Transcript The Art of Orthokeratology

GOV & VIPOK Updates
The Ideal Ortho-K Patient
Suitable candidates for Ortho-K
 Age of Patient – older than 6 years
 Spherical refractive power +5D to -10.00D
 Cylindrical refractive power:
 -1.50D or less W-T-Rule astigmatism
 -0.75D or less A-T-Rule astigmatism
 Children with progressive myopia
 Patients free of corneal pathology
 Patients that are committed to initial and ongoing
cost of treatment
Screen for a healthy cornea
 Don’t fit when:
 Cornea is distorted
 Eye Rubbing (treat allergies & habit)
 Soft or RGP imprints (allow rehabilitation)
 Corneal abnormalities
 Irregular corneal astigmatism
 Keratoconus
 Pellucid Marginal Degeneration
 Lid or corneal pathology is present
Topographer
Calibrate
Topographer!
Topographer
 Accuracy depends on:
 Software algorithms used to reconstruct corneal
shape (update software)
 Stability of the patient’s tear film during capture (use
wetting drops)
 Head position & movement during capture
 Lid aperture (open eyes)
 Number of reading done to get statistically
significant accuracy
 Take multiple readings
 Omit high & low values
Cylinder Rules
 <1.50D W-T-R
 <0.75D A-T-R
 Cyl ≤ ½Sph
 -0.50 / -1.50 – Problem
 -3.00/-1.00 – Fine
Empirical fitting
vs.
Systemised Fitting Systems
Empirical Fitting Systems
 Corneal information is given to lab
 Lab designs lens
 Lens works
 Or it doesn’t!
Systemised Fitting Systems
General fitting process:
 Initial lens is chosen from chart
 Fit with diagnostic trial lenses and evaluate
NaFL pattern – Look for Bull’s eye pattern
 Initial lens should not be too flat and should
move 1 – 2mm on blink
 Evaluate after 30 min using the topographer
 Does the Px show a central flattening effect ?
Systemised Fitting Systems
General fitting process
 If diagnostic lens looks acceptable, allow Px
to wear overnight and evaluate the next
morning
 If the lens is too tight or too loose a different
lens can be chosen from trial set and refitted
Systemised Fitting Systems
Lens adaptation and follow-up
 Centration is critical.
 Movement: 1 – 2 mm with blinking.
 Flourescein pattern: Bulls eye pattern.
Fitting the Ortho-K Lens
Flourescein patterns:
The Orthokeratology Company
 GOV – Global Ortho-K Vision
 Vipok II – Non Conformed <-5.00D
 XMJ– Conformed <-5.00D
 XM – Conformed >5.00 <10.00D
 H – Hyperopia
 HP – Hyperopia Presbyopia
 MP – Miopic Presbyopia
 Post Lasik & Keratoconus
 Website (Plan Date Jan 2008)
 Ordering
 Blog
 Px & Prac Education
The GOV System
 Advanced inventory system
 Multi-curve aspheric conformed Reverse Geometry
Lenses
 Simple method for myopia & hyperopia correction
 You are in control of the lens fit – not laboratories
 Correct from +5.00D to -10.00D
GOAL
A simple method to start Orthokeratology allowing
for growth into fitting higher powers with the
confidence that there is a support group.
Benifits
Simple effective system
 You choose the appropriate lens and make
changes
 Immediate dispensing – (full trial set)
 Efficient and effective method to increase
turnover
 Develop a specialty Ortho-k practice
 Confidently fit with GOV support
GOV TM
lens details
 Base curve
 Hydraulic massage to central cornea
 Conformed fitting curve (1st reverse zone)
 Space for tear circulation & tissue molding
 Alignment curve (2nd reverse)
 Peripheral compression & centration
 Peripheral curve
 Tear reservoir for cornea wetting
Predetermined OAD (lens size)
 OADs of trial lenses are predetermined
 Flatter Ks accompany larger corneas
 Steeper Ks accompany smaller corneas
KM range
OAD
% of HVID
Best-fit HVID
40.00 ~ 42.25
11.2 mm
96%
11.3~11.9 mm
42.50 ~ 43.75
10.8 mm
94%
11.2~11.6 mm
44.00 ~ 47.50
10.4 mm
93%
10.8~11.4 mm
Fitting GOV TM Lenses
 External ocular exam
 Measure refraction, keratometry & HVID
 Select K-code by Mean K
 Select Power-code by S.E.
