Fitting RGP and Orthokeratology lenses - Day 3

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Slide 5

Lens materials vary in permeability. High Dk used for post operative corneas and extended wear. Important to note is not to suddenly change a patient from PMMA to high Gas perm material. Sensitivity to materials may arise but is very rare.

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The following is a schematic diagram of the various lens parameters. Almost all of these can be altered except the Base Curve. If a flatter or steeper Base curve is requiresd for optimum fit, a new lens has to be made. Very little to do to tighten a lens. Lenses can be made loose very easily through modification.

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The following is a schematic diagram of the various lens parameters. Almost all of these can be altered except the Base Curve. If a flatter or steeper Base curve is requiresd for optimum fit, a new lens has to be made. Very little to do to tighten a lens. Lenses can be made loose very easily through modification.

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While all practitioners will be different, we would expect that “base curve”, “diameter” and “power” would be the bare minimum--unless a number of practitioners are already simply calling in “K’s” and Rx. There may be some who determine “lens material” and a small number who recommend “replacement cycle”. It would not be expected that any of the other parameters would be absolutely necessary in the determination of an RGP lens.

Slide 143

This may seem like a no-brainer, but this concept is very important for rigid lens fitters to understand. Everyone has fallen victim to assuming that a patient with a moderate amount of refractive astigmatism is a perfect candidate for spherical rigid lenses without determining where the astigmatism is located. This will be very important for those new rigid lens fitters so that they don’t become discouraged when they begin to fit their patients. At the bottom of page #13, there is a worksheet for the attendees. This worksheet is designed to point out the discrepancy between the amount of refractive and the corneal astigmatism. While we know that the true amount may be different when an over-refraction is performed, the important message is for the attendees to be able to recognize the disparities. WORKBOOK #13

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However, when there is a great deal of difference between the flattest and the steepest keratometer reading, fitting a spherical lens will result in areas that have too much bearing and too much lift. The key is here is the presence of bearing and lift in the same patient. If there was simply too much lift in all meridians, the lens would be made steeper. Conversely, if there was too much bearing in all meridians, the lens would be made flatter. Point out that there is too much bearing and too much lift on this graphic of a spherical lens on an astigmatic cornea. While this will accomplish our two fundamentals (movement up and down and not side to side), it won’t do so without compromising the patient’s cornea and comfort. Point out that areas of excessive lift will irritate the lower lid and may cause discomfort, lens awareness, and glare. Point out the area of excessive bearing that will occur on the horizontal meridian. Over a period of time this may become desiccated and stained. While many patients may learn to adapt to this type of lens fit over a period of time, they don’t have to! WORKBOOK #5

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Let’s look at an example. The above graphic illustrates a 42.00 D spherical lens on a cornea with the meridians 42.00 @ 180 / 45.00 @ 90. The lens with a base curve of 42.00 D shows good alignment in the horizontal meridian, but there is excessive lift in the vertical meridian. This illustrates what may happen when a spherical lens is placed on an eye with 3.00 D of corneal astigmatism. WORKBOOK #6

Slide 146

These are simply guidelines and are in no way meant to be rules for the fitting of bitoric lenses. However, if the attendees remember the criteria that need to be fulfilled in an RGP fit, they can choose the lens parameters that will best suit each patient’s cornea. Underscore that a fit is not final until the lens has been placed on the eye, evaluated with fluorescein and checked for movement and positioning. While we may start with a lens with a horizontal meridian on flat “K”, it may ultimately be that the best base curve choice is steeper than “K” or flatter than “K”. The purpose to teaching this method of fluorescein interpretation and the fundamentals of RGP fitting is so that the attendees have the tools to fit each and every patient that presents in their practices, rather than only those whose corneas will follow a cookbook method or a single example. “Give a man a fish, they eat for a day. Teach a man to fish, they eat for a lifetime.” WORKBOOK #7

Slide 147

These are simply guidelines and are in no way meant to be rules for the fitting of bitoric lenses. However, if the attendees remember the criteria that need to be fulfilled in an RGP fit, they can choose the lens parameters that will best suit each patient’s cornea. Underscore that a fit is not final until the lens has been placed on the eye, evaluated with fluorescein and checked for movement and positioning. While we may start with a lens with a horizontal meridian on flat “K”, it may ultimately be that the best base curve choice is steeper than “K” or flatter than “K”. The purpose to teaching this method of fluorescein interpretation and the fundamentals of RGP fitting is so that the attendees have the tools to fit each and every patient that presents in their practices, rather than only those whose corneas will follow a cookbook method or a single example. “Give a man a fish, they eat for a day. Teach a man to fish, they eat for a lifetime.” WORKBOOK #7

