By Eyecare NGOverview | Development | Symptoms | Risk Factors | Prevention | Diagnosis | Treatment
Cataract is the clouding of the natural lens in the eye resulting in decreased vision and reversible blindness. It mostly occurs in the elderly. However, a small percentage of cataract cases are people of other age groups. Learn more about cataract in children
The natural lens in the eye is clear and transparent. It works with the cornea to focus light rays on the retina. When the lens becomes cloudy, it reduces the amount of light that gets to the retina resulting in decreased vision. The progression of the clouding of the lens occurs gradually over time. The cloudier the lens gets, the poorer the vision in the affected eyes until the cloudy lens is removed via surgery.
How cataract develops
The natural lens in the eye is made up of water and proteins which are arranged neatly and in an orderly manner such that the lens is clear and transparent, thereby allowing light to pass through it. As we get older, the protein fibres of the lens start changing. They get denatured and degraded resulting in clouding of the lens. This clouding on the onset is usually thin and covers a small area of the lens. Over time, it thickens and gradually progresses until the whole lens is affected making it difficult to see with the affect eyes.
Symptoms and signs
There may be no symptoms at the early stages of cataract development but as the cataract progresses the following symptoms may be observed:
Frequent changes of eyeglasses: As cataract develops, there may be changes in the refractive status of the eye. Initially, change in glasses may be all that is required until the vision can longer be improved with glasses. Sometimes those that wear glasses to read may notice that they can read without glasses. This is called ‘second sight’. It doesn’t last and usually, the person becomes completely blind some period after experiencing ‘second sight’.
Glare or scattering of light: Cataract can cause glare. It makes light appear brighter and more discomforting especially that from oncoming vehicles. This may make it difficult for people with cataract to drive at night.
Bright colours appear dull: Bright colours may appear dull to people with cataract because of the reduced light that gets to the retina.
Haloes: Sometimes, cataract can cause rainbow-like colours to be seen around bright lights because of scattering of light by the cloudy lens.
Factors that can increase the risk of developing cataract include:
- Increasing age
- Exposure to ultraviolet rays and other radiations.
- Diabetes Mellitus
- Prolonged use of steroids
- Some medications such as statin
- Eye injuries
- History of eye surgery
- Alcohol consumption
- High myopia
- A family history of cataract
- Some illnesses such as Galactosemia, Down’s syndrome and Rubella
Prevention of cataract
There is no general consensus on how to prevent cataract. However, it is believed that taking good care of the eyes and eating foods rich in certain nutrients can reduce the risks of developing the cataract. Here are some ways to reduce the risks of cataract:
- Eat a healthy diet: Diets rich in vitamin E, vitamin C, omega 3 fatty acids, Lutein and Zeaxanthin may reduce the risk of developing cataract. These nutrients have antioxidant properties which help keeps the eyes healthy. Some sources of vitamin E are spinach, almonds and sunflower seeds. Omega 3 fatty acid rich foods include fish, nuts, and soybeans. Lutein and zeaxanthin can be found in spinach and other green leafy vegetables while Vitamin C is abundant in citrus and other fruits.
- Protect your eyes from UV rays and other types of radiation: Wear sunglasses with adequate UV protection. Also, use protective eyewear if you are involved in activities that expose your eyes to harmful radiation.
- Avoid eye injuries: Taking necessary precautions to prevent eye injuries is important to reduce the risk of developing cataract. To avoid injuries, prevent accidents and use appropriate safety eyewear during work and play.
- Quit smoking: Smoking is known to contribute to denaturing of protein fibres of the lens. Quitting this habit can reduce the risk of developing cataract.
- Get proper care and treatment for other health problems: Conditions like diabetes increase the risk of developing cataract. Ensuring that these conditions are properly managed can reduce this risk.
To diagnose cataract, an eye doctor would usually perform the following tests:
- Visual acuity measurement: This determines how well you can see a chart placed at 6 metres (20 feet).
- Slit lamp examination or penlight examination: This is done to examine the structures of your eyes including the lens.
- Intraocular pressure measurement: The intraocular pressure may be measured to rule out high pressure and glaucoma.
- Internal eye examination: The inner structures of the eye are examined if it is possible to view them through the cloudy lens. The eye doctor may instil some eye drops that will dilate the pupil and allow a better view of the lens and retina.
Cataract is treated surgically. For people who do not want cataract surgery at the early stages, prescription eyeglasses may improve vision. These may be changed a few times until the cataract progresses to a stage where eyeglasses no longer improve vision.
When glasses can no longer improve vision or vision has become so poor that daily activities are affected, surgery is the only treatment option
Cataract surgery involves removing the cloudy natural lens and implanting an artificial lens in the same position where the natural lens was located. This artificial lens is known as intraocular lens.
Cataract surgery is performed under local anaesthesia and on an out-patient basis. After surgery, the eye is usually patched for a day and medications given to prevent infections and control inflammation. Eye pressure reducing drugs may also be given if intraocular pressure is elevated. Due to increased light sensitivity following the surgery, sunglasses are required to protect the eye from sunlight.
Weeks or months after cataract surgery a full eye examination is usually done and any residual refractive error found can be corrected with eyeglasses.
Complications of cataract surgery
Most cataract surgeries are successful. The following complications may, however, occur in some cases.
- Eye infection
- Retinal detachment, a situation whereby the retina separates from its supportive tissue in the eye
- Swelling of structures in the eye including the cornea (the transparent structure at the front of the eye coloured part of the eye) and macula (the part of the retina that provides the sharpest vision)
- Increased intraocular pressure
- Endophthalmitis, that is, the inflammation of the whole eyes normally caused by bacteria.
- Posterior capsular opacification: This is the clouding of the lens capsule in which the intraocular lens was inserted. It is a late complication of cataract surgery that usually occurs months or years after surgery.
Early detection and treatment of any of these complications are key to avoid loss of vision.