 Order lenses Empirically and/or with trial fit
K-code / Power-code / Color / Material / OAD
 Lens size
 Predetermined
 Match Corneal size by Best-fit HVID
Orthokeratology
The GOV System
K-code:
Mean K = (Steep K + Flat K) / 2

Carry value up to 2 decimal places (0.01)

Km in Diopters
Power Calculation:
SE = Spherical Spec power – [K astigmatism / 2]

Spherical power must not be vertexed

K astigmatism = steep K – flat K (in Dioptres)
Mean K/ S.E
-1.50
-2.00
OAD 11.2 mm
-2.50
-3.00
-3.50
-4.00
-4.50
-5.00
Best fit cornea 11.3~11.9 mm (OAD=95-97% of HVID)
A 39.87~40.11 (40.00)
40.00/-1.5
40.00/-2.0
40.00/-2.5
40.00/-3.0
40.00/-3.5
40.00/-4.0
40.00/-4.5
40.00/-5.0
B 40.12~40.36 (40.25)
40.25/-1.5
40.25/-2.0
40.25/-2.5
40.25/-3.0
40.25/-3.5
40.25/-4.0
40.25/-4.5
40.25/-5.0
C 40.37~40.66 (40.50)
40.50/-1.5
40.50/-2.0
40.50/-2.5
40.50/-3.0
40.50/-3.5
40.50/-4.0
40.50/-4.5
40.50/-5.0
D 40.67~40.86 (40.75)
40.75/-1.5
40.75/-2.0
40.75/-2.5
40.75/-3.0
40.75/-3.5
40.75/-4.0
40.75/-4.5
40.75/-5.0
E 40.87~41.11 (41.00)
41.00/-1.5
41.00/-2.0
41.00/-2.5
41.00/-3.0
41.00/-3.5
41.00/-4.0
41.00/-4.5
41.00/-5.0
F 41.12~41.36 (41.25)
41.25/-1.5
41.25/-2.0
41.25/-2.5
41.25/-3.0
41.25/-3.5
41.25/-4.0
41.25/-4.5
41.25/-5.0
G 41.37~41.66 (41.50)
41.50/-1.5
41.50/-2.0
41.50/-2.5
41.50/-3.0
41.50/-3.5
41.50/-4.0
41.50/-4.5
41.50/-5.0
H 41.67~41.86 (41.75)
41.75/-1.5
41.75/-2.0
41.75/-2.5
41.75/-3.0
41.75/-3.5
41.75/-4.0
41.75/-4.5
41.75/-5.0
I 41.87~42.11 (42.00)
42.00/-1.5
42.00/-2.0
42.00/-2.5
42.00/-3.0
42.00/-3.5
42.00/-4.0
42.00/-4.5
42.00/-5.0
J 42.12~42.36 (42.25)
42.25/-1.5
42.25/-2.0
42.25/-2.5
42.25/-3.0
42.25/-3.5
42.25/-4.0
42.25/-4.5
42.25/-5.0
OAD 10.8 mm
Best fit cornea: 11.2~11.6 mm (OAD=93-95% of HVID)
K 42.37~42.66 (42.50)
42.50/-1.5
42.50/-2.0
42.50/-2.5
42.50/-3.0
42.50/-3.5
42.50/-4.0
42.50/-4.5
42.50/-5.0
L 42.67~42.86 (42.75)
42.75/-1.5
42.75/-2.0
42.75/-2.5
42.75/-3.0
42.75/-3.5
42.75/-4.0
42.75/-4.5
42.75/-5.0
M 42.87~43.11 (43.00)
43.00/-1.5
43.00/-2.0
43.00/-2.5
43.00/-3.0
43.00/-3.5
43.00/-4.0
43.00/-4.5
43.00/-5.0
N 43.12~43.36 (43.25)
43.25/-1.5
43.25/-2.0
43.25/-2.5
43.25/-3.0
43.25/-3.5
43.25/-4.0
43.25/-4.5
43.25/-5.0
O 43.37~43.66 (43.50)
43.50/-1.5
43.50/-2.0
43.50/-2.5
43.50/-3.0
43.50/-3.5
43.50/-4.0
43.50/-4.5
43.50/-5.0
P 43.67~43.86 (43.75)
43.75/-1.5
43.75/-2.0
43.75/-2.5
43.75/-3.0
43.75/-3.5
43.75/-4.0
43.75/-4.5
43.75/-5.0
OAD 10.4 mm
Best fit cornea: 10.8~11.4 mm (OAD=92-94% of HVID)
Q 43.87~44.11 (44.00)
44.00/-1.5
44.00/-2.0
44.00/-2.5
44.00/-3.0
44.00/-3.5
44.00/-4.0
44.00/-4.5
44.00/-5.0
R 44.12~44.36 (44.25)
44.25/-1.5
44.25/-2.0
44.25/-2.5
44.25/-3.0
44.25/-3.5
44.25/-4.0
44.25/-4.5
44.25/-5.0
S 44.37~44.66 (44.50)
44.50/-1.5
44.50/-2.0
44.50/-2.5
44.50/-3.0
44.50/-3.5
44.50/-4.0
44.50/-4.5
44.50/-5.0
T 44.67~44.86 (44.75)
44.75/-1.5
44.75/-2.0
44.75/-2.5
44.75/-3.0
44.75/-3.5
44.75/-4.0
44.75/-4.5
44.75/-5.0
U 44.87~45.11 (45.00)
45.00/-1.5
