A cataract is the clouding of the eye's natural lens. Ageing is the most common cause, though trauma, certain medications and other eye conditions can also lead to it. The only effective treatment is surgery, in which the clouded lens is replaced with an artificial lens calculated for that eye.
What Is a Cataract?
A cataract is the clouding of the eye's natural lens. The lens sits just behind the coloured part of the eye (the iris) and focuses light onto the retina. As it loses transparency, light no longer passes through cleanly and the image becomes hazy. Cataract is one of the most common causes of visual loss worldwide, particularly in older adults, and if left untreated it can progress to severe visual impairment.
Cataract is usually linked with ageing, but it can also develop for other reasons, and it can be present in newborns and children. It is not a tumour or a growth over the eye; it results from changes in the proteins that make up the lens itself.
Causes of Cataract
Ageing (age-related cataract): The most common cause, as the proteins in the lens break down over time.
Congenital cataract: Present at birth, often due to genetic factors or infection during pregnancy. See the congenital cataract page.
Trauma or injury: Blunt or penetrating injury to the eye can lead to cataract formation.
Systemic disease: Conditions such as diabetes increase the risk of cataract.
Prolonged steroid use: Long-term use of corticosteroid medication can contribute to cataract development.
Intraocular inflammation: Conditions such as uveitis can accelerate cataract formation.
Radiation and UV exposure: Prolonged exposure to sunlight or radiation raises the risk.
Previous eye surgery: Cataract can develop earlier after some procedures, such as retinal surgery.
Symptoms of Cataract
Blurred, cloudy or hazy vision.
Sensitivity to light (photophobia) and glare from oncoming headlights when driving at night.
Faded, yellowed or dull colours.
Poor night vision.
Double vision or ghosting in one eye.
Frequent changes in spectacle prescription. Some patients find that for a period they can read without glasses while their distance prescription shifts.
Needing progressively more light to read or to do close work.
Cataract generally progresses slowly. Sudden loss of vision is not explained by cataract and calls for investigation of another cause.
How Is Cataract Diagnosed?
Visual acuity test: Distance and near vision are measured.
Slit-lamp examination: The front of the eye and the lens are examined in detail, and the type and density of the cataract are established.
Tonometry: Intraocular pressure is measured to assess coexisting conditions such as glaucoma.
Fundus examination: The retina and optic nerve are examined. If another condition limits vision, the expected benefit of surgery is judged accordingly.
Biometry: The power of the lens to be implanted is calculated with dedicated instruments. The accuracy of this calculation directly determines how much spectacle correction is needed afterwards.
Corneal topography: The amount of astigmatism and the shape of the cornea are assessed; this is necessary when a toric or multifocal lens is being considered.
When Should Cataract Surgery Be Performed?
Waiting for a cataract to become "ripe" is no longer necessary. The measure is how much the cataract restricts daily life: difficulty driving, difficulty reading, glare and occupational demands all inform the decision.
In some situations waiting is not appropriate: when the lens has hardened to the point of making surgery more difficult, when it raises intraocular pressure, or when it prevents adequate examination of the retina. In children, timing matters far more, because visual development is still under way.
Cataract Treatment and Surgery
The only effective treatment for cataract is surgery. Drops, medication, glasses and exercises cannot restore the transparency of the lens.
Phacoemulsification (phaco): The most widely used technique today. The eye is entered through an incision of about 2 mm in the cornea, and the clouded lens is broken up with ultrasonic energy and removed.
Preserving the capsule: The lens capsule, thinner than onion skin, is preserved during the procedure, and the artificial lens is placed inside it.
Anaesthesia and duration: Surgery is performed under topical or local anaesthesia in most patients and usually takes 15 to 30 minutes.
Same-day discharge: Patients normally go home on the day of surgery.
Sequencing the two eyes: When both eyes have cataract, the operations are planned separately rather than in the same session.
Whether eyelid surgery and cataract surgery can be performed together is one of the most frequent questions. Combining them in a single session is not appropriate; an interval of about one month is suitable. For lid surgery see the droopy eyelid (ptosis) page.
Intraocular Lens Options
The lens to be implanted is calculated from preoperative measurements and chosen individually, according to the structure of the eye, any coexisting eye disease and the patient's daily habits.
Monofocal lenses: The type used for many years. They give clear vision at a single distance. Set for distance, the patient sees far without glasses and uses reading glasses for near work.
Multifocal and trifocal lenses: These allow clear vision without glasses at far, intermediate and near distances. Because halos and glare at night can occur, they are not suitable for every eye.
Toric lenses: These correct astigmatism at the same time as the cataract, and are available in both monofocal and multifocal forms.
EDOF (extended depth of focus) lenses: These give continuity at far and intermediate distances, with more limited support for near work.
No lens type suits every patient. Retinal disease, advanced dry eye, irregular astigmatism or previous refractive surgery all change the choice. We discuss this in detail at the consultation.
In the short video below I explain cataract surgery and where the smart lens fits in.
Recovery After Cataract Surgery
Mild stinging, burning, itching and light sensitivity are usual in the first few days.
Vision generally improves markedly within days, while full stabilisation takes a few weeks.
The eye drops prescribed should be used regularly for the period advised.
Rubbing the eye and exposure to dirty water and dust should be avoided in the early weeks.
Heavy lifting and prolonged bending forward are restricted for a period.
A new spectacle prescription is taken once the eye has settled.
Attending follow-up appointments matters for monitoring healing.
Risks and Possible Problems
Cataract surgery is a common procedure with well-documented outcomes, but like any operation it carries risk. Possible problems include intraocular infection, a rise in intraocular pressure, corneal oedema, retinal swelling, retinal detachment and displacement of the implanted lens. These are uncommon, and most can be treated when recognised in time.
Vision may become blurred again months or years after surgery. This is often described as the cataract "coming back", which is not accurate. It is clouding of the capsule left in place (posterior capsule opacification), and it is cleared with a painless laser procedure. A cataract that has been removed does not return.
Reducing the Risk of Cataract
Wear sunglasses to protect your eyes from ultraviolet light.
Stop smoking; smoking is among the factors that accelerate cataract formation.
Keep systemic conditions such as diabetes under control.
Do not continue long-term steroid treatment without medical supervision.
Use protective eyewear for hazardous work and sports.
Have regular eye examinations; cataract progresses insidiously and people often do not notice how much vision they have lost.
Cataract seriously affects the quality of vision, but it is treatable. With early diagnosis, correct timing and a lens chosen to suit the individual eye, sight is largely restored.
Ayşe Dolar Bilge MD, FEBOphth. Ophthalmologist, Oculoplastic Surgery
English
