Myopia (short-sightedness)

Short-sightedness, or myopia, is a very common eye condition that causes distant objects to appear blurred, while close objects can be seen clearly.

Short-sightedness can range from mild, where treatment may not be required, to severe, where a person's vision is significantly affected. The condition usually starts around puberty and gets gradually worse until the eye is fully grown, but it can also develop in very young children.

Signs include:

• Finding it difficult to read at a distance
  
• Sitting close to the TV
• Complaining of headaches or tired eyes
• Regularly rubbing your eyes

Hyperopia (long-sightedness)

Long-sightedness affects the ability to see nearby objects. You may be able to see distant objects clearly, but closer objects are usually out of focus.

It often affects adults over 40, but can affect people of all ages – including babies and children. Long-sightedness can affect people in different ways. Some people only have trouble focusing on nearby objects, while some people may struggle to see clearly at any distance.

If you're long-sighted, you may:

• find that nearby objects are fuzzy and out of focus, but distant objects are clear
• have to squint to see clearly
• have tired or strained eyes after activities that involve focusing on nearby objects, such as reading, writing or computer work
• experience headaches

Children who are long-sighted often don't have obvious issues with their vision at first. But if left untreated, it can lead to problems such as a squint or lazy eye.

Presbyopia (aging of the lens)

After age 40, the lens of the eye becomes more rigid and does not flex as easily. As a result, the eye loses its focusing ability and it becomes more difficult to read at close range. This normal aging process of the lens can also be combined with myopia, hyperopia or astigmatism.

Astigmatism

Astigmatism usually occurs when the front surface of the eye, the cornea, has an asymmetric curvature. Normally the cornea is smooth and equally curved in all directions, and light entering the cornea is focused equally on all planes, or in all directions.

In astigmatism, the front surface of the cornea is curved more in one direction than in another. This abnormality may result in vision that is much like looking into a distorted, wavy mirror. Usually, astigmatism causes blurred vision at all distances.