Simplifying Soft Torics - SECO2011.com

DISCLOSURE STATEMENT 

CEO Visioncare Research Ltd 

Consultant for: Johnson & Johnson, Alcon, 

CooperVision, Ocutec, Bausch & Lomb 

Welcome to SECO 2009 

SECO 2011 

March 2-6, 2011 

Soft Toric Lens Fitting – The Simpler Way 

Graeme Young MPhil, PhD, FCOptom, DCLP, FAAO 

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Soft Toric Lens Fitting – The 

Simpler Way 

Graeme Young MPhil PhD FCOptom DCLP FAAO


BACKGROUND 

Astigmatism and its prevalence 

A short history of toric soft lenses (TSLs). 

Who to fit with TSLs 

TORIC SOFT LENS (TSL) DESIGNS 

Methods of stabilization 

Factors affecting stabilization 

Branded toric soft designs 

FITTING TSLs - PREPARATION 

Empirical vs. diagnostic fitting 

Hydrogel vs. silicone hydrogel 

Replacement period 

Selection of design/brand 

FITTING TSLs – POWER DETERMINATION 

Refraction 

Vertex correction 

Cross-cylinder calculations 

FITTING TSLs – AXIS DETERMINATION 

TSL vs Rx axis 

Assessment of orientation 

Adjustment for rotation 

FITTING TSLs – LENS FIT ASSESMENT 

Settling time 

Basic soft lens fit 

Orientation stability 

CUSTOM TSLs 

Who to fit with custom TSLs 

Fitting procedure 

Examples 

PROBLEM SOLVING 

Discomfort 

Poor VA 

Unstable vision 

Corneal staining 

Other physiological problems 

CASE EXAMPLES & DISCUSSION

Astigmatism & its Prevalence

Astigmatism & its Prevalence 

sphere / cylinder x axis 

-3.00 / -1.50 x 180 

In plus cylinder form: 

-4.50 / +1.50 x 90 

-4.50D 

-3.00D

Prevalence 

80% 

70% 

60% 

50% 

40% 

30% 

20% 

10% 

0% 


How many patients need TSLs? 

Prevalence of threshold astigmatism by patient (Px) and eye. 

N=11,624 

0.75D M 

47% 

0.75 B 

24% 

1D M 

32% 

≥0.50DC ≥0.75DC ≥1.00DC ≥1.25DC ≥1.50DC ≥1.75DC ≥2.00DC 

Cylinder (D) 

Eyes 

Px BE 

Px One Eye



cylinder 

axis



• Approx 50% of pxs have significant astigmatism 

• Approx one-third of CL pxs need astigmatic correction 

• Only ~21% of soft lenses fitted are torics in US (Morgan 2011) 

• Disproportionately high % of CL drop-outs are astigmats 

51%: �0.75DC both eyes or �1.50DC one eye 

(Young, Veys, Pritchard, Coleman 2002)

Short History of Toric Soft Lenses?


Rules of thumb 

• 1.00D or more of astigmatism


Rules of thumb 

• 1.00D 0.75D or more of astigmatism 

• Sphere power - 

1/4 of sphere power usually acceptable 

e.g. -5.00/-1.25 x 5 � 

-2.00/-1.25 x 5 � 

• WTR vs. ATR vs. Oblique astigmatism

Vertical world

With vs. against the rule 

Against ↕ 

With ↔


Indications for toric soft lenses 

(vs. rigid lenses) 

• Rigid lens intolerance 

• ATR astigmatism 

• Difference in corneal & refractive astigmatism 

• Existing spherical soft lens wearers 

• Sports or part-time use


Contra-indications for TSLs 

• Successful rigid lens wearer 

- px’s assessment 

• Cylinder > sphere power 

e.g. -0.50 / -1.75 x 180 

• Monocular pxs. 

• Small palpebral aperture 

• Tight lids 

Possibly


BACKGROUND 














Refraction 



- BREAK - 






Settling time 



CUSTOM TSLs 



Examples 


Discomfort 

Poor VA 





Toric Soft Lens Designs 

Methods of Stabilisation


Factors Affecting Stabilisation 

‘Watermelon seed principle’ 

Hanks AJ. Contact Lens Forum 

1983; 8(9)31-35

Static 

lid force 

Dynamic 

lid force 


Forces acting on a TSL 

Gravity 

Static 

lid force 

Dynamic 

lid force

Factors Influencing Toric Soft Lens Fit

Factors Influencing Toric Soft Lens Fit 

Patient factors vs. orientation 

PATIENT 

FACTORS 

Palpebral 

aperture 

Myopia 

Lower central 

lid angle 

Inter-canthal 

angle 

Upper central lid 

angle 

ORIENTATION 

Orientation 

stability 

Re-orientation 

speed 

Orientation 

Inf.-temporal 

Solid line: P


Inter-canthal angle vs. orientation 

Orientation (º) 

40 

30 

20 

10 

0 

-10 

-20 

-30 

-40 

Inferior 

Nasal 

Inferior 

Temporal 

y = -1.3293x + 3.3593 

R 2 = 0.172 

-15 -10 -5 0 5 10 15 

Inter-canthal Angle (º)


