That’s the title of a new article authored by a strabismus surgeon, Dr. Burton Kushner, published online 09-14-19 by the Journal of the American Association for Pediatric Ophthalmology and Strabismus. The background of the article begins: “Surgery for intermittent exotropia performed at a very young age has poorer sensory outcomes than surgery performed later; moreover, postoperative recurrence is common, regardless of age.”
The conservative measures that Dr. Kushner employed in his published review of record was either periods of alternating occlusion or minus lens over-correction, typically the former and sometimes the latter. Of equal interest is a new article published in the September issue of the journal Ophthalmology by PEDIG.
This latest PEDIG publication reports the results of IXT2, or Intermittent Exotropia Study 2, titled: Three-Year Observation of Children 3 to 10 Years of Age with Untreated Intermittent Exotropia. The conclusion reads: “Among children 3 to 10 years of age with IXT for whom surgery was not considered to be the immediately necessary treatment, stereoacuity deterioration or progression to constant exotropia over 3 years was uncommon, and exotropia control, stereoacuity, and magnitude of deviation remained stable or improved slightly.” It is interesting to note the parameters by which PEDIG defines deterioration by the three year period, which is either meeting a motor criterion of constant exotropia ≥10 prism diopters at distance and near, or a near stereoacuity criterion of ≥2-octave decrease from the best previous measure.
Obviously this leaves a wide range of latitude, from a clinical perspective. Those of you dealing with children who have IXT know that many parents express concern if their child’s exotropia converts from IXT occurring periodically to an XT occurring most of the time. Or if it converts to constant XT either at distance or near. Or if it switches its pattern from unilateral to alternating. Parents would likely consider this to be deterioration even though it may not meet PEDIG criteria for the term, if you get my drift.
Naturally there are other non-surgical “conservative” treatments for IXT other than alternating occlusion and over minus spectacles, which optometrists have employed successfully for many years, and most recently virtual reality. The basis for this is ironically revealed in a May 2013 article in EyeNet, the magazine of the American Academy of Ophthalmology. Titled New Research Sheds Light on Intermittent Exotropia, the article quotes pediatric ophthalmologist Sean Donahue, a prominent member of PEDIG, as follows: “These kids may do well for three years, but the problem with intermittent exotropia is that it is not an eye problem or an eye muscle problem. It’s a problem with the brain. That’s why all of the putative treatments—whether they are some type of eye exercises or vision training or eye muscle surgery—have a high risk of recurrence; they don’t fix the brain. That is the big black box that we eventually have to get to the bottom of. What we are currently doing with surgery is an orthopedic solution to a neurologic problem.”
Kudos to Dr. Donahue for noting this, but we can take it a step further. Read: The Shape of the Sky: The Art of Using Egocentric Stereopsis in the Treatment of Strabismus, an article published in Vision Development and Rehabilitation in 2016 authored by our colleague Dr. David Cook, and it will be obvious that when it comes to stabilizing alignment, optometric vision therapy works on the brain as much as the eyes. It still mystifies me why, after all these years, there isn’t more synergy on these cases between ophthalmology and optometry. As pediatric ophthalmologist Dr. Tom Lenart has noted regarding his experiences with collaboration, “In most instances when the child has vision therapy the outcome is more stable, and in some cases surgery can be avoided altogether”.