Brief and salient points about Toric intraocular lenses

2.  Modern cataract surgery is more of refractive
surgery.
 Myopia & hypermetropia can be corrected using
appropriate spherical powers of IOL’s.
 However approximately 20% of patients who
undergo cataract surgery have 1.25D of corneal
astigmatism or more.
 It can be corrected with Toric IOL’s.

3.  Other options for correction of co-existent
cataract and astigmatism
 LRI during cataract surgery( upredictable results)
 Laser procedures postoperatively (are associated with
new set of complications).

4.  First introduced by Shimizu et al in 1994.
 It was nonfoldable 3 piece toric IOL made from
PMMA.
 It had oval optic with loop haptics ,available in
cylinder power 2-3 D.
 Postoperatively 20% IOL’s rotated > 30 degrees and
50% IOL rotated about 10 degrees.

6. Model of Acrysof IQ Toric
Model Cylinder power at IOL
plane(D)
Cylinder Power at
corneal plane(D)
SN60AT3 1.50 1.03
SN60AT4 2.25 1.55
SN60AT5 3.00 2.06
SN60AT6 3.75 2.57
SN60AT7 4.50 3.08
SN60AT8 5.25 3.60
SN60AT9 6.00 4.11
Spherical powers available are 16- 25 D.

7. Factor Affecting Rotation of Toric IOL
(1) IOL material
Hydrophobic Acrylic < Hydrophilic Acrylic < PMMA < Silicon
(2) Overall IOL diameter - Larger diameter prevents rotation .
Toric IOL’s are available nowadays in 11-13 mm overall
diameter.
(3) Haptic design –
Initial concept
- Loop haptics prevent early rotation .
- Plate haptics prevent late rotation.
Recent concept – No difference in incidence of post operative
rotation between plate and loop haptics provided material of
both loop and plate is same.

8. Patient selection
 Regular corneal astigmatism > 1.5 D
 Vision compromising cataract
 Patient wants spectacle independence

9. Facts
 20% of patients with cataract have astigmatism
>1.25 D
 Every incision on cornea induces additonal
astigmatism (SIA).
 Implantation of monofocal lens will require
distance and near correction both in these cases.
 B/L Toric IOL’s give high level of spectacle
independence(97%).
 Requirement of near correction can be overcome by
multifocal toric IOL(AcriLisa multifocal toric IOL)

10. Toric IOL power calculation :
 Precise keratometry
 Surgically induced astgmatism [SIA].

11. Keratometry
 Can be done with
 Manual keratometer
 Automated keratometer with steps of 0.12 only
 Corneal topography
 K readings from all the three show high repeatability
and are comparable.
 Manual keratometer should be calibrated regularly.

12.  Corneal topography is required in case of unusual
reading & poor quality mires.
 Precautions
 Reading must be quick to avoid drying of cornea.
 Don’t rub on the cornea.
 Centration must be proper.

13. Surgically Induced Astigmatism
 Every incision changes the cornea.
 Closer to the centre & larger the incision more
effect on corneal curvature.
 Other factors affecting it are preoprative corneal
astigmatism, suture use and patient’s age.
 In addition there is variability from patient to
patient.
 Overall effect can be summed up with vector
analysis.

14. SIA Calculation
 Obtain SIA calculator
 Fill it for 20-30 cases minimum
 Be precise about axis and incision
 Calculator auto calculates SIA

15. AcrySof Toric IOL Calculator
Data input
 Patient data
 Keratometry
 IOL spherical
power
 Surgically induced
astigmatism
 Incision location
15

16. Output screen
 Recommended IOL
model and spherical
equivalent power
 Optimal axis
placement
 Magnitude and axis
of anticipated
residual astigmatism
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17. Marking of Eye
Instruments
• Bubble marker
• Gravity marker

18. STEPS
A) Reference marking
- Done prior to surgery with patient upright
- Two reference markers placed at limbus 180 degree apart
- Used to align marking instuments for placement of axis
marks
B) Axis marking : Using reference marks as a guide the
patient eye is marked accurately at two positions 180
degree apart
TIPS:-
- Dry the conjunctiva with a swab
- Enhance marking at 3-9 o clock
- Apply mark with twisting action
- It lasts throughout surgery

19. Surgery
• Standard phacoemulsification
• Incision size 1.5 – 3.4 mm
• Well centered rhexis with diameter 5- 5.5 mm with 360
degrees overlap of IOL margin
• Marks on IOL indicate flat meridian or plus cylinder axis of
toric IOL
• Cohesive viscoelastics are preferred.

20. • IOL alignment
 Tap (“nudge”) IOL down into capsular bag to seat
lens onto the posterior capsule.
Gross alignment
OVD removal
Final alignment
If overshoots

21.  If any compromise of zonular integrity or capsule
occurs please switch to standard non toric IOL
Postoperative axis alignment :
 Slit Lamp with dilated pupil
 Wavefront aberrometry in undilated pupil
 Realignment should be done in < 2 wks

22. Complications
 Rotational stability is critical
to effectiveness of toric IOLs.
 1° rotation results in 3.3 %
IOL power loss
 30° rotation negates
cylindrical correction of toric
IOL
 Further rotation induces more
astigmatism
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23. Conclusion
 Bilateral toric IOL implantation shows high
percentage of spectacle independence for
distance vision.