What is presbyopia?
Presbyopia is, generally speaking, an age-related condition. It refers to the loss of autofocusing ability as people get older. Therefore, if someone has presbyopia and good distance vision, then near vision is not so clear because they cannot automatically change the focus from far to near [1].
The generally accepted reason for this is the gradual enlargement and stiffening of the natural crystalline lens within the eyeball. As it gets stiffer, it can no longer change its shape (and focusing power) as it used to when it was younger.
So why does it get larger and stiffer?
The reason is that the lens in the eye consists of cells trapped within a capsule/membrane. These cells slowly grow and multiply during your lifetime, but have nowhere to go. So they get packed more and more tightly within the capsule. If you fill a pillow more and more with cotton/feathers, you can imagine also that it will become harder and harder, and stiffer and stiffer.
What are the risk factors for presbyopia? [2]
- Age. Age is the greatest risk factor for presbyopia. Almost everyone experiences some degree of presbyopia after age 40./li>
- Other medical conditions. Being farsighted or having certain diseases — such as diabetes, multiple sclerosis or cardiovascular diseases — can increase your risk of premature presbyopia, which is presbyopia in people younger than 40.
- Drugs. Certain drugs are associated with premature presbyopic symptoms, including antidepressants, antihistamines and diuretics.
Can young people get presbyopia?
Young people can also get presbyopia if their own natural lens gets injured or removed.
And this is why if a cataract happens in a young (<~40 year old) person, generally surgery is delayed for as long as possible.
In another situation, a person may need to wear reading glasses at a younger than expected age. This can happen if the person is hyperopic (longsighted) as well as nearing the presbyopic age group. Hyperopic people always need some extra focusing effort to make their vision clear, compared to someone who is not hyperopic.
So, as the focusing ability gets less with age, they will be the first ones to feel the effect. Depending on the amount of hyperopia present, reading glasses will often be needed for these people in their late 30s rather than in the 40s as for people who are not hyperopic.
References
1. Presbyopia. Healthdirect.gov.au. Published October 24, 2019.
2. Presbyopia - Symptoms and causes. Mayo Clinic. Published 2017.
