Lecture 20 Scleral lenses Flashcards
What are scleral lenses used for?
*Keratoconus
*Pellucid marginal degeneration
*Post corneal trauma
*Post keratoplasty (tilted graft)
*Post refractive surgery (can develop post refractive surgery ectasia or prescription regression. Difficult to fit with standard lenses)
*Exposure/protective (Sjogren’s, steven Johnson syndrome, bull’s keratopathy. Uncomfortable when blinking over this exposed corneal surface.)
What are the advantages of scleral lenses?
*Lens is comfortable due to fluid layer underneath
*Don’t have to have major surgery like corneal graft
*Easy to fit
*Predictable in how they fit to easier to adjust lens
-you can fit odd shapes
-you can protect corneal surface
-can minimise corneal scarring as no corneal touch
How are mini scleral lenses designed to fit?
What size are mini scleral lenses?
*Designed to vault cornea entirely
*Not contact with cornea means
*Lens should clear cornea and limbus
*Lens should land on the sclera
-15-18mm
How do you decide on the initial lens?
be calculated from topography or OCT or chosen based on tables
fitted by sag/depth and NOT by curvature
What must you look for when assessing the fit o a scleral lens?
*Look for any air bubbles. If there is one remove lens and refill and reinsert.
*Make sure there is complete limbal clearance. Use white light to make sure NAFL layer extends beyond imbus
*Look at scleral landing
*larger diameter lenses have a slightly greater central clearance on initial insertion compared to smaller diameter lens
How can you judge central clearance accurately?
*Do an optic section at 45 degrees
*High mag
*Compare thickness of green fluorescein layer with the thickness of the lens
*Can put px onto OCT to measure central clearance
How can you make sure there is no touch?
*If you see an area if NAFL it doesn’t always mean touch
*Get px to look is 4 positions of gaze. If it disappears, then there is no touch.
How can you assess scleral landing?
*All pressure of lens is at this point
*Want to see blood vessels are continuous through the lens with no breaks or interruptions
*When you take this lens out you will get rebound hyperaemia
*Will see a red limbal ring of hyperaemia
*Some px have toroidal sclera
*Will need to consider toroidal sclera especially in larger diameter lenses (16 mm above)
What signs will you see if you put a standard spherical lens on a toroidal sclera?
what is the solution?
*Likely to get air bubbles
*Lens won’t be comfortable
*Need to put some tourosity on edge of lens
What happens if you have a perfect fit but residual astigmatism?
*Need to put that cyl on front surface
*Need a stabilisation technique to make sure lens wont rotate
*Toric periphery lens will always have flat axis marked
*Record axis of rotation stability
What applications are required for a toric mini scleral lens?
- To stabilise front surface toric
- To fit toric sclera
How do you remove a scleral lens?
*Push under the lens to get an inferior air bubble. Use lids to manipulate lens out
*Scissor technique
*DMV (LENS SUCKER). Px puts sucker at 12 o clock whilst looking down into the mirror holding eyelid up. Don’t use sucker centrally or at 6 o clock.
What care products can you use for scleral lenses?
*Soft lens solutions
*Non preserved saline
*Alcohol based cleaner if necessary if atopic px.
*NO ABRASIVE CLEAERS (will get rid of plasma layer which allows wettability
What obstacles can you get to successful wear?
- Conjunctival prolapse
- Deposits
- Excessive settling back
- Fogging
What is conjunctival prolpase?
What is the management?
*Conjunctiva is sucked up into the space between the lens and the limbus
*Can be in any meridian, quite often inferiorly
*Disappears very quickly post-lens removal
*Indicates that we have over-vaulted limbal area
*Can be over vaulted in height or if the lens lands too far beyond the limbus
