As an adult you can chose when you wear your glasses within reason. If you cannot see to read the driving standard line without glasses then you must wear your glasses to drive. The same goes for any jobs that require a certain vision standard. However, in your own time, it's entirely up to you if you want to see the world in focus or not. I'll give some examples below.
The low to moderate myope (shortsighted person)
You are a low to moderate amount of short sightedness (myopia). For example your glasses prescription has a "-" not a "+" and says between -0.25 to -1.50ish.
In this case your close up vision, if you are under 40, will be perfect. Your distance vision will be blurred to some degree. To most people, having a blur in the distance is acceptable. Glasses make things clearer but unless they are specifically watching tv, going to the cinema playing golf or driving, they don't mind not being able to see far away. Also for short-sighted people, focusing close up is less effort for their eyes without their glasses on.
Some low myopes prefer to have perfect vision all the time so will keep their glasses on all the time. There is no such thing as wearing your glasses too much and making your eyes worse. Think about it, you are correcting your vision back to zero, as if you had no prescription. Would you tell someone with perfect eye sight to get some glasses to blur their eyes so that they don't make their vision worse by having it perfect all the time?? Of course you wouldn't, that would be ridiculous! So when people ask if they should "give their eyes a break" from their glasses, the answer is no!
The opposite should also be considered, will wearing my glasses all the time make my eyes worse? Absolutely not! By correcting your prescription and giving your brain a clear image this will not lead to an increase or decrease in your prescription. If it was going to change it would have changed regardless of whether or not you wore your glasses (I'm only talking about adults here). People think that wearing glasses full time will make their eyes reliant on them. The fact is, your brain will prefer the clearer vision and once you've been wearing your glasses all day, when you take them off you'll realise how blurred it was before you put them on by comparison! If you want to go back to not wearing your glasses then give it a few days without them and your brain will be used to living in a blur like it did before you started wearing glasses.
The moderate to high myope
The next patient is the moderate to high myope. Your glasses prescription is around -3.00 to -6.00. Now most of these people will wear there glasses all the time because anything past 20-33 cm is out of focus.
When these patients reach their early 40s they realise they can focus better without their glasses on so they lift them up or remove them to read. As long as their eyes remain healthy, they will always be able to see close up without with glasses because this is naturally where their vision is focused, with no effort from their eye muscles.
When it gets to the point where they have to lift up their glasses to see anything that is close up, approximately age 50-60, they find the glasses are on and off all day long. This is the point they usually switch to a bifocal or varifocal. Even then, when reading a book these patients will often take their glasses off and use their natural focal point again.
The low hyperope (longsighted person)
Next is the low hyperope. This time the glasses prescription has a "+" not a "-" on front of the numbers. Eg +1.00 to +3.00ish. As a young person you can use the muscles that change the shape of your lens (inside your eye) to focus long sightedness and see fine.
Long sight means the eye is too short or the lens inside the eye is too weak. By using the eye muscles either side of the lens to increase the power of the lens, we can bring the focal point that was behind the retina, to be focused clearly onto the retina.
When we are young we can do this all day long with no problems. As we age however, the lens inside the eye gets thicker and the muscles find it more difficult to pull it into shape to focus over any long sight. This can lead to eyestrain and headaches. At this point the low hyperope will usually start to wear glasses, not necessarily to improve the vision but to relax the eye muscles and relieve eyestrain, hopefully prevent the headaches they may have been getting.
Whatever your prescription, when we focus for close up, we do the same, use the muscles in our eyes to increase the strength on the lens to bring near objects into focus. So someone who is longsighted and doing a lot of close work, may find they need to use their glasses to relive some of this strain as their eyes will be trying to focus over the long sight and then extra focusing for close up objects too.
The astigmat. Is that a real word? Who knows! I'm talking about patients with astigmatism. Now you can be long-sighted or short-sighted with astigmatism.
It basically means your lens in your eye or cornea at the front of your eye (or both) are more curved in one direction than the other. This is sometimes referred to as "rugby ball shaped eyes". Now that is a massive exaggeration as your astigmatism would be off the charts if the 2 curvatures were that different but plenty of opticians use this analogy. Also it is only talking about the shape of your cornea and lens, not the whole eye.
Basically having astigmatism means you have 2 focal points in your eye. If you have some long-sight with this then your eye muscles can pull the 2 focal points as close to the retina as possible. If you are short-sighted with astigmatism then your glasses will do this for you. If there is only a small amount of astigmatism -0.25 or -0.50 then you might not need this corrected, especially if it is fairly straight (near to 90 axis or 180 axis on your prescription). If your astigmatism is higher than this or if it is at an oblique angle like 130 or 50 then you're more likely to want to wear glasses to improve the vision.
If you are wearing glasses then any astigmatism will be corrected. We would only leave it uncorrected if you didn't want glasses at all. Astigmatism can also lead to eyestrain and headaches if uncorrected although this varies from person to person.
If you are interested, always ask your optician if you aren't sure whether you are long-sighted or short-sighted and if you have astigmatism. Don't be afraid to ask questions about how often to wear your glasses if you're not sure. Hopefully this blog will help you make up your own mind. I must reiterate, this advise is only for adults. See my last blog about the plastic brain for more info about children's vision. Do not tell a child not to wear their glasses unless you have been specifically told by their own optician/orthoptist/ophthalmologist, especially if the child is under 8 years old.
As always, any questions for me, comment below.