Contact Lens History & Materials

1. HISTORY,
MATERIAL,
NOMENCLATURE
Of Contact Lenses
Presentor:- Dr.Pushkar Dhir
Moderator :- Dr.OP Gupta
Moderator:- Ms Sheeba

2. D VINCI CODE
• In 1508, Leonardo da Vinci sketched
the first forms of new refracted surface
on the cornea.
• He used the example of a very large
glass bowel filled with water;
immersion of the eyes in water
theoretically corrected vision.
• Sketches of a schematic eye
• Describes the mechanism of image
formation from the cornea to the
optic nerve
• Some drawings may represent the
idea of a ‘contact’ lens
??DUMBULDORE??

4. RENÉ DESCARTES
(1637)
• Understood that better vision could be achieved by enlarging the
retinal image
• Sketched an elongated tube filled with water placed against an
eyeball
• Demonstrated the principal of the telescope, not the contact lens
H2O

5. D GAME CHANGER
ADOLF E FICK (1888)• Fick was born in Germany in 1852.
• Used blown glass shells which
appeared to be well tolerated.
• Observed corneal clouding,
conjunctival and limbal injection.
• Discussed the need for lens
disinfection and the concept of
adaptation to lens wear.
• Observed that corneal clouding did
not occur as quickly if an air bubble
was inserted behind his lens along
with a 2% glucose solution.

6. FA MÜLLER and SONS (1887)
• Artificial eye makers in Wiesbaden, Germany
• Made lenses from blown glass
• Very regular curvature, no sharp edges at the corneo-scleral junction
• Designed a lens for ptosis correction

7. CARL ZEISS of JENA (1911)
• Made lathe cut lenses from molds
• Lathe cutting resulted in a better optical
performance
• First commercially available trial lenses
• Complete trial set contained 21 lenses
• Lenses were afocal
• Fitting determined by fluorescein and
white light

8. 8
Evolution of Contact Lens
PMMA
40s 50s 60s 70s 80s 90s 2000
Silicone
Hydrogel
+ silicone to increase Dk
+ surface treatment to
resist deposit
+ water to improve Dk
& comfort
Hydrogel (HEMA based)
Low water High water
Ionic Non-ionic
+ silicone to increase Dk
RGP

9. • In 1954,
• Professor Otto Wichterle &
Dr Drashoslav Lim suggested
to experts in the medical
plastics field that a plastic
which more closely simulated
living tissue would be more
suitable for orbital implants
than the metallic elements
being considered.

10. IDEAL MATERIAL
 BIOCOMPATIBILITY- should not harmful
 OPTICAL PROPERTIES- transparent
 GAS PERMEABILITY – wearing time
 TOLERANCE –gas permeability and design.
 MOULDING
 STERILITY
 STABILITY - in all dimentions
 SURFACE CHEMISTRY - easily wettable

11. CONTACT LENS
CLASSIFICATION
BASED ON
PURPOSE OF
USE
Optical
Therapeutic
Cosmetic
ANATOMICAL
LOCATION
Scleral contact
lenses
Semi-scleral
contact lenses
Corneal contact
lenses
NATURE OF
LENS
Rigid non-gas
permeable
contact
lenses(PMMA)
Rigid gas
permeable
contact
lenses(CAB)
Soft contact
lenses(HEMA)
BASED ON
WATER
CONTENT
BASED ON
WEARING
SCHEDULE
Daily wear
contact lenses
(hard contact
lenses)
Extended wear
contact lenses
(soft contact
lenses)
Disposable
contact lenses

12. 12
Uses of Contact Lens
Purpose
Cosmetic
Spherical
Toric
Presbyopic
Optical
Keratoconus
Bandage Lens
Drug Delivery
Myopia Control
Therapeutic
Enhances
Performance
Color Filters

13. C L WHICH COVER
THE CORNEA & THE
CONJUNCTIVA
OVERLYING THE
SCLERA
CONTACT LENSES THAT
COVER
THE CORNEA, BRIDGE
THE LIMBUS &
LIE PARTIALLY ON THE
CONJUNCTIVAL TISSUE
CONTACT LENSES
THAT
CONFINED TO
THE CORNEA

14. CLASSIFICATION OF CL BASED ON THE
MATERIAL

15. NON GAS
PERMEABLE
GAS
PERMEABLE
PMMA, Lucite,
Plexiglass, Perspex
Advantages-
1. Lighter than glass
2. Non toxic
3. Easy to manufacture
Disadvantages
1. 1-2% water content
2. Dk = 0(not gas permeable)
1. Cellulose Acetate Butyrate
2. Silicone acrylate
(Copolymer of pmma & silicone
containing vinyl monomer.
3. Silicone-
D-Lack of wet ability , not popular.
A- used in paeditaric aphakic in 1st yr of
life because eof high oxygen perm +
tight fit
4. Styrene
5. Fluoropolymers- for extended wear.
RIGID GAS
PERMEABLE
A-Low oxygen permeability – Dk of 4.5-10
Relatively good wet ability – better than PMMA.
Dis-Good protein resistance but prone to lipid
deposits

