Southern Cross Medical Library

Southern Cross Medical Library

Cataracts are when the lens of the eye becomes cloudy. This restricts the amount of light that reaches the retina and affects vision.

Cataracts tend to develop slowly over a period of years. In the early stages they may not produce any symptoms. However, without treatment (normally surgery) cataracts will get worse and eventually lead to complete blindness. In New Zealand, cataracts are a leading cause of vision loss in older adults.

Causes and risk factors

The most common cause of cataracts is ageing, while other causes include other medical conditions, eye injuries, genetic defects and reaction to some medications.

Cataracts are a natural part of ageing and are common in people over 60 years old. Most elderly people with cataracts have no other contributing health conditions or eye diseases.

Diagram of a human eye

Cataracts can also exist at birth (congenital cataracts) due to a faulty gene, and can develop in children (childhood cataracts) associated with infection or trauma during pregnancy. Cataracts in new-borns and children are rare.

Other factors that may increase the risk of developing cataracts include:

  • A family history of cataracts
  • Diabetes
  • High blood pressure
  • Other eye conditions such as uveitis
  • Previous eye surgery, injury or inflammation
  • Long-term use of corticosteroid medication (eg: prednisone, prednisolone)
  • Excessive exposure to sunlight
  • Smoking
  • Drinking too much alcohol
  • Poor diet.

Cataracts can affect one or both eyes.

Signs and symptoms

Signs and symptoms of cataracts can include:

  • Cloudy, blurry, fuzzy, foggy, or filmy vision
  • A noticeable cloudiness in the pupil
  • Sensitivity to light or glare from lights, eg: from headlights when driving at night
  • A decrease in distance vision but an improvement in near vision
  • Double vision (diplopia) or halos around lights
  • Frequent changes in eye prescriptions
  • Colours look faded or yellowish
  • Poor vision at night
  • Needing brighter light for reading and other close-up tasks.


Either a GP or optometrist may make an initial diagnosis after testing your vision and examining your eyes.

If cataracts are suspected, a referral to an eye specialist (ophthalmologist) is usually recommended. The eye specialist may carry out more detailed examinations of the eye and vision in order to determine the exact location and extent of the cataracts. They will then recommend appropriate treatment.

Cataracts can be classified according to which part of the lens they affect. The location and extent of the cataract also determines the extent of the vision impairment. For example, vision may be significantly impaired if the centre of the lens is affected (nuclear cataracts); however, if the edges of the lens are affected (cortical cataracts) vision impairment may be barely noticeable.

Treatment and surgery

The symptoms of early cataracts may be improved with new prescription glasses and stronger lighting. However, once cataracts progress to the point that impaired vision reduces your quality of life and interferes with daily activities, surgery is the only effective treatment.

Cataract surgery involves removing the clouded lens and replacing it with a clear plastic lens known as an intraocular lens (IOL). The aim of surgery is to restore vision (particularly distance vision) as much as possible. IOLs of differing magnifying power can be used to help correct pre-existing short-sightedness (myopia), long-sightedness (hyperopia), or problems with the shape of your cornea (astigmatism).

Cataract surgery is most commonly performed as a day-stay procedure and is usually carried out under a local anaesthetic with mild sedation.

Surgery involves making a small incision in the front of the eye, through which the old lens is removed and the artificial IOL is inserted. The incisions are usually made using a hand-held microscopic blade but, in recent times, laser cataract surgery has allowed computer-guided, bladeless incisions to be made.

Laser cataract surgery should not be confused with laser eye surgery (PRK and LASIK), which is used to correct problems with the eye's ability to focus.

If cataracts affect both eyes, only one eye is operated on at a time. It is usually recommended that the eye is well healed before the other eye is treated. This is generally at least one month.


Patients are normally sent home after a few hours of recovery in the clinic or hospital, and when the sedation has worn off. An eye pad is usually positioned over the eye for the first night in order to protect the eye.

It is usual to feel some mild pain and discomfort in the eye after cataract surgery. This can usually be well controlled with medications such as paracetamol.

While it may take a day or two for the eyes to synchronise, people generally report that vision improves quickly, being able to return to normal activities within about two weeks. Distance vision returns but reading glasses will still be required for fine or detailed visual tasks.


Cataract surgery is generally safe and the risk of developing serious complications is small.

The most common complication is a condition called posterior capsule opacification (PCO), which involves a skin or membrane growing over the back of the lens implant months or years after surgery causing vision to become cloudy again. PCO can be treated with a simple laser eye surgery to cut away the membrane.

Cataract surgery also carries a risk of infection and bleeding inside the eye and increased risk of retinal detachment. However, most complications can be treated with medication or further surgery.


Cataracts cannot be prevented. However, certain approaches may delay or reduce the chances of them developing.

Wearing sunglasses that protect the eyes from ultraviolet light is recommended. A diet high in fruits and vegetables, limiting alcohol use, and quitting smoking are also thought to be beneficial.

Optimal management of health conditions that can increase the risk of developing cataracts (eg: diabetes) is advised. If corticosteroids are being taken on a long-term basis, it is recommended that a GP or optometrist checks the eyes regularly for signs of cataract development. Even if corticosteroids are not being taken, regular eye examinations are advised for those over 40 to detect cataracts and other eye problems at their earliest stage of development.


Mayo Clinic (2018). Cataracts (Web Page). Rochester, MN: Mayo Foundation for Medical Education and Research. [Accessed: 04/06/20]
NHS Choices (2017). Age-related cataracts (Web Page). Redditch: National Health Service (NHS) England. [Accessed: 05/06/20]
NHS Choices (2018). Childhood cataracts (Web Page). Redditch: National Health Service (NHS) England. [Accessed: 04/06/20]
Ocampo Jr, V.V.D. (2018). Senile cataract (age-related cataract) (Web Page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. [Accessed: 04/06/20]
O’Toole, M.T. (Ed.) (2017). Cataract. Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MI: Elsevier.

Last Reviewed – June 2020

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The purpose of the Southern Cross Medical Library is to provide information of a general nature to help you better understand certain medical conditions. Always seek specific medical advice for treatment appropriate to you. This information is not intended to relate specifically to insurance or healthcare services provided by Southern Cross.