Influence of frosted haptics on rotational stability of toric intraocular lenses

Abstract

We investigated the unfolding property and rotational stability of a new toric intraocular lens (IOL); TECNIS toric II (toric-II, ZCW, Johnson & Johnson) that is an improved version of TECNIS toric IOL (toric-I, ZCV). Both IOLs are based on an identical platform, except for the frosted haptics with toric-II IOL. The study consisted of two parts; experimental study and clinical, retrospective, case series. Experimental study indicated that the overall time from IOL ejection to unfolding to 11 mm was significantly shorter with toricII than toric-I IOLs (p = 0.032), due to the earlier separation of the haptics from the optic with toric-II IOL. Clinical study included 131 eyes of 99 patients who had undergone phacoemulsification and toric IOL implantation. At 3 months postoperatively, toric-II IOL showed significantly better rotational stability than toric-I IOL, including smaller residual manifest astigmatism (p = 0.018), less amount of axis misalignment from the intended axis (p = 0.04), lower incidence of misalignment > 10º (p = 0.0044), and less degree of prediction errors (p = 0.043). Postoperative uncorrected distance visual acuity tended to be better in the toric-II than in the toric-I groups, with marginal statistical difference (p = 0.057). TECNIS toric II IOL with the frosted haptics showed significantly better rotational stability than its predecessor, probably due to quicker unfolding and greater friction with the capsular bag.

Figure 1

The petri dish filled with balanced salt solution and polar grid of concentric circles with 1-mm steps placed at the bottom. The unfolding process of toric intraocular lenses after ejection from the injector was video-recorded and analyzed.

Figure 2

Elapsed time for each unfolding step of toric intraocular lenses. After the lens was ejected from the injector, the haptics started to move earlier with toric-II than with toric-I IOLs. Thereafter, the unfolding process of both toric IOLs were similar and the time course was parallel. The overall time from IOL ejection to unfolding to 11 mm was significantly longer with toric-I than with toric-II IOLs (p = 0.032).

Figure 3

Amount of residual manifest astigmatism was significantly smaller with toric-II than with toric-I IOLs (p = 0.018).

Figure 4

Amount of axis misalignment from the intended axis was significantly smaller with toric-II than with toric-I IOLs (p = 0.04).

Figure 5

Percentage of eyes with misalignment > 10° was significantly smaller with toric-II than with toric-I IOLs (p = 0.0044).

Figure 6

Double-angle plots of refractive astigmatism prediction errors evaluated with centroids, standard deviation of the centroids, and 95% confidence ellipses of the prediction errors. Prediction errors were smaller with toric-II than with toric-I IOLs. Each ring = 0.50 diopters (D).