This document summarizes various contact lens manufacturing techniques. It discusses soft lens manufacturing methods like moulding, spin casting, and lathing. It describes how these techniques work, their advantages and disadvantages. Rigid gas permeable contact lenses are lathed from cylindrical buttons using back surface and front surface lathes. Additional processes for both soft and rigid lenses include edge polishing, marking, fenestration and final inspection. The document is intended as an overview of contact lens manufacturing processes.

1. Contact lens manufacturing techniques
By,
Manoj K.M, B.Sc. Optom

2. Introduction
Medical devices that rests against the highly sensitive eyeball
Contact lens needs to be of the highest quality in terms of their
physical construction
Devices that correct optical defocus, the optical quality of contact
lenses must be higher
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3. Soft lens manufacturing methods
 Moulding
 Spin casting
 Lathing- xerogel
 Moulding/ lathing combination
 Spin casting / lathing combination
 Moulding-stabilized soft
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4.  Starts with an anhydrous button
 Strict control of environment factors especially humidity
 Numerical control increases both the complexity of the design and level
of production
 Diamond tipped tool
 Cleaning and hydration
 Sealed in normal saline
 Packed product and the autoclaved (120 degree for at least 20 minutes)
Lathing
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5. Lathing
Image courtesy: Nathan Efron and Steve Newman, Second edition Contact lens practice
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6. Advantages Disadvantages
Well established technology Labour intensive
Wide range of parameters High cost per lens
Suits most materials Variable surface finish
Starts depend on capital
budget
Volume production difficult
Lathing
Image courtesy: Nathan Efron and Steve Newman, Second edition Contact lens practice
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A laboratory using the labour-intensive method of lathe cutting
to manufacture soft contact lenses

7.  Raw materials are liquid monomers
 Male and female mould
 Monomer’s introduced into spinning mould
 Centrifugal force and gravity defines the back surface and BOZR
 Mould defines the front surface
 Front surface finish depends on mould finish
 Back surface depends on surface tension and other properties
of the resulting polymer
Spin casting
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8. Spin casting
Image courtesy: Nathan Efron and Steve Newman, Second edition Contact lens practice
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9. Advantages
 Accurate reproducibility
 Precision moulds
 Controlled spin speed
 Generates free form fluid surface
 Surface and interstitial imperfections are least
Disadvantages
 Edge thickness
Image courtesy: Nathan Efron and Steve Newman, Second edition Contact lens practice
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A manufacturing line for spin casting soft contact lenses.

10.  Dominant technology in high volume lens manufacture
 Matching male and female moulds
 Monomer in liquid form- introduced into a concave female
mould-front surface
 Ultraviolet transparent male mould clamped with the female
mould in controlled environment
 Polymerisation-UV light
Cast moulding
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11. Cast moulding
Image courtesy: Nathan Efron and Steve Newman, Second edition Contact lens practice
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12. Advantages Disadvantages
Low cost Expensive to start production
Volume production Expense limits and parameter
range
Good surface quality and
reproducibility
Not all materials suitable
Complex designs possible Stock lenses
Cast moulding
Image courtesy: Nathan Efron and Steve Newman, Second edition Contact lens practice
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Generating a metal master tool
A manufacturing laboratory for cast moulding soft
contact lenses.

13. Reverse Process III
 Combinations of spin cast and lathe cut
 Spin casting the front surface and body
 Lathing the back surface to define BOZR and design
OR
 Spin casting the body and back surface
 Lathing the front surface to give BVP and design
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14. Moulding/lathing combination
 Moulding the back surface and body of the lens
 Lathing the front surface
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15. Stabilized soft moulding
 Inert water substitute is mixed with lens monomers before
polymerisation
 Water replaces the substitute at hydration
 Significantly less expansion on hydration
 Better optical quality and surface finish
 Quicker hydration
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16. Rigid lens manufacturing
Raw materials
 Flat cylindrical buttons of 12.7 mm diameter and 4.3 mm
circumference thickness
 Supplied in various colours and the trade name imprinted
on one surface of the button
 Super gas-permeable with Dk values over 150
 Used the latest rigid gas permeable materials
Image courtesy: Nathan Efron and Steve Newman, Second edition Contact lens practice 16
Rigid lens buttons

17. Generating the lens back surface
 Button is first secured in a carrier or dolly
 Button clamped to a back surface lathe
 Set spinning at high rate about its central axis
 Diamond tipped tool
To obtain smooth and high quality finish
To the required size of the finished lens
 Button released from the lathe and given a brief polish
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18. Image courtesy: Nathan Efron and Steve Newman, Second edition Contact lens practice
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Back surface lathe
Button about to be mounted in dolly.
Button–dolly assembly is
collected in lathe

19. Image courtesy: Nathan Efron and Steve Newman, Second edition Contact lens practice
19
Back surface curve being cut into the button with a
diamond-tipped tool
Back surface polishing.

20. Generating the lens front surface
 The button needs to be fixed on to mount, or arbour – Blocking
 The arbour can be metal or plastic cylindrical tool,
one end dome shaped
 Heats the arbour approx. 800 C and applies low melting point wax
to dome end, or in case of plastic tool, applies UV sensitive which can
be cure to hard form
 Arbour button clamped into a front surface lathe
 Centration under magnification
 Cut is made from the edge to the centre with diamond-tipped cutter,
then with fine diamond tipped cutter
 Button is released from the lathe and mounted to polishing machine
(30 secs to 2 mins)
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21. Image courtesy: Nathan Efron and Steve Newman, Second edition Contact lens practice
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Blocking the button on to a brass arbour Front surface lathe
Front surface curve being cut into the button
with a diamond-tipped knife.
Front surface polishing.

22. Engraving, marking and fenestration
 Near finished lens still mounted on arbour
 Engraving-pantographic device
 Engrave on the lens against a stainless steel master template
 Typical engraves since R and L, then BC and total diameter
 Fenestrations can be introduced into the lens using a laser (done
in finished lens)
Image courtesy: Nathan Efron and Steve Newman, Second edition Contact lens practice 22
Near-finished lens form wax-mounted
on the brass arbour
Pantographic system for lens engraving
Laser system for toric lens scribe marking and
Introducing fenestrations.

23. Edge polishing and final inspection
 Edge polishing can be done by using a polishing machine
 The lens surface on to a concave rubber cap support
 The spindle rotates around the long axis and lowered on to a flat rotating
polishing pad and moved slowly from side to side
 After polishing, the edges are inspected using a 10X hand magnifier
 Any irregularities can be rectified manually by polishing the lens
Image courtesy: Nathan Efron and Steve Newman, Second edition Contact lens practice 23
Two lenses suction mounted to the spindles of an
edge-polishing machine, ready to be lowered on to
rotating pads.
Inspecting the lens edges using a 10× hand
magnifier Manual polishing of the lens edge.

24. References
 Second edition, Nathan Efron, Contact lens practice
 IACLE module 2
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25. Thank you !