This document discusses various methods for manufacturing soft contact lenses, including molding, spin-casting, and lathing. Molding involves polymerizing liquid monomers in a mold, while spin-casting uses centrifugal force to shape lenses as monomers polymerize on a spinning mold. Lathing starts with buttoning a lens blank and using tools to shape the lens surfaces. Combination methods are also discussed. Tinting methods include dissolving dyes into the monomers before polymerization or applying reactive dyes after lensing is complete.

1. SOFT CONTACT LENS
MANUFACTURING

2. SOFT LENS MANUFACTURING METHODS
 Molding
 Spin-casting
 Lathing
 Molding/lathing combination
 Spin-casting/lathing combination
 Molding - stabilized soft

3. SOFT LENS MANUFACTURING MOLDING
 Starts with liquid monomers
 Requires controlled environment,
especially humidity, and often needs to be
O2-free
 Polymerization initiator required (usually
UV)
 Subsequent steps.

4. SOFT LENS MANUFACTURING MOLDING

6. SOFT LENS MANUFACTURING LATHING
 Starts with an anhydrous button
 Requires strict control of environment especially
of humidity
 Cleaning and hydration required upon completion
 Lens sealed in normal saline
 Packaged product then autoclaved
(121oC for 15 minutes)

8. SOFT LENS MANUFACTURING
SPIN-CASTING
 Starts with liquid monomers
 Monomers introduced into spinning mold
 Centrifugal force and gravity defines back
surface shape and BOZR.
 Secondary manufacturing methods – edge
finishing.

9. SOFT LENS MANUFACTURING
SPIN-CASTING

10. SOFT LENS MANUFACTURING
SPIN-CASTING/MOULDING COMBINATION
 front surface - spin-cast
 Back surface - moulded

11. SOFT LENS MANUFACTURING
SPIN-CASTING/LATHING COMBINATION
 back surface - spin-cast
 Front surface - lathed

12. SOFT LENS MANUFACTURING
STABILIZED SOFT MOLDING
 Developed for volume production
 An inert water substitute is mixed with
lens monomers before polymerization
 Water replaces the substitute at
hydration

13. SOFT LENS MANUFACTURING
STABILIZED SOFT MOLDING
 Better optical quality
Quicker hydration
 Enhanced reproducibility

14. SOFT LENS MANUFACTURING
ASPHERIC
 Template-following lathe
 ‘Plunge’ tool, full or half diameter
 x,y numerically controlled lathe
 Molding - single/double-sided or
spin-casting

15. SOFT LENS MANUFACTURING
TORIC
 Toric machining
 Crimped then worked as a sphere
 Dual-axis ‘flying’ cutter (slab-off torics)
 Molding - single/double-sided or spin-
casting
 Combinations of the above

16. FRONT SURFACE TORIC GENERATOR
(FLYING CUTTER)
rB = Radius of rotation - lens button
rC = Radius of travel - traversing cutterMotor
Button path
Rotating lens button
rB & rC define the readii
of the principal meridians
Traversing cutter axis
Traversing cutter
Cutter path rC
Motor

17. SOFT LENS MANUFACTURING
BIFOCALS
 Concentric (annular) with
- Distance centre
- Near centre
- Distance centre, progressive near
- Best suited type –molding or spin
casting.

18. TINTING
SOFT CONTACT LENSES

19. SOFT LENS MANUFACTURING
TINTED LENSES
 Vat tinting
 Reactive dyeing
 Concentric rod casting
 Front surface printing/stamping
 Lamination
- hand-painted
- incorporated photograph
- opaque ink stamping

20. TINTED SOFT LENSES
TINTING PROCESS
 Dye or pigment is dissolved in monomer before
mixing and polymerization.

21. TINTED SOFT LENSES
OPAQUES
Lamination was the original method
• Artwork on scl -
- the image is hand painted
- a stock image is inserted
- a thin photograph is used
- an opaque ink is stamped

22. • Additional polymer cast over artwork
• Lens completed using conventional methods

23. ---By C.Irine Jeba.