Types of cataracts
There are various known types of cataracts (based on underlying causes, as well as where they develop in the eye/s) which can occur. These are:
- Age-related (or senile) cataracts: The formation of cataracts becomes fairly common in individuals 80 years of age and older, but can cause noticeable symptoms in individuals after the age of 60 as well. Some people may develop cataracts as early as middle age (40 or 50 years of age) too. The majority of age-related cataracts develop as a result of protein clumping (usually around the nucleus portion of the lens), which tends to slowly increase in size. Over time the cataract become larger and gradually results in vision becoming duller and blurrier. The lens of the eye also slowly changes colour and typically becomes yellowish / brownish. This tinted colour change gradually produces the same hue change to vision as well. More advanced hue tint changes can make it increasingly difficult for a person to perform normal routine activities due to decreased visual ability. Tint changes also make it more difficult for individuals to identify purple and blue colours, often interpreting the colour as much darker than it actually is (i.e. black).
- Nuclear cataracts: These cataracts develop in the middle portion of the lens, causing a yellowish / brownish discolouration in the centre (a nucleus). This type can also result in near-sightedness. The denser the discolouration, the blurrier vision becomes over time, along with increased difficulty in distinguishing between colours.
- Cortical cataracts: These form around the edges of the nucleus (lens), creating a wedge shape or the development of streaks along the outer lens cortex. The cataract begins as a whitish tint and slowly progresses with streaks edging closer to the centre of the nucleus. This then progressively interferes with the ability of light to pass through the lens centre.
- Posterior subcapsular cataracts: This type of cataract affects the back of the lens and generally forms quicker than a nuclear or cortical cataract type. The cataract initially forms as a small opaque area at or near the back of lens of the eye, but normally directly in the path of where light would normally enter. This type disrupts vision relating to reading ability, causes halos and glare (especially around lit up areas at night) and may reduce visual ability in bright light.
- Congenital cataracts: A baby is born with cataracts (in one or both eyes) due to infectious causes, injury or impaired development in the uterus during pregnancy (intrauterine infection or trauma). A baby may also be born with a susceptibility for developing cataracts within his or her first year of life.
- Secondary cataracts: These types of cataracts normally occur as a result of other existing problems such as medical conditions, exposure to toxic substances, radiation or UV light, as well as long-term use of diuretics or corticosteroid medications used to treat various health concerns.
- Traumatic cataracts: This type refers to cataracts which develop as a result of penetrative or blunt injury to the eye. The development of cataracts, however, may not occur directly following injury and can take a few years to develop.
- Radiation cataracts: Radiation based treatments, such as those used for cancer, may sometimes cause the development of this type of cataracts.
Clouding (occurring in a specific location of the eye lens) may be defined as:
- Anterior (front)
- Central (nucleus)
- Posterior (back)
- Peripheral (cortical)
Sometimes clouding can affect more than one portion of the lens too. Cataract formation may also be defined as mild, moderate or severe, as well as early or advanced. A totally clouded or opaque eye (almost entirely white in colour) is known as a ‘mature cataract’ or ‘ripe’ (the opposite is known as an ‘immature cataract’).