My 6 month old son has a large alternating outward deviation of the eyes.  We noted this since he was born.  What is the optimal time for surgery with this kind of deviation?  Is the outcome of surgery promising?

Infantile or congenital exotropia is a rare type of exodeviation.  Most parents notice the constant deviation by the age of six months but the onset is usually earlier.  The condition is likely caused by an arrest in the normal development of the ability of the eyes to converge early in life.  The amount of deviation is usually more than 40 prism diopters because of the tight lateral rectus muscles.  Rarely, the oblique muscles may also be overacting and contractured, producing a vertical component to the deviation, making the pattern of deviation more complex.  Oblique overactions usually present after one year of age and is more commonly seen in infantile esodeviation.

The approach to treatment starts with the management of amblyopia or “lazy eyes”, if present, either through occlusion therapy or patching of the dominant eye, or rarely, through the correction of any significant refractive error.  Amblyopia is present in 25% of cases due to the misalignment rather than any inequality in refractive error.

As in any kind of deviation, surgery should align the eyes by 2 years of age, in order to achieve optimal motor and sensory outcome.  Thinking that early surgery may be beneficial, some surgeons consider doing surgery after 6 months of age.  Children with this condition have poor fusion potential, developing peripheral fusion in only 50% of the time, with some gross stereopsis.

The goal of surgery is to achieve a small amount of esotropia immediately after the surgery because there is a natural tendency for the eyes to drift outwards.  The success for surgery is not very high.  Undercorrections are common because the surgical tables used as guide in determining the amount of muscle surgery does not consider the presence of tight or contractured muscles, such as found in infantile XT.  Therefore a second surgery is sometimes necessary to correct any residual deviation or any overaction of the oblique muscles.