It includes soft Toric stabilization technique, toric contact lens fitting.

1. SOFT TORIC CONTACT
LENS
-ADITI VORA

2. ASTIGMATISM
• Astigmatism is a refractive condition in
which a point object is not rendered as
a point image by an optical system
instead parallel rays comes to focus in
2 focal lines rather then a single focal
point.

3. CLASSIFICATION & TYPES
• Simple Hyperopic astigmatism
• Compound Hyperopic astigmatism
• Simple Myopic astigmatism
• Compound Myopic astigmatism
• Mixed astigmatism

4. CLASSIFICATION BY STRUCTURE
• Corneal astigmatism
• Lenticular astigmatism
• Internal astigmatism
• Total astigmatism

5. CLASSIFICATION BY THE TYPE
• Regular astigmatism
• Irregular astigmatism
Classification by Orientation
• With-the-rule
• Against-the-rule
• Oblique

6. WHAT IS TORIC LENS ?
• Toric lens is a lens used to correct Astigmatism or
Cylindrical number as it contains cylindrical component
which standard soft contact lenses do not have.
SPHERICALLENS TORIC LENS

7. DESIGNS & METHODS OF STABILIZATION OF
TORIC SCL
1. The Watermelon seed principle
• If a fresh seed of (watermelon) is squeezed between the thumb
and forefinger it is rapidly expelled from the convergent (v-
shaped) space between the fingers. Expulsion is a direct result of
one of the two force of vectors of the pressure applied by each
finger to the seed’s tapered surface. One vector attempts to
compress the seed, the other attempts to expel the seed.
• Expulsion is facilitated by the ‘slippery’ moist surface of the seed.
The contact lens analogy to the watermelon seed is the tapered
lens edge, especially the taper created by either prism ballast or
double slab-off design.

8. PRISM BALLAST
• In its simplest form this lens design incorporates a base down
prism and relies on lid forces (mainly upper lid forces) acting on
the thickness differences induced by the base down prism
(thickness taper) to orient the lens on the eye.
• The thinner portion of the lens locates under the upper eyelid,
which then squeezes the thicker portion of the lens towards the
lower lid (the watermelon seed principle).
• Gravity has been shown not to play a part in the axis location.
• Base down prism of 1 to 1.5 prism diopters is used. This increases
the thickness of the less inferiorly therefore less oxygen is
transmitted through the inferior side of the lens and also lead to a
decrease in comfort, especially against the lower lid.

9. DYNAMIC STABILIZATION OR DOUBLE
SLAB-OFF
• This technique also relies on the interaction between lids and
the lens to achieve stabilization. Both eyelids play an active
role unlike with prism-stabilized designs that involve
interaction primarily from the upper lid.
• Stabilization is achieved by designing thin zone superior and
inferior to the optic zone.
• The interaction of thin zones with the lids especially with the
upper lid position and stabilizes the lens on the eye and gave
rise to the term dynamic stabilization.

10. REVERSE PRISM
• This design is an evolutionary and logical follow-on form true
prism ballast designs. Because of the lens thickness inherent in
the incorporation of prism, and the resultant need to chamfer
(base up) interests of comfort, it was logical to incorporate
both prism (base down) and the inferior chamfer (base up) into
an integrated design, which should be both thinner and more
comfortable.

11. PERI-BALLAST
• This technique starts with a minus carrier design.
• To create a prism base down effect, the superior carrier is
slabbed-off or chamfered superiorly to reduce its thickness and
influence.
• This process allows the lens periphery to position comfortably
under the lids.

12. TRUNCATION
• Truncating the lens by removing part of the lower portion of
the prism-ballasted lens is generally no longer carried out. It is
not considered a current technique but can be employed as a
last resort.

