Multi-focal spectacles?!
Question:
Multi-focal spectacles?
food for thought: how can myopia (short-sightedness) and hyperopia (long-sightedness) occur simultaneously in a person? my mom recently got multi-focal spectacles, which is why i'm wondering.
from what i understand, myopia occurs because the image falls in front of your retina, while hyperopia occurs because the image falls at the back of your retina. if they were both to the same degree, wouldnt they cancel each other out? perfect vision again then, haha :)
otherwise, if your myopia is to a higher degree than your hyperopia or vice versa, wouldnt one kind of lens suffice? as in, you're either long sighted, or short sighted coz they cancel each other out. no two ways about it, no?
any opthalmologists or optometrists? thank you in advance
Answers:
No one can be hyperopic and myopic in the same eye...
What your mom is experiencing is called presbyopia! No matter what type of refractive error you have this will happen to everyone. Presbyopia is a natural part of aging and is not a disease...just a condition!
The crystalline lens inside of our eye normally helps us focus on objects at near. To help us focus on objects at near it changes shape. As we age our crystalline becomes more rigid and looses its ability to change shape.... when this happens we begin to have difficulty seeing at near distances. This progresses and the lens becomes more rigid until you can no longer read at near distances. This process becomes noticeable around age 40 and progressively gets worse until late 50's where it levels off.
When a person is myopic their eyeball is too long.... when a person is hyperopic their eyeball is too short....
Presbyopia mimics the same condition as hyperopia...but they have different underlying causes.
Anyways to answer the other part of your question... when you are myopic.... you will always be myopic! When a myopic person hits around age 40 and becomes presbyopic.... if they have a lower prescription (like under -3.00) then they actually can take their glasses off to read! But they still will have trouble seeing in the distance!
Anyways I hope this helps a bit....and I have posted some links with more info on presbyopia if you are interested! :)