Week 2.04 Scleral Lenses Flashcards
What’s the issue with corneal lenses and irregular corneas
- rest on cornea
- difficult/impossible to align lens to eye
- Pressure on high areas
- unstable, uncomfortable
- corneal staining
- scarring
What’s the advantages of scleral lenses
- minimal movement
- No contact between lens and cornea
- no tear flow under lens so no FB issues
- vision can be better
- no exposure so less staining
- long term - less likely to proceed to graft
What’s disadvantages of scleral lenses
- lower oxygen transmission
- foggy vision
- increased inflammation
- epithelial changes
- handling
- vision can be worse
- inflammatory response can be worse if lens fit poor
What are the different zones of scleral lenses
Optical zone: central area of lens - focusing power
Front optic zone: control central thickness of high power lenses
Transition zone: controls clearance over peripheral cornea and limbus
Landing zone: part of the lens that supports weight
What are the two design options for a scleral lens
Prolate - mountain dome shape
Oblate - flat top mountain
Why fit scleral lenses
Keratoconus
Post Refractive surgery
Corneal scarring
Lid abnormalities
High refractive error
Why do we need to be cautious with px with unstable glaucoma
Scleral lenses resting on trabecular mesh work so can cause spike in IOP
Fitting goals
1: align optic zone with cornea
Prolate - steeper centrally, flatter peripherally
Oblate - flatter centrally, steeper peripherally
2: clearing the corneal apex - no touch
3: align landing zone to scleral profile
How to assess the landing zone
- blanching
- impingement - edge of lens digging in to conjunctiva
- Compression
How to prepare a scleral lens
Rub lens with base permeable lens conditioning solution
Rinse inside of lens thoroughly with preservative free saline
Fill the lens to overflowing saline and dip fluorescein in to create dilute fluorescein solution
What’s the average diameter of scleral lens
Corneo-scleral - 13-16mm
Full scleral - 15.4 - 18.5mm / 20 to 23
