Timing of Surgery for Infantile Esotropia – Is Earlier Better?

    While some are "stretching" the upper limits for treating amblyopia, others are exploring lower age ranges for surgically treating large-angle infantile esotropia. One of the theories contends that if children’s eyes can be successfully aligned at a very early "critical" age, they will have a better chance for development of brain centers which control binocular visual function, including the appreciation of "depth perception," which is usually reduced in these cases.

    A recent exchange in the "Letters to the Editor" section of Ophthalmology (2001; 108: 6-7) highlighted this issue.Two well-known strabismologists (Dr. Norman Fisher from San Jose, Dr. Malcolm Ing from Honolulu) commented on a paper by my fellowship mentor, Dr. Eugene Helveston from Indianapolis (Results of early alignment of congenital esotropia, Ophthalmology 1999;106: 1716-26). Dr. Helveston’s report summarized long-term follow-up of a series of very young infants operated in the early 1990’s. The average age of these children was just over 4 months, and all had very large esotropia angles. All underwent an initial operation recessing both medial rectus muscles to compensate for this deviation.

    The initial results were excellent: all infants were aligned immediately post-operatively; but over the next 5 to 7 years, 70% changed enough to need at least one additional operation. Several required multiple operations. No child developed "normal" binocularity as measured using tests of "fine" stereoscopic depth perception (although isolated case reports have documented this in other authors’ papers). "Sub-normal" binocularity as judged from other tests of motor and sensory function was demonstrable in a number of cases.

    Dr. Fisher questioned the use of a "uniform" surgical approach as opposed to "selective" case-by-case procedures sometimes involving 3 or 4 extraocular muscles at the outset. Dr. Helveston noted that this is a valid approach but pointed out that all of his cases were well-aligned initially. The adverse alignment changes developed later as these children continued to grow. Dr Ing summarized his assessment of the current status of thinking about the issue in general:

    I would like to think that these observations validate the approach I have used to treat these cases since I entered practice. I feel that surgery should be planned when the examiner is convinced that the clinical information is complete and the observations reproducible for consecutive visits. This includes prism measurements at distance and near (to assess the possibility of a "high AC/A ratio"), up and down (looking for "A" or "V" patterns), gaze to either side (looking for inferior or superior oblique muscle dysfunction), and cycloplegic refraction (to evaluate possible hyperopia, which could cause an accommodative component to the deviation).

    I rarely encounter an infant who cooperates well enough for all of this information to be gathered and verified until the 9 to 12 month age range. I have occasionally observed markedly esotropic infants to spontaneously straighten their eyes by one year of age (and this has been documented by others). Others were markedly crossed when younger, but later exams showed less or even no deviation at distance – the hallmark feature of "high AC/A ratio" accommodative esotropia. These youngsters have controlled their near esotropia while wearing bifocal glasses. I would like to think that this selective, somewhat delayed approach has contributed to a relatively low re-operation rate for my infantile esotropia cases (10% for cases followed over 5 years).

    In the coming years, I would like to see research which could better define the central nervous system mechanisms underlying infantile/congenital esotropia. Conceivably, this could lead to selective pharmacologic rather than surgical treatment for this problem. Until then, we will continue to deal with this problem surgically – with the same vaguaries and uncertainites that have plagued previous generations of strabismologists.

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