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 lampa@pacificu.edu

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.