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Loretta Szczotka-Flynn, OD, PhD

Fitting Large Diameter Lenses to Irregular Corneas

Course Description

• This course will discuss a variety of large diamter lenses suited to treat the irregular cornea. The following designs and fitting techniques will be covered: Intralimballenses, scleral and semi-scleral lenses, piggyback fitting, and hybrid lenses.

Learning Objectives

• Learn the various large diameter options

• Understand when to select a particular design

• Learn step by step fitting approach for intralimbal lenses

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Specialty Lens Options for the Irregular Cornea

• Small diameter Corneal Lenses

• Large Diameter Corneal Lenses

• Soft Lenses– Piggyback

• Hybrid

• Semi-Scleral

• Scleral

"Using a Systematic Approach when Fitting Keratoconus, Irregular and Post Surgical

Corneas"

• Always fit within the limbus as a first option• Use high or hyper Dk materials eg Boston XO2 or Menicon Z

Mini sclerals

Large Diameter Corneal LensesRose K2 IC

11.2mm diameter (Available 9.4mm – 12.0mm)Posterior Aspheric Aberration Control Optics

Dyna Intralimbal K-Max10.4 – 12.0 Diameter, 11.2mm standard 11.5, 12.0. 12.5 DiameterSpherical Posterior Optics Spherical Posterior Optics

TITAN Limbal11.3mm - 12.3mm Diameter 11.0mm Standard DiameterSpherical Posterior Optics Spherical Posterior Optics

FTP G.B.L.10.4mm – 11.4mm Diameter 11.2mm Standard DiameterSpherical Posterior Optics Spherical Posterior Optics

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Identifying cone type using a topographer( difficult without a topographer)


Corneas"

Indications - When to use ??

• Pellucid Marginal degeneration- PMD• Keratoglobus• Lasik induced ecstasia• Post graft

PMDPMD Globus


Corneas"

Lasik

• What to look for in a fitting set

- Comprehensive BC range 6.0 to 8.6

– Some designs automatically account for the likelihood of oblate shape in flatter corneas and incorporate reverse geometries in flatter bases

Eg Rose KIC Increased reverse geometry as BC flattens

– Large optic zone (may be aspheric) – vaults graft or irregular zone

– OZ decreases as BC steepens


Corneas"

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For keratometers :Choose first trial lens 0.3 mm flatter than the steepest corneal meridian

Assess in order :

1. central fit and any heavy corneal contact areas2. peripheral fit- particularly noting tight and loose areas3. diameter – should sit approx. 1mm inside the limbus4. location 5. movement

Eg. 6.8mm/5.5mm First trial lens 5.5mm +0.3 = 5.8mm


Corneas"

1. Central fit

Flat

OK / steep

Steep


Corneas"

2. Peripheral fit

Very tight periphery( std steep EL)

Tight periphery( standard EL)

Ideal periphery( std flat)


Corneas"

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EDGE LIFT (peripheral fit)

Peripheral fit is Singularly the most important fitting factor for a successful comfortable fit.


Corneas"

EDGE LIFT

• Standard 65%

• Increased 20%

• Decreased 10%

• Other lifts 5 to 10%


Corneas"

What to look for in a fitting set:IS THE AEL SET FOR EACH INDIVIDUAL BASE CURVE

AND DIAMETER?Lift factor effects every SC outside the OZ

EXAMPLE OF LIFTS


Corneas"

How labs specify edge lift values

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Quadrant Specific Design Options

Inferior Quadrant Control


Corneas"

Quadrant Specific Design OptionsAsymmetric Corneal Technology

• Available from a few laboratories

• Manufacturing procedure that steepens one or more quadrants– Typically only need the inferior quadrant only

steepened

• Creates a more personalized fit

• Provides a more comfortable and stable lens

• Improves Visual Acuity

Example of quadrant specific steepening which allows the steepening of the inferior quadrant only


Corneas"

Quadrant Specific Design OptionsAsymmetric Corneal Technology

Inferior Quadrant Control

Excessive lift Excessive lift corrected with inferior

quadrant control

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Examples using asymmetric corneal technology• Some labs allow 3 standard grades • Some labs have option to specify degree of tuck

in steps by mm (0.4 to 1.5mm) or u

Grade 1 ( 0.7mm steeper)

Grade 2 (1.0mm steeper)

Grade 3 (1.3mm steeper)


Corneas"

Use Asymmetric Corneal Technology

Blanchard

ACT grade 1 (0.7mm)

ACT grade 2 (1.0mm)

ACT grade 3 (1.3mm)

ROSE K2 IC

ROSE K2 IC ACT GRADE 2

Lens Dynamics

Steepen/flatten 15 steps in either direction

1 step steep 30 u

1 step flat

50 u

NO ACT WITH ACT

ACT - Improved comfort , lens stability and vision


Corneas"

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3. Diameter- intra limbal ( approx. 0.5mm inside limbus)

Use minimum OD to achieve centration and comfort

Ideal Slightly largeLarge


Corneas"

4. Location - Tend to locate over steepest point on cornea

Remedies• Steepen BC• Increase diameter• Correct edge lift• Consider piggybacking


Corneas"

5. Movement

Must move sufficiently to achieve tear exchange!

