Pediatric Ophthalmology Consultants

Focus Effort and its Relationship to Crossing of the Eyes


Focus not required when looking at something over 20’ away. Focus effort (accommodation) needed to look at something closer. The brain also moves the eyes inward (convergence) with focus effort. Nature’s perfect plan is to provide a clear picture with proper focus and proper aiming.

Sometimes nature’s perfect plan is upset. Too much inward movement (convergence) takes place with focus effort (accommodation). This occurs without farsightedness but is much more common with farsightedness.

Anything reducing focus effort may straighten crossed eyes. Glasses with or without bifocals may be prescribed. Drops or ointments may be necessary. If these things work to keep the eyes straight then eye muscle surgery is not indicated.

When straight eyes begin to cross, it is probably the result of some unusual or inappropriate focus effort. Glasses will usually put these eyes straight. Any child with significant farsightedness should have a trial with glasses before having surgery to straighten crossed eyes.

What if glasses straighten?

The child whose eyes are held straight by glasses will be seen once or twice a year. On each visit an attempt will be made to weaken the glasses. Children whose eyes are adequately straight with proper glasses are not candidates for surgery. Children whose eye alignment improves but not satisfactory may need surgery and glasses.

When glasses straighten a child’s eyes those glasses can usually be weakened and hopefully eliminated as a child grows older. Farsightedness reduces with age. Less farsightedness provokes less focus effort (accommodation). The system also may furnish focus with lesser amounts of inward movement of the eyes.

Parents are delighted when the eyes straighten with proper glasses. They may notice the eyes cross again when the glasses are removed. Sometimes that crossing appears worse than before. Crossing of the eyes upon removal of the glasses suggests only that the glasses are helping. Crossing upon removal may continue until the child either outgrows the farsightedness or readjusts the relationship between focus effort and convergence. Most children whose crossed eyes are straight with glasses begin to maintain good alignment without glasses for ages nine to twelve years. The child with significant farsightedness or other significant optical problems may never be able to maintain good eye alignment without glasses or contacts. (Contact lenses may be substituted for glasses as the child ages).

What if glasses do not straighten?

Strabismus (misaligned eyes) is different in all children. When glasses do the “whole job” nothing further is required. When glasses improve but “don’t do the whole job” surgery is the treatment. Strabismus, like so many other conditions, requires an individualized treatment plan. Treatment goals, briefly stated are to make your child see well with each eye individually; to make the eyes as straight as possible so that they can function as a pair, and to improve appearance. We try to reach these goals by the safest, fastest most effective means. Surgery is the last resort.


Credits: Journal of American Association for Pediatric Ophthalmology and Strabismus


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