to reduce the thickness of the regular lenses we can use the high
index lenses. High index lens materials are thinner than their regular
glass or plastic counterparts. The benefit is that if you have a strong
prescription, you are no longer forced into unsightly "Coke-bottle"
lenses. Just about every eyeglass wearer can get attractive lenses
that complement their appearance, rather than detracting from it.
index" means that the lenses are constructed of a plastic or glass
material that has a higher index of refraction. The "index of refraction"
refers to the speed that light travels as it passes through the
Myopia /and or astigmatism.
In cases of myopia or myopia combined with astigmatism the edges
of the lens are thick as the degree of myopia rises. The solution
for more attractive lenses is to use lenses with a refractive index
that is higer than the ordinary. The common lenses have a refractive
index of 1,5. Today's technology can manufacture lenses with a reftactive
index as high as 1,9. The suggested index to use depents on the
degree of your myopia.
That means for degree of mypia:
- 0 - 2 , the suggested
refractive index is 1,5 or 1,6,
- 2 - 3 the suggested refractive
index is 1,6 or 1,7,
- 3 - 5 the suggested refractive
index is 1,7
- 5 - 8 the suggested refractive
index is 1,8
- > 8 the suggested refractive
index is 1,9.
In cases of hypermetropia over the 2-3 degrees of prescription we
have the problem of the high central thickness. the result is ,
heavy lenses, magnification and distortion of your eyes. But there
isalso another problem associated with not only the appearance of
the glasses but with the vision as well. In such cases the ordinary
sferic lenses present the so called sferical distortions at their
edges. That means you will have distorted vision looking through
these glasses looking at the left of right side.
The solution is to use high index lenses aspheric. The aspheric
lenses have a different design that makes them flatter in order
to achieve less thickness at the center. Yhe result is a thinner
lens, lighter-weight, with less peripheric distortions and less
magnification of the eyes. You can see clearly the difference in
the vision performance on the two lenses in the pucture above.
Thinner Lenses | Clearer
antireflective lenses | Lighter
Generally | Eyeglasses: Frames
| Lenses |Sunglasses