Refractive errors, also known as ametropias, are common eye conditions that cause blurred or distorted vision. They affect the eye’s ability to focus light correctly on the retina, resulting in vision problems. The main refractive errors include myopia, hyperopia, astigmatism, and presbyopia.

1. Myopia

Myopia, also known as nearsightedness, is characterized by difficulty seeing distant objects clearly. It generally occurs when the eyeball is too long in relation to the eye’s optical power. Images are focused in front of the retina rather than directly on it, causing blurred distance vision. People with myopia can usually see nearby objects clearly but require eyeglasses or contact lenses to correct their distance vision.

2. Hyperopia

Conversely, hyperopia, also known as farsightedness, occurs when the eye is shorter than normal or when the cornea is too flat. This causes light to focus behind the retina, resulting in blurred near vision. People with hyperopia can often compensate when looking at nearby objects, but they may experience difficulty seeing them clearly, particularly as they age.

3. Astigmatism

Astigmatism results from an irregular curvature of the cornea or lens, causing images to appear blurred or distorted at all distances. People with astigmatism may experience unclear or distorted vision both near and far. This condition can occur alongside myopia or hyperopia and often requires cylindrical corrective lenses to improve visual clarity.

4. Presbyopia

Presbyopia is an age-related condition that usually becomes noticeable in the early to mid-forties. It results from a loss of flexibility in the eye’s natural lens, reducing the ability to focus on nearby objects. Symptoms include difficulty reading at close range and performing tasks that require detailed near vision. People with presbyopia may need reading glasses or progressive lenses to correct their near vision.

5. Anisometropia

Anisometropia occurs when the two eyes have different refractive errors. For example, one eye may be myopic while the other is hyperopic. This can cause double vision, headaches, or eye strain. Correction may include contact lenses or eyeglasses with a different prescription for each eye.

An accurate diagnosis of refractive errors is essential for proper correction. Eye-care professionals, such as optometrists and ophthalmologists, perform eye examinations to measure refractive errors and prescribe appropriate optical corrections. Treatment options include eyeglasses, contact lenses, and, in some cases, refractive procedures such as laser eye surgery.