Week 3 - Soft Toric Lenses Flashcards
Why are there markings on a soft toric lens?
so that rotation of the cylinder can be observed
What are the 5 soft toric designs
- Prism Ballasted
- Truncated
- Front surface toric
- Back toric lens
- Bitoric lens
What are the 5 advantages of soft toric lenses? (comfort/design/position/works for/modality)
- Good comfort compared to RGP’s
- Thin lens overall
- Cosmesis (restores to original position)
- Works for all type of astigmatism including oblique astigmatism
- Disposable lenses
What are 5 disadvantages to Soft Toric lenses? (thickness/comfort/risk of/time/other)
- Thickness at prism position – reduces oxygen transmissibility
- Discomfort at lower lids for sensitive lids
- Risk of edema with low DK material
- Takes time to assess the orientation
- Stabilization differs from design to design.
What is a prism ballast design toric lens? 2
-1.0 or 1.5 (max 3 prism dioptres) prism base down in lens which means gravity spins the thickest part towards the lower lid
-thinner portion interacts with upper eyelid
A dynamic stabilisation soft toric is thicker at the ends in the horizontal meridian.
Fitting is dependent on how the lids interact with the front surface of the lens
What are the two different designs?
dual thin zone
accelerated stabilization design
What is a peri-ballast design soft toric lens? 4 (lens design/prism?/oxygen flow)
-thins out the top of the lens hence only works on minus (thickest edges)
-prism free optical portion
-prism-like rotational stabilization effect
-enchances oxygen transmissibility
Who does a peri-ballast soft toric work better for?
someone who is a high minus power lenticular carrier
What is a truncation soft toric lens design?
by removing 1 - 1.5mm chord from the lower edge of the lens
What can the be expected from a truncation soft toric lens? (fit/comfort/observation/suitability) 4
- Excellent stability
- Poor comfort
- Easy to observe on the eye
- Not suitable for oblique astigmatism
A Back Surface Toric works well with a px with high amounts of corneal astigmatism because the astigmatism is curved into the back of the lens so fits in ‘like a puzzle piece’ meaning it is a very stable lens. T/F
TRUE
How is a back surface toric lens made more stable?
add in a prism ballast
What does LARS stand for?
LEFT ADD RIGHT SUBTRACT
If the lens rotates clockwise (to the left) what do we do to the axis?
If the lens rotates anti-clockwise (to the right) what do we do the axis?
add the axis rotation (100, rotates 30 clockwise, order 130)
subtract the axis rotation (100, rotates 30 anti-clockwise, order 60)
What are 4 common contact lens complications?
- Giant Papillary Conjunctivitis
- 3 and 9 o’clock staining
- Vascularization (neo if new)
- Stromal Oedema
