oc-sag · 3/19/18 3 study instrument eyes ave oc-sag h 15mm±sd range u waterloo1 oct n=40 3740 sd...

3/19/18

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BEYOND BASE CURVE& THE ART OF SOFT LENS FITTING

Eef van der Worp optometrist PhD FAAO FIACLE FBCLA FSLSwww.clspectrum.com/nov2017

‘2017 the year of the “attack on the integrity of the contact lens

prescription.” Jason Nichols

“ Currently, we are trying to find eyes that best conform to our limited arsenal of soft lenses

available “

“ The goal is to turn that around; to measure the eye in detail and to find or design the best

possible lens shape for that eye “

BEYOND BASE CURVE

BEYOND BASE CURVE

Many factors related to drop-outs and comfort we have no say and no control over as ECPs.

What we do have control over is the lens fit.

X-RAYSOFT LENS FITTING

OC-SAG

http://www.clspectrum.com/nov

3/19/18

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OC-SAG5.7%

Greg DeNaeyer OD, Don Sanders MD PhD , Eef van der Worp OD PhD, Jason Jedlicka OD, Langis Michaud OD, Sheila Morrison OD

28.6%

40.7%

26%

CLASSIFICATION

HANSMADER

Tsag-NsagCentration

0

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60

70

80

90

100

0 0.1 0.2 0.3 0.4 0.5 0.6

Tsag-Nsag

Larger lens, better centration…?

Line of SightDistance Optic

+

Near Optic

MultifocalsMyopia Control

Wavefront Correction

Centration

MATTHEWLAMPA–PACIFICU

OC-SAG

Consequently, keratometry can be considered an oversimplified predictor of soft lens fit, and previous studies

have shown that there is no strong correlation between keratometry readings and the best-fitting soft contact lens.

Modeling of the principal factors of lensfit with corneoscleral measurements showed that central keratometry was a poor predictor of contact lens fit. The addition of videokeratoscopy data did not improve the

prediction in this study; however, incorporation of corneoscleral topography from the OCT data strengthened

the predictive power of the model.



“ Both base curve and diameter are surrogate

measures for lens sag … increasing sag reduces

movement and consequently improves comfort

within the limits of acceptable fitting.”

3/19/18

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Study Instrument Eyes Ave OC-SAG H 15mm±SD

Range

U Waterloo1 OCT n=40 3740 SD ± 190 3140 - 4040 (900)Pacific U 2 OCT n=55 3735 SD ± 186 3290 - 4170 (880)Visioncare Research3 OCT n=50 3740 SD ± 160 3230 - 4100 (870)Ritzman Master Thesis4

OCT n=39 3740 SD ± 210 -

Groenhof5 ESP n=86 3755 SD ± 207 3290 - 4280 (990)Stortelder6 ESP n=214 3650 SD ± 200 3010 - 4210 (1200)Harkness Master Thesis7

OCT n=52 3728 SD ± 188 3390 - 4180 (790)

ESP n=52 3680 SD ± 203 3280 - 4140 (860)Medmont* n=52 3732 SD ± 159 3426 - 4073 (647)

U of Montreal8 ESP n=14 3630 SD ± 205 3490 - 4060 (570)Medmont* n=14 3741 SD ± 95 3560 - 3911 (351)

Study Instrument Eyes Ave OC-SAG H 15mm±SD

Range

U Waterloo1 OCT n=40 3740 SD ± 190 3140 - 4040 (900)Pacific U 2 OCT n=55 3735 SD ± 186 3290 - 4170 (880)Visioncare Research3 OCT n=50 3740 SD ± 160 3230 - 4100 (870)Ritzman Master Thesis4

OCT n=39 3740 SD ± 210 -

Groenhof5 ESP n=86 3755 SD ± 207 3290 - 4280 (990)Stortelder6 ESP n=214 3650 SD ± 200 3010 - 4210 (1200)Harkness Master Thesis7

OCT n=52 3728 SD ± 188 3390 - 4180 (790)

ESP n=52 3680 SD ± 203 3280 - 4140 (860)Medmont* n=52 3732 SD ± 159 3426 - 4073 (647)

U of Montreal8 ESP n=14 3630 SD ± 205 3490 - 4060 (570)Medmont* n=14 3741 SD ± 95 3560 - 3911 (351)

