Metamorphopsia is a visual defect that causes linear objects, such as lines on a grid, to look curvy or rounded. It’s caused by problems with the eye’s retina, and, in particular, the macula.

The retina is a thin layer of cells at the back of the eye that sense light and sends — via the optic nerve —impulses to the brain, allowing you to see. The macula sits in the center of the retina and helps you to see things in clear detail. When either of these things is impacted by disease, injury, or age, metamorphopsia can result.

Metamorphopsia affects central vision (versus peripheral, or side vision) and distorts the appearance of linear objects. It can occur in one eye or both. When you have metamorphopsia, you may find that:

  • Straight objects, like a signpost, appear wavy.
  • Flat things, such as the sign itself, look rounded.
  • Shapes, such as a face, can appear distorted. In fact, some have likened metamorphopsia to looking at a Picasso painting, with its multidimensions.
  • Objects appear smaller than they are (called micropsia) or larger than they are (macropsia). According to research published in Ophthalmic Research, micropsia is more common than macropsia.

Metamorphopsia can be a symptom of a variety of eye disorders that affect the retina and macula. These include:

Age-related macular degeneration (AMD)

This is a common, degenerative disorder affecting the macula, the part of the eye that lets you see things in sharp focus and fine detail. The National Eye Institute reports that age-related macular degeneration (AMD) is:

  • the leading cause of vision loss among those 50 and older
  • not apt to occur until after age 60
  • linked to genetics
  • possibly related to environmental factors like diet and smoking

In one study looking at AMD and metamorphopsia:

  • 45 percent of study subjects had visual distortions of lines (for example, newsprint or computer displays)
  • 22.6 percent noticed distortions of window frames and bookshelves
  • 21.6 percent had distortions of lines of bathroom tile
  • 18.6 percent experienced distortions of faces

Wet AMD is far more likely to produce metamorphopsia than dry AMD. Wet AMD is a rare disorder in which blood vessels leak blood and fluid and as a result, damage the macula. In dry AMD, the macula gets thinner due to age and fatty proteins (called drusen) clump under the surface, causing vision loss.

Epiretinal membranes (ERMs)

ERMs (epiretinal membranes) are also called macular puckers. They’re caused by a defect in the surface lining of the retina. This defect can be caused by age, retinal tears, and diseases like diabetes, which affect vascular regions in the eye.

ERMs begin by cells growing on the smooth retinal membrane. This cellular growth can contract which pulls on the retina and causes distorted vision.

About 20 percent of Americans over the age of 75 have ERMs, although not all cases are severe enough to require treatment.

Macular edema

This is a condition in which fluid builds up in the macula. This fluid can leak from surrounding blood vessels that become damaged due to:

  • diseases like diabetes
  • eye surgery
  • certain inflammatory disorders (such as uveitis, or inflammation of the eye’s uvea or middle layer of the eye)

This extra fluid causes the macula to swell and thicken, causing distorted vision.

Retinal detachment

When the retina detaches from the structures that support it, vision gets impacted. This may occur due to injury, disease, or trauma.

A detached retina is a medical emergency and requires immediate treatment to prevent permanent vision loss. Symptoms include “floaters” (specks in your vision) or flashes of light in your eyes.

Macular hole

As the name implies, a macular hole is a small tear or break in the macula. This break can happen due to age. It occurs when the gel that gives the eye its round shape shrinks and contracts, pulling away from the retina and causing tears.

Macular holes usually occur in those over 60. If one eye is affected, you have a 10 to15 percent chance of developing it in the other eye.

Doctors use several techniques — most involving charts or graphs with lines — to help diagnose metamorphopsia. People who see distortions in the lines when there aren’t any are more likely to have a retina or macular problem and subsequent metamorphopsia.

  • Amsler grid. Your doctor may ask you to look at something called the Amsler grid. Much like the grid paper used in geometry class, it has evenly spaced horizontal and vertical lines with a central focal point.
  • Preferential hyperacuity perimeter (PHP). This is a test in which dotted lines with manufactured distortions are flashed before you. You’ll be asked to pick out which lines are misaligned and which aren’t.
  • M-charts. These are charts with either one or two vertical lines made up of small dots, again with a central focal point.

Since metamorphopsia is a symptom of a retina or macular problem, treating the underlying disorder should improve the distorted vision.

For example, if you have wet AMD, your doctor may recommend laser surgery to stop or slow blood leaking from faulty vessels in your retina.

If you have dry AMD, you might be advised to take certain supplements, like vitamins C and E, lutein and zeaxanthin which have been shown to slow the disease.

If you have a detached retina, surgery to reattach it will be necessary. Any related metamorphopsia should improve — but it may take time. In one study, more than half of study subjects still had some metamorphopsia a year after successful surgery for a detached retina.

The distorted vision that is a hallmark of metamorphopsia is a common symptom of retina and macular eye problems. Depending on the underlying condition and its severity, the metamorphopsia may be significant or not. In general, however, once the eye disorder causing the vision problem is treated, the metamorphopsia improves.

Talk to a doctor if you notice any changes in your vision. As with many things, earlier detection and treatment result in a better outcome.