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Contact Lenses > scleral lenses > Flashcards

scleral lenses Flashcards

1
Q

what are scleral lenses?

A

a lens which extends out onto the sclera
used to describe RGP lenses of diameters over approx 14 mm

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2
Q

what is teh approx size of a scleral lens?

A

14 mm but can be up to 22mm

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3
Q

what were the first type of scleral lenses?

A

glass shells

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4
Q

disadvantages of EARLY scleral lenses?

A

0 oxygen permeability
high chance of damage to the eye if the lens was to break

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5
Q

advantages of PMMA

A

durable
doesnt break into shards like glass does

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6
Q

why use scleral lenses now?

A

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

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7
Q

why use lenses in px’s with eye disease?

A

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

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8
Q

size of a full scleral lens:

A

18-24 mm

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9
Q

size of mini scleral lens

A

15-18 mm

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10
Q

corneo/semi scleral:

A

13-15 mm

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11
Q

advantages of fitting a mini scleral

A

you can fit really odd shapes
protect the corneal surface
minimise corneal scarring

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12
Q

which type of scleral lens vaults the cornea completely?

A

mini scleral

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13
Q

how do you fit a mini scleral?

A

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)

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14
Q

where should a mini scleral land?

A

on the sclera

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15
Q

does a mini scleral touch the cornea?

A

no

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16
Q

does a mini scleral touch the limbus?

A

no

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17
Q

how do you insert a mini scleral?

A

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

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18
Q

what are you looking for when fitting a mini scleral?

A

central clearance
limbal clearance
scleral landing

19
Q

how do you assess if you have enough clearance?

A

use an optic section
compare the thickness of the nafl layer with the thickness of the lens

20
Q

how long do you need to leave the lenses in before you asses the fit?

A

60 mins

21
Q

why do you need to leave the lenses for a white before you assess the fit?

A

they settle back into the spongy conjunctiva - therefore apical clearance will be lower afterwards

22
Q

why is it important to clear the limbus?

A

can be uncomfortable
it is where the limbal stem cells are
responsible for epithelial cellular production

23
Q

what does an inappropriate scleral landing look like?

A

this

24
Q

when would you use a toric mini scleral?

A

highly toric sclera
good fit with spherical but has residual astigmatism

25
Q

what does a toric mini-scleral look like?

A
26
Q

what extra measurement do you need to record when assessing toric mini sclerals?

A

axis of rotational stability

27
Q

what specifications do you need to fit a toric mini scleral?

A

sag of toric diagnostic
trial lens power
over-refraction
modifications to limbal fit or scleral landing
axis of rotation markers

28
Q

how to remove the lenses?

A

use a suction cup thing in the superior portion of the lens NOT THE MIDDLE

29
Q

what solution do you use with a mini scleral?

A

not GP solutions
preservative free saline
alcohol based cleaner if necessary

30
Q

what are some obstacles to successful wear?

A

conjunctival prolapse
deposits
excessive settling back
fogging

31
Q

what is conjunctival prolapse

A

conjunctiva sucked up under lens to cover limbus
can be in any meridian

32
Q

if you have conjunctival prolapse do you need to do anything about it?

A

no

33
Q

when does conjunctival prolapse occur?

A

if the limbus is over vaulted

34
Q

lens diameter for a mini scleral?

A

3.5mm larger than the visible iris diameter

35
Q

are deposits on the fromt or back of the lens?

A

can be front or back

36
Q

which side of the lens is more difficut to clean?

A

inside (esp high depth) - consider using Progent for these patients

37
Q

what can front surface deposits lead to??

A

poorly wetting lens

38
Q

what do you do for patients who’s lenses settle back more than normal?

A

choose a larger lens with a lerger landing zone to spread the weight more evenly

39
Q

when does fogging occur?

A

after a few hours of wear
worse in the first month of wear

40
Q

does fogging go away?

A

no - px adapts

41
Q

who is fogging more common in?

A

atopic px’s

42
Q

what is fogging>

A

lipids from conjunctival goblet cells
used to be considered mucin

43
Q

management of fogging

A

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)

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