3. TORIC INTRAOCULAR LENSES
• First – Shimizu et al in 1994 , non-foldable 3
piece toric iol made from PMMA with oval
optic and loop haptics.
• Postoperative rotational stability of toric iol
also depends on the iol material and iol
design.
4. IOL MATERIAL
• IOL biomaterial is of great influence on the
postoperative rotation.
• STAAR toric IOL and the MicroSil toric IOL
were made from silicone material and showed
relatively high postoperative misalignment
rates.
• Currently available toric IOLs are usually made
of acrylic material.
5. • After implantation of the toric IOL in the
capsular bag, the anterior and posterior
capsules fuse with the IOL which prevents IOL
rotation.
• Hydrophobic acrylic IOLs showed the highest
adhesive properties, followed by hydrophilic
acrylic IOL, PMMA IOLs and finally silicone IOLs.
6. IOL DESIGN
• The overall IOL diameter has been shown to be a
major factor in the prevention of IOL rotation.
• Chang compared two different sizes of the same
toric IOL: the STAAR model with a diameter of
10.8 mm and the STAAR model with a diameter
of 11.2 mm. The longer STAAR model was found
to have a much better rotational stability
compared to the shorter STAAR model.
7. • Currently available toric IOLs however have a
total IOL diameter ranging from 11.0 mm to
13.0 mm.
• Regarding the IOL haptics design, two
different IOL designs are available: plate
haptic IOLs and loop haptic IOLs.
8. • Buckhurst et al. hypothesize that loop haptic
IOLs have a better early rotational stability
compared to plate haptic IOLs due to the
longer haptics and consequently more contact
between haptics and capsular bag.
9. • Prinz et al. recently compared plate-haptic
and loop-haptic acrylic IOLs and did not find a
significant difference in rotation.
• This indicates that for acrylic IOLs, plate and
loop haptics demonstrate equally good
rotational stability.
10.
11.
12. SUCCESSFUL OUTCOME
• Good patient selection
• Preoperative workup
• IOL calculation
• Good surgery with centered IOL.
13. PATIENT SELECTION FOR TORIC IOL
• Ideal patient – with regular corneal
astigmatism between 1 to 3D.
• Toric IOLS have been successfully implanted in
cases with post keratoplasty astigmatism after
complete suture removal.
14. RELATIVE EXCLUSION CRITERIA
• Irregular astigmatism
• Post refractive surgery
• Corneal dystrophies
• Corneal edema
• Problems encountered during surgery
(including pupil damage, posterior capsule
integrity , vitreous loss ,poor iol centration
and discovery of zonular instability)
16. KERATOMETRY
• Various methods of keratometry: IOLMaster
automated keratometry, manual keratometry,
autokeratorefractometry, corneal topography,
or a combination of these techniques.
• Keratometry measurements obtained by
automated keratometry, manual keratometry
and corneal topography have been shown to
have a high repeatability and are generally
well comparable between Devices.
17. SURGICALLY INDUCED ASTIGMATISM
• Surgeon specific criteria
• Total astigmatism should include the SIA.
• SIA may be calculated with the help of online
calculators (www.doctor-hill.com)
18. BIOMETRY
1. Axial length measurement should ideally be done
with IOL master or lenstar however immersion
scan may also be used
2. Only corneal astigmatism should be used for IOL
calculation.
3. Various companies providing toric IOLs have their
online IOL calculators which calculate power
according to surgeons comfort and also suggest
the steepest axis for incision making thereby
giving least residual astigmatism.
19. MARKING TECHNIQUE
• Accurate marking of the alignment axis should
be performed with the patient in an upright
position in order to prevent cyclotorision in the
supine position.
• Firstly the horizontal axis is marked
preoperatively at the slit lamp with the coaxial
thin slit turned to 0-180 degrees. Marking is
done with either sterile ink or a needle or a
bubble marker.
21. • Intraoperatively, the preoperative horizontal
marks are used to position an angular
graduation instrument. The actual alignment
axis is marked using a toric axis marker.
23. NEWER TECHNIQUES
• Newer techniques have become available for
intraoperative toric IOL alignmen :-
1. Iris finger printing technique
2. Intraoperative wavefront aberrometry
3. Real time eye tracking
24. SURGERY
• Phacoemulsification technique with 1.5 to 3.4
mm limbal incision depending on the toric iol.
• A well centered capsulorrhexis with 360
degree overlap of the IOL optics should be
achieved.
• After the phacoemulsification is completed
and the foldable toric IOL is inserted through
the limbal incision.
25. ALLIGNMENT OF TORIC IOL
• First, gross alignment is achieved by rotating
the IOL while it is unfolding, until
approximately 20 to 30 degrees short of the
desired position.
• Final alignment of the toric iol is done after
the removal of the viscoelastic substance.
26. • In the event of a complication during surgery
which may affect the stability of the toric IOL,
such as zonular damage, vitreous loss,
capsulorrhexis tear, or capsular rupture,
conversion to a standard non-toric IOL may be
required.
27. POST OPERATIVE AXIS MEASUREMENT
• Clinically – using a slit lamp with a rotating slit.
Since the IOL marks are located at the
periphery , full mydriasis is required.
• Objective method – wave front aberrometry
combined with corneal topography.
28. DISADVANTAGES OF TORIC IOLs
• Improper alignment or rotation of the iol after
surgery may result in more residual
astigmatism than predicted.
• For every 1 degree the toric iol axis is off from
the true postoperative axis of astigmatism,
there will be a 3.3% loss of toric correction.
• Astigmatism more than 4D at corneal plane
still remains dificult to correct with toric iol.
