
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.
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.
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.
While all practitioners will be different, we would expect that “base curve”, “diameter” and “power” would be the bare minimumunless 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.
This may seem like a nobrainer, 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 overrefraction is performed, the important message is for the attendees to be able to recognize the disparities. WORKBOOK #13
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
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
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
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
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
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
Fitting RGP and Orthokeratology lenses Chris Eksteen Charl Laäs
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
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
RGP Lens Designs
Lens materials Polymethylmethacrylate ( PMMA) / 912 Low GP  1030 Dk Medium GP  3059 Dk High GP  60100 Dk Super GP  100+ Dk Careful changing from PMMA to RGP lenses
Lens Descriptions
Lens Descriptions
Central Zone
Lens Periphery
Lens Periphery
Aspheric Periphery
Aspheric Lens
Front Surface
RGP Lens Design Diameter Base curve Power Lens material Intermediate curve Center thickness Edge design Axial edge lift Optic zone diameter Peripheral curve
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
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
Lens Designs Tricon Parameter: BC: 7.00  10.00mm Oz: 7.00mm Peripheral Curves: Steep Normal Flat Diam: 9.20mm
Lens Designs Mina Used for near spherical corneas Fitted on flattest K Parameter: BC: 7.00  10.00mm Oz: 7.60mm Diam: 8.60mm
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
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
Lens Designs Keratocon Used for Keratoconic corneas Parameter: BC: 4.50  8.00mm Oz: 7.00mm Diam: 9.20mm
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
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
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
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
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
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
Lens Designs Translating / Fused Segment Bifocal 1  Distance Zone 2  Reading Zone And
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
Lens Designs Concentric Multivision Lens Hybrid concentric, spheric multivision lens Parameter: BC: Any Oz: Any Diam: Any
Lens Designs Reverse Geometry Lens Used for Orthokeratology Post refractive fits Parameter: Oz: 4.5 – 6.5mm Diam: 9.00 – 11.00mm
SAG Philosophy
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)
Corneal Shape Indices Eccentricity value (e) Shape factor (p) Asphericity (Q) These are interrelated mathematically: p=1e2 p=1+Q Q=e2
Sagittal Height (Sag) Chord Sag(z)
Tear Layer
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
Tear Layer… Ideal TLT for contourdesign lenses is approximately 1525 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
…Tear Layer Sodium Fluorescein (NaFl) is used clinically to evaluate the Tear Layer Minimum TLT to render fluorescein visible is approx 1520 Microns Important in evaluating lenses with TLT’s of <20 Microns, eg Keratoconus and Orthokeratology
Lens Construction Formulae Lens Sag = Corneal Sag + TLT (Microns) over the chord of common contact between the two surfaces
Lens Construction Formulae Corneal Sag = Ro = Apical radius y = Half chord p = Shape factor
Lens Construction Formulae Calculation for multicurve 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
Lens Construction Formulae
Lens Construction Formulae p X0 X2 X1
Lens Construction Formulae Sag = R1 = BOZR, D1=BOZD, R2=BPR1, D2=BPD2, R3=BPR3 and D3=BPD3
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 Yaxis of a graph The Xaxis represents the half chord lengths from the center of the cornea to the edge of the lens
Lens Construction Formulae The graph represents the tear layer profile of the lens
Lens Construction Software Tear layer profile in relationship to physical fit and fluorescein pattern
SAM / FAP Rule
Steep Add Minus (SAM) Steep fit creates positive tear layer
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
Flat Add Plus (FAP) Flat fit creates negative tear layer
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
BOZR Changes
Back Optic Zone Radius (BOZD) Small OZ Large OZ
BOZD  7.80mm C3 7.82_7.80/8.45_8.90/10.25_9.50  Diam
BODR  7.00mm (Smaller) C3 7.82_7.00/8.45_8.90/10.25_9.50  Diam
BOZD – 8.50mm (Bigger) C3 7.82_8.50/8.45_8.90/10.25_9.50  Diam
Back Optic Zone Radius (BOZR) To keep the same corneatolens 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
Back Optic Zone Radius (BOZR) C3 7.75_7.60/8.85_8.60/9.97_9.20  Diam
Back Optic Zone Radius (BOZR) C3 7.80_7.60/8.85_8.60/9.97_9.20  Diam BOZR flatter by 0.05mm
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
Edges
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
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
Axial Edge Lift (AEL) Vertical distance from lens edge to an extension of the BCR
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
Radial Edge Lift (REL) Distance from lens edge perpendicular to an extension of the BCR
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
Concept of Edge Lift Steep BOZR Flat BOZR BC + 1.00 BC + 3.00
Concept of Edge Lift Steep BOZR Flat BOZR BC + 1.00 BC + 3.00
Concept of Edge Lift Steep BOZR Flat BOZR
Constant Axial Edge Lift (CAEL) CAEL lenses are multicurves 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
