Most cataracts are caused by aging. A cataract is a natural clouding of the lens of the eye that happens to everyone with time. Every eye has a lens that is located right behind the iris (or the colored part of the eye). The natural lens of the eye helps to focus the light to the back of the eye and create a clear image. Over time, usually due to aging and sometimes from other causes, the lens can become cloudy. This change is called a cataract. It affects the way the light is focused to the back of the eye and, therefore, affects the eye’s ability to see a clear image.
There are several different factors that can cause a cataract to form. The most common reason for cataract formation is aging. Over time the lens becomes cloudy and develops a yellow color. This is typically a very slow process that happens over many years or even decades. These cataracts are called nuclear cataracts or nuclear sclerosis. This change in the lens causes a very gradual blurring of the vision and often leads to a yellow tint to the vision. Due to the slow, progressive change symptoms are often not noticeable until they start interfering with daily activities. Other common symptoms include glare from bright sunlight or headlights when driving at night and need for more light with fine vision like reading. Factors that have been found to contribute to formation of nuclear cataracts are UV exposure, smoking and previous eye surgeries.
A posterior subcapsular cataract (PSC) is another type of cataract. This occurs when a haziness forms on the back side of the lens and causes many of the same symptoms as nuclear cataracts including blurred vision, glare with lights and need for better lighting. PSC often forms much faster than nuclear cataracts and patients often notice progressive worsening of the vision over months or years. PSC cataracts can occur as a result of aging but can also be associated with other medical conditions including diabetes, use of oral steroids, and other eye diseases such as retinitis pigmentosa.
Cataract From Trauma
Trauma to the eye or head is another cause of cataract formation. Unlike other types of cataracts, traumatic cataracts often form instantly or very quickly after the injury and cause a dramatic decrease in vision. Traumatic cataracts can form after both blunt trauma (such as a fist or fall) and after trauma which penetrates the eye (for example, from a knife or nail). Damage to other ocular structures at the time of injury can sometimes increase risk of complications during removal of traumatic cataracts.
Cataracts can also form prior to or shortly after birth and these are called congenital cataracts. These cataracts are less common than the cataracts which present in adults, however, they can interfere with important eye development in the first few years of life and lead to permanent vision loss if not corrected. Congenital cataracts are sometimes associated with other medical conditions, however, they can also be inherited or appear without a known cause.
Treatment for cataracts requires cataract surgery which removes the clouded natural lens of the eye and replaces it with an artificial lens implant. This surgery is performed in a surgery center or hospital as an outpatient, meaning the patient is sent home the same day as surgery. Significant vision improvement is commonly noticed after cataract surgery and some people are eligible for upgraded lens implants which reduce glasses dependence after surgery. An evaluation with an ophthalmologist will determine if cataracts are affecting vision in a significant way to need cataract surgery.
Basic Clinical Science Course (BCSC) of the American Academy of Ophthalmology. Section 11. 2006 – 2007
Cataract in the Adult Eye: Surgery and Diagnostic Procedures. Preferred Practice Patterns.American Academy of Ophthalmology. September 2006