lecture 3 considering patient needs Flashcards
When was the contact lens specification rule made?
what must it include?
1989 section 25 (5)
(a) the name and address of the individual.
(b) if the individual has not attained the age of sixteen on the day the specification is issued, his date of birth;
(c) the name and registration number of the person signing the specification.
(d) the address from which the person signing the specification practices.
(e) the name of the practice on whose premises the fitting was done.
(f) the date the fitting was completed.
(g) sufficient details of any lens fitted to enable a person who fits or supplies a contact lens to replicate the lens.
(h) the date the specification expires; and
(i) such information of a clinical nature as the person fitting the lens considers to be necessary in the case
What needs can a px have?
1.Comfort
2.Outside activities (UV block)
3.Hygiene limitations (what task are they doing?)
4.Critical vision (how important is vision? Fine level of detail?)
What are the types of modality?
*Daily
*2 weekly
*Monthly
*Annual
What should Dk/t be for daily and extended wear?
*Daily wear: To have 0% corneal swelling, DK/t should be 37
*Extended wear: To have 4% swelling, DK/t should be 125
What are the limitations of Dk/t?
Generally quoted for a prescription of -3.00. lenses with a higher power will be thicker.
What is the Dk/t of hydrogel lenses?
What is the Dk/t of silicone hydrogel lenses?
What should you consider about high prescriptions?
What should you consider about SiHy lenses?
*The maximum Dk/t is 40 but the reality is 22-28
*Dk/t values tend to be from 40-160, typically 100-130 region
*Oxygen should not be a concern when considering daily wear in silicone hydrogels
*For high prescriptions, consider oxygen in the centre and periphery. Look for clinical signs.
More important to consider mechanical issues, tear exchange and if there is irritation with SiHy. These occur due to low water content.
What material has a low water content?
What does water content affect?
silicone hydrogel
*We consider water content in a hydrogel lens because the higher the water content, the more oxygen can get through.
*Silicone hydrogels have less water content due to oxygen getting through silicone material
the more water content, the more flexible the lens
What is considered low, medium and high water content?
low: 35-40%
medium: 50-55%
high: 65%
What effect does water content have on a px with dry eyes?
*People with dry eyes are aqueous deficient or lack good tear quality (tears dry out to quickly)
*If px with dry eyes put in a lens with a high-water content, it will feel comfortable at first but lens will dry out. Lens Looks to reabsorb fluid. Les reabsorbs the tears in the eyes.
*LOW WATER CONTENT IS GOOD FOR PX WITH DRY EYES.
*If px finds lower water contact comfortable at start of the day, it’s unlikely for them to find is uncomfortable towards the end of the day.
Which material has a lower modulus?
hydrogel lenses