Excessive movement Insufficient movement

Increase diameter Decrease diameterSteepen BC Flatten BCReduce the edge lift ( steepen) Increase edge lift


Corneas"

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Masking the Corneal Contour

Semi-scleral lens designs

• Jupiter Lens – Essilor/Medlens

– 15.6 mm diameter

– 18.2 mm diameter

– Posterior surface:• Consider reverse geometry

– 2D or

– 4D reverse

• So2Clear (aka Macrolens)– Dakota Sciences– Diameter: 9.0-15.0 mm– BC: 5.82-9.00 mm

– http://www.soclearlens.com/FittingGuide.pdf

Semi-scleral lens designs

• MSD Lens – Blanchard Labs

– 36 lens trial lens set• Saggital depth

• Limbal clearance

– 15.8 mm OAD

– Custom curves • available

• ABBA Mini Scleral• 13.5 mm OAD

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Case Examples

BC 0.5-1D flat

Ideal BC

BC 0.5-1D steep

INTRALIMBAL LENSES

• Dyna Z Intralimbal

• GBL Lens

• Rose K2 IC

PRACTICE PEARL #5:

Utilize “Asymmetric Corneal Technology”

aka steep/flat option

EXAMPLE: POST PK FOR KC

Steepest SynergEyes PS available

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Intralimbal Lens with ACT

Blanchard

ACT grade 1 (0.7mm)

ACT grade 2 (1.0mm)

ACT grade 3 (1.3mm)

ROSE K2 IC

ROSE K2 IC ACT GRADE 2

Lens Dynamics

Steepen/flatten 15 steps in either direction

1 step steep 30 u

1 step flat 50 u

The best thing to come along for the post-keratoplasty

patient:

THE SOFT LENS!!!

Contact Lens SelectionSOFT LENSES

PK/DALK• Bandage lens indications

– persistent epithelial defects

– epithelial filaments

– extreme height discrepancies at graft-host junction

• Bandage lens selection– Silicone hydrogels!!

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Low Dk SOFT LENSESfor post transplant

• Residual ametropia correction– Discouraged due to potential NV and

graft rejection

– NV removes immuno-privileged status of graft

Silicone Hydrogel Lenses

• Spheres– Doubtful unless used as piggyback

• Torics• Any Silicone Hydrogel Stock Toric

• Definitive Silicone Hydrogel Custom– Material by Contamac

» Lenses machined by Xcel, Art Optical, plus others

Material Properties of Silicone Hydrogel Lenses Currently Available in the United States

(in order of increasing Dk)

*Lathe Cut; **Dk X10-11

(cm2/sec)[mlO2/mlXmmHg)

241.4140Air Optix Night & Day

Aqualotrafilcon A

480.75128Biofinitycomfilcon A

331.2110Air Optix Aqualotrafilcon B

380.72103Acuvue Oasyssenofilcon A

460.5100Avairaenfilcon A

361.199PureVision and

PureVision 2balafilcon A

321.182O2 Optix Customsilficon A*

470.4360Acuvue Advance and

Advance Plusgalyfilcon A

740.3560Definitiveefrofilcon A*

480.7155I-Day Acuvue TruEyenarafilcon B

Water Content (%)Modulus (Mpa)Dk**LensMaterial

Comparison: etafilcon A has a water content of 58%, Dk 21, and MPa 0.3

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Piggyback Lens Systems

• Advantages– Comfort

– Freedom from mechanical trauma

• Disadvantages– Two lens per eye daily

management

– Optics?

– Coatings

Piggyback lenses

PRACTICE PEARL #7:– Steep BC needed for some oblate grafts

Material: sifilcon A

*Recommended base curve for initial evaluation

Handling tint: Light green

Wearing schedule: Daily wear

Dk, Dk/t: 82, 117@ -3.00D

Sphere powers (D): +20.00D to -20.00D, in 0.25D steps

Water content: 32%

Modulus: 1.1 MPa

Replacement schedule: Quarterly

Center thickness: 0.07mm @ -3.00D

Diameter (mm) Available base curves (mm)13.214.014.8

7.4, 7.7, 8.0,* 8.37.8, 8.1, 8.4,* 8.7, 9.08.0, 8.3, 8.6,* 8.9, 9.2

Material: sifilcon A

*Recommended base curve for initial evaluation

Handling tint: Light green

Wearing schedule: Daily wear

Dk, Dk/t: 82, 117@ -3.00D

Sphere powers(D): +20.00D to -20.00D, in 0.25D steps

Water content: 32%

Modulus: 1.1 MPa

Replacement schedule: Quarterly

Center thickness: 0.07mm @ -3.00D

Diameter (mm) Available base curves (mm)13.214.014.8

7.4, 7.7, 8.0,* 8.37.8, 8.1, 8.4,* 8.7, 9.08.0, 8.3, 8.6,* 8.9, 9.2

O2 Optix Custom Sphere Parameters

PRACTICE PEARL #6:Steep base curves often needed for piggybacks

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Predicted Tear Oxygen Tensions

