Toric IOLs and cataract surgery - patient selection, advantages, limitations, complications, management

1. TORIC IOL’S
and
CATARACT SURGERY
Dr Brad Townend
BSc(Med), MBBS, MPH, MMed, FRANZCO
Gosford and Wyong Eye Surgery

2. Toric IOL
Correction of corneal
astigmatism

4. Conoid of Sturm

6. Q1: Astigmatism is:
A What you have when you don’t have a
stigma
B Uncorrectable with glasses or intraocular
lenses
C Able to be ignored in intraocular lens
selection
D A difference in the curvature and therefore
focusing power of the cornea at 90 degree
axes

10. WHY ARE TORICS GOOD?
• Usually result in low residual astigmatism
• Higher visual outcome demands from patients
• Toric IOL’s are superior and more predictable in
reducing corneal astigmatism than limbal relaxing
incisions (Mingo-Boton et al, JCRS 2010)

11. TORIC LIMITATIONS
• Neutralise corneal astigmatism in the plane of
the Effective Lens Position (ELP)
 Higher order aberrations (Hayashi et al, JCRS 2012)
• Time consuming
• Reliability of outcomes

12. THRESHOLD FOR USE
• 1.5 Dioptres of corneal astigmatism

13. WHY LESS THAN
PERFECT?
Not an exact science

14. WHY LESS THAN
PERFECT?
Limited range of lens powers

15. WHY LESS THAN
PERFECT?
Approximation of final anterior
chamber depth

16. WHY LESS THAN
PERFECT?
Keratometry axis variable

20. WHY LESS THAN
PERFECT?
MARKING
– Patient’s head not straight
– Big and blotchy pen tips
– Markings wash away!
– Parallax error

21. WHY LESS THAN
PERFECT?
Surgically Induced Astigmatism variable
– Size of keratome blade
– Superior vs Temporal incision location
– Anterior vs Posterior wound

22. WHY LESS THAN
PERFECT?
• Lens rotation in bag post-operatively
– Worse with long axial length (Shah et al)
– Most occurs in first week
– ? Intra-operative re-positioning
– <10 rotation  <0.5D change (generally)
• Lens skewed in bag
• Lens not centred in bag

23. WHY LESS THAN
PERFECT?
• Irregular capsulorhexis size or shape can mean
final effective lens position is not as predicted
 unpredicted anti-astigmatic effect
• Anterior chamber depth consideration critical
to accuracy of toric outcome

24. WHY LESS THAN
PERFECT?
No consideration of
posterior corneal surface

25. WHY LESS THAN
PERFECT?
Cascade of potential error

26. Q2: Which of the following is NOT a
limiting factor in toric lens surgery
A Approximation of final anterior
chamber depth
B Keratometry axis variability
C Surgical wound induced astigmatism
D The availability of Tim Tams in the tea
room of the Day Surgery

27. Improving Toric
Outcomes
• Counsel patients appropriately
• Plate haptic lenses offer better
capsule stability and less rotation
post-operatively

28. Improving Toric
Outcomes
• Use a formula that utilises ACD
– E.g. Haigis or Holladay2
• Await technology and mathematics that will
allow assessment and utilisation of posterior
corneal surface in lens power and axis
estimates

29. Improving Toric
Outcomes
• Manage paralax error
– ASICO electronic toric marker
• Built-in protractor

30. Improving Toric
Outcomes
• Surgically Induced Astigmatism (SIA)
– Mark wound location with toric marker
– Use consistent keratome size
– Concentrate on making a consistent ant-post
position of your wound
– Perform a good surgical audit to calculate your SIA
• Key contributor to toric outcome (W Hill, JCRS, 2008)

31. Improving Toric
Outcomes
• Toric lenses are being used more frequently
• Potential to improve patient outcomes
significantly
• Understand their limitations and use initiative
to minimise these

32. Q3: Toric IOL’s:
A Take less surgical time than standard
spherical IOL’s
B Require less pre-operative planning than
standard spherical IOL’s
C Require less pre-operative discussion with
patients than standard spherical IOL’s
D Minimise but rarely completely eliminate
the effect of corneal astigmatism