Resource Centre - Cateracts

Below is a comprehensive description of symptoms, long-lasting effects and tips for prevention of cataracts.

What are Cataracts?
Causes and Risk Factors of Cataracts
Symptoms of Cataracts
Different Types of Cataracts
How is a Cataract Detected?
Who is Affected by Cataracts?
Treatment of Cataracts
Benefits and Risks of Cataract Surgery
Prevention of Cataracts

What are Cataracts?

The lens is the part of the eye found between the iris and the vitreous humour. Its function is to refract light as it passes through the eye to focus it upon the retina. The opaqueness of a cataract prevents the light from passing through the lens and reaching the retina, therefore, interfering with vision.

Causes and Risk Factors of Cataracts

There are many different causes of cataracts, most of which generate a change in the normal chemical structure of the lens. There are also many risk factors, which can be associated with the development of cataracts. The causes and risk factors of cataracts include:

Age
The majority of cataracts develop, as people get older, this is because the process of ageing causes a change in the chemical composition of the lens and makes it cloudy. Cataracts formed this way are called age-related cataracts.
Congenital
Some cataracts are hereditary and are present in children at birth. This could be because of medication that the mother has taken or because of an illness or condition the mother contracts during pregnancy. These types of cataracts are called congenital cataracts.
Diabetes and other medical conditions
Diabetes affects the eye in a number of ways, for instance it can cause diabetic retinopathy and the condition can also evoke cataracts.
Diabetes is represented by an increased level of blood sugar levels, which result directly in the formation of cataracts. Other conditions that can cause cataracts are glaucoma and iritis. Cataracts that are formed this way are called secondary cataracts.
Medication
Several medications are associated with cataract formation, these include: oral steroids, long-term use of aspirin and drugs that contain cortisone.
Physical injury
Physical injury to the eye may cause damage to the lens and lead to the formation of cataracts, for example: a blow to the eye, chemical burns or radiation exposure. Cataracts formed from physical injury are called traumatic cataracts.
Smoking and Alcohol
Both of these things have been associated with cataract formation. Smokers are twice as likely to develop cataracts than non-smokers and cataract patients are recommended to limit alcohol consumption.
Ultra-violet light
Exposure to ultraviolet radiation causes changes in the chemical composition of the lens and studies show that it increases the speed of cataract development.
Free radicals
Diarrhoea, dehydration and low levels of calcium are also associated with cataract formation.

Symptoms of Cataracts

The following are the some symptoms of cataracts:

Problems in quality of vision
- Cloudy vision
- Blurry vision
- Poor night visionDouble vision
Problems with colour:
- Colours seem less vivid
- Difficulty in distinguishing differences in colours
- A yellow tint to vision
Problems with light:
- Halos appear around lights
- Sensitivity to light
- The need for brighter light whilst reading or doing detailed tasks
Eye strain and headaches
Increased blinking
Frequent changes in glasses and contact lenses prescriptions
Second Sight - A temporary improvement in close-up vision and detailed tasks as the lens changes shape.

Different Types of Cataracts

Cataracts can be classified both by their location and also their mechanism of formation. The location of a cataract and can be sorted into three different types: cortical, nuclear and subcapsular. The mechanism of formation can be described as age-related, congenital, secondary and traumatic.

Cortical cataract – a cortical cataract is formed in the periphery of the lens and extends into the centre. These types of cataracts are most common in patients with diabetes.

Nuclear cataract – a nuclear cataract is located in the centre of the lens and is the most common form. This type of cataract is normally associated with increasing age and the lens slowly becomes hardened and yellow slowly over time. This cataract affects a person’s ability to see objects in the distance more than it affects their near sight.

Subcapsular cataract – a subcapsular cataract develops at the posterior part of the lens and is the most common type of cataract in young people, people who use steroids and people with diabetes. Unlike a nuclear cataract, a subcapsular cataract affects near-sightedness much more then far-sightedness.

Age-related cataract - Please see the ‘Age-related’ paragraph in Causes and Risk Factors of Cataracts.

Congenital cataracts – Please see the ‘Congenital’ paragraph in Causes and Risk Factors of Cataracts.

Secondary cataracts – Please see the ‘Diabetes and other medical conditions’ paragraph in Causes and Risk Factors of Cataracts.

Traumatic cataracts – Please see the ‘Physical injury’ paragraph in Causes and Risk Factors of Cataracts.

How is a Cataract Detected?

Cataracts are detected in unborn babies through the use of ultrasound. It is very important that cataracts are detected early as if left untreated, they could cause blindness soon after the birth of the baby. In adults, cataracts are generally detected in a routine eye exam. During this examination, three tests can be performed to diagnose cataracts:

The first is called the visual acuity test, which is used to measure how precise your eyesight is at different distances. This test is pain-free and involves reading letters of various sizes off a chart, which is a certain distance away from you.

The second test is called a tonometry test and the function of this is to measure the fluid pressure inside the eye. Eyedrops are used to numb the surface of the eye and then pressure is applied to the eye. As well as detecting cataracts, this test is useful for diagnosing glaucoma as well.

The final test is called a pupil dilation exam and in this test eyedrops are used to dilate the pupil, so that the ophthalmologist can examine the lens and the retina much more efficiently. Both the tonometry test and the pupil dilation exam may be mildly uncomfortable, but they are pain free and provide a way to accurately diagnose cataracts and other eye conditions.