Slide 148

There are a range of parameters that can be chosen for this vertical meridian. We do not need to have the attendees focus on the choice of a specific number. Instead, we want to be able to teach them the strategy for choosing this lens parameter. If the attendee can be comfortable with what the end result must be, they can be empowered to fit any lens on any cornea, rather than follow a recipe. However, even with our best intentions, there may be a number of attendees who would prefer to start fitting RGP torics by having a “formula” to begin with. If you have a specific formula that you use, please feel free to pass that along to the group, underscoring that there are a number of parameters choices that will meet success for each patient. The message is one of simplicity! This is also a good time to mention the wonderful support that their local lab can offer in the choice of parameters for these types of lenses. WORKBOOK #7

Slide 149

There are a range of parameters that can be chosen for this vertical meridian. We do not need to have the attendees focus on the choice of a specific number. Instead, we want to be able to teach them the strategy for choosing this lens parameter. If the attendee can be comfortable with what the end result must be, they can be empowered to fit any lens on any cornea, rather than follow a recipe. However, even with our best intentions, there may be a number of attendees who would prefer to start fitting RGP torics by having a “formula” to begin with. If you have a specific formula that you use, please feel free to pass that along to the group, underscoring that there are a number of parameters choices that will meet success for each patient. The message is one of simplicity! This is also a good time to mention the wonderful support that their local lab can offer in the choice of parameters for these types of lenses. WORKBOOK #7

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Fitting RGP and Orthokeratology lenses Chris Eksteen Charl Laäs

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Thought of the Day “When you make a mistake, there are only three things you should ever do about it: admit it, learn from it, and do not repeat it.” ~ Paul “Bear” Bryant

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Day 3 Fitting principles of RGP lenses Lens Designs Sagittal heights Axial edge lifts (AEL) Oz changes Edge changes Fitting Basic RGP designs Spherical corneas Astigmatic Corneas Spherical designs Toric Periphery designs Back Toric designs Practical

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RGP Lens Designs

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Lens materials Polymethylmethacrylate ( PMMA) / 912 Low GP - 10-30 Dk Medium GP - 30-59 Dk High GP - 60-100 Dk Super GP - 100+ Dk Careful changing from PMMA to RGP lenses

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Lens Descriptions

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Lens Descriptions

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Central Zone

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Lens Periphery

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Lens Periphery

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Aspheric Periphery

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Aspheric Lens

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Front Surface

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RGP Lens Design Diameter Base curve Power Lens material Intermediate curve Center thickness Edge design Axial edge lift Optic zone diameter Peripheral curve

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Lens Designs C2 / Bi - Curve Two (2) curves on the posterior (back) surface Parameter: BC: 4.50 - 16.00mm Oz: Any Diam: 7.50 - 12.00mm

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Lens Designs C3 / Tri - Curve Three (3) curves on the posterior surface Parameter: BC: 4.50 - 16.00mm Oz: Any Diam: 7.50 - 12.00mm

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Lens Designs Tricon Parameter: BC: 7.00 - 10.00mm Oz: 7.00mm Peripheral Curves: Steep Normal Flat Diam: 9.20mm

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Lens Designs Mina Used for near spherical corneas Fitted on flattest K Parameter: BC: 7.00 - 10.00mm Oz: 7.60mm Diam: 8.60mm

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Lens Designs C4 / Four Curve Four (4) curves on the posterior surface Parameter: BC: 4.50 - 16.00mm Oz: Any Diam: 7.50 - 12.00mm

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Lens Designs Tetracon Used for low astigmatic corneas Parameter: BC: 7.00 - 10.00mm Oz: 7.00 or 7.50mm Diam: 8.40 or 9.70mm

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Lens Designs Keratocon Used for Keratoconic corneas Parameter: BC: 4.50 - 8.00mm Oz: 7.00mm Diam: 9.20mm

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Lens Designs C4 LDL Used for post refractive conditions Parameter: BC: 7.00 - 10.00mm Oz: 8.80 or 9.00mm Peripheral Curves: Steep Normal Flat Diam: 10.50 or 11.00mm

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Lens Designs Multi - Curve Multiple (>4) curves on the posterior surface Parameter: BC: 7.00 - 10.00mm Oz: 7.30 or 8.00mm Diam: 9.30 or 9.80mm

