Podcast
Questions and Answers
What is the primary advantage of using HDS - Hyperpurified Delivery System in fluorosiloxane acrylates?
What is the primary advantage of using HDS - Hyperpurified Delivery System in fluorosiloxane acrylates?
What is the primary purpose of the GP design?
What is the primary purpose of the GP design?
What is the characteristic of a fitting steep lens?
What is the characteristic of a fitting steep lens?
What is the minimum amount of astigmatism required for a toric GP lens?
What is the minimum amount of astigmatism required for a toric GP lens?
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What is the purpose of the toroidal zone in a toric GP lens?
What is the purpose of the toroidal zone in a toric GP lens?
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What is the primary advantage of using a back surface toric lens?
What is the primary advantage of using a back surface toric lens?
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What is the purpose of the liquid lens in a toric GP lens?
What is the purpose of the liquid lens in a toric GP lens?
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What is the result of using a spherical lens on a toric cornea?
What is the result of using a spherical lens on a toric cornea?
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What is the primary concern when fitting a patient with high astigmatism using RGP toric lenses?
What is the primary concern when fitting a patient with high astigmatism using RGP toric lenses?
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What is the recommended adjustment when the difference in K readings is less than 1DC?
What is the recommended adjustment when the difference in K readings is less than 1DC?
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What type of RGP material is more prone to lens flexure?
What type of RGP material is more prone to lens flexure?
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What is the primary advantage of back-surface toric (BST) lenses?
What is the primary advantage of back-surface toric (BST) lenses?
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What is the purpose of the peripheral toric curve(s) in RGP toric lenses?
What is the purpose of the peripheral toric curve(s) in RGP toric lenses?
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What is the recommended approach when adjusting the spectacle Rx for CL rotation?
What is the recommended approach when adjusting the spectacle Rx for CL rotation?
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What is the effect of a steep lens on the tear lens?
What is the effect of a steep lens on the tear lens?
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What is the primary disadvantage of RGP toric lenses?
What is the primary disadvantage of RGP toric lenses?
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What is the recommended trial lens diameter for patients with wide palpebral apertures?
What is the recommended trial lens diameter for patients with wide palpebral apertures?
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What is the optimal fitting characteristic of an RGP toric lens?
What is the optimal fitting characteristic of an RGP toric lens?
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What type of lens is used when there is ocular astigmatism with a spherical cornea?
What type of lens is used when there is ocular astigmatism with a spherical cornea?
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What is the purpose of prism ballast in Translating Bifocal lenses?
What is the purpose of prism ballast in Translating Bifocal lenses?
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What is the effect of a thicker lens in Translating Bifocal lenses?
What is the effect of a thicker lens in Translating Bifocal lenses?
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Why is the BOZD 1-1.5mm smaller than the total diameter (TD)?
Why is the BOZD 1-1.5mm smaller than the total diameter (TD)?
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What is the effect of a steep BOZR on the tear lens power?
What is the effect of a steep BOZR on the tear lens power?
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What is the purpose of selecting a RGP material with high DK?
What is the purpose of selecting a RGP material with high DK?
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What is the effect of a centre thickness that is too thin?
What is the effect of a centre thickness that is too thin?
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Why is the lens fitted 0.1mm flatter than the flattest K?
Why is the lens fitted 0.1mm flatter than the flattest K?
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Which of the following RGP materials is known for its good wettability and fewer deposits?
Which of the following RGP materials is known for its good wettability and fewer deposits?
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What is the primary concern when fitting a patient with high astigmatism using RGP toric lenses?
What is the primary concern when fitting a patient with high astigmatism using RGP toric lenses?
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What is the purpose of the peripheral toric curve(s) in RGP toric lenses?
What is the purpose of the peripheral toric curve(s) in RGP toric lenses?
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What is the recommended adjustment when the difference in K readings is less than 1DC?
What is the recommended adjustment when the difference in K readings is less than 1DC?
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What is the primary advantage of using a back-surface toric (BST) lens?
