Toric SCL Anatomy & Fitting - Contact Lenses I Summer 2026

1) Back surface

2) Power Curve

Where can we put the toric correction in a RGP?

bitoric

Balancing the toricity on the front and back surface of an RGP is called what

40%

What is the estimated prevalence of astigmatism?

toric soft lenses

85% of patients (with cyl -0.75 to -1.75) preferred _____ over spherical soft lenses

large diameter spherical RGPs

Many patients prefer _____ over toric soft Cls

increases

As age of a patient increases, cyl magnitude (increases/decreases)

ATR

As age of a patient increases, (ATR/WTR) magnitude increases

All contact lenses will rotate on the eye without stabilization

Why do toric lenses need stabilization?

-surface tension/tear film quality

-back surface toricity

-lid/lens interaction

What are the causes of CLs rotation?

with corneal toricity

The back surface toricity of CLs will rotate to align with what?

-watermelon seed effect

-powers (thickness) in each meridian

-patient lid position (more under examination/fitting)

What are the lid/lens interactions that may contribute to lens rotation?

-Eyelids adhere to lenses and cause both vertical movement and rotation

-The lids will push the thick part of the CLs between the 2 lids when patient blinks. This helps the thin parts of the lens NOT interact with the lids.

What is the "Watermelon Seed Principle" of CLs rotation & eyelid interaction?

Need to thin and steepen peripheral/mid-peripheral areas

How do you DECREASE lid interaction d/t the Watermelon Seed Principle?

Cylinder

_____ alone (without other strategies) will affect lens rotation

Lens thickness variation -- both in toric power curve and toric BCR Cls

What does cylinder in SCLs create?

Vertical

WTR CLs are thicker in the (Vertical/horizontal) meridian

horizontal

ATR CLs are thicker in the (Vertical/horizontal) meridian

Asymmetric thickness

Where are oblique lenses thickest?

parallel

When a CLs has an oblique axis of 90º, the thicker meridian will be _____ to the upper eyelid

often very little rotation

Describe the rotation of a 90º axis Cls?

perpendicular

When a CLs has an axis of 180º, the thicker meridian will be _____ to the upper eyelid

Rotation temporal or nasal

Describe the rotation of a 180º axis Cls?

neither perpendicular or parallel

When a CLs has an oblique axis of 45º, the thicker meridian will be _____ to the upper eyelid

at 10 ociock position

With a 45º oblique cyl axis Cls, where will the ticker edge encounter the upper lid?

-Nasal rotation OD

-Temporal rotation OS

Describe the rotation of a 45º oblique axis Cls?

neither perpendicular or parallel

When a CLs has an oblique axis of 135º, the thicker meridian will be _____ to the upper eyelid

at 2 ociock position

With a 135º oblique cyl axis Cls, where will the ticker edge encounter the upper lid?

-Temporal rotation OD

-Nasal rotation OS

Describe the rotation of a 135º oblique axis Cls?

downward; greatest

With an oblique axis CLs, the rotation will be ____ on the side with the _______ thickness

Within 20º of axis 90 or axis 180

An oblique Cls will have the least rotation when?

Oblique axis

What cyl location is MOST LIKELY to rotate on the eye?

Higher

(higher/lower) cyl powers are more likely to rotate on the eye

with corneal toricity

All lenses with a toric BCR that touches the cornea will rotate to align how?

the cornea

Toric SCLs will align with and conform to what?

No

Do SCLs have a lacrimal lens?

No -- this is only for RGPs with a lacrimal lens

Do you have to apply SAM FAP with a BCR change in a SCL?

in the central optic zone

Toricity in a SCL is only where?

to reduce peripheral lens thickness and lid interaction

Why is toricity ONLY in the central optic zone of a SCL?

8.4 to 8.9mm

What is the typical BCR range of a Toric SCL?

Yes

Are Toric SCLs and spherical SCLs similar in BCRs?

No

Do toric SCLs usually come in MORE THAN ONE BCR option / brand?

14.4 to 14.5 mm

What is the OAD range for Toric SCLs?

1.0

The OAD for a toric SCL is about _____mm larger than a spherical SCL

true

True or False:

BCR is OFTEN toric in a toric SCL, but the exact values are not published

toric BCR

Multiple studies suggest that a ______ is more rotationally stable than spherical BCR

deeper

Toric SCLs are _____ than spherical lenses in order to improve stability

Toric Lens Anatomy -- Sagittal Depth (Pic)

Toric Lens Anatomy -- Sagittal Depth (Pic)

1) Ballasted (prism or peri-)

2) Thin zones

What are the 2 major front-surface strategies for toric lens stabilization?

true

True or False:

The strategy for toric lens stabilization varies by company

front surface toricity

The back surface toricity of a SCL is often added to the ______

change stabilization strategy (company)

When a toric SCL is NOT working for a patient d/t stabilization issues, the best strategy is usually to do what?

-Watermelon Seed effect

-Weight (minimal)

-Center of gravity downward

How are prism-ballast lenses stabilized?

-Lower inferior Dk/t

-Lower lid discomfort

-Vertical prism will be unequal in a unilateral fit

What are the disadvantages of prism-ballast lenses?

-Watermelon Seed effect

-Weight (minimal)

-Center of gravity downward

How are peri-ballast lenses stabilized?

