What is a cataract?

A cataract is a condition of the eye in which the eye’s natural lens turns cloudy and your vision clarity decreases. This happens because the proteins in the lens clump around and form an opacity. The opacity may be complete or partial depending on the age or maturity of the cataract.

Normally, the eye lens is clear and transparent and serves the function of directing the rays of light from an object to converge exactly on the retina of the eye, which is situated on the posterior wall of the eyeball. This is what makes you clearly see the object you are watching.

When the eye lens develops a cataract, the rays of light from an object entering the eye lens are not properly refracted and do not converge to meet on the retina due to the opacity developed in the cataract lens.

The object is, therefore, not viewed clearly or not viewed at all depending on the maturity of the cataract.

It is difficult to say how quickly a cataract will mature. Most of the time, cataracts develop gradually over a span of years and you do not experience any visual problem early on.

However, generally, when a cataract comes on later in life due to aging, it typically develops slowly over a period of years. However, one that begins earlier in life and due to other reasons such as diabetes, can progress more rapidly.

In the early stages, stronger lighting and eyeglasses can help you to deal with the visual problem, but as the cataract matures and the opacity increases, surgical treatment becomes necessary.

Types of cataracts

Cataracts are typed according to their location in the eye lens. The opacity can develop in the center portion, the outer part, and the back surface.

  • Nuclear cataracts. Nuclear cataracts also referred to as Nuclear sclerotic cataracts, develop at the center of the eye lens (the nucleus of the lens) and are the ones that the opthalmologist sees more often. This type usually improves your near vision initially and you are able to read better. But, as the cataract develops it becomes denser and the lens turns yellow and then brown. It gradually begins to cloud your vision and you find it difficult to distinguish between shades of color.
  • Cortical cataracts. Cortical cataracts affect the edges of the lens and first appear as wedge-shaped opacities on the outer edge of the lens cortex pointing towards the center of the eye. Your vision becomes hazy and foggy. They make it difficult to face a glare and you will find it difficult to drive at night. Since they cause problems with near and far vision you tend to go for treatment early.
  • Posterior subcapsular cataracts. These are cataracts that occur at the back of the lens. This type of cataract starts as a small, white opaque area that obstructs the path of light. It interferes with your near vision making reading difficult and causes halos around lights at night. It tends to progress more rapidly than other cataracts. You see them more in diabetic patients and in those who have taken corticosteroid medicines for a long time.
  • Congenital cataracts. These are cataracts you’re born with or develop early in childhood. The cause is usually genetic or it may be associated with an intrauterine infection or trauma. These types of cataracts may be unilateral or bilateral. While in some cases they may be insignificant, in others they may cause profound visual impairment wherein surgery is the only option.

Causes and risk factors

1. Advancing age cataract is the most common type of cataract and is due to advancing age.

2 . A secondary cataract develops due to a secondary cause such as

    • Due to eye surgery after Glaucoma
    • Diabetes
    • Prolonged use of medications like steroids, major tranquilizers, and diuretics
    • Excessive exposure to ultraviolet rays, which are present in sunlight. The use of sunglasses or a broad-rimmed hat helps to prevent this type of cataract.
    • Heavy consumption of alcohol
    • Excessive smoking

3. Traumatic cataracts are those, which occur due to trauma to the eye. It can be a blunt trauma or a penetrating ocular injury. Blunt trauma can cause cataracts even after a few years.

4 . Cataracts due to radiation exposure can develop due to exposure to cosmic radiation. For this same reason, pilots and astronauts are at a greater risk of developing cataracts. Exposure to high levels of radiation can cause diminished vision in as little as two years.

5 . Congenital cataract is seen in newborn babies. It develops due to hereditary enzyme defects. Vision may or may not be affected. Surgery is advised if vision is impaired.

6.  Iodine deficiency can also cause cataracts.

Other causes include:

How does a cataract develop? Pathophysiology

The lens of the eye is made of water and specific proteins, which give the lens flexibility, transparency, and clarity.

With advancing age and due to the causes mentioned above, the structure of these specific proteins of the eye lens change, and the lens loses its flexibility and transparency, leading to a gradual clouding of the lens and the development of opacity.

This blocks the light as it passes through the lens, preventing a sharply defined image from forming on your retina. This causes a blurring of vision.

Cataracts generally develop in both eyes, but the development is not even. The cataract in one eye may be more advanced, causing a difference in the clarity of vision between the two eyes.


A cataract is a painless condition and its symptoms are only related to vision.

Initially, the cataract may affect only a part of your lens in which case you may not notice any vision problems. With time, as the cataract grows and clouds more of the lens, the signs and symptoms of the cataract begin to manifest. They include:

  • The blurring of vision. You can compare it to vision through the dirty and soiled glass.
  • You will need bright light to read.
  • Night vision is impaired.
  • Colors seem to lose their brightness.
  • There is a frequent need to change prescriptions for eyeglasses.
  • Sunlight, oncoming car headlights, etc appear too bright.
  • You will see “halos” around lights
  • There may be double vision in one eye
  • Please note that the cataract does not cause any pain or swelling of the eyes. Any such symptoms are due to some other eye pathology and should be referred to an ophthalmologist.

How you can prevent cataracts?

There is no definite method that will help you prevent cataracts or slow the progress of an existing one. However, experts seem to think that some strategies may help.

  • Use sunglasses and a broad-brimmed hat when you are out in the sun.
  • If you are diabetic, keep your blood sugar under control.
  • If you are hypertensive, keep your pressure within normal limits.
  • Do not use medicines without advice from your physician. They could predispose to cataract formation.
  • Avoid alcohol and smoking.
  • Stay at a healthy weight. If you are obese, promptly start to lose weight.
  • Incorporate plenty of fruits and vegetables into your healthy diet. They are rich in antioxidants, which can help in preventing diseases including cataracts.