essentials of orthokeratology
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Essentials of Orthokeratology Disclosures:
Alcon Bausch + Lomb Contamac CooperVision Johnson & Johnson SpecialEyes Valley Contax
Matthew J. Lampa, OD, FAAO [email protected]
Essentials of Orthokeratology
Early Attempts to Reduce Corneal Curvature
Ancient Chinese used sandbags on eyes at night to flatten corneal
curvature.
Evolution of Orthokeratology 1960 to 1990 Keratometry
1990 to Today Corneal Mapping
Contemporary OK / Corneal Reshaping
• Reverse geometry lens designs. • Stable, high Dk lens materials. • Overnight reshaping modality. • Instruments for detailed topographic analysis. • Improved fitting techniques. • Greater understanding as to how OK works.
How Does It Work ??? Epithelial
Redistribution ???
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Control Control
Epithelial Cell Compression
Compression
Normal
Intercellular Fluid Transfer Gap Junctions: Small protein channels that permit cell contents to
move from one cell to another.
Central Epithelium
Mid-peripheral Epithelium
Control Control
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#1 Epithelial Cell Retention?
14 Days Post CRT
• Alterations in cell apoptosis • Decreased cell sloughing • Increased cell mitosis
#2 Peripheral Cell Migration?
Axial Display Tangential Display OK… How It Works • Cellular compression with
intercellular fluid transfer • Increased cell mitosis • Increased cell retention • Localized stromal remodeling ? • Multifactoral
Methods Jennifer Choo et.al. 15 Two-year old cats Randomly fitted with myopic OK and Alignment fitting GP lens
Same diameter: 12.3 mm Same thickness: 0.16 mm
Slit Lamp Examination Corneal Topography
To confirm appropriate corneal changes
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Normal Cat Epithelium
Control
Right Eye Left Eye
Four Week Epithelial Thickness Changes
1 2 3 4 5
Jennifer Choo OD PhD
1
2 3 4
5
LM Post Corneal Reshaping
Left Eye
LM Tangential Display Change in Epithelial Thickness
4 weeks 8.4 microns
Jennifer Choo OD PhD
Pre Post
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Axial Power Display -5.00 D. Change
5.0 mm Treatment
50 microns
Munnerlyn Formula Depth of the Treatment Zone Equals
Optical Zone Diameter ² X Refractive Error 3
Treatment Zone Diameter = 5.0 mm OZ Squared 5.0 x 5.0 = 25 Times the Refractive Error = -5.00 D. 125 Divided by 3 = 42
Tissue Change = 42 microns
5.0 mm Treatment
5.0 mm Pupil
Munnerlyn Formula Depth of the Treatment Zone Equals
Optical Zone Diameter ² X Refractive Error 3
Treatment Zone Diameter = 2.0 mm OZ Squared 2.0 x 2.0 = 4.0 Times the Refractive Error = -5.00 D. 20 Divided by 3 = 7
Tissue Change = 7 microns
Munnerlyn’s Formula -5.00D. Treatment Amount of Zone Tissue Change 1.0 mm 2 microns 2.0 mm 7 microns 3.0 mm 15 microns 4.0 mm 27 microns 5.0 mm 42 microns
6.0 mm 60 microns
Scanning Electron Microscopy Average Human Hair “75 microns thick”
SEM 100 X
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Scanning Electron Microscopy Average Human Hair “75 microns thick”
7 microns
1000 X
Pre-Fit
Post-Fit
Patient BY -11.50 D. Change
The Reversibility of Corneal Reshaping
Recovery of Epithelial Changes
4 Week
Discontinue Lens Wear
1 Day
4 Week
1 Week
1 2 3 4 5 1 2 3 4 5
Lens Designs for Corneal Reshaping • Corneal Refractive Therapy • BE Design • Contex E System • DreimLens • Emerald Design • NightForm • Controlled Kerato-Reformation • R&R Design • NightMove • Vipok • Fargo Design • OrthoFocus • Wave System • Reversible Corneal Therapy
#1 Alignment / Fitting
Curve
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#1 Alignment / Fitting Curve
#2 Base Curve BOZR
#1 Alignment / Fitting Curve
#2 Base Curve
#3 Reverse Curve
Current Fitting Techniques Empirical (K’s & Rx) Fitting Techniques
Topography Fitting Techniques Inventory Fitting Techniques
K’s 42.75 @ 180 / 43.75 @ 90 (7.90 / 7.70 mm)
7.90 mm 7.70 mm
Base Curve Radius BOZR
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BC / BOZD / Jesson Factor -0MR: -3.50 sphere Target Rx: -3.50 D. (-0.75 D.) = 4.25 Flat “K”: 42.75 D. (7.90 mm) BOZR: 4.25 FTK = 38.50 8.75 mm
Alignment Curve
Alignment Curve
BC BOZD 8.75 mm 38.50 D.
Alignment Curve 7.90 mm 42.75 D.
Corneal Topographers • CZM Atlas 9000
• Keratron Scout/Piccalo • Medmont Studio • Oculus EasyGraph/Keratograph • Tomey TMS 1-4
38.50 D.
Alignment Curve 42.75 D 7.90 mm
Base Curve. BOZR 38.50 8.75 mm
Alignment Curve
5 microns
Reverse Curve
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Current Fitting Techniques Laboratory (K’s & Rx) Fitting Techniques
Topography Fitting Techniques Inventory Fitting Techniques
Topography Based OK Systems
Centered Central Smiley Treatment Island Face
Current Fitting Techniques Laboratory (K’s & Rx) Fitting Techniques
Topography Fitting Techniques Inventory Fitting Techniques
Base Curve Return Zone Depth Landing Zone Angle
6.0 mm OZ
Anatomy Of the CRT Lens Pre-Fitting Corneal Topography for CRT…Patient SW
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Patient SW K’s: OD 43.87 / 7.70 @ 163 / 44.25 . 7.63 @ 074
OS 43.87 / 7.70 @ 174 / 44.87 / 7.52 @ 084 Rx: OD -2.25 -0.25 x 180 20/20 6/6
OS -2.50 -0.50 x 170 20/20 6/6
Patient SW Dispensing Visit
Right Eye Left Eye
8.3 .525 33 8.4 .550 33
Overnight Lens Wear Overnight Lens Wear
Optimum Fitting Relationship Opt
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Patient SW – AM Visit Right Eye Left Eye
Inadequate Sagittal Depth – Too Shallow
.550 RZD .525 RZD
BC Return Zone Depth
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Astigmatism Management
x
.75. D (0.15 mm) of Corneal Astigmatism
Incomplete Astigmatism Limbus-to-Limbus Incomplete/Central Limbus-to-Limbus
1.50 D. Corneal Cylinder 1.50 D.Corneal Astig 1.87 D Corneal Astig.