Cataracts are changes in clarity of the natural lens inside the eye that gradually degrade visual quality. The natural lens sits behind the colored part of the eye (iris) in the area of the pupil, and cannot be directly seen with the naked eye unless it becomes extremely cloudy. The lens plays a crucial role in focusing unimpeded light on the retina at the back of the eye. The retina transforms light to a neurologic signal that the brain interprets as vision. Significant cataracts block and distort light passing through the lens, causing visual symptoms and complaints.
Cataract development is usually a very gradual process of normal aging but can occasionally occur rapidly. Many people are in fact unaware that they have cataracts because the changes in their vision have been so gradual. Cataracts commonly affect both eyes, but it is not uncommon for cataracts in one eye to advance more rapidly. Cataracts are very common, affecting roughly 60% of people over the age of 60. When people develop cataracts, they begin to have difficulty doing activities they need to do for daily living or for enjoyment. Some of the most common complaints include difficulty driving at night, reading, participating in sports such as golfing, or traveling to unfamiliar areas; these are all activities for which clear vision is essential.
All cataracts are fundamentally a change in the clarity of the overall lens structure; however, cataracts may result either early in life or as a result of aging, and different portions of the lens may be more affected than others. Cataracts that occur at birth or present very early in life (during the first year of life) are termed congenital or infantile cataracts. These cataracts require prompt surgical correction or they may prevent the vision in the affected eye from developing normally. When the central portion of the lens is most affected, which is the most common situation, these are termed nuclear cataracts. The outside of the lens is called the lens cortex, and when opacities are most visible in this region, the cataracts are called cortical cataracts. There is an even more specific change that occasionally happens, when the opacity develops immediately next to the lens capsule, either by the anterior, or more commonly the posterior, portion of the capsule; these are called subcapsular cataracts. Unlike most cataracts, posterior subcapsular cataracts can develop rather quickly and affect vision more suddenly than either nuclear or cortical cataracts.
Having cataracts is often compared to looking through a foggy windshield of a car or through the dirty lens of a camera. Cataracts may cause a variety of complaints and visual changes, including blurred vision, difficulty with glare (often with bright sun or automobile headlights while driving at night), dulled color vision, increased nearsightedness accompanied by frequent changes in eyeglass prescription, and occasionally double vision in one eye. Some people notice a phenomenon called “second sight” in which one’s reading vision improves as a result of their increased nearsightedness from swelling of the cataract. A change in glasses may help initially once vision begins to change from cataracts; however, as cataracts continue to progress and opacify, vision becomes cloudy and stronger glasses or contact lenses will no longer improve sight.
Cataracts are usually gradual and usually not painful or associated with any eye redness or other symptoms unless they become extremely advanced.
The standard cataract surgical procedure is typically performed in either a hospital or in an ambulatory surgery center. The most common form of cataract surgery today is a process called phacoemulsification. With the use of an operating microscope, your surgeon will make a very small incision in the surface of the eye in or near the cornea. A thin ultrasound probe is inserted into the eye that uses ultrasonic vibrations to dissolve (phacoemulsify) the clouded lens. These tiny fragmented pieces are then suctioned out through the same ultrasound probe. Once the cataract is removed, an artificial lens is placed into the same thin capsular bag that the cataract occupied. This intraocular lens is essential to help your eye focus after surgery.
As the natural lens plays a vital role in focusing light for clear vision, artificial-lens implantation at the time of cataract surgery is necessary to yield the best visual results. Because the implant is placed in or near the original position of the removed natural lens, vision can be restored, and peripheral vision, depth perception, and image size should not be affected. Artificial lenses are intended to remain permanently in place, require no maintenance or handling, and are neither felt by the patient nor noticed by others.
There are a variety of intraocular lens styles available for implantation, including monofocal, toric, and multifocal intraocular lenses.