Transcript INFLUENCE OF A CAPSULAR TENSION RING ON THE OCULAR

INFLUENCE OF A CAPSULAR TENSION
RING ON THE OCULAR ABERRATIONS
AFTER CATARACT SURGERY:
A COMPARATIVE STUDY
Charlotte ROHART1, Gilles Chaine1, Damien GATINEL2
1Hôpital
Avicenne, Bobigny, France
2Fondation ophtalmologique A. de Rothschild, Paris, France
Chicago - ASCRS 2008
PURPOSE
• To evaluate the effect of a capsular tension
ring (CTR) on ocular tilt and high-order
aberrations (HOA) in patients who underwent
cataract surgery
NO FINANCIAL INTEREST
Patients and methods
• Prospective randomized controlateral eye study
• Informed consent was obtained from all patients
• Inclusion criteria : patients had to be atleast 50 years
with a diagnosis of cataract in both eyes that was
nontraumatic origin and a difference of less than 2D
of predicted IOL power between both eyes
SURGERY
• 40 eyes of 20 patients who underwent bilateral cataract
surgery were divided into 2 groups :
Eyes that received the CTR
and an intraocular lens (IOL) =
CTR group = 20 eyes
+
• CTR = Flexi Ring (Zeiss-Ioltech)
• IOL = Acrysof MA60AC (Alcon)
• One surgeon (DG)
Fellow eye that did not
receive a CTR but IOL only
= IOL group = 20 eyes
Wavefront acquisition and analysis
• Total optical aberrations were measured
using the NIDEK OPD-SCAN at least one
month after cataract surgery for a 6 mm
pupil diameter after pharmaceutical
dilatation out to the sixth Zernike order
• Ocular aberrations were analyzed to
determine if there was a statistically
significant difference between groups using
the Student t-test
• A p < 0.05 was considered stastically
significant
RESULTS
•
•
•
•
40 eyes of 20 patients
No intraoperative complications
Mean age : 67.9 ± 11.1 years (54-82)
No stastically difference between groups in
mean BCVA, spherical equivalent, corneal
curvature and IOL power
OCULAR ABERRATIONS
•
There was stastistical significant difference (p<0.05)
in tilt (p=0.009) and coma aberrations (p=0.03)
CTR group > IOL group

In CTR group the RMS for tilt and coma were 1.02 and
0.42 µm respectively.

In IOL group, the RMS for tilt and coma were 0.59 et
0.29 µm respectively.
RMS wavefront error for total aberration, tilt, total
high-order, coma, trefoil, tetrafoil, spherical and
secondary astigmatism
2.5
p = 0.39
2
CTR group
1.5
p=0.009
RMS
1
IOL group
p=0.11
p=0.03 p=0.14 p=0.10 p=0.49
0.5
p=0.09
0
Total
Tilt
H-O
Coma Trefoil
Aberration
T4foil
Sph
Astig II
DISCUSSION
• In the current study, we found that there were
greater tilt and coma-like aberrations in eyes with a
CTR than eyes without a CTR (p<0.05)
• Although the corneal high order aberrations were
not measured we are believe the source of the
difference between groups is a internal origin as
there was minimal trauma cornea during surgery
• The CTR maintains the capsular bag’s contours and
improves anatomic IOL centration1
• The CTR may increase the anatomic IOL centration in
capsular bag but this does not translate into better
optical IOL centration, as coma and tilt were
significantly lower in eyes without CTR
• This suggests that optimal anatomic IOL centration does
not correspond to optimal IOL position and subsequent
visual quality
• From this observation, we believe the landmark or
reference for optimal IOL centration to achieve better
visual quality remains to be determined
• Ideally, the optimal optical IOL centration could be
characterized by the position that minimizes the total ocular
coma
• In this situation, the coma aberrations of the cornea would be
compensated by those induced an adequately positionned
IOL
• Tabernero found that horizontal coma compensation was
significantly larger in hyperopic eyes where angle Kappa tends
to be larger2
• Our results are consistent with these findings in which the
compensation for horizontal coma tends to increase with the
relative decentration of corneal and internal optics
CONCLUSION
• We found that improving the anatomical centration
and reducing the tilt of an IOL using a CTR does not
improve the optical quality of the pseudophakic eye
• This is likely an issue that will need to be adressed for
the design of new IOLs aimed at balancing the coma
induced by the cornea and due to global ocular tilt
References
1.
Hara T, Hara T, Yamada Y. « Equator ring » for maintenance of the completely circular contour of the capsular bag equator after
cataract removal. Ophthalmic Surg 1991; 22:358-359
2. Tabernero J, Benito A, Alcon E, Artal P. Mechanism of compensation of aberrations in the human eye. J Opt Soc Am A Opt Image
Sci Vis 2007; 24:3274-83