Week 10 - Keratoconus Flashcards

Question

Parameters for RGP:

Answer 1

• BOZR 5.60 - 8.20 mm • BOZD 8.60 - 9.60 mm • BVP usually myopic • Peripheral curves often need to be modified to fit contour of cone (either reduced or increased edge lift around whole lens, or by segment) • Material: -focon • Handling tint: blue, green or violet • Unplanned replacement schedule... Should last a year minimum

Answer 2

Four zones created: • Slight apical touch • Paracentral clearance • Mid-peripheral bearing • Peripheral clearance

Answer 3

• Piggyback - RGP over plano soft monthly or daily disposable. • Can improve comfort and centration • More hassle for I&R and cleaning, higher risk of complications as px has 2 lenses on eye

Answer 4

• Good initial tolerance, wear time can be built quickly • Large diameter, flare not problematic • Vision good in mild - moderate KC • Stable fit - don't tend to fall out or displace

Answer 5

• Don't mask irregularity as well as hard lenses - VA not as good in moderate to advanced KC • Can have thick edges (but silicone hydrogel materials tend to avoid hypoxic problems) • Higher infection risk than with RGPs It can be difficult to ensure stable vision in high cyls

Answer 6

• BOZR 7.40mm - 9.40mm • BOZD 14.00mm - 15.50mm • BVP usually myopic with astigmatism - can go up to +/- 30.00DS or -15.00D • Peripheral curves often need to be modified to fit contour of cone (either reduced or increased edge lift around whole lens, or by segment) • Material: -filcon. Tend to be higher modulus than other soft lenses to mask irregularity • Handling tint: none or pale blue • 3-12 months replacement schedule depending on material

Answer 7

• Tight/steep soft lenses - Limbal compression - Hyperaemia often seen after removal • Flat soft lens - Excessive lag on eye movements and blink - Rotation of marking seen - Variable vision - Increase lens awareness

Answer 8

• PROS - Acuity of RGP but with better comfort Don't displace or fall out like RGPs can • CONS - Can be difficult to insert & remove - Bubbles can form at junction - Solution must be suitable for both materials - Time consuming to fit

Answer 9

• Large diameter RGP material (14-16mm) • Fitted to vault whole cornea with lens resting on sclera • Liquid reservoir between cornea and lens

Answer 10

• GOOD ACUITY • LESS LID INTERACTION SO CAN BE MORE COMFORTABLE THAN RGPS • TUCKED UNDER LIDS SO NO ISSUES WITH LENSES DISPLACING OR FALLING OUT - GOOD FOR ADVANCED CONES • HELPFUL IF IRREGULAR AREA OF CORNEA VERY PERIPHERAL

Answer 11

• DIFFICULT TO INSERT AND REMOVE - HAVE TO GO IN FULL OF SALINE, REMOVED LIKE A BIG RGP OR WITH SUCKER • DIFFICULT TO JUDGE FIT - PX HAS TO INSERT WITH SALINE WITH ADDED FLUOROSCEIN AS THERE IS NO TEAR EXCHANGE • HAVE TO ENSURE LIMBAL HEALTH ISN'T COMPROMISED • NOT IDEAL IF INFLAMMATION OF OCULAR SURFACE AS NO TEAR EXCHANGE

Answer 12

• Atopic/allergic keratoconjunctivitis. A lot of patients with keratoconus have seasonal or year-round dust, animal hair or pollen allergies • Always take a medical and ocular history at the start of the fit appointment. • Examine the tarsal plate by everting the lids • Consider starting patient on topical antihistamines or mast cell stabilisers before proceeding with fitting to get any ocular allergy under control • Explain any potential problems to the patient

Answer 13

• Patients could be wearing lenses for the next 50 years! • CLAPC, hypoxia or dry eye could be an issue • Patients who are attending for topography every 6 -12 months to check for progression have to leave their lenses out for 2 weeks prior to topography to ensure scans are accurate.