What is the primary advantage of using a back-surface toric (BST) lens?
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What is the effect of a steep lens on the tear lens?
What is the effect of a steep lens on the tear lens?
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What is the recommended approach when adjusting the spectacle Rx for CL rotation?
What is the recommended approach when adjusting the spectacle Rx for CL rotation?
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What is the primary disadvantage of RGP toric lenses?
What is the primary disadvantage of RGP toric lenses?
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What is the recommended trial lens diameter for patients with wide palpebral apertures?
What is the recommended trial lens diameter for patients with wide palpebral apertures?
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What is the primary reason for using Fluorosiloxane Acrylates?
What is the primary reason for using Fluorosiloxane Acrylates?
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What is the effect of a spherical lens on a toric cornea?
What is the effect of a spherical lens on a toric cornea?
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What is the purpose of the AERCOR Technology?
What is the purpose of the AERCOR Technology?
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What is the result of using a liquid lens with a TD +0.50mm?
What is the result of using a liquid lens with a TD +0.50mm?
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What is the primary advantage of using a toroidal periphery in a toric GP lens?
What is the primary advantage of using a toroidal periphery in a toric GP lens?
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What is the recommended approach when ordering a back surface toric lens?
What is the recommended approach when ordering a back surface toric lens?
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What is the effect of a central steeping of the cornea on the peripheral curve?
What is the effect of a central steeping of the cornea on the peripheral curve?
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What is the primary concern when fitting a patient with high astigmatism using GP lenses?
What is the primary concern when fitting a patient with high astigmatism using GP lenses?
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What is the primary advantage of using a front surface toric lens?
What is the primary advantage of using a front surface toric lens?
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What is the result of using a lens with a centre thickness that is too thin?
What is the result of using a lens with a centre thickness that is too thin?
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What is the effect of a steep BOZR on the tear lens power?
What is the effect of a steep BOZR on the tear lens power?
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What is the primary purpose of the edge lift in RGP lens design?
What is the primary purpose of the edge lift in RGP lens design?
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What is the recommended approach when fitting a translating bifocal lens?
What is the recommended approach when fitting a translating bifocal lens?
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What is the primary advantage of using a high DK RGP material?
What is the primary advantage of using a high DK RGP material?
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What is the characteristic of a concentric bifocal lens?
What is the characteristic of a concentric bifocal lens?
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Why is the BOZD 1-1.5mm smaller than the total diameter (TD)?
Why is the BOZD 1-1.5mm smaller than the total diameter (TD)?
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Study Notes
Flouro-Siloxaine Acrylates
- Fluorine monomer added to SA, resulting in lower surface charge, better wetting, and less deposits, although it attracts lipids and mucus
- Dk 40 - 100+, susceptible to scratching and lens flexure
- HDS - Hyperpurified Delivery System removes inefficient Si molecules, resulting in higher permeability (40 Dk) and improved surface wettability with high % MMA
AERCOR Technology
- Oxygen permeable backbone replaces impermeable PMMA traditional polymer foundation, allowing high DK/t and material strength
- Permits reduction in silicone (Boston EO)
- Surface treated with plasma, graft polymerization, and hydrolysable lens to improve wetting
