Astigmatism occurs when the cornea, the clear, dome-shaped tissue that covers the front of the eyeball is more oval or egg shaped like a football instead of round like a basketball. This creates two focal points instead of one. As a result, light rays entering the eye are focused to a blurry spot rather than a sharp point on the retina in the back of the eye.
Farsightedness, or hyperopia, is the condition in which the eye focuses on distant objects better than on objects closer to the eye. The focal point in hyperopia is beyond the horizon so nearby objects appear very blurry, but in severe cases even distance vision can be somewhat distorted. This happens when light rays refract, or bend, incorrectly in the eye. The eye is designed to focus images directly on the surface of the retina; when the cornea is incorrectly curved, light rays focus behind the surface of the retina, producing a blurry image.
Hyperopia can be treated in a variety of ways. The most common is a pair of reading glasses or contact lenses. Hyperopia can also be treated with invasive or non-invasive medical procedures, including the laser surgeries PRK (photorefractive keratectomy), LASIK (laser-assisted in situ keratomileusis), and cataract surgery.
Nearsightedness, or myopia, is a vision condition in which nearby objects are clear and distant objects appear blurry. This may be caused by excess corneal curvature or an eye that is longer than normal , both of which affect the way light is bent upon entering the eye and whether it focuses properly on the retina. In myopia, the light rays are focused in front of the retina.
Eyeglasses and contact lenses are common methods of correcting nearsightedness. Eyewear may be used for certain activities, like watching television or driving, or for all activities. Alternately, vision correction procedures such as LASIK, PRK, and even cataract surgery are highly effective at treating this condition.
Presbyopia is a natural change in our eyes’ ability to focus. It occurs when the soft crystalline lens of the eye loses flexibility and starts to harden. This loss of flexibility affects the lens’ ability to focus light in the eye, causing nearby objects to look blurry. Presbyopia happens to everyone starting in our 40s or 50s – even in patients who have had laser vision correction.
The effects of presbyopia can be corrected with glasses or contact lenses, including bifocals and multifocals; multifocal lens implantation, including Crystalens™, ReZoom® and ReSTOR®; and monovision refractive surgery. Laser surgeries such as LASIK and PRK cannot correct presbyopia because they reshape the cornea rather than treat the lens unless a monovision treatment is performed.