A cataract is a condition which causes clouding of lens in the eye resulting in blurry vision. The lens is situated behind the iris, the coloured portion of the eye, and is usually not visible. When a cataract occurs, the lens becomes cloudy and when very advanced a cataract can cause the pupil to appear white. 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 with in the lens.
- Nuclear cataract is when the cloudiness is present in the centre of the lens.
- In Cortical cataract, the cloudiness is seen in the outer peripheral region or cortical region of the lens, and more commonly causes glare symptoms.
- Subcapsular cataract usually occurs at the back of the lens capsule or subcapsular region. This type develops quicker and can have a greater impact on the vision 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.
What causes 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 newborns as an inherited disorder or can develop in infants, for example 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. Prolonged use of corticosteroid medications including inhalers and eye drops increases the risk of cataract.
- 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.
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, unless they are causing other complications in 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.
How is cataract diagnosed?
To assess the impact of cataract on your vision your surgeon and her staff will perform a Visual Acuity Test where you read an eye chart from particular distance with one eye at a time. Your surgeon 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.
What is the treatment?
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.
Sometimes cataracts need to be removed to allow patients to continue to drive within legal vision requirements. At other times the cataract needs to be removed for other reasons for example, to allow sufficient view to monitor and treat macular and retinal disease, or if the cataract is causing problems with pressure or inflammation in the eye.
Surgery is usually performed on one eye at a time with a few weeks 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 anaesthesia. The cloudy lens is removed and replaced with a clear artificial intraocular lens (IOL), which is placed in the lens capsule that surrounded the original natural lens.
Multifocal lenses are a type of IOL The IOL (intraocular lens) used in cataract patients that enables you to view both far distance and near distance objects without using glasses. Traditionally, monofocal lenses are implanted at the time of cataract surgery where the patient is able to see far distance and additional glasses or lenses are required to enable near vision or to read. Cataract surgery can also treat patients with short -sightedness, long- sightedness, astigmatism, and presbyopia.
Another technique to decrease the dependence on reading glasses, while also not needing glasses for distance, is called blended vision, also called monovision.
There are pros and cons to both blended vision and multifocal IOLs and not all patients are suitable. Your surgeon will discuss your visual needs and desired refractive outcomes, discuss your options and customise the treatment to your specific needs and suitability.
Following surgery your surgeon will prescribe eye drops to prevent infection and treat normal inflammation. Follow up visits are scheduled to monitor healing and to check for any complications from surgery.