The document discusses the history and process of manufacturing glass and lenses. It provides details on: 1) Glassmaking has been traced back to 3500 BC based on the oldest glass beads, though its discovery is unknown. Glass was initially used for jewelry before being made into art objects in 16th century BC. 2) When heated to high temperatures, sand melts and becomes glass through a molecular structure change. 3) Lens manufacturing involves measuring a patient's prescription, selecting frames, grinding lenses to the correct optical power, and fitting lenses into frames through processes like cutting, edging and mounting. 4) Resin and glass are the two main materials used for ophthalmic lenses.

1. OPTOM FASLU MUHAMMED

2.  History doesn't show when people first began
to manufacture glass or even who discovered
how to turn sand into glass.
 What we do know is that the oldest pieces of
manufactured glass are beads that date to
around 3500 BC.

3.  Glass was primarily used as jewelry until the
16th century BC when artisans discovered how
to fashion glass into vases and other art objects.
 The first written manual containing instructions
on how to make and shape glass dates to 650
BC.
 Glass was so precious and hard to come by that
glass objects were used as currency by ancient
Romans, Egyptians and Greeks.

4.  When sand is heated to 1700 degrees Celsius
it melts. The molecular structure of sand
changes during the heating and subsequent
cooling and becomes glass.
 Glass is prized for being chemically inert and
tolerant of high temperatures.

5.  When someone needs glasses, the first
requirement is an eye examination in the
doctor’s office to determine the correct lens
prescription. The next step takes place in the
optical dispensary, where a frame is chosen.
 Traditionally the optical laboratory consists
of two main areas, a surfacing laboratory and
a finishing laboratory.

6.  One area creates the needed lens power,
usually by a process called lens surfacing,
which is performed at a facility referred to as a
surfacing laboratory.

7.  The second area takes the correctly powered
lens and finishes it.
 Finishing is accomplished through optical
positioning of the lens and grinding of the
edges so that the lens fits the shape of the
chosen frame. The area where this occurs is
known as the finishing laboratory.

8.  Ophthalmic lenses may be divided into the
following three broad categories:
• Single vision lenses
• Segmented multifocal lenses
• Progressive addition lenses

9.  These lenses have the same power over the
entire surface of the lens.
 Single vision lenses are used when the same
optical power is needed for both distance and
near vision.
 They also are used when a person requires no
prescription for distance but needs reading
glasses.

10.  Single vision lenses are edged from lenses
kept in stock at the finishing laboratory.
 Because these lenses are finished optically to
the correct power on both the front and back
surfaces, they are called finished lenses.

11.  Finished lenses are also referred to as uncuts
because they have not yet been “cut” to the
correct shape and size.
 When single vision lenses are in uncut form
and do not require surfacing, they are called
stock single vision lenses.

12.  The surfacing laboratory starts with a lens
having only one surface that is ready to use, or
“finished.” This is usually the front surface.
 The laboratory must grind and polish the
second surface to the required power.

13.  A lens with only one of the two surfaces
finished is called a semi finished lens
because it is only half finished. The prefix semi
means half.
 Finished uncut and semi finished lenses have
not been edged. Before a lens has been edged
it is called a lens blank.

14.  Segmented multifocal lenses have more
than one power. Each power is located in a
distinct area of the lens bordered clearly by a
visible demarcation line.
 When two different areas exist, the lens is
called a bifocal .
 When three areas exist, the lens is called a
trifocal.

15.  Progressive addition lenses are used as an
alternative to a segmented multifocal lens.
They have distance power in the upper half of
the lens.
 Lens power gradually increases as the wearer
looks down and inward to view near objects.

16.  All the ophthalmic lenses currently available
in the ophthalmic industry are:
• Glass material
• Resin material

17. Process 1
 Mix silica with a small amount of sodium
bicarbonate or potash and limestone.
 The silica comes from sand or pulverized
sandstone.
 The sodium bicarbonate is baking soda and
helps lower the melting point of the silica.

18.  Potash is sodium containing potassium in
a water-soluble form and also lowers the
melting point of silica.
 The limestone stabilizes the mixture and
makes the glass stronger.

19.  Heat the mixture to approximately 2,500
degrees F in a melting furnace for 24 hours.
This allows the mixture to melt and mix
thoroughly and allows any bubbles in the
molten glass to rise to the surface.

20.  Allow the mixture to cool several hundred
degrees.
 This brings the glass to a point where it's
workable.
 At this point it can be blown or drawn into
whatever shape is desired. In manufacturing,
glass is typically pulled into flat sheets.

21.  Allow the molten glass to run into a wide,
shallow channel of liquid tin, over which three
separate rollers simultaneously flatten, smooth
and draw out the glass.
 Glass floats even as it's cooling. The liquid tin
bath gives it a semi-solid surface on which to rest
without sticking to that surface as it dries. This
also keeps the glass from wrinkling on contact
with a cooler surface.

22.  Roll the glass via a series of rollers into a
cooling oven or kiln. This oven lets the glass
cool in a controlled manner from the
approximately 1,000 degrees F it has currently
reached.
 The glass rolls along a series of rollers until it
cools enough to cut, about 350 degrees F.

23.  Place the sheets into a large, flat area and
continue cooling via high-speed fans. Glass
reaches its final rigid state here.

24.  Score the glass with a carbide tipped scoring
tool. Snap it by rolling it over a slightly higher
roller, which acts as a fulcrum. Place the glass
in storage until needed.

