Refractive Errors

Understanding Your Vision

The most common impairment of vision is caused by errors in refraction (or focus). Refraction occurs when light enters the eye through the cornea and lens. Refractive errors result when light rays do not come to a focus on the retina, causing the conditions of myopia (nearsightedness), hyperopia (farsightedness), or astigmatism.

Today, experts at the Cornea and Laser Eye Institute – Hersh Vision Group can diagnose and treat refractive errors and corneal disorders using sophisticated equipment and advanced procedures.

There are three available methods to help correct refractive errors. The first two use lenses to redirect the incoming light to focus and include glasses and contact lenses. The third is an excimer laser refractive procedure such as LASIK or LASEK/PRK which can reshape the cornea to better focus incoming light.

The patient who is completely satisfied with glasses or contact lenses may not choose a refractive procedure. These procedures are designed to decrease dependency on glasses and contact lenses for those people who have trouble with them, or feel they would benefit in their daily activities by having less dependency on glasses or contacts.

1. Nearsightedness (myopia)

A nearsighted patient cannot see clearly at a distance. This results from light being focused before it reaches the retina. Therefore, images are unfocused.

Treatment alternatives:
LASIK (Laser in situ keratomileusis)
PRK/LASEK (Photorefractive keratectomy/epithelial LASIK)

2. Astigmatism

With astigmatism, the cornea is football shaped, not round. This leads to images being unfocused.

Treatment alternatives:
PRK/LASEK (Photorefractive keratectomy/epithelial LASIK)
Intacs for keratoconus

3. Farsightedness (hyperopia)

A farsighted patient can see clearly at a distance, but cannot see images that are near. This results from light not being focused strongly enough to form a clear image on the retina.

Treatment alternatives:
LASIK (Laser in situ keratomileusis)
PRK/LASEK (Photorefractive keratectomy/epithelial LASIK)

4. Presbyopia

After about 40 years of age, the lens of the eye cannot focus strongly for closeup vision and reading glasses become necessary. This occurs at earlier ages in patients who are farsighted.


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