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Lens Designs TP / Asticon Normal spherical base curve with toroidal peripheral flange Delta K >2.50D & < 3.50D Parameter: BC: 7.00 - 10.00mm Oz: 6.80/7.80 or 7.00/8.00mm Diam: 9.20 or 9.40mm

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Lens Designs Back Toric Complete back toroidal surface Delta K > 3.50D Parameter: BC: Any Oz: 7.00 or 7.50mm Diam: 9.20 or 9.50mm

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Lens Designs Front Surface Toric Lenticular or residual astigmatism Prism ballast lens: 1.00 - 2.50 prism Spherical base curve Parameter: BC: 7.00 - 10.00mm Oz: 7.00 or 7.50mm Diam: 9.00 or 9.50mm

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Lens Designs Bi - Toric Corneal astigmatism with residual or lenticular astigmatism Lens has a toric back surface with a toroidal front surface Parameter: BC: Any Oz: 7.00 or 7.50mm Diam: 9.20 or 9.50mm

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Lens Designs Translating / Fused Segment Bifocal 1 - Distance Zone 2 - Reading Zone And

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Lens Designs Translating / Fused Segment Bifocal Prism ballast: 1.00 - 2.50 prism D Add: 1.50 - 3.00D Lens truncated to position height of segment Diameter: vary in size

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Lens Designs Concentric Multi-vision Lens Hybrid concentric, spheric multi-vision lens Parameter: BC: Any Oz: Any Diam: Any

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Lens Designs Reverse Geometry Lens Used for Orthokeratology Post refractive fits Parameter: Oz: 4.5 – 6.5mm Diam: 9.00 – 11.00mm

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SAG Philosophy

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Corneal Shape Corneal shape is best described as a prolate (flattening) ellipse Gradual flattening from center to periphery Corneal shape is clinically quantified using: Keratometry readings (Paracentral, at 300) Apical radius of curvature (R0) Axial and tangential radii (Ri) Corneal shapes indices (e, p and Q)

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Corneal Shape Indices Eccentricity value (e) Shape factor (p) Asphericity (Q) These are inter-related mathematically: p=1-e2 p=1+Q Q=-e2

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Sagittal Height (Sag) Chord Sag(z)

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Tear Layer

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Tear Layer Thickness (TLT) Defined as the difference in sag of cornea and sag of contact lens at the apex of the cornea over the common chord

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Tear Layer… Ideal TLT for contour-design lenses is approximately 15-25 microns Necessary for: Promoting effective tear exchange Positive and negative fluid forces to control lens movement and centration Preventing posterior lens surface damaging corneal epithelium

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…Tear Layer Sodium Fluorescein (NaFl) is used clinically to evaluate the Tear Layer Minimum TLT to render fluorescein visible is approx 15-20 Microns Important in evaluating lenses with TLT’s of <20 Microns, eg Keratoconus and Orthokeratology

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Lens Construction Formulae Lens Sag = Corneal Sag + TLT (Microns) over the chord of common contact between the two surfaces

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Lens Construction Formulae Corneal Sag = Ro = Apical radius y = Half chord p = Shape factor

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Lens Construction Formulae Calculation for multi-curve lenses is more complex Sag of all component curves added to sag of BOZR over the chord of the BOZD E.g Tricurve = p = Xo+X1+X2 Xo=Primary sag of BOZR at the BOZD X1= Sag of BPR1 at the BPD1 – sag of BPR1 at the BOZD X2 = Sag of BPR2 at the TD – Sag BPR2 at the BPD1

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Lens Construction Formulae

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Lens Construction Formulae p X0 X2 X1

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Lens Construction Formulae Sag = R1 = BOZR, D1=BOZD, R2=BPR1, D2=BPD2, R3=BPR3 and D3=BPD3

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Lens Construction Formulae A useful extension to this form of mathematical construction is to calculate the sags of the lens and cornea over small (0.10mm) chord increments and subtract the corneal sag from the lens sag The values are then represented on the Y-axis of a graph The X-axis represents the half chord lengths from the center of the cornea to the edge of the lens

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Lens Construction Formulae The graph represents the tear layer profile of the lens

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Lens Construction Software Tear layer profile in relationship to physical fit and fluorescein pattern

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SAM / FAP Rule

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Steep Add Minus (SAM) Steep fit creates positive tear layer

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Steep Add Minus (SAM) To compensate for positive tear layer a minus power is added to RGP lens For every 0.05mm BC radius change steeper, add –0.25D power to RGP lens to keep the same refractive power

