A cataract is a condition which causes clouding of the lens in the eye resulting in blurry vision.
The lens is situated behind the iris, the dark portion of the eye, and is not visible. When a cataract occurs, the lens becomes cloudy and is seen as a white cloudy ball in the centre of the iris.
The lens is made up of mostly water and proteins. These specific proteins provide its transparent structure. Any structural change in these proteins can alter the clarity of the lens and negatively impact vision.
Types of Cataract
There are three types of cataracts classified according to their location in the eye.
- Nuclear cataract is when the cloudiness is present in the centre of the lens.
- With cortical cataract, the cloudiness is seen in the outer peripheral region or cortical region of the lens.
- Subcapsular cataract occurs at the back of the lens capsule or subcapsular region. This type develops quicker and can appear more suddenly than the nuclear and cortical cataract.
Cataracts are also classified according to the cause, either as age related cataract, congenital cataract, secondary cataract or traumatic cataract.
A cataract can occur due to many reasons.
Age – As people age, changes can occur in the structure of the lens protein leading to cataract.
Congenital causes– A cataract can occur in newborns as an inherited disorder or can develop in infants because of infections in the mother during pregnancy such as rubella, herpes simplex and syphilis.
Secondary causes– Cataracts can form as a complication of other diseases such as diabetes. Prolonged use of corticosteroid eye drops increases the risk of cataract.
Trauma – Certain injuries to the eye may result in formation of a cataract. A cataract may also develop years after the injury.
Other causes include excessive exposure of the eyes to UV rays, X-rays and other radiation during radiotherapy.
Cataracts usually develop very slowly and are not associated with any pain or redness of the eye. Your vision gradually becomes blurred as if you are looking through the dirty lens of a camera. Some patients may see a halo around bright lights. Others find the glare from the sun and head lights of approaching cars at night annoying. Some patients present with double vision in the affected eye and colours may appear dull or muted. In others, frequent prescription changes for glasses or contact lens may become necessary.
To assess the impact of the cataract on your vision your doctor will perform a visual acuity test where the patient reads an eye chart from a particular distance with one eye at a time.
The doctor then examines the cornea, iris, and lens individually using an intense ray of light from a slit lamp to detect any abnormalities.
For the retinal exam, eye drops are added to dilate the eye and the retina is examined for any abnormalities using an ophthalmoscope.
Once a cataract develops it cannot be cured by eye drops or medication. Patients with mild cataracts may be helped by using strong bifocal glasses and using appropriate light while reading.
Surgery is the only treatment for cataract and is recommended based on the severity of the disease and the impact on the daily activities of the patient. Patients usually make the decision to have surgery when the symptoms negatively impact their lifestyle.
Surgery is performed on one eye at a time with a 3 to 5-day gap in between the two operations. Cataract surgery is done on an outpatient basis where the patient can go home the same day. The area around your eye is numbed by local or topical anesthesia depending on the doctor’s decision and patient’s comfort. The cloudy lens is removed and replaced with a clear acrylic lens in the same lens capsule as the natural lens.
There are four types of surgical procedures to treat cataract:
The most common procedure used is phacoemulsification where your surgeon uses an ultrasound probe to break up the lens which is then removed by suction. The advantage is that the incision is very small, around 1.8 to 2.8 mm, depending on the choice of lens, foldable or non-foldable. The incision heals on its own and does not require any eye patch or stitches. This surgery takes less than 30 minutes.
The second type of surgery is extracapsular cataract surgery. This is performed when the lens is too dense and cannot be removed by phacoemulsification. The incision is larger as the complete lens is removed as a single piece. The healing process for this type of surgery is longer and requires an eye patch temporarily over the eye after the surgery.
The third type of surgery is called small-incision cataract surgery or SICS. This is performed by making an incision of 6-7 mm in the form of a tunnel through the sclera and cornea. The lens is removed and replaced with a rigid lens implant through this tunnel. No sutures are needed as the tiny incision will heal naturally by itself. Laser technology has evolved in cataract surgery and is the fourth type of surgery called Femtosecond-assisted laser cataract surgery. This surgery involves accurately focusing a high-speed laser beam on the corneal tissue to incise it and remove the cataract. Your surgeon can perform various parts of the procedure with this laser technique including making corneal incisions, circular symmetrical opening in the lens capsule and breaking the lens easily into fragments by softening it.
Advantages of this laser technology include accurate intraocular lens positioning, precise corneal incisions, reduced ultrasound energy and gentle removal of the softened cataract through phacoemulsification. It also corrects a type of refractive error called astigmatism.
Various types of intra ocular lenses are used during cataract surgery. These include:
Monofocal lens: this type of lens does not provide correction for near sightedness or astigmatism and corrects vision for only one distance- either far, intermittent or near. As a result, the patient will require glasses or contact lenses after the surgery for the best possible vision.
Multifocal lens provides correction for both distance vision and near vision simultaneously but does not correct astigmatism. The disadvantage however is that it causes comparatively more glare than the monofocal lens.
Premium intraocular multifocal lens, also called toric lens, provides correction for astigmatism as well as distance and near vision. The advantage of a toric lens is that the patient does not need to wear glasses or contact lenses for normal vision after the surgery.
Accommodative lens are very flexible and mimic the movements of the natural eye lens by changing its shape inside the eye. This allows the eye lens to easily accommodate the change in focus for close and distant objects.
Post -Operative Care
Following surgery, your doctor will prescribe eye drops to prevent infection and inflammation. A follow up visit is scheduled to monitor healing and to check for any complications from surgery. Once complete healing occurs glasses are ordered for optimal vision, if required, depending on the type of intraocular lens inserted in the eye by your surgeon.
Risks and complications
Cataract surgery is one of the safest surgeries to undergo. Complications are rare but can occur and need to be addressed as soon as possible to prevent any vision loss.
Complications can include persistent inflammation, infection, increase in intraocular pressure, or peeling of the retina at the back of the eye. In rare cases the cataract seems to reappear after a few months or years following surgery with a cloudy appearance in the field of vision. This occurs due to cloudiness of the capsule and not the implanted acrylic lens. It is called a secondary cataract and can be treated by a simple laser surgery to create a hole in the lens capsule where the cloudiness is visible.
Cataracts may be prevented by maintaining a healthy life style.
- Fruits and vegetables are a good natural source of vitamins and antioxidants important in the normal growth, functioning and prevention of age related damage to the eye lens. A diet rich in fruits and vegetables can help prevent cataracts.
- Not smoking or quitting if you do smoke lowers your risk of developing cataracts.
- Regular exercise and maintaining a healthy body weight also helps to prevent cataracts.
- Increased triglycerides are a risk factor for cataract. Keeping blood levels of triglycerides under control through diet restrictions helps in preventing cataracts.
- Diabetes greatly increases the risk of developing a cataract. Diabetics should check and control blood sugar levels regularly.
- Wearing sunglasses with UV- protection when outside protects the eyes from damage by the sun’s harmful UV rays.
Cataracts are a slow developing disease which normally does not get detected early. Regular eye exams by an eye specialist can help in early detection of the disease.