scleral lenses Flashcards
what are scleral lenses?
a lens which extends out onto the sclera
used to describe RGP lenses of diameters over approx 14 mm
what is teh approx size of a scleral lens?
14 mm but can be up to 22mm
what were the first type of scleral lenses?
glass shells
disadvantages of EARLY scleral lenses?
0 oxygen permeability
high chance of damage to the eye if the lens was to break
advantages of PMMA
durable
doesnt break into shards like glass does
why use scleral lenses now?
IRREGULAR ASTIGMATIC PX’S for example:
keratoconus
pellucid marginal degeneration
post corneal trauma
post refractive surgery
exposure/protective
soft lens wearers who find them uncomfortable, dust under hte lens or if the eyes are too difficult to fit
why use lenses in px’s with eye disease?
those with sjrogens, bulls eye keratopathy, steven-johnsons syndrome
allows the cornea to be cushioned, lids no longer touch cornea, lens is not touching cornea
size of a full scleral lens:
18-24 mm
size of mini scleral lens
15-18 mm
corneo/semi scleral:
13-15 mm
advantages of fitting a mini scleral
you can fit really odd shapes
protect the corneal surface
minimise corneal scarring
which type of scleral lens vaults the cornea completely?
mini scleral
how do you fit a mini scleral?
fit from a fitting set
initial lens calculated from topography or OCT based on sag/depth (rather than curvature) OR THE LENS TABLE
LENS SHOULD CLEAR THE CORNEA (NO TOUCH), AND THE LIMBUS
lens should lanf on the sclera (all the weight of the lens)
where should a mini scleral land?
on the sclera
does a mini scleral touch the cornea?
no
does a mini scleral touch the limbus?
no
how do you insert a mini scleral?
have px look down with nose pointing down
px holds lower lid
practitioner holds upper lid with one hand
put LOTS of saline in the lens
(when fitting mix the nafl fluoret in the saline)
put lens on eye
what are you looking for when fitting a mini scleral?
central clearance
limbal clearance
scleral landing
how do you assess if you have enough clearance?
use an optic section
compare the thickness of the nafl layer with the thickness of the lens
how long do you need to leave the lenses in before you asses the fit?
60 mins
why do you need to leave the lenses for a white before you assess the fit?
they settle back into the spongy conjunctiva - therefore apical clearance will be lower afterwards
why is it important to clear the limbus?
can be uncomfortable
it is where the limbal stem cells are
responsible for epithelial cellular production
what does an inappropriate scleral landing look like?
this
when would you use a toric mini scleral?
highly toric sclera
good fit with spherical but has residual astigmatism
what does a toric mini-scleral look like?
what extra measurement do you need to record when assessing toric mini sclerals?
axis of rotational stability
what specifications do you need to fit a toric mini scleral?
sag of toric diagnostic
trial lens power
over-refraction
modifications to limbal fit or scleral landing
axis of rotation markers
how to remove the lenses?
use a suction cup thing in the superior portion of the lens NOT THE MIDDLE
what solution do you use with a mini scleral?
not GP solutions
preservative free saline
alcohol based cleaner if necessary
what are some obstacles to successful wear?
conjunctival prolapse
deposits
excessive settling back
fogging
what is conjunctival prolapse
conjunctiva sucked up under lens to cover limbus
can be in any meridian
if you have conjunctival prolapse do you need to do anything about it?
no
when does conjunctival prolapse occur?
if the limbus is over vaulted
lens diameter for a mini scleral?
3.5mm larger than the visible iris diameter
are deposits on the fromt or back of the lens?
can be front or back
which side of the lens is more difficut to clean?
inside (esp high depth) - consider using Progent for these patients
what can front surface deposits lead to??
poorly wetting lens
what do you do for patients who’s lenses settle back more than normal?
choose a larger lens with a lerger landing zone to spread the weight more evenly
when does fogging occur?
after a few hours of wear
worse in the first month of wear
does fogging go away?
no - px adapts
who is fogging more common in?
atopic px’s
what is fogging>
lipids from conjunctival goblet cells
used to be considered mucin
management of fogging
don’t over vault the limbus
use a single non-preserved and un-buffered saline to fill the lens
experiment with filling the lens with non-preserved artificial tears (hycosan)
