What is cataract? What are its causes and symptoms?

cataract symptoms

Cataract is a condition that affects the eye over a period of time. Typically, it occurs when protein clumps up in the form of a thin film in the eye, clouding the lens and reducing the amount of light that reaches the retina. This is because the lens of the eye is composed mostly of water and proteins. Over time, as proteins break down, they stay on in the eye. These lingering proteins make the lens cloudy, and as a result, clear vision is impaired. As time passes, the cataract gets more severe and clouds more of the lens.

The lens is clear in a patient who does not have cataract. For proper sight, light passes through a clear lens which lies behind the iris (colored part of the eye). The lens focuses the light on the retina. Then the brain and eye coordinate to process information in the form of a picture. When cataract clouds over the lens, the eye cannot focus light in the ideal way, so the image, or picture that is seen is blurred or foggy.

Cataracts, affect different parts of the lens and are classified under:

  • Posterior subcapsular cataracts
  • Nuclear cataracts in the center of the lens
  • Cortical cataracts on the side of the lens, which appear as small streaks

Most cataracts are age-related — they occur as we get older. As per the National Blindness and Visual Impairment Survey India, 2015-19, cataract has been identified as the leading cause of blindness in people above 50 years. However, cataract is a condition that is treatable if diagnosed and surgically removed in time.

Types of cataracts

There are five predominant types of cataracts and the treatment for each type is cataract surgery.

  1. Age -related cataract: This is the most common type of cataract. It appears with the onset of age.
  2. Traumatic cataract: This type of cataract is caused by serious eye injuries which have caused damage your lens. The cataract might form soon after the injury, or, in some cases, many years later
  3. Radiation cataract: It can be caused by certain types of radiation including ultraviolet (UV) rays from the sun and radiation treatment for cancer
  4. Pediatric cataract: This type is usually congenital and occurs at birth or in early childhood. Although rare, they are usually genetic
  5. Secondary cataract: Sometimes, after cataract surgery, the patient may develop a condition called secondary cataract or posterior capsule opacification. The condition makes their vision cloudy again. This condition is also called after-cataract and is quite common.

What causes cataract?

In addition to age, certain other factors are known to cause cataract. These include:

  1. Health problems, like diabetes: Although the reasons are not fully understood, people with diabetes mellitus statistically face a 60% greater risk of developing cataracts
  2. Cigarette smoking: Doctors believe smoking contributes to cataracts by altering the cells of the lens through oxidation. There is also evidence that smoking leads to the accumulation of heavy metals like cadmium in the lens. Research has found that smokers have double the risk of developing cataracts compared with non-smokers. This risk is triple for heavy smokers.
  3. Too much alcohol: Several studies have indicated increased cataract formation in patients with higher alcohol consumption. Moderate to low consumption, however is not known to lead to cataract.
  4. Obesity: Obesity can cause cortical cataracts, a condition where light is scattered by a defective lens, and the adipose tissue present in excess weight releases a chemical called leptin, which is a source of oxidative stress that can damage the eye
  5. High Blood PressureOphthalmologists believe that High blood pressure is known to cause elevated inflammation, which may result in cataracts over time.
  6. High myopia: Research reveals that individuals with early onset of high myopia are more likely to develop cataracts in their later years. The increasing axial eyeball length in myopic eyes may prevent nutrient delivery to the rear side of the lenses. As a result, the lenses lose their clarity and begin forming cataracts.
  7. Family history of cataracts: Individuals with close blood relatives who have had cataracts are more likely to develop cataracts than those with no family history.
  8. Eye injury, eye surgery:  Trauma to the eye, caused by a blunt or penetrating object, electric shock, chemical burns or ionizing radiation can lead to traumatic cataract even years after the injury
  9. Radiation treatment on your upper body: The lens of the eye is one of the most radiosensitive tissues in the body. Exposure to ionizing radiation treatment above the torso can cause cataract formation which can develop over a span of a few years to decades
  10. Spending a lot of time in the sun: Frequent, direct exposure to sunlight causes the proteins of the eyes’ natural lenses to start clumping together. Over time, this forms a cataract
  11. Prolonged use of steroids (medicines used to treat a variety of health problems, like arthritis and rashes): Long-term consumption or high-doses of steroids can promote cataract formation. Individuals taking a combination of oral and inhaled steroids are at the highest risk

What are the symptoms of cataract?

Cataract can manifest itself in several ways. The most common symptoms of cataracts include

  1. Blurred vision: Cloudy, misty, blurry, foggy or filmy images
  2. Double vision: The person sees a double image where there should only be one. The two images can be side by side, on top of one another, or both
  3. Increased intolerance to glare: Sensitivity to bright sunlight, lamps, torches or headlights
  4. Appearance of halos around lit objects: Clouding of the lens can cause diffraction of light entering the eye, which means a person with cataract may see halos around light sources
  5. Faded appearance of colors: When protein deposits accumulate on the eye’s crystalline lens and turn it opaque, vision which was once clear becomes cloudy and colors which were once bright begin to fade

Poor night time vision: As cataracts become more advanced, they take a yellow or brown tinge and affects night vision. This makes nighttime activities such as driving difficult.

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