Aniseikonia

What is aniseikonia?

Aniseikonia (pronounced “an-EYE-sy-CO-nee-uh”) is an eye condition that affects the size or clarity of something you’re looking at. If you have aniseikonia, you’re aware of a difference between what you see in one eye compared to the other. It happens when there’s a difference in how each of your eyes magnifies objects you see.

When your eyes work like they should, the magnification in both eyes is the same (or so close to it that your brain can adjust for the difference). When the magnification in each eye isn’t the same, the size or shape of objects you see can look different to each eye. Your brain has trouble because your eyes aren’t reporting the same thing.

Think of it like you’re standing between two people who are both shouting very loudly at you, and each is saying something different. It can feel challenging to try and understand either (and you might get a headache if you try) because they’re competing for your brain’s full attention. Aniseikonia is like that, but with your eyes. And because your eyes are crucial for balance, coordination and more, this condition’s effects can spill over and cause problems in many parts of your daily life.

Are there different types of aniseikonia?

There are two main types of aniseikonia:

• Optical aniseikonia. This kind of aniseikonia happens because of differences in how light enters and passes through each of your eyes.
• Retinal aniseikonia. This kind of aniseikonia happens because of differences between the retinas at the backs of your eyes.

What are the symptoms of aniseikonia?

When your eyes work together properly, your brain can process the signals from each eye and “fuse” them together into a single, seamless picture. Your brain can adjust for small differences, so milder aniseikonia doesn’t usually cause symptoms. But if the differences are big enough, your brain can’t adjust, and that’s when symptoms happen.

Symptoms can include:

• Eye misalignment (strabismus)
• Coordination and balance difficulties
• Diplopia (double vision)
• Dizziness
• Eye strain or eye fatigue (asthenopia)
• Headaches

Children, in particular, may also develop lazy eye (amblyopia). That’s because their visual system hasn’t finished developing and tries to compensate for the difference between eyes. As it does, it stops using the input from one eye and the unused eye drifts out of alignment.

What causes aniseikonia?

There are many different causes of aniseikonia. Your type of aniseikonia may vary depending on what’s causing it, whether it’s conditions in your eye, brain or a result of a medical procedure. Certain medications can also cause changes that lead to aniseikonia. Your eye care specialist, healthcare provider and/or pharmacist is the best source of information about medications that might do this.

Optical changes

Aniseikonia can happen when something affects how light passes through your eyes to your retinas, including:

• Differences in how well you can see with each eye (anisometropia)
• Corneal diseases, especially ones that distort the cornea’s shape, like keratoconus
• Lens conditions like one-sided cataracts or having a missing lens (aphakia)
• Eye injuries that change the shape of your cornea, lens or other parts of your eye.
• Connective tissue disorders like Marfan syndrome or Ehlers-Danlos syndrome

Retinal changes

Retinal conditions that can cause aniseikonia include:

• Macular pucker
• Retinal injuries, like tears or detachments
• Conditions that compress your retina and optic nerve, like glaucoma
• Central serous retinopathy
• Diabetes-related retinopathy
• Wet age-related macular degeneration

Optical procedures

Medical procedures that can cause aniseikonia include:

• Laser vision correction surgeries like LASIK, photorefractive keratotomy (PRK) or small incision lenticule extraction (SMILE)
• Eye lens replacement with an artificial intraocular lens (IOL)

Procedures like vitrectomy or scleral buckle that replace the vitreous humor in your eye with silicone oil or a gas bubble to help your eye maintain its shape while it heals

How is aniseikonia treated?

Aniseikonia treatment varies depending on the type you have.

• Optical aniseikonia. The main treatments for optical aniseikonia are eyeglasses or contact lenses. Vision correction surgery may also help.
• Retinal aniseikonia. Retinal aniseikonia is harder to treat. It usually involves treating the underlying cause, if possible. It can also involve special glasses made with iseikonic lenses. “Iseikonic” means these lenses balance magnification for both of your eyes.

If none of the above treatments work or aren’t an option to begin with, the only remaining way to treat this condition is a method called “occlusion.” That means covering one eye entirely with a patch or something similar. Doing that keeps your brain from having to process two sources of competing input. Fortunately, this isn’t usually necessary.

Is aniseikonia preventable?

Aniseikonia often happens unpredictably, so there’s no way to prevent it entirely. But you can take steps to reduce your risk of developing it or limit how severe it gets.

• Get regular eye exams. An eye care specialist can often detect many vision issues that could lead to aniseikonia. Early detection can help prevent aniseikonia or limit how severe it becomes and how much it disrupts your life.
• Manage or monitor chronic conditions. Many chronic conditions can cause eye changes that lead to aniseikonia (either directly or indirectly). Monitoring and managing chronic conditions can catch them early or limit their impacts on your sight.
• Don’t ignore symptoms. Diagnosing aniseikonia early can help limit how this condition affects you. And more importantly, it can help uncover underlying conditions that need early diagnosis and treatment.

What’s the outlook for aniseikonia?

In general, aniseikonia isn’t dangerous, but it can be disruptive. And while aniseikonia itself isn’t curable, some of the conditions that cause it can be. But even if your aniseikonia isn’t curable, your eye care specialist can help you manage this condition.

When should I see my eye care specialist?

Talk to your eye care specialist if you experience any changes in your vision or other symptoms of aniseikonia, especially if they start to interfere with your usual activities. Your eye care specialist will tell you how often to come in for eye exams, and this can sometimes vary.

What should I ask my provider about aniseikonia?

If you have aniseikonia, you may want to ask your eye care specialist the following:

• What should I expect?
• Will my aniseikonia go away?
• What are my options for treatment?
• Can I continue doing my regular activities with aniseikonia?
• How often should I have follow-up appointments?