GP Design
- Designed to match back surface to fit cornea, preventing indentation and allowing tear circulation, not causing lid irritation and decentration
- TD large enough to encompass BOZD and peripheral curves, with minimal lid irritation and assisting centration
- Cornea is aspheric central steeping and flatter towards periphery, peripheral curve aligns to cornea, ensuring good fit
Fitting Steep vs. Flat
- Fitting Steep: Central pooling, minimal movement on blink, good centration, and air bubble
- Fitting Flat: Central touch, excessive movement of lens, blinking and eye rotation, uncomfortable
Liquid Lens
- 0.05mm = 0.25D, TD +0.50mm = flatter BOZR 0.05mm
Toric GP
- Spherical lens on toric cornea can cause excessive lens awareness, rocking, poor vision due to flexure, and centration
- >2.00D astigmatism can be corrected with toric GP, with toroidal periphery providing better stability and comfort
- Tear film corrects some astigmatism; toroidal periphery gives better stability and comfort
Back Surface Toric
- For difference in K in excess of 0.50mm, improved physical fit and visual performance
- Order empirically using K9s, spec Rx, and BVD
- Rx in minus cyl form (Sphere @flat, Sphere + Cyl @ steep)
- Lens will align with principal meridian, no stabilization required
Bi-toric
- Toroidal front and back surface, used when back surface toric leaves residual astigmatism (ocular not equal to corneal astigmatism)
- Order and fit in the same way as back surface toric (add residual astigmatism to steeper meridian)
- No stabilization is required
Front Surface Toric
- Used when there is ocular astigmatism with a spherical cornea, lens needs to orientate correctly
- Stabilization is required
- BOZR and TD selected as spherical GP, specify astigmatism and axis, and request prism ballast
- Reorder to account for any rotation if necessary
Translating Bifocal
- Near vision in the lower half of CL, lenses translate upwards and outwards as eye looks down and convergence due to upper lid traction at the edge of lens
- Design: Prism ballast stabilization, solid image jump with down gaze unless OC aligned
- High refractive index so less jump
- Back surface solid tears neutralize 2/3 power of add, front surface segment = glare and flare
- D seg and Executive style bifocal
Toric GP Fitting
- Successful but limited to GP wearers, niche
- Fitting: typical PD on downgazes assumed to be 3.5-4mm, typical GP movement is 2mm on downgaze
- Add set 3mm from geometric center of lens
- Thicker lenses less likely to ride high on blink, reduced comfort and oedema
- Lens must rise ½ of PD
- If eyelid below limbus, translating not recommended
- Generally fitted 0.1mm flatter than flattest K to allow close alignment and adequate edge clearance
Concentric Bifocal
- Central optical zone smaller than pupil, either distance and near surround or vice versa
- Reduced contrast and VA due to blurred image
- Haloes, near impairment with pupil constriction with D centre, decentration causes blur
- Pupil dependent
Care System
- Boston 2 step (Cleaner and conditioner) or GP multi-action and flat case
RGP Material Selection
- Corneal O2 requirements: DK, Thins lens more O2, thick lens easier to handle
- Centre thickness: consider edge form, maximum wearing time
- Wettability: ability of tears to form a stable layer on top of the CL
- Flexure: can cause residual astigmatism on toric corneas, especially true on thinner lenses
- Compliance: common RGP materials include silicone acrylate, fluorosilicone acrylate, and fluorosiloxanyl
RGP Toric Fitting
- CL Types: Front-surface toric (FST), Back-surface toric (BST), Bitoric (Bitor), and Peripheral toric
- Problems: poor vision, poor centration, CL rocking on the flat meridian, unstable CL fitting, CL flexure, harsh bearing areas, corneal distortion, spectacle blur, discomfort, poor blinking, and epithelial damage
- Advantages: stabilized CL fitting, improved CL-cornea fitting relationship, cylindrical correction maybe less than with toric SCLs, and better corneal physiology than toric SCL
Flouro-Siloxaine Acrylates
- Fluorine monomer added to SA, resulting in lower surface charge, better wetting, and less deposits, although it attracts lipids and mucus
- Dk 40 - 100+, susceptible to scratching and lens flexure
- HDS - Hyperpurified Delivery System removes inefficient Si molecules, resulting in higher permeability (40 Dk) and improved surface wettability with high % MMA
AERCOR Technology
- Oxygen permeable backbone replaces impermeable PMMA traditional polymer foundation, allowing high DK/t and material strength