14. FITTING TORIC SOFT CONTACT LENSES
• Three fitting techniques:
• Diagnostic
• Trial
• Empirical

15. TORIC SCL MEASUREMENT OF LENS ROTATION
Rotation is measured by laser marks which are at 3,6 and 9
o’clock positions
Rotation can be measured by :-
Narrow Slit – Lamp Beam
Protractor Scale on the eye piece of K
Spectacle Trial Frame
Rotation is measured by laser marks which are at 3, 6 and 9
o’clock positions
Rotation can be measured by :-
Narrow Slit – Lamp Beam
Protractor Scale on the eye piece of K
Spectacle Trial Frame

16. TORIC FITTING PROCEDURE AT A GLANCE
• Step 1- Perform Refraction & write prescription in –ve cyl form.
e.g. – Spectacle prescription -3.00/-2.00 x 180.
• Step 2- Perform Keratometry Add 0.80 mm to flattest meridian
• Step 3- Perform Vertex distance Compensation for sphere & cyl
separately.
e.g. -3.00 /-1.75 x 180
• Step 4- Choose a toric trial lens (as close as to spectacle
prescription.)
• Step 5- Assess contact lens (Coverage, Centration, Movement,
Comfort) (till this stage spherical & toric fitting is same)
• Step 6- Asses Rotation (for axis finalization)-(LARS Left Add
Right Subtract)

17. TORICAXISFINALIZATION TORICAXIS
FINALIZATION
• 3 things can happen while assessing Toric lens rotation
No rotation or minimal rotation of 5 degrees
Rotation to L.H.S ( with reference to
Practitioner)
Rotation to R.H.S(Practitioner)
• THUMB RULE
LARS- Left Add Right Subtract

18. LENS ROTATION - 10°
• Rx required -3.00/-1.00 x 10
•Anticlockwise - subtract order -3.00/-1.00x180
•Clockwise - add order -3.00/-1.00x20

19. EXAMPLE 1
• Spectacle Pres. -6.00/-3.00 x180
• Vertex Dist -5.50 / -2.50 x 180
• Trial lens - -3.00 /-1.25 X 180 @ 8.6mm
• Rotation to R.H.S by 15degrees
• Subtract- 180 - 15= 165degrees
• Final lens prescription:-
• -5.50/-2.50 x165 degrees @ 8.60mm

20. EXAMPLE 2
• Spectacle Pres. -6.00/-3.00 x180
• Vertex Dist -5.50 / -2.50 x 180
• Trial lens - -3.00 /-1.25 X 180 @ 8.6mm
• Rotation to R.H.S by 15degrees
• Subtract- 180 - 15= 165degrees
• Final lens prescription:-
• -5.50/-2.50 x165 degrees @ 8.60mm

21. EXAMPLE 3
• Spectacle pres: -1.00/-3.00 x120
• Trial lens: -2.00/-0.75 x 908.30
• Rotation to R.H.S by 10
• Answer - -1.00/-2.75 x110 8.30 mm

22. TORIC SCL ASSESSMENT OF FIT
• Good fit-
Full corneal coverage,
Good centration and movement, quick return to axis if
mislocated
• Tight fit
Good centration, initially comfortable,
Little or no movement.
Slow return to axis if mislocated.
• Loose fit
Excessive movement,
Poor centration,
Uncomfortable.
Lens orientation unstable and inconsistent.

23. THINGS TO REMEMBER
• Do not make any changes in trial lens axis
• Trial lens (Diagnostic lens ) fitting is a very reliable and
scientific method of fitting Toric lenses
• Choose trial lens axis as close as possible to spectacle axis
• If trial lens axis & spectacle axis are different then do not
attempt over refraction as it can lead to confusion
• Final lens Base Curve should be same as Trial lens base
Curve
• Like the trial lens, final lens would also show similar
rotation

24. BRANDS OF TORIC LENS
• Alcon
• Bausch + Lomb
• Cooper Vision
• J&J
• Custom made soft torics are also available from companies
like Flexilens / Purecon etc .

25. SUMMARY
• BAUSCH & LOMB MASTER MIND 3 MODULE
• ICAL

26. THANK YOU