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.
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.
- Sub-capsular cataract occurs at the back of the lens capsule or sub-capsular 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: Cataract can occur in new borns as inherited disorder or can develop in infants because of infections in mother during pregnancy such as rubella, herpes simplex and syphilis.
- Secondary causes- Cataract can form as a complication of other diseases such as glaucoma and diabetes. Oral cortisone almost always causes cataract eventually.
- Trauma – Certain injuries may result in formation of a cataract. 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 one of the eyes and the colours appear dull or muted. In others, frequent prescription changes for glasses or contact lens may become necessary.
To assess the impact of cataract on your vision your doctor will perform a visual acuity test where the patient reads an eye chart from 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.
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. The patient usually makes the decision to have surgery when the symptoms negatively impact their lifestyle.
Surgery is usually performed with a one week gap in between the two operations. Cataract surgery is done on an outpatient basis where the patient can go home the same day. The eye and area around the eye is numbed using local or topical anaesthesia where no needles are required. There are many choices for the patient regarding what type of plastic lens is used, as this can potentially correct both distance and near visual requirements. The cloudy lens is removed and replaced with a clear plastic lens in the same lens capsule as the natural lens.