Varifocals -The strength of the lens varies accross their surface.
For - No horizontal line between near and far that makes you look old.
Against - distortion, difficulty to get used to them in the first place and high price.
You pays your money and makes your choice. I wear bifocals because I do woodwork and varifocals make it difficult to judge a straight line making the quality of the work suffer.
They can be made as strong as you like especially if you pay for high quality lenses. However your optician may council against having a greater difference between near and distance as this increases the distortion. But you are the customer you can have what you want.
Prescription - the measurement for the lenses needed to correct your vision.
It is definitely worth collecting your prescription. (And perhaps spending a little time learning to understand it). If you do, then you can order your spectacles on line and pay £40 rather than £150.
'Window' - Near portion on bifocals.
Most bi-focals are 'd types'. This means that the near portion is like a 'D' with the flat bit horizontal positioned in the frame just below your pupil.
Older glasses often had a circular near portion or the whole of the bottom of the lenses being a near portion (sometimes called O and E types). I wish I could get E types these days as I like the big near area for woodwork. The Ds come in different sizes and I would definitely go for a large one especially if you have large frames.
Deterioration with implanted lenses
Implanting lenses is exactly the same operation as the one performed in a modern cateract removal operation.
The old natural lens is emulsified and sucked out and a new plastic one is put in its place. Since this operation was invented (by an Englishman called, If my memory serves, Ridley) old people that have had to have their lenses removed because they had gone cloudy (cateract) no longer have to wear bottle glasses.
The operation does not prevent all the other eye problems of old age (how could it?) but it does remove the lenses that may have developed cateracts. One problem with implanted lenses is that they can sometimes get an increasingly opaque film on the back of them. This is usually removed by laser.
Voluntary Eye Surgery - of any type.
There are lots of companies advertising lasering of eyes to correct short sightedness. This has been a boon for many people but there is a significant minority who wish they had never had it done. The advertising is very posotive and never gives the negatives. Whatever elective surgery you are considering be sure to find out the cons as well as the pros before making a decision. It's your eyesight/body, be sure to spend more time reasearching the pro's and con's than you would if choosing a new car.
This message was last edited by tteedd on 26/10/2012.
This message was last edited by tteedd on 26/10/2012.