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Flat Add Plus (FAP) Flat fit creates negative tear layer

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Flat Add Plus (FAP) To compensate for negative tear layer a positive power is added to RGP lens For every 0.05mm BC radius change flatter, add +0.25D power to RGP lens to keep the same refractive power

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BOZR Changes

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Back Optic Zone Radius (BOZD) Small OZ Large OZ

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BOZD - 7.80mm C3 7.82_7.80/8.45_8.90/10.25_9.50 - Diam

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BODR - 7.00mm (Smaller) C3 7.82_7.00/8.45_8.90/10.25_9.50 - Diam

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BOZD – 8.50mm (Bigger) C3 7.82_8.50/8.45_8.90/10.25_9.50 - Diam

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Back Optic Zone Radius (BOZR) To keep the same cornea-to-lens relationship in spherical lenses: Increase BOZD by 0.50mm for every 0.05mm flatter BOZR Decrease BOZD by 0.50mm for every 0.05mm steeper BOZR

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Back Optic Zone Radius (BOZR) C3 7.75_7.60/8.85_8.60/9.97_9.20 - Diam

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Back Optic Zone Radius (BOZR) C3 7.80_7.60/8.85_8.60/9.97_9.20 - Diam BOZR flatter by 0.05mm

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Back Optic Zone Radius (BOZR) C3 7.80_8.10/8.85_9.10/9.97_9.70 - Diam BOZR flatter by 0.05mm and BOZD increased by 0.50mm

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Edges

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Concept of Edge Lift Relates to the lens design off the eye Describes the edge shape formed by the series of peripheral curves Specified in an axial and radial direction

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Axial Edge Lift (AEL) Distance between a point on the back surface of a lens at a specific diameter and the extension of the back central optic zone measured parallel to the lens axis

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Axial Edge Lift (AEL) Vertical distance from lens edge to an extension of the BCR

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Radial Edge Lift (REL) Distance between a point on the back surface of a lens at a specific diameter and the extension of the back central optic zone measured along the radius of the latter

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Radial Edge Lift (REL) Distance from lens edge perpendicular to an extension of the BCR

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Concept of Edge Lift Current edge designs are usually defined in respect of AEL The usual value of AEL varies between 0.09mm and 0.15mm Given the same increase in peripheral curves the steeper lens will have a greater AEL

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Concept of Edge Lift Steep BOZR Flat BOZR BC + 1.00 BC + 3.00

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Concept of Edge Lift Steep BOZR Flat BOZR BC + 1.00 BC + 3.00

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Concept of Edge Lift Steep BOZR Flat BOZR

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Constant Axial Edge Lift (CAEL) CAEL lenses are multi-curves designed to give the same AEL over the whole range of BOZ Radii for a given TD Average CAEL for TD of 8.60 = 0.105mm Average CAEL for TD of 9.20 = 0.11mm Average CAEL for TD of 9.60 = 0.14mm

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Constant Axial Edge Lift (CAEL)

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Concept of Edge Clearance Relates to the lens on the eye Estimated by the fluorescein pattern Ideal peripheral clearance is 60-80 microns Equivalent to AEL of 0.12 to 0.15mm

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Aligned Periphery

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Loose Periphery

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Tight Periphery

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Eccentricity and TLT

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Eccentricity and TLT e=0.30 e=0.45 e=0.60

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Eccentricity and TLT e=.45 e=0.30 e=0.60

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Eccentricity and TLT e=0.30 e=0.45 e=0.60

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Edge Shape

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Edge Shape Important for comfort Must be smooth and well finished Should blend into the final curve Helps with lens removal

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Who to fit with RGP lenses

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Ideal Candidates Patient Lifestyle & Personal Choice Issues Excellent vision Full time lens wear (Daily/Extended) Healthy lens option Easy care and handling Durable lens option

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Ideal Candidates Patient Lifestyle & Personal Choice Issues Easy insertion and removal

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Ideal Candidates Patient Anatomy and Refractive Issues Corneal astigmatism Refractive astigmatism

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Ideal Candidates Patient Anatomy and Refractive Issues Myopia, Hyperopia, Presbyopia Irregular astigmatism

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Challenging Candidates Patient Lifestyle & Personal Choice Issues Patients that require immediate comfort Part time lens wearers Men

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Challenging Candidates Patient Anatomy and Refractive Issues Patients with significant amounts of against-the-rule corneal astigmatism Keratoconus

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Challenging Candidates Patient Anatomy and Refractive Issues Post trauma patients Penetrating Keratoplasty