25. Oxides :-are used in the lens compositions
primarily into two major categories:
(a) Network Formative Oxides :– Network
formative oxides are used at the base of any
composition which could almost form a lens
on their own. For example, SiO2, B2O3,
P2O5.

26. (b) MOdifier Oxides: – They are
used to modify the basic properties contributed
by formative oxides. These may range from
viscosity to electric properties or from
chemical resistance to coefficient of
expansion. For example, K2O, Na2O, BaO.
 According to composition, some oxides
behave either as formatives or as modifiers.
They are called intermediary oxides. For
example, AI2O3, ZnO, TiO2

27.  Have the basic function of eliminating gaseous
inclusions (bubbles) in molten glass. Examples
are Antimony Oxide, Alkaline Nitrates.

28.  Complete absence of colorants is essential to
obtain clear ‘white’ glass.
 When added deliberately, they lead to
selective absorption for each wavelength in the
spectrum and so determine the tints. Example:
Cobalt oxide gives rise to blue, Nickel oxides
for brown.

29. The most common glasses
currently popular in the
industry for ophthalmic
lenses

30.  Crown is the most commonly used glasses for
spectacle lenses.
 Their composition is characterized by high
silica, lime and sodium.
 Some crown glasses through the addition of
metal oxides like nickel and cobalt show
specific tints and absorbent properties.

31.  Borosilicate with a high boron content.
 Microcrystals of silver halide which are
responsible for the photochromic phenomenon

32.  Lead oxide has been traditionally included in
the glass composition to produce high index
glasses. This produced “flint” glass.
 Lead oxide is replaced by titanium oxides,
thus preserving high index while reducing
glass density.
 Niobium, zirconium and strontium are also
included for adjusting optical properties.

33. resiN MATeriAL

34.  Resin lenses are made up of small molecular
units called monomers which link together to
form long chain known as polymers and the
process of linking the monomers together is
known as polymerization.
 There are two processes to make resin lenses:
1. Thermosetting
2. Thermoplastic

35.  Thermosetting and thermoplastic differ
basically in the lining up of the molecules in
their structure.
 Thermosetting are cross linked molecular
structure, resembles a ladder with extra rungs.
 They do not melt or flow when heat is applied
and makes the material less flexible.
 CR39,Most hi-index resin lenses are made by
thermosetting process

36.  Thermoplastic are not cross-linked molecular
structure. Molecular chains are independent of
each other, looks like a ladder without rungs.
 Optically they are not so stable during process.
They soften under heat and therefore, good for
injection molding process.
 They are very sensitive to abrasion.
Polycarbonates are the good examples.

37. (A) Thermoplastic (B) Thermosetting

38. Lens surfacing

41.  Spectacle lens manufacturing involving many
steps ,collectively called as Lens surfacing.
 Marking
 Blocking
 Grinding
 Smoothing
 Polishing
 De –blocking & cleaning.

42.  To correctly locate the lens for different stages
of surfacing ,certain markings are essential.
 Optical center position ,cylinder axis, base
apex direction in case of prism.
 Done by marking with suitable ink or jugging
at blocking stage.

45.  The block holds the lens in place through
entire surfacing process.
 Alloy or wax is used to hold the lens blank to
the surfacing block.

47.  Block assures proper
alignment in grinder
 Alloy creates bond with
the lens & tape
 Alloy is melted and
reused

48.  Note the various openings that
hold block in the correct
position

49.  Optical surfaces on glass are produced by the
process of grinding and polishing.
 Roughing
First stage is removing the unwanted
materials from the lens surface. This is
followed by trueing and smoothing.

50.  Roughing is performed by machines known as
surface generators and the process is termed as
generating.
 The grinding agent is usually a diamond –
bonded disc or wheel, termed as lap.

53.  Presently the polishing tools are lined with
pads cut from polyurethane sheets.

54.  The process of polishing is completed ,the lens
is separated from its holder ( De- blocking )
and cleaned properly.
 Lacquer can be used for cleaning.

56. GLAZING

57.  Glazing refer to the process fitting lenses to a
spectacle frame or mount.
◦ Laying off
◦ Lens cutting
◦ Lens edging
◦ Springing in and rimless fitting.

58.  Marking of cylinder axis ,optical center in the
correct position relative to the lens shape.
 Can be use focimeter ,marking devices and a
specially designed protractor.

59. Optic center Marking
Axis Marking
Earth line Marking
Frame shape Marking

61.  Scoring a slightly oversize outline of the
desired shape on one surface of the uncut lens
and removing the waste.
 Lens cutting can be performed entirely by
hand or with the aid of a wheel cutter.

62.  With automatic edging machines.

63. Mini bevel edge Groove edge Flat edgeBevel edge

64. Manual edging
Auto edging

66. Pattern edging (semi auto)
Pattern less edging (fully auto)

68. Pattern size (A)
(B)
Location of nasal side
180* Cutting line
Frame Difference
Mechanical center
Physical pattern

69. Physical Pattern

70. Steps
Lens marking Pattern cuttingLens selection

71. Pattern fixing Lens blocking

72. Lens chucking

74. Pattern less edger Frame tracer

75.  The final step of fitting well edged lenses into
rimmed plastic frame is known as springing
In .
 Fitting of lenses to rimless mounts is called
Rimless fitting.

76. Lens Insertion

77. Thank u……