Who is Affected by Cataracts?

Approximately 0.4% of babies suffer from congenital cataracts [1], people under the age of 40 are most likely to develop traumatic cataracts [2] and it is much more common for older people to suffer from age-related cataracts [3]. It is estimated that by the time you are 80, there will be a 50% chance that you will have a cataract [4] and that just less than three quarters of people will have had a cataract by the time they are 85 years old [5]. Women are slightly more affected by cataracts than men [6].

References:

[1] - Kelly Burgess, Congenital Cataracts – Treatment Options for Newborns - http://babiestoday.com/

[2] - University of Missouri, Health Care, Cataracts – Frequently Asked Questions - http://www.muhealth.org/

[3] - Dr Rob Hicks, Cataracts, BBC Health - http://www.bbc.co.uk/health/

[4] - University of Missouri, Health Care, Cataracts – Frequently Asked Questions - http://www.muhealth.org/

[5] - Dr Rob Hicks, Cataracts, BBC Health - http://www.bbc.co.uk/health/

[6] - Dr Rob Hicks, Cataracts, BBC Health - http://www.bbc.co.uk/health/ AND Healthwise, Who is affected by cataracts - http://health.msn.com/

Cataract Treatment

When a cataract has only just started developing, glasses, contact lenses and stronger lighting may help to improve vision. However, when the cataract starts to affect daily life and it becomes increasingly difficult to drive, read or watch TV, then cataract surgery should be considered.

Cataract surgery consists of removing the damaged lens and replacing the cloudy one with a substitute, an intraocular lens (IOL). There are three types of surgical procedures to remove cataracts:

Extracapsular surgery – in this procedure, an incision is made in the cornea and the hard part of the lens is surgically removed, therefore, the incision is relatively larger than the one in phacoemulsification. Once the hardened part of the lens has been taken out, the rest of the lens is removed through suction, the posterior capsule (the outer covering of the lens) is left intact and an IOL inserted.

Phacoemulsification – this procedure is different to extracapsular surgery as a smaller incision can be made in the cornea. This is because a probe is inserted into the eye and ultrasound waves are used to break down the lens, the liquefied lens can then be removed by suction. As in extracapsular surgery, the posterior capsule is left in the eye and a new artificial lens is inserted.

Intracapsular surgery – this procedure is rarely performed as it introduces a greater chance of complications in the eye, for example, glaucoma. It is only performed when the lens has been displaced or dislocated. In intracapsular surgery, the whole of the lens and the lens capsule is removed.

Phacoemulsification, intracapsular surgery and extracapsular surgery normally takes between 20 – 30 minutes and the wound heals naturally. Eye drops or medication may be taken to promote healing and glasses or an eye shield may be used to protect the eye.

Benefits and Risks of Cataract Surgery

As with any type of surgery, cataract surgery has both benefits and risks associated with it. Patients who have had cataract surgery enjoy a greater quality of life as their eyesight improves, allowing them to enjoy a range of activities. For example, people who have had cataract surgery are much more likely to drive than people who haven’t had surgery to remove their cataracts. It also reduces the probability of being in a car accident by over half. It is a fact that cataracts can cause blindness, so any treatment that will prevent this from happening is a benefit.

Unfortunately, the surgery also has rare risks, some of these include:

Choroidal haemorrhage – a choroidal haemorrhage is when the choroid, the middle layer of the eye, begins to bleed. The risk of this has been greatly reduced as much smaller incisions can be made in the eye.

Cystoid macular edema – sometimes after cataract surgery, the macula swells. This is because fluid, which has leaked from blood vessels in the retina, accumulates there. This condition is very rare and can be treated with anti-inflammatory eyedrops.

Endophthalmitis – endophthalmitis is an inflammation of the eye, caused by an infection inside the eye. To prevent this topical antibiotics are taken and equipment is sterilised.

Posteriorly dislocated lens material – another risk of cataract surgery is that bits of the natural, cloudy lens break off and enter the vitreous humour. This can be treated by a vitrectomy to remove the unwanted lens material.

Retinal detachment – retinal detachment is when the sensory layer of the retina peels away from the support layer. Cataract surgery can increase the chances of getting this condition, but it can be treated through a pneumatic retinopexy and cryotherapy.

Prevention of Cataracts

There are many different lifestyle choices that you can make to prevent or slow the development of cataracts.

Ultraviolet light is a key contributor in cataract formation and therefore, wearing sunglasses which filter out UVA and UVB rays will reduce the risk of cataracts.
A healthy diet containing lots of fruit and vegetables, antioxidants, vitamins (especially vitamin B and E) and omega-3 fatty acids have been shown to decrease the risk of cataract formation.
On the other hand, studies have shown that smoking and a large fat intake will increase the development of cataracts.
Another way to prevent cataract formation is to have an overall healthy lifestyle and try to prevent yourself from developing any other conditions of the eye which will lead to secondary cataracts forming, for example diabetes.

Although cataracts are becoming more and more common in old age, it is possible to slow their development. However, cataract surgery is so common and successful (over 90% success rate), that even if you do develop cataracts, they should not affect your daily life too much.

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