A cataract is a clouding that develops in the crystalline lens of the eye, varying in degree from slight to complete opacity and obstructs the passage of light. Cataracts typically progress slowly to cause vision loss, and are potentially blinding if untreated. The condition usually affects both eyes, but almost always one eye is affected earlier than the other.
Signs and symptoms
As a cataract becomes more opaque, clear vision is compromised. Colors become less vivid and glare can be a problem, as light is scattered by the cataract into the eye. Early in the development of age-related cataract, the power of the lens may be increased, causing nearsightedness (myopia).
Several factors can promote the formation of cataracts, including:
- long-term exposure to ultraviolet light
- exposure to ionizing radiation
- secondary effects of diseases such as diabetes or hypertension
- advanced age
- trauma (possibly much earlier in life)
- positive family history of early onset cataracts
- some drugs can induce cataract development
Although cataracts have no scientifically proven prevention, wearing ultraviolet-protecting sunglasses or UV filtering contact lenses may slow the development of cataracts.
The operation to remove cataracts can be performed at any stage of their development. There is no longer a reason to wait until a cataract is “ripe” before removing it. However, because all surgery involves some risk, it is usually worth waiting until there is some change in vision before removing the cataract.
Cataract surgery consists of removing the lens, but leaving the majority of the lens capsule intact. High frequency sound waves (phacoemulsification) are used to break up the lens before extraction. The cataractous lens is removed and replaced with a plastic lens (an intraocular lens implant) which stays in the eye permanently.
Cataract operations are usually performed using a local anaesthetic, and the patient is allowed to go home the same day. Until recently, implanted lenses were optically simple and provided clear, but often less than perfect distance vision. Improvements in intraocular lens technology allow implanting a multifocal lens to create a visual environment in which patients are less dependent on glasses. In addition, intraocular lenses are now available to correct preexisting astigmatism.
Serious complications are possible after cataract surgery, including sight threatening infection (endophthalmitis) and retinal tears or detachment. A common complication following cataract surgery is posterior capsular opacification – a condition in which the eye structure holding the implant (posterior capsule) gets cloudy. This occurs in 30 – 50% of all patients having cataract surgery but is easily cleared post surgically with a brief outpatient procedure using a YAG laser.
In the United States, age-related lenticular changes have been reported in 42% of those between the ages of 52 and 64, 60% of those between the ages 65 and 74, and 91% of those between the ages of 75 and 85.