What is a cataract?
A cataract is a clouding of the lens of the eye. Just as a cloudy camera lens would reduce the quality of a photograph, a cataract makes the vision blurry. The following image shows a clear lens above and a cloudy lens (cataract) below:
What causes cataracts?
Cataracts are most often the result of aging, but there are a number of causes. Vitrectomy surgery almost always causes progression of a cataract. Other relatively common causes of cataracts include inflammation inside the eye, diabetes, taking corticosteroid medications (e.g., prednisone) and eye injuries.
Where is a cataract located in the eye?
The lens of the eye, where cataracts develop, is located immediately behind the iris, which is the colored part of the eye that makes the pupil (the hole in the iris). Light enters the eye through the cornea, on the very surface of the eye, and then passes through the pupil, the lens and the vitreous (the gel in the back of the eye) before reaching the retina, located along the back of the eye. The following image shows all of these structures with labels:
The following video describes how the eye sees, including how the lens focuses light on the retina:
What part of the lens becomes cloudy when a cataract develops?
Most cataracts involve clouding of the "nucleus", which is the inner part of the lens. Less often, clouding can develop in the back portion of the lens, just inside the "capsule", which is the outer lining of the lens. You can think of the lens like an M&M candy; the nucleus is like the chocolate center, and the capsule is like the outer candy coating. The following video describes a "nuclear" cataract:
How is a cataract treated?
Cataract surgery is used to treat a cataract. Thinking of the lens as an M&M candy, the surgeon makes a hole in the front portion of the "candy coating" (capsule), scoops out the cloudy "chocolate center" (nucleus) and then places a man-made lens implant inside what remains of the capsule. Below is a drawing of how cataract surgery works:
Below is a photograph from an actual cataract operation:
The photograph below shows a lens implant sitting where the cataract once was:
The following video describes how cataract surgery is performed:
Can a cataract come back after it is removed?
Once the contents of the lens have been removed in cataract surgery, they do not return. However, the clear lining of the lens, called the "capsule", can become cloudy following cataract surgery. This is known as a "secondary cataract" or "after cataract". A laser can be used to restore clear vision by creating a hole in the cloudy capsule. The following video describes the procedure, known as "YAG posterior capsulotomy":
Will the patient continue to need glasses after cataract surgery?
The strength of the implant can be tailored for the patient to reduce or eliminate the need for glasses. Lens implants are now available that can correct the distance vision and the near vision, in which case the patient may not even require reading glasses. Some patients do require glasses for distance vision and/or near vision after cataract surgery. The following video describes how lens implants (also known as "intraocular lens implants", or "IOL's") work:
Are there more than one kind of lens implant (IOL)?
Yes. The surgeon can insert one of several different types of lens implants, depending on how the patient wants to correct the vision. The following video describes the "monofocal" IOL:
The following video describes the patient's options for monofocal IOL's:
The following video describes a condition called "presbyopia", where the eye is unable to focus on objects that are close, as in reading:
The following video describes the "multifocal IOL", which enables the patient to see objects close up and far away:
The following video describes the "accommodative IOL", which also enables the patient to see objects close up and far away, but works differently from the multifocal IOL:
Astigmatism is often confusing to patients. It is a common condition in which the eye does not focus light in a uniform way. Imagine that you have a basketball, and you cut it exactly in half. Each half of the basketball would resemble the cornea, which has a spherical surface. If that surface is perfectly spherical, there is no astigmatism. However, many people have corneas whose shape resembles half of a football rather than a basketball, where the curvature is not uniformly spherical. As a result, the eye does not focus light in a uniform manner. This is astigmatism. The following video describes the "toric IOL", which corrects astigmatism:
How is cataract surgery different from retina surgery?
Cataract surgery is usually shorter in duration than retina surgery, although some vitrectomies can be almost as short with current instruments and techniques. Unlike retina surgery, patients often see better the first day after cataract surgery. Both cataract surgery and retina surgery are often painless, but the patient is more likely to experience discomfort after retina surgery than after cataract surgery. Also unlike retina surgery, patients do not have to maintain any certain head position after cataract surgery.