2.02 Lenticular lenses

lenticular lens definition SLIDE 3

a lens where the powered portion of the lens is smaller than the frame aperture into which it is glazed

why are lenticular lenses used

to reduce the weight and thickness of high power lenses

• can be used for high plus and high minus lenses

• very common for correcting aphakic patients

what is this type of lens called SLIDE 4

positive full aperture lens

what is this type of lens called SLIDE 4

cemented lenticular lens

positive powered portion is cemented to carrier

what are these parts of a lens called SLIDE 4

powered portion

plano/flat carrier

what is this type of lens called SLIDE 5

solid convex lenticular

positive power

whole lens is made from one piece of plastic

what is this type of lens called SLIDE 6

blended lenticular

positive powered

blends the transition between edge of powered portion and carrier

positives and negatives of blended lenticular lenses

+blended lenticular gives a good cosmetic result

-theres greater distortion at the periphery of the lens experienced by the wearer

what is this type of lens called SLIDE 7

bi lenticular

plus powered (gives very high +ve power)

useful as a low vision aid

lenticulation on both sides of lens

what is this type of lens called SLIDE 8

full aperture minus powered lens

what is this type of lens called SLIDE 8

hand flattened lens

minus power

the safety chamfer/ safety bevel applied to the lens is cut a bit deeper. this reduced the edge thickness, but also reduces the size of the powered area of the lens (less power in the periphery)

what is this type of lens called SLIDE 9

cemented lenticular

minus power

what is this type of lens called SLIDE 10

solid concave lenticular

minus power

what is this type of lens called SLIDE 11

minus powered lens with a positive margin/carrier

flattens/thins lens edge and gives a better cosmetic result

what is this type of lens called SLIDE 12

blended lenticular

minus power

negative centre, smoother transition to carrier

what is this type of lens called SLIDE 13

profile/step lenticulars

improve cosmetic appearance by making the shape of the powered area the same as (but smaller than) the eye shape of the frame

how are profile lenticulars made

the standard lens is edged to the correct size/shape to fit into the frame.

the edge profile is ground again to reduce the size of the powered area therefore reducing the edge thickness

what is the 38mm referring to

what is the 68 referring to

SLIDE 14

38 = size of powered portion

68 = total diameter of carrier

positive of a higher refractive index lenticular lens

thinner and lighter

what does a reduction in abbe number lead to - positives and negatives

+good cosmetic result

-fall off in chromatic performance - pt notices colour fringes around targets

-more expensive

negatives of glass lenses

-expensive

-brittle

-safety issues

equation to determine field of view through an ophthalmic lens SLIDE 24

list the issues for a lenticular lens weaer

field of view

peripheral distortion in blended lenticulars

‘jack in the box’

explain the issue of peripheral distortion in blended lenticular SLIDE 26

applies to positive and negative versions

benefit of better cosmetic appearance of the lens, and absence of the classic ‘ring scotoma’

warn pt to not read anything through the blended zone

explain the ‘jack in the box’ issue

same as a ‘jump’ in a bifocal

object ‘jumps’ into view when its in the lenticular portion

what is a fresnel lens SLIDE 29

a lens form where the thickness and wight is reduced by removing lens substance from ‘rings; of lens material

lens keeps the same power

made from lots of little prims made up in a sheet. can be stuck onto lenses/ temporary specs following surgery that renders the patient aphakic

what are fresnel lenses used in

lighthouse optics

theatre

tv spotlights

specialist ophthlamic lenses

transient or unstable binocular vision problems

• stroke pts

• trauma pts

positives of fresnel lenses

+thin

+light