Charlotte ROHART1, Gilles Chaine1, Damien GATINEL2 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 : CTR = Flexi Ring (Zeiss-Ioltech) IOL = Acrysof MA60AC (Alcon) One surgeon (DG) Eyes that received the CTR and an intraocular lens (IOL) = CTR group = 20 eyes 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

CTR group > IOL group 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.

p=0.11 p=0.10 p=0.49 p=0.09 Trefoil

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  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 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