A minus carrier is used over the entire lens, the lens is then thinned superiorly

How do peri-ballast lenses work?

No

Is there any optic zone prism in a peri-ballast lens?

Blink stabilized, watermelon seed principle for both lids

How do dual slab off Toric SCLs work?

Stable in tilted head position such as laying down

What is the dual slab off "claim to fame"?

ATR

The thickness in dual slab off SCLs strategy is similar to an (ATR/WTR) lens

-truncation (not common)

-superior only lenticular, lid-attached

What are the OTHER not-yet marketed stabilization strategies for SCLs?

-cut off inferior edge of the lens

-the lens will line up with the lower lid

What is truncation strategy?

Often uncomfortable d/t increased innervation of the lower lid

What are the disadvantages of the truncation strategy?

-Superior only lenticular with additional 4 & 8 o'clock thick zones

-Movement of the lens is controlled by upper eyelid attachment

Describe a lid attached toric SCL fit strategy

must insert the CLs in the proper orientation

What is a disadvantage of a lid attached toric SCL fit?

Toric Lens Anatomy -- Axis Markings (Pic)

Toric Lens Anatomy -- Axis Markings (Pic)

-Poor VA with spherical soft lens

-RGPs difficult to fit or not tolerated (ATR astig or discomort)

-Higher sphere vs cyl

Who are the ideal Toric SCL Candidates?

-Cylinder greater than sphere power

-Oblique cylinders

What patients may be PROBLEMATIC for Toric SCLs fitting?

spherical SCLs

Selection and examination of Toric SCL is similar to ______

Yes

Should you consider the consistency of refractive and corneal cylinder when fitting toric SCLs?

No

Does corneal toricity always equal refractive astigmatism?

1) Select a toric soft CLs (Disposable, commonly fitted, custom)

2) Assess fit and vision

3) Troubleshooting

What are the steps to Toric SCL Fitting?

-Rx needed after vertexing each meridian separately

-Evaluate corneal sagittal depth (choose deeper or shallower lens when needed)

-Dc/Axis selection

-Lid configurations

What are the considerations to keep in mind when fitting a Toric SCL?

-0.75, -1.25, -1.75, -2.25, sometimes -2.75

What are the disposable, commonly fitted cyl power options that are usually available?

lower

If the exact cylinder power is NOT available for a Toric SCL, you should usually select the (lower/higher) cyl power

Check sph on over-refraction to maintain SE

If you choose the lower cyl power when fitting Toric SCL, what do you need to do?

true

True or False:

Some practitioners fit symptomatic -0.50DC into a -0.75 Toric SCL

Yes

Can you make a custom toric SCL with any cylinder power?

10

Commonly fitted cyl axis options for disposable toric SCLs were available in every ____º

Yes

Are custom toric SCLs available in every axis?

Chose the closest or bias towards 90º or 180º

If the exact axis you want is not available for a toric SCL, what should you chose instead?

-170º, 180º

-Likely chose the 180º axis

If you need a 175º lens, what are the options for axis you can choose? What is the best option?

-130º, 140º

-Chose 140º axis

If you need a 135º lens, what are the options for axis you can choose? What is the best option?

-050, 040

-Chose 050º axis

If you need a 045º lens, what are the options for axis you can choose? What is the best option?

a trial with the same desired cyl power and axis BUT the closest sphere power

If the desired lens you need is available but missing from your trial lens inventory, you should select what?

True -- this is why it is OK to chose the closest sphere power if the one you want is not available

True or False:

A toric SCL with a different sphere will still have the same meridional thickness differences that impact rotation as the desired lens

true -- this is why it is OK to chose the closest sphere power if the one you want is not available

True or False:

You can assess rotation and order trials with the correct sphere and any rotation correction applied

Yes

Does lid interaction impact a toric SCL fit?

-May interact with a ballasted lens

-Try a SCL with thin zones

When the lower eyelid is ABOVE the limbus, how may this interact with a toric SCL fit?

-Upper lid will encounter thick regions differently

-May require troubleshooting to find the best design

If a patient has a slanted upper eyelid (temporal or nasal), how may this interact with a toric SCL fit?

Prism ballasted

What type of SCL will have prism within the optical zone?

Apply lens with toric markings at the desired position. This is at 6:00 oclock for most lenses.

You should apply a toric SCL at the desired position? What is the desired position?

Yes

Should you teach your patients to insert their toric CLs at the 6:00 oclock position?

10-15

You should allow toric SCLs to settle for ______ minutes

-Centration

-Coverage

-Movement

-Orientation

-Compensate for rotation, as needed

-Over-refraction

How to assess fit of a toric SCL?

true

True or False:

You should assess centration, coverage, and movement with a blink in a toric SCL. This is all the same as a spherical SCL.

-Stability

-Rotation

What should you measure regarding the orientation of Toric SCLs?

True

True or False:

You need to measure the exact amount of rotation of a toric SCL

stability

Push up movement should be used to assess ________ of a toric SCL

-Lens should move with push up like spherical lens

-You can also push up and rotate slightly to see how quickly it returns to resting orientation

Describe the push up test for toric SCL

-Evaluate rotation by comparing the laser marking to expected position (6 oclock usually)

-Measure the rotation in degrees

How to properly assess the rotation of a toric SCL?