What is anisometropia?

Anismetropia is a difference in refractive error (prescription) between the two eyes.

How can laser eye surgery cause anisometropia? (posted: jan 2005)

The three basic mechanisms which cause anisometropia are overcorrection, undercorrection, and regression resulting in a different amount of refractive error in one eye versus the other.

Some other variations include: (a) failed attempt at monovision, where there was an intent to achieve different refractive errors in each eye but too large a gap was left, and (b) cases where only one eye was treated, either because the patient chose to do one eye at a time or because there was a complication or poor outcome in the first eye which made surgery for the second eye inadvisable or undesirable.

How is anisometropia diagnosed?

Anisometropia is detected with a basic manifest refraction (the "better 1, better 2?" test to determine your prescription in each eye).

How can anisometropia be corrected? (posted: jan 2005)

The options for correcting anisometropia depends on the severity. Tolerance for anisometropia varies with the individual and tolerance can sometimes be acquired over time. The common rule of thumb is that the average person can correct up to 2 dioptres of difference between the eyes with glasses. After that, the options are contact lenses and more surgery. More surgery in this case means a retreatment ("enhancement") to correct the refractive error.

The most challenging cases we come across are typically those where the patient has a large imbalance and has excessively dry eyes and/or is contact lens intolerance for some reason. For such patients, further surgery may appear to be the only option, however, their existing dry eye condition, or causes thereof, may also make further surgery inadvisable. Sometimes a large gas permeable lens - scleral or mini-scleral - can help to treat both the vision imbalance and the dry eye at the same time.

Where can I get more information about anisometropia?

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