45.00/-2.0
45.00/-2.5
45.00/-3.0
45.00/-3.5
45.00/-4.0
45.00/-4.5
45.00/-5.0
V 45.12~45.36 (45.25)
45.25/-1.5
45.25/-2.0
45.25/-2.5
45.25/-3.0
45.25/-3.5
45.25/-4.0
45.25/-4.5
45.25/-5.0
W 45.37~45.66 (45.50)
45.50/-1.5
45.50/-2.0
45.50/-2.5
45.50/-3.0
45.50/-3.5
45.50/-4.0
45.50/-4.5
45.50/-5.0
X 45.67~45.86 (45.75)
45.75/-1.5
45.75/-2.0
45.75/-2.5
45.75/-3.0
45.75/-3.5
45.75/-4.0
45.75/-4.5
45.75/-5.0
Y 45.87~46.11 (46.00)
46.00/-1.5
46.00/-2.0
46.00/-2.5
46.00/-3.0
46.00/-3.5
46.00/-4.0
46.00/-4.5
46.00/-5.0
Z 46.12~46.36 (46.25)
46.25/-1.5
46.25/-2.0
46.25/-2.5
46.25/-3.0
46.25/-3.5
46.25/-4.0
46.25/-4.5
46.25/-5.0
ZA 46.37~46.66 (46.50)
46.50/-1.5
46.50/-2.0
46.50/-2.5
46.50/-3.0
46.50/-3.5
46.50/-4.0
46.50/-4.5
46.50/-5.0
ZB 46.67~46.86 (46.75)
46.75/-1.5
46.75/-2.0
46.75/-2.5
46.75/-3.0
46.75/-3.5
46.75/-4.0
46.75/-4.5
46.75/-5.0
ZC 46.87~47.11 (47.00)
47.00/-1.5
47.00/-2.0
47.00/-2.5
47.00/-3.0
47.00/-3.5
47.00/-4.0
47.00/-4.5
47.00/-5.0
ZD 47.12~47.36 (47.25)
47.25/-1.5
47.25/-2.0
47.25/-2.5
47.25/-3.0
47.25/-3.5
47.25/-4.0
47.25/-4.5
47.25/-5.0
ZE 47.37~47.66 (47.50)
47.50/-1.5
47.50/-2.0
47.50/-2.5
47.50/-3.0
47.50/-3.5
47.50/-4.0
47.50/-4.5
47.50/-5.0
Prescribe Empirically
 Km: 42.87 x 44.75 @ 90
RX: - 3.50 - 1.50 x 180
 Determine K-code
Mean K=(42.87 + 44.75) / 2 = 43.81
K-code = 43.75
 Determine Power-code
S.E.= - 3.50 – [(44.75-42.87) / 2] = -4.44
Power-code= -4.50
 Empirically ordered by
XMJ / (43.75) / -4.50 / 10.8 mm
Empirically with trial fit
 Prescribe a looser lens empirically
 Subtract 0.50D from K code (flatter K code)
 Add +0.50 D to power-code (less minus)
 Order lens by: XMJ / (43.25) / -4.00 / 10.8 mm
 Prescribe a tighter lens empirically
 Add 0.50 D to K code (steeper K code)
 Add -0.50 D to power code (more minus)
 Order lens by: XMJ / (44.25) / -5.00 / 10.4 mm
Prescribe by over refract trial lens
 Select first trial lens by mean K
XMJ/(43.75)/-3.00, if fit is loose
try XMJ/(44.25)/ -3.00 to tighten AC
 Over refraction of XMJ/(44.25)/-3.00 = –1.50 D
Power-code = -3.00 + (-1.50) = -4.50
 Order M4 lens by:
XMJ/(44.25)/-4.50/10.4 mm
(Predetermined OAD)
As simple as 1-2-3
 Select K-code
 Determine Power-code
 Verify OAD (Lens size)
Aligned Fit
Good compression
Good Seal off
Good Seal off
Trouble Shooting
Ideal fit
Trouble Shooting
Bull’s Eye Pattern
Trouble Shooting
Alignment Fit
Alignment Fit
Steep Fit
No Compression
Flatten alignment curve
 Up the column
Steep Fit
4 Steps
Steep Fit
Steep fit – 6 Steps
Trouble Shooting
Central Islands
Steep Fit
No Compression
Central Island
Small areas of distortion along or near
the visual axis
Central Island
Cause:
 Alignment curve too tight
 Excessive uncorrected astigmatism resulting in
unequal forces on the cornea
Solution:
 Decrease sagittal depth of lens by flattening
alignment curve
 move up the column
 Decentered lens must be centered
 Flatten the BC if caused by uncorrected
astigmatism
 move one column right.
