considering and fitting CLs Flashcards
What must we do when fitting?
- Record relevant info
- Appropriate advice, written on how to clean, maintain and wear the lenses
- Must give the CL specifications
What to consider if doing outside activities?
UV block
Where can I research contact lenses?
ACLM website
What are the advantages of RGP as a practioner?
We can correct astigmatism better
dryness is less at end of day
advantages of SiHy ?
- comfortable to wear - enhanced wettability and slower dehydration
- less hypoxia
disadvantages of sihy?
- not always MAX comfort due to increased modulus –> foreign body sensation (POSSIBLE)
REMINDER - which deposits are found on a SiHy lens?
lipids (think of anisha and sundeep)
REMINDER - which deposits are found on a hydrogel lens?
proteins
What the disadvantages for dailies?
Cost and some lenses certain powers aren’t available
Why is oxygen reduction an issue?
hypoxia –> neovascularisation, oedema ect
what dk/t is needed for dailies?
37
what dk/t is needed for overnight wear?
125
how much corneal swelling is normal overnight?
4%
if hypoxia is a concern what lenses should you consider?
SiHy
what do you need to consider when giving lenses with a high rx?
For a high Myope +14 :
- Check the periphery for any oxygen issues
High plus:
- Check for a centre issues
Do not assume thought. We have to chec
what is important to consider with SiHys?
mechanical issues and tear exchange
what is a limitation with hydrogels dk/t?
in theory = 40
reality = 22-28
meaning there will be some swelling
what is theoretical dk/t for a SiHy and realistic? what does this mean for the px?
theoretical = 40-160
reality = 100-130
wearers can wear these lenses for a longer amount of time
why are there more mechanical issues with sihy?
less water
why is water content more important in hydrogels than sihy?
in sihy the silicone allows oxygen to pass, in hydrogels the water is needed for oxygen to pass
what is considered as a low water content lens?
35-45%
what is considered as a medium water content lens?
55%
what is considered a high water content lens?
65%
how does water content affect the flexibility of the lens?
the higher the water content, the higher he flexibility
why does a px have dry eye?
they lack aqueous or poor tear quality
what is a low TBUT?
less than 10 seconds
what happens if you put a high water content lens in a dry eye?
It will act like a sponge and will want to absorb more water to maintain the shape of the lens making the eye more dry –> end of day comfort will be worse too.
if someone has dry eye - what kind of lens do you want to give them?
LOW WATER CONENT
What is the modulus of a lens?
how well a material can resist deformation
what is stiffer - monthly or daily?
monthly
Which soft lens has a higher modulus?
siHy (1-0.7)
which soft lens has a lower modulus?
hydrogels (0.3-0.5)
Why is modulus more relevant in monthly?
if edge profile is off px will find it uncomforable when they blink
what are the 3 scenarios where considering oxygen is more important?
high prescriptions
extensive wear
history of hypoxia
do you need to stress about oxygen?
no - consider with v high rx or EW
is there an exact science for choosing CLs?
no LOL use your common sense when fitting