Constant Axial Edge Lift (CAEL)
Concept of Edge Clearance Relates to the lens on the eye Estimated by the fluorescein pattern Ideal peripheral clearance is 6080 microns Equivalent to AEL of 0.12 to 0.15mm
Aligned Periphery
Loose Periphery
Tight Periphery
Eccentricity and TLT
Eccentricity and TLT e=0.30 e=0.45 e=0.60
Eccentricity and TLT e=.45 e=0.30 e=0.60
Eccentricity and TLT e=0.30 e=0.45 e=0.60
Edge Shape
Edge Shape Important for comfort Must be smooth and well finished Should blend into the final curve Helps with lens removal
Who to fit with RGP lenses
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
Ideal Candidates Patient Lifestyle & Personal Choice Issues Easy insertion and removal
Ideal Candidates Patient Anatomy and Refractive Issues Corneal astigmatism Refractive astigmatism
Ideal Candidates Patient Anatomy and Refractive Issues Myopia, Hyperopia, Presbyopia Irregular astigmatism
Challenging Candidates Patient Lifestyle & Personal Choice Issues Patients that require immediate comfort Part time lens wearers Men
Challenging Candidates Patient Anatomy and Refractive Issues Patients with significant amounts of againsttherule corneal astigmatism Keratoconus
Challenging Candidates Patient Anatomy and Refractive Issues Post trauma patients Penetrating Keratoplasty
Challenging Candidates Patient Anatomy and Refractive Issues Post refractive procedures Orthokeratology But even these patients can be successful if they are motivated
Fitting Spherical Corneas
The Basic Fit Alignment / on K 20 micron apical clearance Bright edge Good movement
The Basic Fit Steep fit Excessive central pooling Peripheral sealing Excessive movement
The Basic Fit Flat fit Central touch Excessive edge lift Excessive movement
Lens Designs Bicurves Two (2) curves on posterior (back) surface Parameter: BC: 4.50mm to 16.00mm Oz: Any Diam: 7.50mm to 12.00mm
Lens Designs Tricurve Three (3) curves on posterior surface Parameter: BC: 4.50mm to 16.00mm Oz: Any Diam: 7.50mm to 12.00mm
Lens Designs Tricon Parameter: BC: 7.00mm to 10.00mm Oz: 7.00mm Peripheral Curves: Steep Normal Flat Diam: 9.20mm
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
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
RGP Lens Selection
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
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
Back Optic Zone Diameter (BOZD) Often predetermined by Lab 1.50mm > max pupil size Size Small (<7.30mm) Medium (7.307.90mm) Large (>7.90mm)
Fitting Astigmatic Corneas
Understanding Astigmatism
Astigmatism Regular With the rule Against the rule Lenticular Irregular
Astigmatism With the Rule
Astigmatism Against the Rule
Astigmatism Oblique
Astigmatism Regular
Astigmatism Irregular
Astigmatic RGP Lenses
Don’t Judge to Quickly
Regular Astigmatism Lenses to use Small spherical lenses Aspheric lenses Front surface toric Toric periphery Back surface toric Bitoric
Spherical Lenses Fit central cornea Very narrow axial edge lift Fit on alignment or slightly steeper Centration very important
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
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
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
Lens Designs Multicurve Multiple curves on posterior surface Parameter: BC: 7.00mm to 10.00mm Oz: 7.30mm or 8.00mm Diam: 9.30mm or 9.80mm
Lens Designs Asphericcurves
Lens Designs Aspheric Fit Too Flat Ideal Fit Too Steep
Astigmatism Toric Periphery Spherical BOZR Toric back peripheral radii – stability Good for cornea where peripheral toricity > central toricity Front surface usually spherical
Lens Designs Asticon / TP Normal spherical base curve with toroidal peripheral flange Parameter: BC: 7.00mm to 10.00mm Oz: 6.807.80mm or 7.008.00mm Diam: 9.20mm or 9.40mm
TP Fluorescein Pattern
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
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
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
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
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
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)
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 ?
Lens Designs Back Toric Complete backtoroidal surface Parameter: BC: Any Oz: 7.00mm or 7.50mm Diam: 9.20mm or 9.50mm
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
Lens Designs Bitoric 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
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
Astigmatism Fitting Categories
Astigmatism Fitting Categories
Asticmatic Cornea Spherical lens Spherical Rigid Contact Lenses can only Impact the Astigmatism Found on the Surface of the Cornea
Spheric on Toric shape
Astigmatism
Astigmatism When there are significant areas of bearing and lift, a special RGP lens can be created
45.00 42.00 Astigmatism
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”
Double the Curves… Double the Fun
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”
Double the Curves… Double the Fun
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
Astigmatism With the rule
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)
Astigmatism With the rule
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
Astigmatism With the rule
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)
Astigmatism With the rule
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
Astigmatism Against the rule
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)
Irregular Astigmatism
Common Refractive Procedures Radial Keratotomy PRK LASIK/LASEK Intacts Orthokeratology
Astigmatism Irregular Corneal graft Trauma Post refractive surgery Keratoconus (full section)
Astigmatism Irregular
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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