Patient factors vs. orientation 

PATIENT 

FACTORS 

Palpebral 

aperture 

Myopia 

Lower central 

lid angle 

Inter-canthal 

angle 

Upper central lid 

angle 

ORIENTATION 

Orientation 

stability 

Re-orientation 

speed 

Orientation 

Inf.-temporal 

Solid line: P

Stabilisation 

Effect of gravity


50 

40 

30 

20 

10 

Stabilisation 

Effect of gravity & dynamic upper lid force 

0 

0 10 20 30 40 

40 

35 

30 

25 

20 

n=10 15 

Time (no. of blinks) 


0 

Green lines indicate blink 

Time (4 blinks)

Blink-induced Rotation

Prism Ballasted Soft Toric 

Thickness Profile 

Horizontal iso-thickness

Prism Ballasted Toric Thickness Profile

Dynamic stabilization 

Lo-torque 


Branded TSL Designs 

Horizontal iso-thickness 

Accelerated stabilization 

Precision balance 8-4 

B 

A 

C 

A 

C 

B

A A 

B B 

C 

C 


Lo-torque 

1. 360 degree comfort chamfer 

2. Prism Ballasting stabilising geometry 

3. Refined optic zone 

4. Balanced vertical thickness profile


Precision balance 8-4


Horizontal iso-thickness


Accelerated stabilization


BACKGROUND 














Refraction 



- BREAK - 






Settling time 



CUSTOM TSLs 



Examples 


Discomfort 

Poor VA 





How to fit toric soft lenses 

Traditional method 

1. Insert trial lens approx. 1.0mm flatter than 

mean-K, closest to Rx 

2. Allow to settle for 20-30 minutes 

3. Assess rotation from vertical (usually inf-nasal) 

4. Do sphero-cylindrical over-refraction 

5. Order lens based on: 

lens power + orientation + over-refraction 

6. Repeat steps 1-5 until suicidal

How to fit toric soft lenses 

Simple method 

1. Do accurate refraction � 

2. Insert lens nearest to refraction (vertex- 

corrected) - with goal of dispensing � 

3. Allow 5-10 minutes settling � 

4. Assess for fit and orientation � 

5. If necessary change lens to allow for rotation 

6. Repeat steps 2-5



Daily: Part-time 

Previous history 

2-, 4-weekly: Default 

>Monthly: Hard-to-fit 

High Rxs


Design / brand 

• Silicone hydrogel vs. conventional 

hydrogel 

• Rx availability 

• Lid shape 

• Inventory

Disposable TSLs

Disposable Soft Toric Lenses 

Acuvue Toric +6 to -9 

Biomedics Toric +4 to -6 

Spheres (D) Cyls (-ve) Other 

0.75 - 1.75 

in 0.50 steps 

0.75, 1.25, 1.75, 

2.25 

Dble slab-off 

Predictable 

orientation 

Focus Toric +4 to -6 1.00, 1.75, 2.50* 2 BCs 

Proclear Toric +4 to -6 

Soflens 66 Toric +6 to -9 

Frequency Excel 

(Vertex) Toric 

+6 to -8 

0.75, 1.25, 1.75, 

2.25 

0.75*, 1.25, 1.75, 

2.25, 2.75* 

0.75 – 2.25 

in 0.50 steps 

2 BCs: 8.4, 8.8 

Wider range in XR 

version 

Rel. large & loose 

Also XR: 

3.75 cyl in 5° axes

SiH Soft Toric Lenses 

Acuvue Advance for Astigmatism 47 +6 to -9 

Acuvue Oasys for Astigmatism 38 +6 to -9 

WC (%) Spheres (D) Cyls (-ve) Other 

0.75, 1.25, 1.75, 

2.25* 

0.75, 1.25, 1.75, 

2.25* 

Avaira Toric 48 0 to -6 0.75, 1.25, 1.75 

Air Optix for Astigmatism 33 +6 to -10 

Biofinity Toric 48 +8 to -10 

Purevision Toric 36 +6 to -9 

0.75, 1.25, 1.75, 

2.25* 

0.75, 1.25, 1.75, 

2.25 

0.75, 1.25, 1.75, 

2.25 

Predictable 

Limited axes 

outside 0 to -6: 

H&V +/-10 

All axes 

14.0mm

Daily Disposable Toric Lenses 

Spheres (D) Cyls (-ve) Other 

Focus Dailies Toric +4 to -8 0.75, 1.50 

1-Day Acuvue for 

Astigmatism 

Plano -9.00 

0.75 – 1.75 

in 0.50 steps 

Limited axes - 

70,90,110,160,180,20 

14.2mm 

Limited axes 

90,180,20,160


Empirical vs. diagnostic vs inventory fitting 

• Empirical 

• Diagnostic 

– basic fit 

– orientation 

• Inventory (fitting bank) 

