Refractive error

Refractive Errors: An Overview

A refractive error refers to a group of eye disorders resulting from the eye's inability to correctly focus light onto the retina. This is primarily due to the shape and structure of the eye. The most common types of refractive errors are astigmatism, myopia (nearsightedness), and hyperopia (farsightedness).

Illustration of light focusing in various refractive errors.

Types of Refractive Errors

Astigmatism

• Definition: Astigmatism arises when the cornea or the lens inside the eye has an uneven curvature.
• Symptoms: Vision may be blurry at any distance and might be accompanied by eye strain or headaches.
• Causes: Most cases are hereditary, but it can also be due to an eye injury or surgery.

Myopia (Nearsightedness)

• Definition: Myopia is a condition where distant objects appear blurry while close objects can be seen clearly.
• Symptoms: Difficulty seeing distant objects, such as road signs or a blackboard.
• Causes: An elongated eyeball or a cornea that is too curved.

Hyperopia (Farsightedness)

• Definition: Hyperopia means that the light entering the eye is focused behind the retina. Close objects appear blurry, while distant objects are usually clear.
• Symptoms: Nearby objects, like reading material, appear blurry.
• Causes: A shortened eyeball or a flat cornea.

Causes of Refractive Errors

While the precise etiology of refractive errors can vary, general causes include:

• Genetics: Refractive errors can run in families.
• Age: Presbyopia is an age-related condition where the eye's lens loses flexibility, making it difficult to focus on close objects.
• Environmental factors: Excessive near vision tasks, like reading or computer use, might be associated with developing myopia.
• Trauma or surgery: Injuries or specific surgeries can change the eye's structure, leading to refractive errors.

Diagnosis and Treatment

Refractive errors are diagnosed using a comprehensive eye examination, which might include:

• Visual acuity test
• Refraction test
• Eye focusing and movement tests

Treatment options include:

• Eyeglasses or Contact Lenses: The most common correction method.
• Refractive Surgery: Procedures like LASIK can reshape the cornea.
• Orthokeratology: Special contact lenses worn overnight to reshape the cornea temporarily.

Prevention and Management

While refractive errors can't be entirely prevented, regular eye examinations ensure early detection and appropriate intervention. Protecting the eyes from excessive strain by following the 20-20-20 rule (every 20 minutes, look 20 feet away for 20 seconds) can also be beneficial.

Conclusion

Refractive errors are common vision problems that occur when the eye fails to focus light uniformly on the retina. Though they can cause vision disturbances, various treatments are available to restore clear vision.

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Source: Data courtesy of the U.S. National Library of Medicine. Since the data might have changed, please query MeSH on Refractive error for any updates.

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