This document discusses lens design parameters and special lens designs used for high plus and high minus prescriptions. It describes key considerations in lens design like surface curvature, optical indices, element spacing, and aspheric lenses. Special lens designs discussed include lenticular lenses, multidrop lenses, and myodiscs for high prescriptions. Aspheric lenses are described as having non-uniform curvature across the surface to reduce thickness and improve cosmesis for high plus and minus prescriptions.

1. SPECIAL LENS DESIGNING, LENTICULAR
LENS,ASPHERIC LENS AND OTHERS
NISHITA AFRIN
B.OPTOM
3rd YEAR (3rd BATCH )
ICO ,CU

2. INTRODUCTION
• Before a lens can be constructed it must be , designed .That
is to say , the radii of curvature of the surfaces, the thickness,
the air spaces, the diameters of the various components and
the types of glass to be used must all be determined and
specified
LENS DESIGNING PARAMETERS –
-surface curvature
- optical indices
- number of elements
- spacing of elements

3. • DEGREE OF FREEDOM –
- Focal lengths
- magnification
- physical constraints like weight

4. PRINCIPALS OF LENS DESIGN
vertex distance
vertex distance
vertex distance
C

5. PRINCIPALS OF LENS DESIGN

6. LENS VARIABLES
• The number of lenses per aperture
• The index of refraction
• Lens thickness
• Vertex distance
• Lens form

7. 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

8. 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

10. • 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.
29 October 2014 10

11. PRINCIPAL OF ASPHERIC LENS

12. WHY WE NEED TO CHOOSE ASPHERIC LENSES
• 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.
29 October 2014 12

13. 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.

16. HIGH PLUS LENS DESIGN
• Regular spheric lenses
• Lenticulars plus design
• Multidrop lenses

17. REGULAR SPHERIC LENS

18. LENTICULAR PLUS LENS
CARRIER
ASPHERIC
LENTICULAR LENS

19. CROSS SECTIONAL VIEW OF SPHERIC
LENTICULAR LENS
Sphere portion
Radius of
spheric
portion

20. RAYS PASSING THROUGH THE SPHERICAL
LENTICULAR LENS

21. CROSS SECTIONAL VIEW OF ASPHERIC
LENTICULAR LENS

22. MULTIDROP LENSES
•
+10D
+11D
+12D
+13D
+14D

23. HIGH MINUS LENS DESIGN
• LENTICULAR MINUS LENS DESIGNS
• THE MYODISC
• THE YOUNGER BLENDED MYODISC
• MINUS LENTICULAR

24. LENTICULAR MINUS DESIGNS

25. THE MYODISC

26. MINUS LENTICULAR
• Made with minus lens
• Carrier is not plano but in plus power
• Outer edge will be thin down due to plus
power

27. THE YOUNGER BLENDED MYODISC
• Less work in laboratory
• erases line between bowl and carrier
• Known as blended myodisc
• There are two options -..

31. 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