If vision in one eye is very different than vision in the other eye due to refractive error, you have anisometropia. Symptoms may include headaches or dizziness. It’s likely that you’ll need corrective lenses.

Overview

What is anisometropia?

Anisometropia means that vision in one eye is worse than the vision in the other due to a difference in refractive error. Anisometropia is pronounced a-nuh-sow-muh-trow-pee-uh.

Refractive error is an imbalance between the light-focusing power of the eye and the length of the eye. This leads to blurred images on the retina. Refractive error is expressed as the glasses’ or contact lenses’ strength in diopters required to bring a distance image into focus on the retina.

One commonly used definition of anisometropia is that the difference in correction between your eyes must be greater than 1 diopter.

What are the types of anisometropia?

There are six clinical types of anisometropia: simple, compound, mixed, simple astigmatic, compound astigmatic and mixed astigmatic.

Simple anisometropia

This type of anisometropia happens when one eye has normal vision and the other eye is nearsighted or farsighted. You can describe the normal eye as being emmetropic.

If you have one normal eye and one nearsighted (or myopic) eye, you have simple myopic anisometropia. Myopia is the medical name for being nearsighted.

If you have one normal eye and one farsighted (hypermetropic) eye, you have simple hypermetropic anisometropia. Hypermetropia and hyperopia are both terms for farsightedness. You might also see the term hyperopic anisometropia.

Compound anisometropia

Compound anisometropia happens when both of your eyes have the same type of vision problem but one eye is worse than the other.

If both of your eyes are nearsighted but one is much more nearsighted than the other, you have compound myopic anisometropia.

If both of your eyes are farsighted but one is much more farsighted than the other, you have compound hypermetropic anisometropia.

Mixed anisometropia

If one eye is nearsighted and the other is farsighted, you have mixed anisometropia. Another name is antimetropia.

Simple astigmatic anisometropia

This type of anisometropia also involves astigmatism. This type of vision problem results from your eye shape. The shape of your eye is like that of a football or the back of a spoon. The shape causes light to refract unevenly. Refraction means that light changes direction when it enters your eye at an angle.

If you have simple astigmatic anisometropia, one eye is normal and the other eye has astigmatism and either farsightedness or nearsightedness.

Compound astigmatic anisometropia

If you have compound astigmatic anisometropia, you have astigmatism in both eyes, but one eye needs much more correction than the other. In this type, both of your eyes are either farsighted or nearsighted.

Mixed astigmatic anisometropia

If you have mixed astigmatic anisometropia, you have astigmatism is both eyes, but one eye is farsighted and the other is nearsighted.

Who does anisometropia affect?

Anisometropia can affect anyone. Having anisometropia can result in having amblyopia and strabismus. Amblyopia is also sometimes called lazy eye. Strabismus is sometimes called crossed eyes.

Anisometropia is a relatively common condition and is estimated to affect up to 28% of people.

Symptoms and Causes

What are the symptoms of anisometropia?

You’re unlikely to know that your child has anisometropia unless you can see that their eyes are crossed or wandering. Children aren’t likely to mention that they can’t see out of one eye as well as they can out of the other. You probably won’t know about anisometropia until you or your child have a vision screening or an eye exam.

Small differences in refractive errors between the two eyes might not cause problems. If there are symptoms from long-term untreated anisometropia, they might include:

What causes anisometropia?

Researchers aren’t sure what causes the refractive errors that result in developing anisometropia. It’s likely that there could be both genetic and environmental reasons behind poor vision.

Anisometropia can happen after cataract surgery is performed on one eye at a time.

Diagnosis and Tests

How is anisometropia diagnosed?

Your eye care specialist will do a thorough eye examination to find out how well you or your child can see.

Management and Treatment

How is anisometropia treated?

Anisometropia is treated by correcting your eyesight through glasses, contact lenses or surgery.

If you or your child has developed amblyopia (one eye is weaker than the other), the treatments may include forcing the brain to use the weaker eye by:

  • Patching the stronger eye.
  • Using eye drops that blur vision in the stronger eye.
  • Using filtered glasses that block vision in the stronger eye.

Outlook / Prognosis

What can I expect if I have anisometropia?

If you have treatment for anisometropia when you’re very young, the outlook is quite good. Your eyesight might stabilize and you may not need corrective lenses.

Older children and adults will probably need to continue to wear corrective lenses.

Prevention

How can I prevent anisometropia?

There’s currently no way to prevent refractive errors.

Living With

When should I see my healthcare provider?

If you see your child squinting or you have any reason to believe your child is having difficulty seeing, contact your healthcare provider. Finding vision problems early leads to early treatment.

Additional Common Questions

What is the difference between anisometropia and astigmatism?

Anisometropia means that the vision in one eye is significantly different than the vision in the other eye. Astigmatism is a vision problem caused by the shape of your eye. Rather than being round, your eye is shaped like a football or the back of a spoon.

What is the difference between aniseikonia and anisometropia?

Aniseikonia refers to what happens when one eye sees an image that’s sized differently than the other eye. The difference in magnification may be happening as a result of anisometropia or because of damage to the retina.

A note from Wockr

Vision is important. Like any other medical problem, finding and treating eye conditions early is best. It’s important to have vision tested in young children and adults on a regular basis. Glasses and contact lenses can correct refractive errors and provide clear vision. Anisometropia is a condition that can be treated with corrective lenses.