Unit 2 Flashcards
Indications for GP and hybrid lenses
- Needs excellent VA/Sharpness * Custom designed lenses
- Borderline and mild dry eyes
- Irregular corneal surface
- Poor VA with glasses and soft lenses * Vision fluctuation with soft toric lenses * High myopia, hyperopia, astigmatism * Ortho K
Contraindications for GP and hybrid
- Ocular inflammation/infection
- Allergies
- Pinguecula/pterygium
- Corneal hypoesthesia (loss of sensitivity)
- Poor lens handling/cleaning/maintenance (too young, elderly) * Immunosuppression
- Needs horizontal prism
- Sports (GP Lenses)
- Hybrids - Lenticular Astigmatism (could be corrected with GP) * Dust/chemical vapors
- Sensitive to foreign body (FB) sensations
- Pregnancy (possibly) – can cause dry eyes and hypoesthesia
What are the main benefits that patients recieve from RGP lens
-Cover corneal astigmatism
-Better clarity
-Mild dry eye
-More oxygen getting to the eye
what are some benefits for the practice that are associated with fitting RGP lenses
Less required stoarge space
Build rapport with px due to all follow up appts
What is the amount of Low DK and what type of CLs
25 to 50 (daily wear and myopes)
What is the amount of High DK and what type of CLs
51 to 100 (Daily wear and hyperopes)
What is the amount of DK and for what type of CLs
> 100 (extended wear)
Surface treatment
-Plasma treatment (electrical surface structure)
-when RGPs contain plasma it makes it hydrophilic (water loving)
Refractive index for flurosilicone acrylate
1.42 to 1.46
refractive index of newer material (HDS)
may be 1.51 to 1.54
Material properties
-wettability
-frictoin (more silicone we have, less friction)
-Oxygen permeability (DK)
-Oxygen transmission (Dk/T)
-Refractive index
-Modulus (flexure of lens)
-Luminance transmission (light)
-Surface hardness
How to manufacture RGP CLs
1.Button of plastic material
2. Lathe cut the base curve (BC) on the back surface
3. Polish the back surface
4. Block the lens * Uses a wax
5. Cut the front surface of the lens
6. Polish the lens
7. Surface treatment (optional)
RGP physical parameteres
-power
-diameter
-base curve
-centre thickness
-peripheral curves
how to measure RGP diamter?
V-gauge
CL loupe
PCR
Peripheral curve radius
PC
peripheral curve
Indications for hybrid
-similar to RGP candidates
-Additional good candidates due to soft skirt
poor candidate for hybrid
soft skirt - beacuse less tear exchange
which manufacture is the major supplier of hybrid lenses
synergeyes
Older deisgn cons
-lower Dk/t
-limited parameters (limited GP / skirt options)
-poor bonding of soft skirt to GP
types of lens deisgns
-for regular corneas
-astigmatism
-kerataconus
-post surgical (oblate)
-presbyopia
Synergeyes Material for soft skirt?
Silicone hydrogel (larafilcon A)
Dk- 84
synergeyes - Matieral for GP centre / diameter and DK
-Petrafocon A
-diamter ; 8.5mm
-DK: 130
hyperbond junction
keeps the RGP and soft skirt together
