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The Orthokeratolgy Company. GOV & VIPOK Updates. The Ideal Patient. 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

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the orthokeratolgy company

The Orthokeratolgy Company

GOV & VIPOK Updates

the ideal ortho k patient
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
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
Topographer

Calibrate Topographer!

topographer1
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
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 systems
Empirical Fitting Systems
  • Corneal information is given to lab
  • Lab designs lens
  • Lens works
  • Or it doesn’t!
systemised fitting systems
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 systems1
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 systems2
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 lens1
Fitting the Ortho-K Lens

Flourescein patterns:

the orthokeratology company
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 – HyperopiaPresbyopia
    • MP – MiopicPresbyopia
    • Post Lasik & Keratoconus
    • Website (Plan Date Jan 2008)
      • Ordering
      • Blog
      • Px & Prac Education
the gov system
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
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
GOVTMlens 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
Predetermined OAD (lens size)
  • OADs of trial lenses are predetermined
  • Flatter Ks accompany larger corneas
  • Steeper Ks accompany smaller corneas
fitting gov tm lenses
Fitting GOVTM 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
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)
slide22

Mean K/ S.E -1.50 -2.00 -2.50 -3.00 -3.50 -4.00 -4.50 -5.00

OAD 11.2 mm 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

Trial set

prescribe empirically
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
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
Prescribe by over refract trial lens
  • Select first trial lens by mean K

XMJ/(43.75)/-3.00, if fit is loose

tryXMJ/(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
As simple as 1-2-3
  • Select K-code
  • Determine Power-code
  • Verify OAD (Lens size)
aligned fit
Aligned Fit

Good compression

Good Seal off

Good Seal off

trouble shooting1
Trouble Shooting

Bull’s Eye Pattern

trouble shooting2
Trouble Shooting

Alignment Fit

steep fit
Steep Fit

No Compression

steep fit1
Steep Fit

4 Steps

steep fit2
Steep Fit

Steep fit – 6 Steps

trouble shooting3
Trouble Shooting

Central Islands

steep fit3
Steep Fit

No Compression

central island
Central Island

Small areas of distortion along or near the visual axis

central island1
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.
flat fit
Flat Fit

Too much bearing

Sideway force induced

Poor Seal off

Poor Seal off

flat fit decentred
Flat Fit Decentred

Good compression

Poor compression

Good Seal off

Poor Seal off

trouble shooting4
Trouble Shooting

Flat Fit – 4 Steps

trouble shooting5
Trouble Shooting

Smiley Face

flat fit decentred1
Flat Fit Decentred

Good compression

Poor seal off

Good Seal off

Poor Seal off

flat fit1
Flat Fit

Smiley Face

Flat fitting lens decentered superiorly

flat fit2
Flat Fit

Smiley Face

Cause:

  • Alignment curve too loose

Solution:

  • Increase sagittal depth of lens by steepening alignment curve
    • move down the column
slide52

Lens Fitting

Loose 0.50 D

Loose 1.0 D

Optimal

Tight 1.0 D

Tight 0.50 D

verifying tightness
Verifying tightness

Tight

4 steps

Properly fitted

Loose

2 steps

Loose

4 steps

power changes2
Power Changes
  • Moving Right = More myopia reduction
power changes3
Power Changes
  • Moving Left = Less myopia reduction
estimate lens size
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
Standard lens sizes
  • Default OAD based on KM
  • KM ranges

40.00 ~ 42.25 11.2 mm

42.50 ~ 43.75 10.8 mm

44.00 ~ 47.50 10.4 mm

big corneas
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 corneas1
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 corneas2
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 corneas3
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
slide65

Lens Size

86% too small

89% too small

95% Optimal

98% slightly large

105% very large

case 1 big cornea1
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 cornea3
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
thank you
Thank you
  • For more information please e-mail met at:

charl@eyevision.co.za