The eye is made up of three main layers:
Cornes
Choroid
Retina
A slight damage to the eye can cause discomfort. A phenomenon called change blindness can occur when a change in the visual stimulus happens without the observer noticing (Ivers, Mitchell
& Cumming,1999).
Some observers sometimes fail to detect image differences. This change is attributed to the failure of human attention .
This can as well be attributed to aging. When a person reaches 40 years old, the vision weakens.
A common condition is called presbyopia. This occurs when one is unable to directly
focus light as a result of hardening of retina.
As a person ages, the muscle fibres of the lens is affected and becomes harder, making it unable to focus on objects that are close (Society of General Physiologists, 2014)