SCL Fit Char

Question 1

What is required at all times regarding coverage?

Answer 1

FULL CORNEAL COVERAGE

Question 2

What three factors affect lens position? [SIL]

Answer 2

Sag, LD, lid interaction (tight lids can push down)

Question 3

• BLINK mvmt: is assessed in ____ gaze. Lag Range?
• UPGAZE mvmt: range?
• is the upgaze blink mvmt ok to be higher than in primary?
• LATERAL LAG range?

Answer 3

PRIMARY: 0.50-1.00mm

• same for upgaze.
• can be up to 2mm in upgaze blink
• LATERAL: 0.50-2.00mm

Question 4

when is push-up movement used?

Answer 4

when inadequate blink mvmt is noted - check to see if it’s fitting too TIGHT (not gonna move) or LOOSE (move excessively)

Question 5

-STEEPER BC and LARGER LD will (increase/decrease) lens mvmt

Answer 5

DECREASE

Question 6

more EYELID interaction will cause (increase/decrease) lens mvmt
-what are two lens characteristics that INCREASE lid interaction? [EMT]

Answer 6

MORE

MODULUS
THICKNESS - increases in EITHER ONE will INCREASE lid interaction (and increase lens mvmt)

Question 7

what effect happens in each thing below produced by DEHYDRATION of a lens?
-BC? LD? Power?

Answer 7

BC: steepen

LD and power: decrease - power becomes more PLUS

Question 8

K mires for STEEP lenses usually ___ after a blink, but ___ over time

Answer 8

STEEP: blur-clear-blur. CLEAR after blink - then blur over time

Question 9

K mires for FLAT lenses usually ___ after a blink, but ___ over time

Answer 9

blur, CLEAR over time (which is why you fit them flat on purpose)

Question 10

where will a STEEP fit lens produce a retinoscopy reflex distortion?
-how about a FLAT fit lens?

Answer 10

STEEP lens: distortion CENTRALLY

FLAT lens: distortion INFERIORLY (yes, inferiorly…sounds wierd)

Question 11

What are 3 other observations indicating a steep fit?

Answer 11

bubbles @ limbus, vessel blanching, lens imprint after removal

Question 12

STEEP lenses AND FLAT lenses have (good/poor) draping over the cornea.

• STEEP lenses: VA WORST (after/before/between) blinks
• FLAT lenses: VA WORST (after/before/between) blinks

Answer 12

POOR draping (both of them). Flat lenses may also move excessively.

• STEEP lenses: bad VA BETWEEN blinks (best VA right after a blink)
• FLAT lenses: bad VA right AFTER blink, then clears as eye stays open

Question 13

What’s the average NATURAL amt of spherical aberration in the eye? Positive or negative SA?

Answer 13

+0.15 microns (not diopters) - PUREVISION has an adjusted (-0.15 micron) lens to reduce SAs

Question 14

What is the MOST convenient, MOST healthy lens class?

-What’s the most COST-effective (cheapest) lens class?

Answer 14

1 day CW (10-14 hrs)

1 yr DW (no sleepy!)

Question 15

what are three “dry eye” materials?

Answer 15

• filcons! [OHD]
• omafilcon
• hioxifilcon
• delefilcon

Question 16

Parameters: LD

• Average LD? Range?
• Approx __-__ LARGER than HVID

Answer 16

avg: 14.0. Range 13.5-15.0

2-3mm LARGER than HVID, or 1-1.5mm LARGER around limbus (scleral drape)

Question 17

Parameters: BC. Avg HVID -just use which available BC?

• LARGER HVID - want a (flatter/steeper) BC.
• usually pick a lens ___D (flatter/steeper) than (flat/steep) K

Answer 17

-avg HVID - use avg or “medium”
larger HVID - use steeper BC (larger sag)
smaller - use flatter (smaller sag)
4D FLATTER THAN FLAT K - allow TEAR EXCHANGE!

Question 18

what is the average HVID? What needs to be used when your pt doesn’t have an avg HVID?

Answer 18

11.8; EFFECTIVE K

Question 19

What 2 factors does “Effective K” incorporate? It’s all in an effort to assist proper __ selection

• cornea is LARGER than 11.8mm, (add/subtract) WHAT? from WHERE? for every HOW MANY mms larger?
• what if cornea is SMALLER than 11.8?

Answer 19

1) central corneal radius (Ks)
2) corneal diameter (HVID)
- proper BC selection
- LARGER: add 1D to the Ks every .2mm LARGER than 11.8
- SMALLER: subtract 1D from the Ks for every .2mm

Question 20

What power do you order for a sph-cyl pt w/ minor cyl?

Answer 20

Sph equivalent of the VERTEXED SR

Question 21

what’s the “normal” CT to order?

Answer 21

0.12 (standard); “thin” = 0.07, “min” = 0.03

Question 22

what’s the lens equilibration time?

Answer 22

5-30 mins

Question 23

what two values do you add to determine the FINAL CLP?

Answer 23

OR, CLP. Compare SE to the SRv; SHOULD be equal/within 0.25D

Question 24

what elements are required in your final SCL order?

Answer 24

BRAND, replacement interval, units - other than that it’s the things YOU decide over:
-BC, Power, LD, tint

Question 25

First parameter change to make?

-steps usually in __-__ mm increments

Answer 25

BC; 0.3-0.4

Question 26

Second parameter change to make?

-what must you ALSO change if you do this?

Answer 26

LD: SMALLER if too much coverage or LARGER if too unstable/loose/decentered.

• MUST also change BC! if you INCREASE CT: FLATTEN bc (the opposite! to counter the effect!)
• remember - a FLATTER BC = BIGGER NUMBER)

Question 27

third parameter change to make? (RARE)

-WHEN do you make it?

Answer 27

CT: hypoxia-related conditions

-or: if it dries too quickly, not enough mvmt, hard to handle

Question 28

LAST parameter change to make?

• what do you do if the lens dries too quickly?
• what do you do if there’s excessive protein deposit?
• when would you INCREASE water content?

Answer 28

Water content

• LOWER water content
• switch to non-ionic, low water (class 1)
• increase if hypoxia-related probz; OR just change to SiHy

Question 29

biggest advantages of SCLs?

Answer 29

better INITIAL COMFORT, flexible wear (easier for part-time), convenience, LESS spectacle blur, ocular health)

Question 30

biggest advantages of GPs?

Answer 30

ACUITY/optics.

-better deposit resistance, durability, FEWER COMPLICATIONS, easier handling/inspection, cheaper!