OC-SAG15 MM CHORD

HORIZONTAL

OC-SAG 15mm H

= 3750 micron Δ=+/- 900μ

ESP - GROENHOF STUDY (N=86): 3755 SD +/- 207

range 3290 to 4280 micron

15 MM CHORDHORIZONTAL

OCT -WATERLOO UNIVERSITY (N=40):3740 SD +/-200

range 3140 – 4040 micron

OCT - PACIFIC UNIVERSITY (N=55): 3735 SD +/-186


OCT - VISIONCARE RESEARCH (N=50):3740 SD +/-160


Δ= +/- 990 μ

OC-SAG

Δ= +/- 900 μOC-SAG 15mm H

= 3750 micron

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60

3100 3200 3300 3400 3500 3600 3700 3800 3900 4000 4100 4200 4300

OC-SAG Frequency

n= 214

Hor SAG

15mm chord

Reinier Stortelder


OC-SAG

OC-SAG range = 900 mircon > CL-SAG range = ?Workbench Tools

CL-SAG

CL-SAG

Optocraft

Van der Worp, Mertz - Contact Lens & Ant Eye 2015 – Volume 38

CL-SAG

Current SH monthly or 2-wk disposable lenses:1. 330 micron

Air Optix8.6/14.2

Biofinity8.6/14.0

Oasys8.4/14.0

Oasys8.8/14.0

Purevision8.3/14.0

Purevision8.6/14.0

Air OptixToric

8.7/14.5

BiofinityToric

8.7/14.5

OasysToric

8.6/14.5

PurevisionToric

8.7/14.0

Air Optix 8.6 14.2 -45 51 -225 87 -170 155 187 275 -184Biofinity 8.6

14.0 45 96 -180 132 -125 200 232 320 -139Oasys 8.414.0 -51 -96 -276 36 -221 104 136 224 -235

Oasys 8.814.0 225 180 276 311 55 380 411 499 41

Purevision 8.314.0 87 -132 -36 -311 -256 69 100 188 -270

Purevision 8.614.0 170 125 221 -55 256 325 356 444 -14

Air Optix Toric 8.714.5 -155 -200 -104 -380 -69 -325 32 120 -339

Biofinity Toric 8.714.5 -187 -232 -136 -411 -100 -356 -32 88 -370

Oasys Toric8.614.5 -275 -320 -224 -499 -188 -444 -120 -88 -458

Purevision Toric8.714.0 184 139 235 -41 270 14 339 370 458

CL-SAG

3/19/18

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Air Optix8.6/14.2

Biofinity8.6/14.0

Oasys8.4/14.0

Oasys8.8/14.0

Purevision8.3/14.0

Purevision8.6/14.0

Air OptixToric

8.7/14.5

BiofinityToric

8.7/14.5

OasysToric

8.6/14.5

PurevisionToric

8.7/14.0

Air Optix 8.6 14.2 -45 51 -225 87 -170 155 187 275 -184Biofinity 8.6

14.0 45 96 -180 132 -125 200 232 320 -139Oasys 8.4

14.0 -51 -96 -276 36 -221 104 136 224 -235Oasys 8.814.0 225 180 276 311 55 380 411 499 41

Purevision 8.314.0 87 -132 -36 -311 -256 69 100 188 -270

Purevision 8.614.0 170 125 221 -55 256 325 356 444 -14

Air Optix Toric 8.714.5 -155 -200 -104 -380 -69 -325 32 120 -339

Biofinity Toric 8.714.5 -187 -232 -136 -411 -100 -356 -32 88 -370

Oasys Toric8.614.5 -275 -320 -224 -499 -188 -444 -120 -88 -458


CL-SAGAir Optix8.6/14.2

Biofinity8.6/14.0

Oasys8.4/14.0

Oasys8.8/14.0

Purevision8.3/14.0

Purevision8.6/14.0

Air OptixToric

8.7/14.5

BiofinityToric

8.7/14.5

OasysToric

8.6/14.5

PurevisionToric

8.7/14.0Air Optix 8.6

14.2 -45 51 -225 87 -170 155 187 275 -184Biofinity 8.6

14.0 45 96 -180 132 -125 200 232 320 -139Oasys 8.4

14.0 -51 -96 -276 36 -221 104 136 224 -235Oasys 8.814.0 225 180 276 311 55 380 411 499 41

Purevision 8.314.0 87 -132 -36 -311 -256 69 100 188 -270

Purevision 8.614.0 170 125 221 -55 256 325 356 444 -14

Air Optix Toric8.714.5 -155 -200 -104 -380 -69 -325 32 120 -339

Biofinity Toric8.714.5 -187 -232 -136 -411 -100 -356 -32 88 -370

Oasys Toric8.614.5 -275 -320 -224 -499 -188 -444 -120 -88 -458

PurevisionToric 8.7

14.0 184 139 235 -41 270 14 339 370 458

Air Optix8.6/14.2

Biofinity8.6/14.0

Oasys8.4/14.0

Oasys8.8/14.0

Purevision8.3/14.0

Purevision8.6/14.0

Air OptixToric

8.7/14.5

BiofinityToric

8.7/14.5

OasysToric

8.6/14.5

PurevisionToric

8.7/14.0Air Optix 8.6

14.2 -45 51 -225 87 -170 155 187 275 -184Biofinity 8.6

14.0 45 96 -180 132 -125 200 232 320 -139Oasys 8.4

14.0 -51 -96 -276 36 -221 104 136 224 -235Oasys 8.8

14.0 225 180 276 311 55 380 411 499 41Purevision 8.3

14.0 87 -132 -36 -311 -256 69 100 188 -270

Purevision 8.614.0 170 125 221 -55 256 325 356 444 -14

Air Optix Toric8.714.5 -155 -200 -104 -380 -69 -325 32 120 -339

Biofinity Toric 8.714.5 -187 -232 -136 -411 -100 -356 -32 88 -370

Oasys Toric8.614.5 -275 -320 -224 -499 -188 -444 -120 -88 -458


CL-SAG

CL-SAGmeets

OC-SAG

BEYOND BASE CURVESOFT LENS FITTING OC-SAG 3613μ

CL-SAG: 3529

Height 8.10

OC-SAG 3613μ

CL-SAG=OC-SAG + …

CL-SAG: 3529

OC-SAG 3667μ

CL-SAG: 3858+ 200μ (from OC-SAG)

