Fitting RGPs

Question 1

on K NaFL pattern

Answer 1

an evenly distributed light green pattern across the cornea with a narrow band of green in the peripheral edge

Question 2

what BC will allow for an on K fit?
Ks
-OD: 45.00/45.00 @ 090
-OS: 45.00/45.00 @ 090
SUBJ
-OD:-2.25 DS
-OD:-2.25 DS

Answer 2

7. 5mm

337. 5/45

Question 3

What GP lens power should be ordered for an onK fit?
-OD: 45.00/45.00 @ 090
-OS: 45.00/45.00 @ 090
SUBJ
-OD:-2.25 DS
-OD:-2.25 DS

Answer 3

-2.25

Question 4

what new power should be ordered if the CL base curve is steepened by 0.1mm

Answer 4

-2.75D

Question 5

how do you always want to fit an RGP

Answer 5

slightly flat to allow for tear exchange

Question 6

flat fit pattern

Answer 6

central touch with a broad green ting of NaFL underneath the peripheral portion of the lens

Question 7

steep fit pattern

Answer 7

bulls eye pattern with central pooling of NaFL and minimal NaFL underneath the periphery of the lens

Question 8

spherical GP lens fit over an ATR cornea pattern

Answer 8

will have a figure 8 pattern of TOUCH along the vertical meridian and pooling along the horizontal meridian and I the peripheral zone

Question 9

spherical GP lens over WRT cornea pattern

Answer 9

dumbbell shaped pattern of TOUCH along the horizontal meridian and pooling along the vertical meridian and in the peripheral zone

Question 10

a spherical GP fit over an astigmatic cornea will have pooling where

Answer 10

in the steep meridian and touch in the flat meridian

Question 11

if you see 3 and 9 staining, what does this typically mean

Answer 11

riding too low

corneal desiccation

Question 12

raising a GP lens

Answer 12

• BC closer to on-K fit
• increase diameter
• decrease center thickness by 0.03mm
• minus carrier lenticular to assist with lid attachment
• flatten the peripheral curves to increased edge lift and lid attachment

Question 13

signs of keratoconnus

Answer 13

FIRST

• Fleischer ring
• Irregular mires
• Reflex scissors
• Striae (Vogt’s)
• Thinning of storm

Question 14

high riding CL results in

Answer 14

corneal warpage with image ghosting

Question 15

diff between flexure and warpage

Answer 15

flexure is ON the eye and warpage is on and off the eye

Question 16

laterally displaced GP lens

Answer 16

its too flat. steepen the fit bit decreasing the BC, increased the OZD, or increasing the overall lens diameter. If this does not work, refit into a minus lens carrier lenticular edge design or a toric back surface design or add toric peripheral curves

Question 17

two main fitting philosophies for fitting RGPs

Answer 17

1. lid attached

2. interpalpebral

Question 18

lid attached RGP fit

Answer 18

the edge of the GP Cl interacts with the superior eyelid margin; this is the most appropriate for patients whose superior eyelid sits at or below the limbus, and the eyelid has normal tension against the globe

Question 19

interpalpebral RGP fit

Answer 19

the edge of the RGP DOES NOT interact with either eyelid margin; this is most appropriate if the superior eyelid is located above the limbus or the patient has tight eyelids against the globe

Question 20

OAD fitting philosophy

Answer 20

consider the fitting philosophy and corneal curvature when determining the most appropriate OAD. an average OAD (9.4-9.6mm) is most appropriate for patients where the upper eyelid is located atop below the superior limbus (lid attachment). A smaller OAD is recommended fort patients who need an interpalpebral fit or have small interpalpebral fissures

Question 21

large OAD/OZDs

Answer 21

steepened the GPCL

Question 22

small OAD/OZD

Answer 22

flatten the GPCL

Question 23

for every 0.4mm increase (decrease) in the OAD/OZD

Answer 23

flatten (steepens) by 0.25D

Question 24

guidlines for fitting spherical RGPS

Answer 24

corneal astigmatism < 2.50D and acceptable residual astigmatism

Question 25

fitting guidlines for front toric RGP

Answer 25

corneal astigmatism <2.50D and unacceptable residual astigmatism

Question 26

fitting guidelines for back surface toric

Answer 26

corneal astigmatism >2.50D and spec astigmatism =1.5 x corneal astigmatism

Question 27

fitting guidelines for bitoric lenses

Answer 27

corneal astigmatism >2.50D and spec astigmatism that does not equal 1.5x the corneal astigmatism

Question 28

fitting guidelines for aspheric RGPs

Answer 28

consider in patients with ATR or borderline astigmatism or in patients who are hypercritical of their vision

Question 29

higher amounts of corneal astigmatism and BC

Answer 29

steeper BC needed for adequate fit, the CT should be increased by 0.03mm with a steeper BC in order to minimize flexure

Question 30

material of RGPs

Answer 30

higher Dk lenses have greater oxygen permeability but also more flexure; increase the CT by 0,03mm in order to minimize flexure. in general, high or hyper Dk lenses are indicated for extended wear, and low Dk lenses are acceptable for daily wear

Question 31

BC guidelines

Answer 31

for a RGP with a 9.4mm OAD and lid attached fit

• if corneal astigmatism is < or equal to 0.75D, fit 0.50D flatter than K; for every 0.50D increase in corneal astigmatism, steepen the BC by 0.25D until a biotic CL is necessary
• because the cornea progressively flattens toward the periphery, selecting a BC that is flatter than K will result in greater alignment between GP CL and the cornea

Question 32

watermelon seed effect

Answer 32

describes the phenomenon where the RGP is posed down and outward, most often due to tight upper lid tension
-an improvement in a lid attachment fit or an interpalpebral fit will help to minimize this effect

Question 33

how to achieve a lid attached fit

Answer 33

large and flat RGP

Question 34

how to achieve an interpalpebral fit

Answer 34

small and steep GP

Question 35

SAM FAP

Answer 35

describes how to change the power of a RGP to compensate for a change in the BC of the CL. Recall that every 0.05mm change in BC, the power should be adjusted by 0.25D