NISHITA AFRIN

B.OPTOM

3rd YEAR (3rd BATCH )

ICO ,CU

SPECIAL LENS DESIGNING, LENTICULAR

LENS,ASPHERIC LENS AND OTHERS

INTRODUCTION

• Before a lens can be constructed it must be , designed .Thatis to say , the radii of curvature of the surfaces, the thickness,the air spaces, the diameters of the various components andthe types of glass to be used must all be determined andspecified

LENS DESIGNING PARAMETERS –

-surface curvature

- optical indices

- number of elements

- spacing of elements

• DEGREE OF FREEDOM –

- Focal lengths

- magnification

- physical constraints like weight

PRINCIPALS OF LENS DESIGN

vertex distance

vertex distance

vertex distance

C

PRINCIPALS OF LENS DESIGN

LENS VARIABLES

• The number of lenses per aperture

• The index of refraction

• Lens thickness

• Vertex distance

• Lens form

SPECIAL LENS DESIGNING

• Any prescriptions above +8.00 D and above -15.00 D require

Special lens designs to provide optimal visual acuity and cosmesis.

Special lenses- 1. ASPHERIC LENSES

2. LENTICULAR MINUS LENS

3. LENTICULAR PLUS LENS

4. MULTIDROP LENSES

5.MYODISC

6. FRESNEL PRISM

7. FRESNEL LENS

ASPHERIC LENSES

A spheric lens surface is regular , like the surface

of a ball or sphere. That surface has one specific

radius of curvature .An aspheric lens surface

changes shape. It does not have the same radius

of curvature over the entire surface

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• The “asphericity” is achieved by flattening the

periphery of the front surface in plus lens and by

steepening the periphery of the front surface in

minus lens and/or by flattening the periphery of

the back surface to reduce the edge thickness.

PRINCIPAL OF ASPHERIC LENS

WHY WE NEED TO CHOOSE ASPHERIC LENSES

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• CHOOSING A FLATTER BASE CURVE WILL

MAKE THE LENS LOOK LESS BULBOUS &

ALSO REDUCE THE

MAGNIFICATION.COSMETICALLY, THE LENS

LOOK MUCH.

• THEY ARE EASILY RETAINED IN THE FRAME

AS WELL.

FITTING GUIDELINES FOR ASPHERIC

• Use monocular IPD

• Measure MRP heights in the conventional manner

.Then subtract 1 mm for each 2 mm of pantoscopic

tilt

• Remember that the laboratory cannot grind prism

for decentration with aspheric lenses. Moving the

optical center away from the center of the aspheric

zone will destroy any aspheric optical advantage.

HIGH PLUS LENS DESIGN

• Regular spheric lenses

• Lenticulars plus design

• Multidrop lenses

REGULAR SPHERIC LENS

LENTICULAR PLUS LENS

CARRIER

ASPHERIC

LENTICULAR LENS

CROSS SECTIONAL VIEW OF SPHERIC

LENTICULAR LENS

Sphere portion

Radius of

spheric

portion

RAYS PASSING THROUGH THE SPHERICAL

LENTICULAR LENS

CROSS SECTIONAL VIEW OF ASPHERIC

LENTICULAR LENS

MULTIDROP LENSES

•

+14D

+13D

+12D

+11D

+10D

HIGH MINUS LENS DESIGN

• LENTICULAR MINUS LENS DESIGNS

• THE MYODISC

• THE YOUNGER BLENDED MYODISC

• MINUS LENTICULAR

LENTICULAR MINUS DESIGNS

THE MYODISC

MINUS LENTICULAR

• Made with minus lens

• Carrier is not plano but in plus power

• Outer edge will be thin down due to plus

power

THE YOUNGER BLENDED MYODISC

• Less work in laboratory

• erases line between bowl and carrier

• Known as blended myodisc

• There are two options -..

REFERENCES

1. CLINICAL OPTICS BY TROY E.FANNIN AND

THEODORE GROSVENOR

2. SYSTEM FOR OPHTHALMIC DISPENSING BY

CLIFFORD W.BROOKS AND IRVIN M.BORISH

3. WEBSITES