Cataracts are a normal part of ageing and are often cited as the leading cause of reversible vision loss in the developed world. Fortunately, cataract surgery is an easily accessible service in our medical system with many highly skilled eye surgeons in both private and public practice.
A cataract is an opacity or clouding of the lens inside the eye, which starts as transparent at birth. As we get older, the lens gradually loses its clarity and becomes hazy. Out of all the types of cataract, age-related cataracts are by far the most common, making cataract surgery one of the most commonly performed procedures in Australia with our ageing population.
Depending on which of the various types of cataract develop in the eye, you will begin experiencing mild vision problems, such as blurry or filmy vision, increased glare sensitivity, or an alteration to your colour perception. In Western civilisation, very rarely does anyone reach complete vision loss from a cataract due to the accessibility of cataract surgery in our society.
Types of Cataract
Eyecare professionals will typically categorise the types of cataract based on their location. Although most cataracts more or less share the same symptoms, depending on the location and nature of the cataract, specific vision problems may be more pronounced with one type of cataract compared to another.
Nuclear sclerosis occurs in the centre of the eye’s lens, called the nucleus. To an optometrist or eye specialist examining your eye, this appears as a brownish-yellowing of the centre of the lens. Nuclear sclerosis can cause vision problems such as mild colour vision loss, as the discolouration of the lens filters certain wavelengths of colour trying to reach the retina at the back of the eye. This type of cataract can also cause what’s known as a myopic shift, where the prescription of the eye becomes more short-sighted.
An anterior cortical cataract grows in the outer layers of the lens, in the fibres surrounding the lens nucleus. These look like bicycle spokes of white or grey opacities. An anterior cortical cataract is commonly associated with glare sensitivity, as the incoming light is scattered by these opacities. Some people with a cortical cataract will experience the opposite of those with a nuclear sclerotic cataract and find their prescription becomes more long-sighted, known as a hyperopic shift.
The third type of cataract is called a posterior subcapsular cataract. These look like white plaques in the centre of the back surface of the lens. Because of this location, posterior subcapsular cataracts are associated with the most vision loss out of all senile cataracts, as well as significant glare sensitivity.
Fortunately, most age-related cataracts are easily managed with cataract surgery. In most cases, it is safe to delay cataract surgery until the vision problems from the cataract progress to a point where it impacts your daily activities, such as if you no longer feel comfortable driving. Your optometrist or ophthalmologist will discuss with you if you have an eye condition that may mean it is better to have cataract surgery sooner than this point.
Another way of categorising the types of cataract is from their underlying cause.
- Age-related cataracts. These are also known as senile cataracts, and as mentioned earlier, make up the vast majority of cataract cases.
- Congenital cataracts. These cataracts are present at birth. Although there is sometimes no identifiable underlying cause, a baby may be born with a congenital cataract if the mother had an illness during pregnancy, such as measles or rubella. Certain medications taken during pregnancy have also been associated with congenital cataracts, such as tetracycline antibiotics. Congenital cataracts have the potential to cause permanent vision loss in babies if not treated promptly, as the visual system is still developing, however, the urgency of cataract surgery will depend on whether the cataract is considered visually significant or not.
- Traumatic cataract. This can happen after an injury to the eye that can either be blunt, like a cricket ball to the eye or penetrating, like a shard of glass. The force of the trauma disrupts the fibres of the lens, causing them to lose their transparency. Electric shocks from lightning strikes or touching a live current can also induce a cataract, in addition to other eye problems. Though most traumatic cataracts will respond well to cataract surgery, the final visual outcome depends on whether other areas of the eye have also sustained any damage.
- Diabetic cataract. Amongst other eye complications, such as diabetic retinopathy, diabetes is also responsible for causing cataracts, resulting in the need for cataract surgery at an earlier average age compared to those without diabetes. Studies have found diabetes is associated with an increased risk of nuclear, cortical, and posterior subcapsular cataracts.
There are various other terms to describe the different types of cataract, such as their appearance – cerulean cataracts appear as blue flecks in the lens while the white opacities of a snowflake cataract, as the name suggests, resemble a snowflake. There is even what’s known as a Christmas tree cataract, which appears as colourful, reflective, needle-shaped opacities in the lens.
The only definitive treatment for cataracts is surgical extraction, though this may not be useful or necessary in all cases.