A cataract is a clouding of the normally clear crystalline lens in the eye. This cloudiness interferes with light passing into the eye and causes varying degrees of visual impairment.
Cataract is the most common cause of blindness in the world. The World Health Organisation estimates that nearly 18 million people or 48% of blind people worldwide are blind in both eyes from cataract, and this number is expected to increase as the world’s population ages.
Cataract may be classified into several types depending on the pattern of lens clouding. However, treatment for the various types of cataract is similar. Cataract usually develops in both eyes of an individual although it can develop at different rates in the two eyes.
Eye with cataract
Eye with Intra-ocular lens implanted
Aging is the main risk factor for cataract development. However, there is no specific age at which cataract will start to develop in an individual but the older one is, the more likely he will develop cataract.
Cataract can also be caused or accelerated by other factors such as injury or surgery to the eye, inflammation of the eye, severe short-sightedness, smoking, long-term ultra-violet light exposure, certain drugs (e.g steroids) and certain medical disorders (e.g diabetes mellitus).
While mild cataract causes little or no interference with vision, more severe cataract can result in marked visual impairment and even blindness. Patients with cataract may experience one or more of the following symptoms:
- Blurry or cloudy vision
- Double or multiple vision
- Glare or light sensitivity
- Poor contrast sensitivity
- Decreased colour appreciation
- Increase in short-sightedness
A cataract is usually diagnosed by a medical doctor or an eye care professional.
Visual Acuity Test, Slit-lamp Examination, Anterior Segment Photography, Visual Field Examination and Dilated Retinal Examination can be performed to determine the presence of a cataract and how it is affecting one’s vision. It is not uncommon for a cataract to co-exist with other eye conditions (eg, glaucoma, macular degeneration, diabetic retinopathy, retinal detachment or stroke) that also affect vision. For this reason, it is very important to have a comprehensive eye examination to diagnose or exclude these other conditions before attributing any vision loss solely to a cataract and prior to any surgical intervention. The presence of such a co-existing condition may affect how the cataract surgery should be carried out and the visual outcome following surgery.
Cataract usually progresses slowly and will not resolve by itself. In its early stages, using higher power correcting lenses, magnifiers or brighter lighting may be helpful for some patients. When the cataract is severe enough to affect an individual’s work, recreation or activities of daily living (eg, driving, reading, golf and watching television), cataract surgery is the only option to restore the lost vision.
Cataract surgery is one of the most common major operations performed world-wide. Current cataract surgery techniques involve removing the cloudy lens and replacing it with a new artificial lens called an intraocular lens (IOL).
There are several techniques of cataract surgery and many types of IOLs currently in use. Each is associated with certain advantages and disadvantages. The two most modern cataract surgery techniques are phacoemulsification and femtosecond laser-assisted cataract surgery (FLACS).
Phacoemulsification is the most common surgical technique used in developed countries for cataract surgery. In this procedure, the surgeon makes two small incisions on the cornea. These incisions are just large enough for surgical instruments to pass through.
First, a circular opening is made on the front portion of the lens capsule. Next, an ultrasonic probe is inserted into the eye to break up the cataract into smaller pieces. These tiny lens fragments are then vacuumed out of the eye. Finally, an IOL is inserted into the empty lens capsule to replace the previous cloudy lens. As the incisions in the cornea are small, they are usually self-sealing and no stitching is necessary.
Femtosecond Laser-assisted Cataract Surgery (FLACS) or bladeless cataract surgery is the latest cataract removal technique available currently. It uses a femtosecond laser (commonly used in LASIK surgery) for increased precision and possibly safety compared to conventional phacoemulsification.
The laser is used to create the corneal incisions and to open the lens capsule with very high precision. In addition, the laser assists in breaking up the cataract before an ultrasonic probe is inserted into the eye to complete the lens fragmentation.
As in phacoemulsification, an IOL is inserted into the empty lens capsule to replace the previous cloudy lens at the end of the surgery. No stitching is necessary as the corneal incisions are small and self-sealing.
As FLACS involves more specialised equipment including the femtosecond laser machine, the procedure is more costly than conventional phacoemulsification.
Cataract surgery is one of the safest major surgeries in the world and is usually performed as a day surgery procedure. It has a very high success rate of more than 98% and carries a small risk of complications in the hands of experienced surgeons. The procedure usually takes about 20 to 30 minutes.
Serious and potentially blinding complications of cataract surgery include:
Posterior capsule tear
The back portion of the lens capsule, known as the posterior capsule, is normally retained during cataract surgery to support the IOL. This posterior capsule may tear or rupture during surgery in about one in 100 cases. Certain eye conditions and types of cataract are associated with a higher risk of this complication. This complication is also associated with a slightly higher risk of infection after surgery (8- to 11-fold higher) and subsequent retinal detachment (about 4%). In the event this occurs, the IOL may have to be placed in a slightly different location from the intended position within the lens capsule.
Infection is a very serious and potentially blinding complication of cataract surgery. The chance of developing an infection after cataract surgery is about 0.1%. The risk of infection is the highest within the first week after the operation. Using antibiotic eyedrops, having good personal hygiene and protecting the eye with a temporary eye shield during this period significantly lower this risk.
Severe bleeding inside the eye is another rare but serious complication and may result in blindness.
Retinal detachment is a rare but serious complication where the retina becomes detached from the eye wall and occurs in about 1 in 3000 cataract surgeries. A separate surgery is necessary to repair the retinal detachment.
Most patients can expect a significant improvement in their vision and quality of life after cataract surgery. In those with other co-existing conditions such as retinal diseases, the final vision may be limited by these other conditions.
Cataract tends to progress with age and its surgery can become more difficult to perform when it is denser and more advanced. A very dense cataract can cause lens-induced complications such as glaucoma and eye inflammation which may lead to permanent blindness. For these reasons, it is advisable not to delay cataract surgery unnecessarily for too long. The outcome of cataract surgery is usually very good except in cases with other co-existing eye problems or serious complications during the surgery.
There is no eyedrop which has been proven effective in preventing cataract formation or progression. Although cataract formation is age-related, its growth may be delayed with the following strategies:
- Wearing of sunglasses to reduce exposure to ultraviolet light when outdoors
- Quitting smoking
- Consuming fruits and vegetables rich in vitamins and antioxidants
- Maintaining good control of diabetes (if present)