AL Noor Eye Hospital


Refractive Errors

Refractive errors are responsible for half of the cases of avoidable vision impairment, with over 153 million people affected globally. If not detected and corrected early, these errors can have negative impacts on eye development, academic performance, and social functioning. In individuals over the age of 50, refractive errors can lead to accidents, social problems, and emotional difficulties. Developed nations experience two-thirds of all vision impairment due to refractive errors and their under-correction.

There are four primary types of refractive errors that affect vision. Myopia, also known as near-sightedness, impairs the ability to see distant objects as the refracted light focuses in front of the retina instead of on it. Hyperopia, or far-sightedness, makes it difficult to see near objects as the refracted light focuses behind the retina. Presbyopia, commonly observed in individuals aged 40 and above, affects the eye’s lenses, causing them to lose their ability to adjust their shape for focusing on nearby objects, particularly during reading. Astigmatism, characterized by blurred vision, is caused by an irregularly shaped cornea and can be symmetrical or asymmetrical. Anisometropia refers to a significant difference in refractive errors between the two eyes, often resulting in a difference in image size and potential fusion difficulties.

Common symptoms of refractive errors include double or blurred vision, rainbow-colored halos around the eyes, constant squinting, headaches, eye strain, difficulty focusing on computer screens or while reading, dizziness, and in some cases, nausea and vomiting.

The accuracy of focus depends on various factors, including the integrity and health of the cornea, lens, and vitreous humor, as well as the shape of the cornea and lens. Changes in these factors with age can lead to refractive errors. An emmetropic eye refers to a normal eye with perfect focus, while ametropia is the global term encompassing any refractive error. Refractive errors occur when there are defects or errors in the corneal curvature, lens shape, anterior chamber depth and health, accommodation power of the eyes, or the diameter and length of the eye from front to back.

The diagnosis of refractive errors involves visual acuity testing, refraction to determine the refractive error, and a comprehensive eye examination. Regular visual acuity testing and refraction should be done every 1 or 2 years, with the aim of detecting refractive errors in children before they interfere with learning. A comprehensive eye examination conducted by an ophthalmologist or an optometrist should accompany refraction.

The treatment options for refractive errors primarily include glasses, contact lenses, and surgery. Glasses are the most common form of treatment, providing the correct power to minimize refractive errors and improve vision clarity. Contact lenses are an alternative for individuals who prefer not to wear glasses, as they sit on top of the eyes and correct refractive errors. Surgery, specifically laser surgery known as LASIK, is considered the most effective treatment option in cases where glasses or contacts are insufficient. However, surgery is typically considered a last resort.

In conclusion, refractive errors are a prevalent eye condition that can significantly impact vision and overall quality of life. Early detection, regular eye examinations, and appropriate treatment options such as glasses, contact lenses, or surgery can help correct refractive errors and improve visual acuity.