This might persist for the rest of her life. I would still recommend activities, but it would revolve more around vsa initially, moving on to vsp. Straightforward reading training is not advised until the mechanical issues are addressed – otherwise everyone will spin their wheels while Alice gets frustrated. I won’t lie, vsa training is a different monster when muscles are rearranged. The goal here is to find the best next option to fully automatic reading, whatever that is – one eye? alternating eyes? more auditory instruction? She will never likely learn to read to her full potential may struggle unless the school moves away from primarily text-based instruction and evaluation. I would start pushing for accommodations now.

In the end, it’s a tough call without more information. ALL kids should be assessed for viability of rehabilitation prior to surgery, period. Otherwise, the risk in no way measures up to the benefits. Implicit in this is that SOME kids will NEED surgery, but rehab needs to be there before and after to improve the odds. Surgeons very often create dyslexics when they ‘fix’ problems that should be addressed behaviourally, and this is extraordinarily frustrating for ‘quacks’ like me (you see, ophthalmologists will call what I do quackery, but they have no reference in reality or experience for making comments like this – I have been in surgical suites, very few OMDs have ever stepped foot in a visual rehab clinic, and there are many such clinics out there).  Don’t be surprised when Alice’s surgeon cannot explain the problem or supply a reasonable solution. Meds, perhaps, after she becomes depressed.

Sorry, I sound so dire and dour, but I can only think of the many faces that I’ve seen with similar issues CAUSED by unnecessary and misguided surgical intervention. See the attached research doc. It’s excellent. Here’s a quote.

“A literature search found not one randomized, double-masked, controlled study, performed by a researcher without a vested interest in the outcome (paraphrasing Levine), that demonstrated a significant improvement in first-, second-, and third-degree fusion caused by strabismus surgery when compared with a control group. And this is a procedure that carries a low but measurable risk of blindness93 or death.94 Paul Romano, M.D., reported that 48% of North American ophthalmologists routinely used only surgery for exotropia, whereas only 5% of international ophthalmologists did. Dr. Romano explained the reasons: U.S. ophthalmologists were paid more for surgery compared with their international coun- terparts, nonsurgical options were time-consuming and not well reimbursed, there is a lack of training in nonsurgical methods, and there is a fear of losing patients to those profes- sionals who were well trained in those methods. Dr. Romano went on to say, ‘‘Optometrists have developed and improved their own non-surgical treatment methods . . . non-surgical treatment is quite effective . . . and . . . surgery is at best only equally effective.’’”

Maybe more than what you were looking for, and not likely the tone you were expecting. I keep telling myself ‘yes, some kids NEED surgery’ and still, that doesn’t change the fact that at least the same outcome can be achieved behaviourally with much better outcomes long-term and no risk to the child.

Read this excellent, but technical, report on the subject by Dr. Daniel Lack: LJS Rebuttal.