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Challenging Candidates Patient Anatomy and Refractive Issues Post refractive procedures Orthokeratology But even these patients can be successful if they are motivated

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Fitting Spherical Corneas

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The Basic Fit Alignment / on K 20 micron apical clearance Bright edge Good movement

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The Basic Fit Steep fit Excessive central pooling Peripheral sealing Excessive movement

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The Basic Fit Flat fit Central touch Excessive edge lift Excessive movement

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Lens Designs Bi-curves Two (2) curves on posterior (back) surface Parameter: BC: 4.50mm to 16.00mm Oz: Any Diam: 7.50mm to 12.00mm

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Lens Designs Tri-curve Three (3) curves on posterior surface Parameter: BC: 4.50mm to 16.00mm Oz: Any Diam: 7.50mm to 12.00mm

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Lens Designs Tricon Parameter: BC: 7.00mm to 10.00mm Oz: 7.00mm Peripheral Curves: Steep Normal Flat Diam: 9.20mm

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Lens Designs Mina Used for near spherical corneas Fitted on flattest K Parameter: BC: 7.00mm to 10.00mm Oz: 7.60mm Diam: 8.60mm

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Lens Designs Four Curve Four (4) curves on posterior surface Parameter: BC: 4.50mm to 16.00mm Oz: Any Diam: 7.50mm to 12.00mm

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RGP Lens Selection

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Back Optic Zone Radius (BOZR) Preferred fitting on alignment or slightly flatter Choose diagnostic lenses with BOZR nearest to flattest K BOZR considered in relation to BOZD Consider additional factors such as lid tension, BVP and centre of gravity

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Total Diameter (TD) Approx 2mm < HVID TD depends on pupil size – low illumination Choice Small (<9.20mm) Medium (9.20 – 9.70mm) Large (>9.80mm) Larger diameter stabilizes fit

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Back Optic Zone Diameter (BOZD) Often predetermined by Lab 1.50mm > max pupil size Size Small (<7.30mm) Medium (7.30-7.90mm) Large (>7.90mm)

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Fitting Astigmatic Corneas

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Understanding Astigmatism

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Astigmatism Regular With the rule Against the rule Lenticular Irregular

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Astigmatism With the Rule

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Astigmatism Against the Rule

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Astigmatism Oblique

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Astigmatism Regular

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Astigmatism Irregular

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Astigmatic RGP Lenses

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Don’t Judge to Quickly

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Regular Astigmatism Lenses to use Small spherical lenses Aspheric lenses Front surface toric Toric periphery Back surface toric Bitoric

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Spherical Lenses Fit central cornea Very narrow axial edge lift Fit on alignment or slightly steeper Centration very important

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Lens Designs Tetracon Used for low astigmatic corneas Parameter: BC: 7.00 - 10.00mm Oz: 7.00 or 7.50mm Diam: 8.40 or 9.70mm

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Lens Designs Multi Flo2 Used for low astigmatic corneas Parameter: BC: 7.00 - 10.00mm Oz: 7.00 or 7.50mm Diam: 8.40 or 9.70mm

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Aspheric Lenses Most aspheric lenses have a narrow edge lift Fit on alignment or flatter to avoid flexure Can mask up to 4.00D astigmatism

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Lens Designs Multi-curve Multiple curves on posterior surface Parameter: BC: 7.00mm to 10.00mm Oz: 7.30mm or 8.00mm Diam: 9.30mm or 9.80mm

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Lens Designs Aspheric-curves

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Lens Designs Aspheric Fit Too Flat Ideal Fit Too Steep

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Astigmatism Toric Periphery Spherical BOZR Toric back peripheral radii – stability Good for cornea where peripheral toricity > central toricity Front surface usually spherical

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Lens Designs Asticon / TP Normal spherical base curve with toroidal peripheral flange Parameter: BC: 7.00mm to 10.00mm Oz: 6.80-7.80mm or 7.00-8.00mm Diam: 9.20mm or 9.40mm

Slide 127

TP Fluorescein Pattern

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Lens Designs Asticon / TP Rule of thumb Subtract K’s Divide by 2 and add 0.10 Add this total to the steepest K = Base curve of Asticon

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Lens Designs Asticon Eg. K’s 7.80/7.40 7.80 – 7.40 = 0.40 / 2 = 0.20 0.20 + 0.10 = 0.30 0.30 + 7.40 = 7.70 Lens base curve = 7.70

