UNIT FOUR - CL Characteristics/Manufacturing Flashcards
LENS CHARACTERISTICS: Oxygen permeability (DK Value)
D= diffusion coefficient for oxygen movement in the lens material K= solubility of oxygen in the material
LENS CHARACTERISTICS: Oxygen transmissibility (DK/L)
D= diffusion coefficient for oxygen movement in the lens material K= solubility of oxygen in the material L= lens thickness
LENS CHARACTERISTICS:
Wettability
Wetting angle
Functional wettability
LENS CHARACTERISTICS:
Heat transfer
………..
LENS CHARACTERISTICS:
Stability
Flexure
Warpage
LENS CHARACTERISTICS:
Durability
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LENS CHARACTERISTICS:
Deposit resistance
………………
LENS CHARACTERISTICS:
Electrostatic properties
Ionic
Non-ionic
LENS CHARACTERISTICS:
Reproducibility
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Rigid lens materials (4 total)
Polymethylmethacrylate (PMMA)
Cellulose Acetate Butyrate (CAB)
Silicone Acrylate (SA)
Fluoride-Silicone Acrylate (FSA)
Rigid lens designs (6 designs)
Spherical Front surface toric Back surface toric Bitoric Aspheric Cosmetic
RIGID LENS MANUFACTURING:
Lathe cut
Liquid monomers Polymerization using heat & UV light Base curve Peripheral curves Anterior curves Edge
RIGID LENS MANUFACTURING:
Cast molded
Base curve
Soft lens materials (3 materials )
Hydroxyethylmethacrylate (HEMA)
Glyceryl Methylmethacrylate (GMMA)
Silicone Hydrogel
Soft lens designs ( 7 total)
Spherical Front surface toric Back surface toric Bitoric Aspheric Cosmetic Therapeutic
SOFT LENS MANUFACTURING:
Lathe cut
Liquid monomers Polymerization using heat & UV light Base curve Peripheral curves Anterior curves Edge Hydration Extraction (rinsing) Inspection
SOFT LENS MANUFACTURING:
Spin cast
Liquid monomers Spinning molds of front surface Polymerization using heat&UV light Edge Hydration Extraction (rinsing) Inspection
SOFT LENS MANUFACTURING:
Cast molding
Liquid monomers Concave&convex molds Polmerization using heat&UV light Edge Hydration Extraction (rinsing) Inspection
Manufacturing concerns
Lens design Material characteristics Production volume Reproducibility Quality control
Manufacturing costs
Research and development
Engineering and equipment
Materials
Labor
Manufacturing methods (4 total)
Lathe cast
Spin cast
Spin cast/lathe cast
Cast molded
Standard Lathe manufacturing process :
Posterior surface
Button mounting
Cutting central posterior curve
Polishing CPC or base curve
Generating secondary and peripheral curves
CNC multi-Axis Lathe Manufacturing Process
Computer entry Network capabilities Base and peripheral curves Aspheric curves Toric curves Edge design
Cast Molded Radius buttons
Liquid monomer
Polymerization in molds
Buttons with finished base curve

Standard lathe manufacturing:
Anterior surface
Blocking
Lathe anterior surface
Edging
What are the three parts that are needed to be inspected?
Base curve and surface quality
Power
Edge
During the inspection process, base curve and surface quality can be inspected by what?
Radiuscope
During the inspection process,power can be inspected by what?
Lensometer or auto lensometer
During the inspection process, edge can be inspected by?
Projection magnifier
What are some of the soft lens additional Procedures?
Hydration, extraction, tinting, wet inspection, final packaging, sterilization, and labeling.
What are some of the contact lens packagings?
Vials(older design) Blister packs (current)
What are some advantages of lathe cutting ?
Design options
Material options
Low volume production
What are some disadvantages of lathe cutting?
Labor costs
Material waste
Reproducibility
What was the original manufacturing process of contact lenses ?
Spin cast
What are the steps of the Spin cast manufacturing process?
1) Stainless steel tools form molds
2) Mold place in spinning cavities in lens production table
3) Liquid monomer is injected into spinning, computer controlled mold
4) Lens form solidifies under UV light
5) Edge is trimmed and rounded
6) lens hydrated and rinsed
What are some advantages of Spin cast manufacturing?
Unit cost
Reproducibility
Comfort
What are some disadvantages of Spin cast manufacturing?
Cost of initial set up
Visual acuity 
What is the most popular method of manufacturing today ?
Cast molding
What is the process for cast molded manufacturing?
1) stainless steel tools form convex and concave plastic injection molds
2) reusable quartz molds may be used
3) concave mold is filled with liquid monomer
4) convex mold is placed on top and clamped
5) polymerization occurs as lenses are exposed to heat and UV light 
What are some of the additional processes for Cast molding ?
Hydration, rinsing, tinting, surface treatment, wet inspection, packaging, and labeling 
What are additional names for cast molding ?
Fully molded, light stream molded, stabilized soft molded, and wet molded.

What are some cast molded lens designs and types?
Frequent replacement, disposable, spherical, toric, and multifocal.
What are some advantages of cast molded manufacturing?
Lower unit cost
Surface quality
Reproducibility
What are some disadvantages of cast molded manufacturing?
Initial set up costs
Limited parameters
Edge finish
