This document discusses hydrogel and silicone hydrogel contact lenses. Hydrogel lenses have advantages like initial comfort but disadvantages such as poor oxygen transmission and dryness. Silicone hydrogel lenses have higher oxygen permeability which makes them more suitable for extended wear and reduces risks of complications. Silicone hydrogels are more expensive than hydrogels but provide benefits like increased comfort, rigidity for easy handling, and surface wettability. The document recommends silicone hydrogel lenses for patients who wear contacts long hours or in low humidity environments.

1. HYDROGELS & SILICONE HYDROGELS
WHEN AND WHY??
Churawan Lal Sahu
M Optom
1Churwan Lal Sahu M Optom

2. HYDROGELS & SILICONE
HYDROGELS
Hydrogels-Advantages
 Offers good initial comfort
 Less Prone to displacement
 Offers Good Centration
 Stabilize promptly after insertion
Churwan Lal Sahu M Optom 2

3. HYDROGELS & SILICONE
HYDROGELS
Hydrogels-Disadvantages
 Poor oxygen transmission
 More dryness
 Greater care and maintenance
 Limited parameters available
Churwan Lal Sahu M Optom 3

4. HYDROGELS & SILICONE
HYDROGELS
Hydrogels-Disadvantages
 Lens handling can be difficult
 Uptake of preservatives
 May discolour with topical medications
Churwan Lal Sahu M Optom 4

5. HYDROGELS & SILICONE
HYDROGELS
Hydrogels-Indications
 Who rarely uses CL
 Who uses CL only for 6-8hours
 Who are concerned about Money
Churwan Lal Sahu M Optom 5

6. HYDROGELS & SILICONE
HYDROGELS
How does the cornea get its O2 if it doesn’t have blood vessels?
 Cornea – Avascular Structure
 O2 required – Principally from the atmosphere
 Reduced oxygen supply can result in changes to the
epithelium, stroma and endothelium
Churwan Lal Sahu M Optom 6

7. HYDROGELS & SILICONE
HYDROGELS
What happens if the eyes don’t get enough oxygen?
 Red Eye
 Polymegathism
 Hypoxia
 Neovascularisation
 Corneal Edema
Churwan Lal Sahu M Optom 7

8. HYDROGELS & SILICONE
HYDROGELS
What happens if the eyes don’t get enough oxygen?
 More prone to deposits
 Dehydration
 Inflammation
 Infections in Extended Wear
Churwan Lal Sahu M Optom 8

9. HYDROGELS & SILICONE
HYDROGELS
Why isn’t DK/t 24 always enough?
 Patients experience increased oxygen need resulting from
environment conditions( Altitude, dryness )
Churwan Lal Sahu M Optom 9

10. HYDROGELS & SILICONE
HYDROGELS
Churwan Lal Sahu M Optom 10
Long wearing days More contact lens users nap
in their lenses:84% !

11. HYDROGELS & SILICONE
HYDROGELS
Requirements for healthy wear
 Oxygen transmissibility DW – Dk/t > 35
 Oxygen transmissibility EW– Dk/t > 125
 Low modulus
 Surface wettability
 Resistant to dehydration
 Biocompatibility
Churwan Lal Sahu M Optom 11

12. HYDROGELS & SILICONE
HYDROGELS
Why silicone hydrogels?
Churwan Lal Sahu M Optom 12
SILICONE
High oxygen
permeability
HYDROGEL
Wettability
Flexibility
Fluid
Transport

13. HYDROGELS & SILICONE
HYDROGELS
Churwan Lal Sahu M Optom 13
Silicone Hydrogels
High DK Hydrophilic
Highly oxygen Permeable , wettable material

14. HYDROGELS & SILICONE
HYDROGELS
Silicone hydrogels: Advantages
 More healthier than conventional SCL
 Increased oxygen transmission
 More resistance to protein deposits
 Less dehydration
 Lower risk of infection
 Lower incidence of complication with EW
Churwan Lal Sahu M Optom 14

15. HYDROGELS & SILICONE
HYDROGELS
Silicone hydrogels: Indications
 High prescriptions
 Wearers who experience end of day discomfort/dryness/redness
 Wearing hours>12-14hrs
 Whose eye requires more oxygen
 Who work long hours in low humidity/air conditioning
Churwan Lal Sahu M Optom 15

16. HYDROGELS & SILICONE
HYDROGELS
Silicone Hydrogels:Properties
1.Oxygen Transmissibility
Churwan Lal Sahu M Optom 16
O2 is transmitted
throught Si
Component
Oxygen
Permeability
Hypoxic Problems
with EW

17. HYDROGELS & SILICONE
HYDROGELS
2.More Comfort
Churwan Lal Sahu M Optom 17
Less Dehydration More Comfort

18. HYDROGELS & SILICONE
HYDROGELS
3.Increased rigidity
 Easily handle
 Corneal astigmatism is masked
Churwan Lal Sahu M Optom 18

19. HYDROGELS & SILICONE
HYDROGELS
4.Surface wettability
 Contact Angle (CA) -Ability of a fluid to spread over a
contact lens surface
 CA more wettable the surface
 Higher Wettability More comfort
Churwan Lal Sahu M Optom 19

20. HYDROGELS & SILICONE
HYDROGELS
Silicone Hydrogels:Disadvantages
 More expensive
 Attract lipid deposits Blurred vision/Discomfort
 Rigid material Adaptation Issues
Churwan Lal Sahu M Optom 20

21. HYDROGELS & SILICONE
HYDROGELS
HYDROGEL
 Combination of polymer&water-
soft with limited oxygen
 Redness around cornea if worn
longer than recommended
 Limited wearing hours
SILICONE HYDROGEL
 Combination of
silicone,polymer&water- soft ,5-6
times more o2 than hydrogels
 Healthier ,whiter eye even if worn
longer
 Long wearing hours
Churwan Lal Sahu M Optom 21

22. HYDROGELS & SILICONE
HYDROGELS
 More water content,more dryness
at the end of the day
 More protein deposits-
compromised comfort
 Difficulty during handling
 Less dryness (low water content
 Less protein deposits-More
comfort
 Very good handling due to shape
factor
Churwan Lal Sahu M Optom 22
HYDROGEL SILICONE HYDROGEL

23. THANK YOU
23Churwan Lal Sahu M Optom