Lec 8 Fitting Keratoconus/Semi Sclerals Flashcards
How to refract on keratoconic
LARGE STEPS
Control accom as most px not presbyopia
+|-1 JCC
Tweek blur checks as VDiff VA means good eye still sees chart
How to find cyl on keratoconus
Screen 1D JCC axis 90/180 and 45/135
Insert 1D or 2D and ask px to rotate till things look best
Methods to select BC for keratoconus
1: start halfway between steep and flat K
2: Use average K reading and include fitting factor based on design
3: Use topography and go 1/3 or 1/4 from steepest
- 1/3 = yellow/orange mod-advanced KC
- 1/4 = yellow/green mild-moderate Kc
4: Diagnostic fit on steep K and change CL till light touch just visible
How to convert between mm to Dioptres
337.5/mm or Dioptre
How to find peripheral curve of keratoconic lens
HAS TO BE DETERMINED DIAGNOSTICALLY
How to find Back Vertex Power of Keratoconic Lens
Find diagnostically with CL on eye and doing over refraction
Advantage of large lenses/semi sclerals
Don’t dislodge
Minimal lid sensation so good comfort
Low % FV getting under lens
Good post surgery option as don’t want to affect surgical parts of cornea
Allows a ptosis prop
Disadvantage of large lens/semi scleral
Manufacturing challenges
Hard to put on eye
Can settle back into eye and tighten up decreasing tear flow
Need sufficient fluid on insertion or otherwise trap bubbles
MOST POPULAR Semi scleral or mini scleral options
Centra SS Max (CLC)
Rose K2 XL (CLC)
How to fit a semi scleral
Select BC with light clearance
- using method for normal vs KC corneas
Check if edge lift needs to be changed to avoid pressure on limbus/seal off/excess lift
Use standard RGP evaluation but aim to get less movement 0.75mm
Who needs semi sclerals
Post graft px
Advanced Kc with large sagging cones as it holds everything in
Pellucid marginal degeneration as steep mostly inferior
Px that can’t adapt to small lenses - awareness
Px with small lenses unstable - pop off eye
What’s a hybrid CL and give examples
Middle part is hard but outer part soft for good fit
Synergeyes - Duette HD
Synergeyes - Ultrahealth with reverse curve