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Astigmatism Front surface toric Spherical back surface with a front surface cylinder to correct residual astigmatism lens needs to be stable to maintain the correct axis

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Lens Designs Front Surface Toric Used for lenticular or residual astigmatism Prism ballast lens: 1.00 to 2.50 prism D Spherical base curve Parameter: BC: 7.00mm to 10.00mm Oz: 7.00mm or 7.50mm Diam: 9.00mm or 9.50mm

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Astigmatism Back Surface Toric Both central and peripheral radii are toric Lens radii follow principal meridians of the cornea Fluorescein appearance identical to spherical lens on spherical eye

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Astigmatism Back Surface Toric Rule of thumb: Fit the one meridian on K or very slightly steeper than K The second meridian is fitted flatter than the steepest K (from 0.10 – 0.30 flatter)

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Astigmatism Back Surface Toric Eg: K’s - 7.80/7.00 Lens of choice 7.80 for the flattest meridian 7.30 for the steeper meridian Lens parameters are therefore 7.80/7.30 Diameter ? Power ?

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Lens Designs Back Toric Complete back-toroidal surface Parameter: BC: Any Oz: 7.00mm or 7.50mm Diam: 9.20mm or 9.50mm

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Astigmatism Bitoric Both central and peripheral back surface radii are toric Combined with front surface cylinder to correct induced astigmatism Stabilization in needed for correct axis orientation

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Lens Designs Bi-toric Used for corneal astigmatism with residual or lenticular astigmatism Lens has a toric back surface with a toroidal front surface Parameter: BC: Any Oz: 7.00mm or 7.50mm Diam: 9.20mm or 9.50mm

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Astigmatism Stabilisation Prism ballast Prism 1.5 to 3.0 Weight difference top to bottom Lens orientates correctly Truncation Chord of 0.50 – 1.00mm cut from lens Lens rests on lower lid

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Astigmatism Fitting Categories

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Astigmatism Fitting Categories

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Asticmatic Cornea Spherical lens Spherical Rigid Contact Lenses can only Impact the Astigmatism Found on the Surface of the Cornea

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Spheric on Toric shape

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Astigmatism

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Astigmatism When there are significant areas of bearing and lift, a special RGP lens can be created

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45.00 42.00 Astigmatism

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Double the Curves… Double the Fun Because a lens should not move from side to side… ...the horizontal meridian should be fit on horizontal “K” or slightly steeper than horizontal “K”

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Double the Curves… Double the Fun

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Double the Curves… Double the Fun Because a lens should freely move up and down… …the vertical meridian should be fitted slightly flatter than vertical “K”

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Double the Curves… Double the Fun

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Astigmatism With the rule 13 year old male Px was told he could not wear contact lenses due to “rugby ball shaped eyes” Rx: - 4.50 / -2.75 X 180 K - readings: 7.82 / 7.24mm

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Astigmatism With the rule

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Astigmatism With the rule RGP Parameters: Asticon - Dk 60 BC: 7.70mm Diam: 9.20mm OZ: 6 x 7mm Power: - 4.75D VA: 6/6 (1.00)

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Astigmatism With the rule

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Astigmatism With the rule 45 year old female Advanced Keratoconus Corneal Graft - Jan 2002 Current Rx: +3.50/-10.50 x 05 K - readings: 8.56 / 6.75mm

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Astigmatism With the rule

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Astigmatism With the rule RGP Parameters: Back Toric - Dk 90 BC: 8.55 / 7.20mm Dia: 9.50mm OZ: 7.5mm Power: +3.00D VA: 6/6 (1.00)

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Astigmatism With the rule

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Astigmatism Against the rule 46 year old male Intolerance to soft contact lenses due to allergies Rx: -2.75 / -2.75 X 80 K - readings: 7.92 / 7.44mm

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Astigmatism Against the rule

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Astigmatism Against the rule RGP Parameters: Multi Aspheric - Dk 60 BC: 7.85mm Dia: 10.5mm OZ: 9.0mm Power: –2.75D VA: 6/5 (1.25)

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Irregular Astigmatism

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Common Refractive Procedures Radial Keratotomy PRK LASIK/LASEK Intacts Orthokeratology

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Astigmatism Irregular Corneal graft Trauma Post refractive surgery Keratoconus (full section)

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Astigmatism Irregular

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Post Refractive Surgery “Good surgeons avoid complications. Great surgeons turn their complications into teaching experiences” Miller N. Am Journal of Ophthalmology 2000;129(6):829

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Thank You www.OrthokInstitute.com

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