Weissman B and Ye P. Calculated tear oxygen tension under contact lenses offering resistance in series: Piggyback and scleral lenses. Contact Lens & Anterior Eye. 29(2006) 231-237.

PRACTICE PEARL #8Watch oxygen delivery in some combinations

Tear Oxygen Tension beneath piggyback lens systems

130140150

125100150

11460150

6920150

1710150

11414060

10910060

996060

572060

91060

5014015

4610015

396015

92015

01015

Open eye pO2SCL Dk/tRGP Dk/t

0

20

40

60

80

100

120

140

160

180

200

F 55 Biomed. Soflen 66 AV2 Proclear AV Adv. PV O2Optix Oasys Biofinity N & D

Dk/t

Dk/tDk/t with low with low DkDk and and Silicone HydrogelsSilicone Hydrogels

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Eye Specific Lens Material Interactions

Menicon Z and Oasys OS

Menicon Z, BXO, HDS 100 and all SH lenses OD resolves temporarily with Plasma Treated lenses

PRACTICE PEARL #9Use soft lens to reshape the corneal contour

Topo over +7.00 Oasys

PRACTICE PEARL #10Piggyback soft lens can act as a prosthetic

device

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Hybrid Lenses

• SynergEyes

family

SynergEyes ® A

SynergEyes ® KC

SynergEyes ® PS

SynergEyes ® M Myopia, Hyperopia, Astigmatism, Presbyopia

Prolate Corneas, Keratoconus

Oblate Corneas, Post-Surgical

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SynergEyes™ A High Dk Hybrid

• Material– Paragon HDS 100 GP

Center (Dk 145) – 27% Water Non Ionic

Skirt (Group I)Design– 14.5 mm over all

diameter– 8.4 mm rigid center– 7.8 mm optic zone

14.5mm

8.4 mm

Non-Ionic27% water Hydrogel Skirt

Non-Ionic27% water Hydrogel Skirt

Paragon HDS 100®Rigid Center

145 Dk

Paragon HDS 100®Rigid Center

145 Dk

SynergEyes Fitting

Lens Movement– .2mm to .3mm

movement with blink

– Slight lag in upward gaze

– Free of scleralimpingement

– Free to move on “push up”

– Free of “edge fluting”

Fluorescein Evaluation

• Apply lens

• Instill high molecule fluorescein

• Observe fluorescein pattern after 20-30 seconds of normal blink

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If edge fluting is observed, select steeper skirt radius

8.208.507.2 (46.87)8.308.607.3 (46.25)8.408.707.4 (45.62)8.508.807.5 (45.00)8.608.907.6 (44.37)8.709.007.7 (43.87)8.809.107.8 (43.25)8.909.207.9 (42.75)9.009.308.0 (42.25)9.109.408.1 (41.62)9.209.508.2 (41.12)

8.108.407.1 (47.50)

SteeperSkirt Curve

Radius

Flatter Skirt Curve

Radius

GP CenterBase Curve

Fluting Picture

Fitting management

SynergEyes® PS Product Description

8.2 mm

14.5mm

Paragon HDS 100 ®Rigid Center

150 Dk(Revised Fatt)

Non Ionic30% water Hydrogel Skirt

Central 6.5mm spherical

SynergEyes PS design

Oblate return curve starts on GP at 6.5mm and extends to soft at 9mm chord

PRACTICE PEARL #11: Return curve can be varied: shallow, median or deep sag

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SynergEyes PS Diagnostic Set ParametersSynergEyes PS Diagnostic Set Parameters

9.59.28.9Plano9.6mm (35.25)

9.59.28.9Plano9.3mm (36.37)

9.28.98.6Plano9.0mm (37.50)

9.28.98.6Plano8.7mm (38.75)

8.98.68.3Plano8.4mm (40.50)

8.98.68.3Plano8.1mm (41.75)

8.68.38.0Plano7.8mm (43.25)

8.68.38.0Plano7.5mm (45.00)

Flat

Skirt

Medium

Skirt

Steep

SkirtPowerBase Curve

The ideal fit

PRACTICE PEARL #12: realize a perfect fit cannot always be achieved!

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