414 lenses - 85% astig. myopes


BACKGROUND 














Refraction 



- BREAK - 






Settling time 



CUSTOM TSLs 



Examples 


Discomfort 

Poor VA 





Top 

Tip 


Power 

Accurate refraction � 

• Don’t rely on someone else’s 

refraction 

• Determine full cylinder 

• Refract cyl. to nearest 2.5 deg 

• Note accurate VA



-4.50/-1.50 x 2



-4.50/-1.50 x 2 � -4.25/-1.25 x 180 

• � -4.00D subtract 0.25D 

� -6.00D subtract 0.50D 

Top 

Tip 

• Err towards lower cyl. power where 

necessary


BACKGROUND 














Refraction 



- BREAK - 






Settling time 



CUSTOM TSLs 



Examples 


Discomfort 

Poor VA 





FITTING TSLs –AXIS DETERMINATION 

TSL vs Spectacle Rx axis

Fitting Soft Torics 

3. Allow 5-10 minutes settling � 

• Insert close to base down position 

• Do quick check on insertion

FITTING TSLs – Axis Determination 

Assessing orientation position 

Graticule


Assessing orientation position 

S66T 

30deg 

AT 

10deg


Decentration may affect apparent orientation

FITTING TSLs – Axis Determination

FITTING TSLs – Axis Determination


Assessing fit and orientation � 

• Assessing orientation over a short period of time 

and note the range 

e.g. 0-7 deg. Nasal 

• Helps when limited by cyl. axis availability 

e.g. RE: -3.00/-1.50 x 5 order -3.00/-1.25 x 180 

• Note also whether unstable 

i.e. > 15 deg. variation


4. Assess for fit and orientation � 

• Assessing orientation over a short period of time 

and note the range 

e.g. 0-7 deg. Nasal 

• Helps when limited by cyl. axis availability 

e.g. RE: -3.00/-1.50 x 5 order -3.00/-1.25 x 180 

• Note also whether unstable 

i.e. � 15 deg. variation

Orientation stability



Clockwise rotation - add to cylinder axis 

Add 

� 

Subtract 

� 

LARS - L add, R subtract

Fitting TSLs - Adjustment for rotation 

Examples 

Example 1: 

-2.00 / -1.25 x 10 rotates 10° CW (LA) 

-2.00 / -1.25 x 20 needed


Examples 

Example 2: 

Spec Rx: -2.00 / -1.50 x 180 

orientates 5-10° Anti-CW (LARS) 

cyls. available = 1.25, 1.75D 

-2.00 / -1.25 x 170 needed


Examples 

Example 3: 

Spec. Rx: -4.25 / -2.25 x 22.5 @12mm 

vertex corrected: -4.00 / -2.00 x 22.5 

cyls. available = 1.25, 1.75, 2.25D 

orientates 0-5° Anti-CW (LARS) 

-4.00 / -1.75 x 20 needed


BACKGROUND 














Refraction 



- BREAK - 






Settling time 



CUSTOM TSLs 



Examples 


Discomfort 

Poor VA 





Custom soft torics 

• Expensive 

• Slow delivery 

• Poor reproducibility 

• Thicker

CUSTOM TSLs 

When to use custom torics 

• Higher cylinders >3.50DC 

• Higher sphere powers 

• Fitting difficulties 

• Bored, in need of a challenge

CUSTOM TSLs 


• Accurate refraction 

• ? Diagnostic lens

Hybrid lenses - Synergeyes


BACKGROUND 














Refraction 



- BREAK - 






Settling time 



CUSTOM TSLs 



Examples 


Discomfort 

Poor VA 





Problem-solving TSLs 

Possible problems include: 

• Poor VA 

• Unstable vision 

• Poor comfort 

• Corneal staining 

• Corneal oedema or other SL findings


Poor Vision 

Possible sources of error include: 

• Lens orientation 

• Lens Rx (inc. prism, distortion) 

• Refraction 

• Human error 

• That’s it


Poor Vision 

• Lens orientation - Rotate and recheck vision 

• Lens Rx - Verify lens power 

(or try another lens, same Rx)


Lens checking


Poor Vision 



(or try another lens, same Rx) 

• Refraction - Check refraction 

• Human error - Check px records, lens labels etc


Poor Vision 



(or try another lens, same Rx) 

• Refraction - Check refraction 

• Human error - Check px records, lens labels etc


Toric Calculators


Oblique cylinder calculator 

www.visioncare.co.uk


Unstable Vision 

Possible causes include: 

• Variable orientation 

• Mis-orientation - stable but with intermittently 

correct orientation 

• Loose fit � excessive movement


BACKGROUND 














Refraction 



- BREAK - 






Settling time 



CUSTOM TSLs 



Examples 


Discomfort 

Poor VA 





Simplifying Soft Torics 

CONCLUSIONS 

Soft torics now much easier due to improved 

designs, better reproducibility & FR options. 

Soft torics are now an integral part of basic CL 

practice.

Thank you 

Akiyoshi's illusion pages www.ritsumei.ac.jp/~akitaoka/index-e

Simplifying Soft Torics - SECO2011.com

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