PRESBYOPIA

DEFINITION OF PRESBYOPIA

The gradual (slow) loss of accommodation as we get older is called presbyopia.

Everyone over the age of 40 to 45 years is affected by presbyopia. Some people, especially those living in the tropics,get presbyopia even earlier than this. This is because everybody loses the ability to accommodate as they age. The loss of accommodative ability and the subsequent onset of presbyopia happens to both eyes at the same rate.People with presbyopia usually find it difficult to read or do any near task. Giving them spectacles for near vision helps them to again do the near tasks that they used to do previously.Near tasks are sometimes referred to as close work, and include all work that requires good vision to see something that is within arm’s reach of a person.If a person can touch what they are looking at (if it is within arm’s length of them), it is considered a near task or close work. Sometimes an early presbyope (someone who is just starting to get presbyopia) will hold things further (and further!) away from their eyes so that they can see it more clearly.This is because less accommodation is needed to see things that are further away from the eyes.

CAUSE OF PRESBYOPIA

Presbyopia is caused by the loss of accommodative ability that is associated with ageing. As we get older, the crystalline lens gradually gets harder and cannot change shape easily when the ciliary muscle contracts. This is a normal, natural aging process. This means that an older person cannot accommodate as easily as a younger person.If the eye does not accommodate when looking at a close object, the object will appear blurry or out of focus.People often make the mistake of thinking that presbyopia is due to a weakness of the ciliary muscle, but this isnot true. The ciliary muscle still works properly, but it has a more difficult job when it has to try to bend the inflexible crystalline lens.

Figure 1: A presbyopic eye with some accommodation remaining.

Light from a close object does not focus on the retina.

Figure 2: A presbyopic eye with no accommodation remaining.

Light from a close object does not focus on the retina.

SYMPTOMS OF UNCORRECTED PRESBYOPIA

People with presbyopia may have trouble with near tasks such as reading, sewing, and sorting rice. When presbyopia starts, they may say things like:

• “I can read in bright sunlight, but not in dim light”
• “My arms are not long enough!”
• “My eyes feel strained when I do a lot of sewing”
• “My eyes get tired when I read”
•  “The writing in the newspaper is too small”
• “I find it difficult to thread a needle”
• “I find it hard to sort the stones from the rice when I’m cooking”
• “The distance looks blurred when I look up after I have been reading for a long time”.