3/19/18

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CL-SAG: 4091

OC-SAG 3667μ

+ 400μ (from OC-SAG)

CL-SAG=OC-SAG + …

OC-SAG vs CL-SAG

Graeme YoungOptometry & Vision ScienceJuly 2014 - Volume 91

This mathematical model shows that ‘lens edge strain’ in a normal eye, with a typical (8.6 - 14.2mm) lens this could be as much as 2.7% strain - but for the same lens on a cornea and/or ocular surface that is flat this would result in a tight

fit showing 8.5% strain.

This mathematical model shows that ‘lens edge strain’ in a normal eye, with a typical (8.6 - 14.2mm) lens this could be as much as 2.7% strain - but for the same lens on a cornea and/or ocular surface that is flat this would result in a tight

fit showing 8.5% strain.

‘edge strain’

Δ = 131 micron

GROENHOF STUDY (N=78)

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OC-SAG Frequency

n= 214

Hor SAG

15mm chord

If RGP: CL-SAG = OC-SAG

Reinier Stortelder

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OC-SAG FrequencyIf RGP: CL-SAG = OC-SAGIf RGP: CL-SAG = OC-SAGOnly 34% (!) would fit

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OC-SAG Frequency

68-78% would fit

“25% falls

outside range”Family vs Specialty

Lowest CL-SAG (3701) – 250 = 3450 micronHighest CL-SAG (4034) – 100 = 3934 micron OC-SAG vs CL-SAG

Graeme Young Optometry & Vision Science July 2014 - Volume 91

‘edge strain’

• 3% edge strain: 14mm on the finger > 14.4 mm on-eye• In theory: change in on-eye BCR from 8.4 to 8.8:

on-eye diameter DECREASES - add 0.2mm

MECHANISM?

3/19/18

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The End

Multifocals

Myopia Control


‘The difference in sagittal height between the CL-

SAG and the OC-SAG (delta-SAG) on average was

131 microns in a clinical setting’

MECHANISM?

Multifocals

Myopia Control


‘The difference in sagittal height between the CL-

SAG and the OC-SAG (delta-SAG) on average was

131 microns in a clinical setting’

Relevance…?


Matthew Lampa & Mark André 2011www.softspecialedition.com

Out-of-standard lenses.

Stock (standard)lenses.

Custom-made lenses.

How can we improve soft lens fitting ?BEYOND BASE CURVE

& THE ART OF SOFT LENS FITTING

Stock lenses

Stock lenses. Basically ‘off the rack’ designs, these lenses have a fixed shape for which the eye care practitioner basically tries to find an eye that fits the given lenses that we have. The more variety there is in stock lenses, the better is the chance to find a lens that best matches a given cornea. These lenses would probably best ‘serve’ the normal, standard eye – or top of the bell-curve of average eyes.

1 Classification


1. Diameter cornea (HVID)

2. Eccentricity

3. Central curves

Glo

bal C

onta

ct 3

/201

7

2. EccentricityEef van der Worp optometrist PhD FAAO FIACLE FBCLA FSLS


Out-of-standardlenses

Out-of-standard lenses. Have a fixed geometry (or maybe a number of geometries, but they are still standard lens designs), but have a parameter range that falls outside that of the standard stock lens range. Examples are higher spherical or cylindrical powers, large or small diameters, etc. They may have to be manufactured individually (lathe-cut), but their design choice is still somewhat limited.

2 Classification


3/19/18

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BEYOND BASE CURVE& THE ART OF SOFT LENS FITTINGSAG calculator

www.softspecialedition.com/world_wide_vision_xiv


Out-of-standardlenses

Use corneal diameter as a leading parameter

rather than central keratometry values and/or

peripheral corneal angles based on topography

2

DIAMETER VS SAG

BC VS SAG

r=0.81

r=0.32

Global Contact 2-2016


Custom-made lenses

Custom-made lenses. Are made truly individually, and specifically for each particular eye. There are no limits to shape, power, design, etc. Practitioners may have these lenses made in a silicone hydrogel material if desired, to benefit from the latest technology in material development. A true ‘taylor fit’, to accommodate the shapes and patterns that may be available on the ocular surface.

3



Custom-made lenses

3 How we can do better (short term): FIT

CB R E X I T

3/19/18

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The End

SURVIVAL OF THE FITTING

THE LEARNING CURVEELEVATING SOFT LENS FITTING

oc-sag · 3/19/18 3 study instrument eyes ave oc-sag h 15mm±sd range u waterloo1 oct n=40 3740 sd...

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