- Permits reduction in silicone (Boston EO)
- Surface treated with plasma, graft polymerization, and hydrolysable lens to improve wetting
GP Design
- Designed to match back surface to fit cornea, preventing indentation and allowing tear circulation, not causing lid irritation and decentration
- TD large enough to encompass BOZD and peripheral curves, with minimal lid irritation and assisting centration
- Cornea is aspheric central steeping and flatter towards periphery, peripheral curve aligns to cornea, ensuring good fit
Fitting Steep vs. Flat
- Fitting Steep: Central pooling, minimal movement on blink, good centration, and air bubble
- Fitting Flat: Central touch, excessive movement of lens, blinking and eye rotation, uncomfortable
Liquid Lens
- 0.05mm = 0.25D, TD +0.50mm = flatter BOZR 0.05mm
Toric GP
- Spherical lens on toric cornea can cause excessive lens awareness, rocking, poor vision due to flexure, and centration
- >2.00D astigmatism can be corrected with toric GP, with toroidal periphery providing better stability and comfort
- Tear film corrects some astigmatism; toroidal periphery gives better stability and comfort
Back Surface Toric
- For difference in K in excess of 0.50mm, improved physical fit and visual performance
- Order empirically using K9s, spec Rx, and BVD
- Rx in minus cyl form (Sphere @flat, Sphere + Cyl @ steep)
- Lens will align with principal meridian, no stabilization required
Bi-toric
- Toroidal front and back surface, used when back surface toric leaves residual astigmatism (ocular not equal to corneal astigmatism)
- Order and fit in the same way as back surface toric (add residual astigmatism to steeper meridian)
- No stabilization is required
Front Surface Toric
- Used when there is ocular astigmatism with a spherical cornea, lens needs to orientate correctly
- Stabilization is required
- BOZR and TD selected as spherical GP, specify astigmatism and axis, and request prism ballast
- Reorder to account for any rotation if necessary
Translating Bifocal
- Near vision in the lower half of CL, lenses translate upwards and outwards as eye looks down and convergence due to upper lid traction at the edge of lens
- Design: Prism ballast stabilization, solid image jump with down gaze unless OC aligned
- High refractive index so less jump
- Back surface solid tears neutralize 2/3 power of add, front surface segment = glare and flare
- D seg and Executive style bifocal
Toric GP Fitting
- Successful but limited to GP wearers, niche
- Fitting: typical PD on downgazes assumed to be 3.5-4mm, typical GP movement is 2mm on downgaze
- Add set 3mm from geometric center of lens
- Thicker lenses less likely to ride high on blink, reduced comfort and oedema
- Lens must rise ½ of PD
- If eyelid below limbus, translating not recommended
- Generally fitted 0.1mm flatter than flattest K to allow close alignment and adequate edge clearance
Concentric Bifocal
- Central optical zone smaller than pupil, either distance and near surround or vice versa
- Reduced contrast and VA due to blurred image
- Haloes, near impairment with pupil constriction with D centre, decentration causes blur
- Pupil dependent
Care System
- Boston 2 step (Cleaner and conditioner) or GP multi-action and flat case
RGP Material Selection
- Corneal O2 requirements: DK, Thins lens more O2, thick lens easier to handle
- Centre thickness: consider edge form, maximum wearing time
- Wettability: ability of tears to form a stable layer on top of the CL
- Flexure: can cause residual astigmatism on toric corneas, especially true on thinner lenses
- Compliance: common RGP materials include silicone acrylate, fluorosilicone acrylate, and fluorosiloxanyl
RGP Toric Fitting
- CL Types: Front-surface toric (FST), Back-surface toric (BST), Bitoric (Bitor), and Peripheral toric
- Problems: poor vision, poor centration, CL rocking on the flat meridian, unstable CL fitting, CL flexure, harsh bearing areas, corneal distortion, spectacle blur, discomfort, poor blinking, and epithelial damage
- Advantages: stabilized CL fitting, improved CL-cornea fitting relationship, cylindrical correction maybe less than with toric SCLs, and better corneal physiology than toric SCL
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Description
Learn about the properties and features of Fluoro-Siloxane Acrylates in contact lenses, including their surface charge, wetting, and permeability. Discover how different technologies, such as HDS and AERCOR, impact their performance.