16. Advantages of Rigid
Contact Lens
• Better Quality of Vision
• More Durable
• Correction Of Astigmatism
• Deposit Resistance
• Less of Chance of infection
• Cost is less
• Less Stable
•  less comfortable,tough
adapataion
Advantages of Soft
Contact Lens
• Very comfortable & easy
to adapt
•  Larger & adhere more tightly
to the cornea
•  No Spectacle Blur
•  Doesn’t correct Astigmatic
Error

17. CLASSIFICATION OF CL BASED ON
THE WATER CONTENT
LOW WATER CONTENT Less then or equal to 50%
HIGH WATER CONTENT Greater than 50%
The amount of fluid taken up by a contact
lens material
Ranges from 38% to 79%
Increase in water content  increases
oxygen permeability
20% increase in water  doubles oxygen
permeability

18. Low Water Content
Advantages:
•Less susceptible to
environment changes
•Low protein deposition
•Ease of manufacture
•More wettable
•Compatible with all lens care
product
Disadvantages:
•Low Dk
•Less flexible
•Thin lenses difficult to handle
High Water Content
Advantages:
•Higher Dk
•More flexible
•Faster restoration of shape
following deformation.
Disadvantages:
•More fragile
•More deposit prone .
•Difficult to manufacture
•Lower tensile strength
•Cannot be made too thin

19. CLASSIFICATION OF CONTACT LENSES
SOFT CONTACT LENSES
Ionic
Nonionic
-
- + -
-
_
_
_
_
_

20. Ionic materials
Advantages:
»More wettable
»Less Denaturation of tear proteins
Disadvantages:
»More deposits prone
»Deposits may be bound

21. CLASSIFICATION OF CONTACT LENSES
Soft hydrogel contact lenses
(FDA classification)
Group-1 Non- ionic, low water content CL
Group-2 Non-ionic, high water content CL
Group-3 Ionic, low water content CL
Group-4 Ionic, high water content CL

22. Contact Lens Parameters
• Base Curve
• Diameter
• Power

23. Base Curve
The curvature of the central part
of the posterior surface of a lens.
It is at optic zone area
Expressed either in millimeters
(mm) of radius of curvature or in
diopters (D)
 Calculated with help of
Keratometer

25. Diameter
–The maximum edge to edge width of a lens
–Measured in millimeters (mm).
–SCL diameter = HVID + (1 to 3mm, average =
2mm)
9.50mm
8.50mm
Total diameter

26. • Power
»The ability of the lens to diverge or converge light
»Measured in diopters (D)
»FRONT VERTEX POWER: It is the reciprocal of the distance from the front surface of
the contact lens to the first focal point
»BACK VERTEX POWER: It is the reciprocal of the distance from the back surface of
the lens to the second focal point
FVP BVP
F1 F2

27. Parameters
of Contact
Lens
Water
content
Center
thickness
Optic
Zone
Sagittal
Depth
Wettability
Oxygen
Permeabi
lity
Oxygen
Transmis
sibility
Lens
Curves
Lens
Design

28. Wettability
The angle that the edge of a bead of water makes with the surface of a contact lens
is called wetting angle
The smaller the wetting angle, the greater the wettability of the lens
In vitro: Wetting angle
- Sessile drop
- Wilhelmy plate
- Captive buble
In vivo: Tear Coverage
Tear Break-up time
Drying time
70


29. • Low Dk material
– Below 20
• Mid Dk material
– 20 to 40
• High Dk material
– 40 to 60
• Hyper Dk material
– Above 60
O2
O2
O2
O2
O2
O2O2
O2
O2
O2
O2
O2
O2
O2
O2
O2O2
O2
O2
O2
O2
O2
O2
O2
O2
OXYGEN PERMEABILITY
GAS TRANSMISSION

30. Oxygen transmissibility
Dk/L
D = Diffusion coefficient (cm/sec)
k = Solubility of gas in the material(cm3/cm2 mm Hg)
L = Thickness of material (mm)
Depends on:
Permeability of the lens material
Thickness of the lens
Temperature at which the test is performed

31. Oxygen transmissibility
The value for Dk/ t will decrease with increasing thickness of the lens
Daily wear, the recommended Dk/ t of a contact lens is around 30
Extended wear, the recommended Dk/ t of a contact lens is 87
 Low Oxygen transmissibility can result in corneal changes:
•Microcysts
•Polymegathism
•Corneal pH
•Edema
•Blebs
O2
O2

32. Ballasted
Lens
Fenestrated
Lens
Lenticular
Lens
Toric
Lens
Truncated
Lens
•Lens is made
thicker at the
bottom in order to
prevent rotation &
maintain
orientation
•Rigid lens +
small holes to
allow more
volume of
oxygen & tear
fluid to reach
cornea
•Commonly used
for aphakic patients
•Lenticular plus
power lenses
usually have thick
central optic zone
and a wide
peripheral bevel
•Used to correct
astigmatism
•In front surface
toric lenses the
two different radii
are found on the
anterior surface of
the lens
•In back toric
surface lenses the
two different radii
are found on the
back surface of the
lens
A lens with an
edge cut off flat
Used in some
toric and bifocal
contact lens
design

33. References
• Introduction: FREE download of the
'IACLE Contact Lens Course'
complete survey to access
• Download the 'IACLE Contact Lens
Course'
• ICLC PPT Contact Lens Fitting
• Making Contacts: Contact Lenses in History -
Insight Optometrists
• contact lens: Definition from Answers.com

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