Alignment Fit
Flat Fit
Too much bearing
Poor Seal off
Sideway force induced
Poor Seal off
Flat Fit Decentred
Good compression
Poor compression
Good Seal off
Poor Seal off
Steepen alignment curve
 Down the column
Trouble Shooting
Flat Fit – 4 Steps
Trouble Shooting
Smiley Face
Flat Fit Decentred
Good compression
Poor seal off
Good Seal off
Poor Seal off
Flat Fit
Smiley Face
Flat fitting lens decentered superiorly
Flat Fit
Smiley Face
Cause:
 Alignment curve too loose
Solution:
 Increase sagittal depth of lens by steepening
alignment curve
 move down the column
Lens Fitting
Loose 0.50 D
Loose 1.0 D
Optimal
Tight 0.50 D
Tight 1.0 D
Verifying tightness
Properly
fitted
Tight
Loose
Loose
2 steps
4 steps
4 steps
Power Changes
Power Changes
 Moving Right = More myopia reduction
Power Changes
 Moving Left = Less myopia reduction
Estimate lens size
 Obtain white to white corneal Diameter by
Topography
 Verify Visible Iris Diameter (VID), horizontal &
vertically manually
 Compare VID to Best-fit VID of the K-code
 If VID too large (larger cornea, smaller lens)
Loose fit, Decentration, Poor effect
 If VID too small (smaller cornea, larger lens)
Tight fit, Lens Bridging, Central island
Standard lens sizes
 Default OAD based on KM
 KM ranges
40.00 ~ 42.25
42.50 ~ 43.75
44.00 ~ 47.50
11.2 mm
10.8 mm
10.4 mm
Big Corneas
Rule of thumb:
 KM =< (flatter) 42.25D
 95% to 97% coverage of VID
 KM between 42.50 – 43.75D
 93% to 95% coverage of VID
 KM => (steeper) 44.00D
 92% to 94% coverage of VID
 93% - 95% coverage of VID would suit most
corneas most of the time.
Big Corneas
 Use existing trial lenses to evaluate alignment
curves
 Determine lens Diameter (OAD)
 93% of VID if KM =>44.00
 94% of VID if KM 42.50-43.75
 96% of VID if KM =<42.25
 It is NOT necessary to alter K-kode (alignment)
when adjusting for OAD
 In high minus lenses (±40% of cases) a flatter
alignment lens will be need later on
Big Corneas
Example:
 V (45.25D) Lens best fit. VID: 12mm
 93% VID coverage = 11.2mm
 94% VID coverage = 11.4mm
 96% VID coverage = 11.6mm
 V lens (KM steeper than 44.00D) = 11.2mm
Big Corneas
Example how to order:
 V Lens best fit. VID: 12mm
 V lens (KM steeper than 44.00D) = 11.2mm
 Eg. 2V04, 11.20mm or XMJ/45.25/-3.00/11.2mm
Lens
Size
86% too small
89% too small
95% Optimal
98% slightly large
105% very large
Case 1 – Big Cornea
Case 1 – Big Cornea
 Male, Age 21
 RIGHT
 KM= 41.72 = H (41.75)
 SE= -1.50D = 01 (-1.50)
 Trial 2H01, 10.4mm or XMJ/41.75/-1.50/10.4mm
 LEFT
 KM= 41.56 = G (41.50)
 SE= -1.50D = 01 (-1.50)
 Trial = 2G01, 10.4mm or XMJ/41.50/-1.50/10.4mm
Case 1 – Big Cornea
Case 1 – Big Cornea (Small lens)
Case 1 – Big Cornea
 HVID = 12.9
 KM > 42.25D
 Rule
 95% HVID
 95% of 12.9 = 12.25mm
 Final lens ordered:
 R: 2H01, 12.2mm
 L: 2G01, 12.2mm
Case 1 – Big Cornea
Thank you
 For more information please e-mail met at:
[email protected]