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Soft contact Lens-manufacturing methods.

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Irine Jeba

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.

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SOFT CONTACT LENS MANUFACTURING
SOFT LENS MANUFACTURING METHODS  Molding  Spin-casting  Lathing  Molding/lathing combination  Spin-casting/lathing combination  Molding - stabilized soft
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.
SOFT LENS MANUFACTURING MOLDING
Soft contact Lens-manufacturing methods.
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)
Soft contact Lens-manufacturing methods.
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.
SOFT LENS MANUFACTURING SPIN-CASTING
SOFT LENS MANUFACTURING SPIN-CASTING/MOULDING COMBINATION  front surface - spin-cast  Back surface - moulded
SOFT LENS MANUFACTURING SPIN-CASTING/LATHING COMBINATION  back surface - spin-cast  Front surface - lathed
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
SOFT LENS MANUFACTURING STABILIZED SOFT MOLDING  Better optical quality Quicker hydration  Enhanced reproducibility
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
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
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
SOFT LENS MANUFACTURING BIFOCALS  Concentric (annular) with - Distance centre - Near centre - Distance centre, progressive near - Best suited type –molding or spin casting.
TINTING SOFT CONTACT LENSES
SOFT LENS MANUFACTURING TINTED LENSES  Vat tinting  Reactive dyeing  Concentric rod casting  Front surface printing/stamping  Lamination - hand-painted - incorporated photograph - opaque ink stamping
TINTED SOFT LENSES TINTING PROCESS  Dye or pigment is dissolved in monomer before mixing and polymerization.
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
• Additional polymer cast over artwork • Lens completed using conventional methods
---By C.Irine Jeba.

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Soft contact Lens-manufacturing methods.