Apart from the obvious use of date of birth to help ensure accurate records are kept, eg to differentiate between a father and son with the same name, it is useful to know a person's age as certain eye conditions are more common in certain age groups.

For example, research shows that presbyopia can be expected at a particular age. Likewise a cataract in a 75 year old might be considered normal, whereas the same condition in a 50 year old would not.