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Stefanie Petrou-Binder MD
in Ludwigshafen

NEW toric IOLs for both aphakic and phakic eyes show less rotation and higher patient satisfaction than previous IOL designs, reported researchers at the DGII conference.
“Intraocular solutions for astigmatism are becoming more and more desirable. They do not need additional corneal manipulation and with the advent of toric IOLs with more stable fixation, lens rotation has been reduced,” said Burkhard Dick MD in a presentation on astigmatism correction.

Dr Dick and his team participated in two large multi-centre trials which investigated toric IOLs in both aphakic and phakic eyes. In a large trial studying aphakic eye implantation of toric IOLs for astigmatism correction, researchers at several large centres compared the efficacy of toric c-haptic IOLs (MS 614; HumanOptics, Germany) to toric z-haptic IOLs (MS 6116; HumanOptics).

The MS 614 is a foldable three-piece silicone IOL with c-shaped haptics and an overall diameter of 14mm, optic diameter of 6.0 or 7.0 mm, with 0° or 7° angulation.
The optic is marked by laser and refraction is -6.0 D to +31 D. The MS 6116 TU is a three-piece toric silicone IOL with a z-haptic design and an angulation of 0°. It has an overall diameter of 11.6mm, 6.0mm optic diameter, a full optic zone and sharp edges.

The anterior surface is spherical, -3.0 D to +31 D, while the posterior IOL surface is toric (cylinder 2.0 D to 12 D).
Dr Dick and his team implanted 25 patients with c-haptic lenses and another 25 with the z-haptic lenses. They monitored the patients at one day, one month, and three months postoperatively for lens rotation.

The investigators noted less than 10° of lens rotation in 68% of the c-haptic patients, while the z-haptic lenses showed less than 10° of rotation in 84% of cases. They observed greater than 10° of lens rotation in 32% of the c-haptic lenses they implanted and in 16% of the z-haptic lenses.

Although z-haptic IOLs tended to show less rotation than c-haptics, there was no statistically significant difference (p=0.07) after three months. Both IOL types fullfil the criteria for toric IOLs (> 80% with IOL rotation under 10°), Dr Dick said.
In a second recent European multicentre trial, Dr Dick investigated the efficacy of toric, phakic iris claw lenses. Eighty patients participated, of whom 61% (43 eyes) were female and 39% (27 eyes) were male. The patients were monitored at one week, four weeks, three months and six months postoperatively. The mean patient age was 35 years, ranging from 22 to 59 years.

The investigators measured k-values, objective refraction (autorefractometer), subjective refraction (spherical refraction, spherical equivalent, subjective cylindrical refraction and axis), corneal topography, and anterior chamber depth. Each value was measured three consecutive times.

A total of 66% of the patients gained up to two lines of vision by six months after surgery. The researchers reported that refraction was stable, with little fluctuation between the one week and six month stages.

There were no vision-threatening complications at the six month mark. The toric phakic IOL proved to be a stable new option with high predictability of refractive and astigmatism correction, and very high patient satisfaction.
Dr Dick explained that the overall goal was to have no postoperative astigmatism and that the percentage of postoperative astigmatism grows along with the degree of IOL displacement.

Although the type of IOL plays a decisive role, he pointed out that preoperative and intraoperative axis marking and verification was vital to the proper positioning of the IOL. The patient must sit upright and fix his gaze on a distant object while the surgeon colour or mechanically marks the conjunctiva or cornea.

In a study from the Journal of Refractive and Cataract Surgery 2000, carried out by the team at the Mainz University, two toric IOLs (Staar) with plate-haptics were investigated. These one-piece, silicone, ship-like IOLs have a 10.8mm or 11.2mm diameter, 6.0mm optic, 2.0 D or 3.5 D torus and fenestrated haptics (1.15mm).
At five months postoperatively, 35% of the C10 lenses showed more than 15° rotation. A little more than 40% of the C11 lenses implanted demonstrated a rotation of more than 15°.

Dr Dick reported that these and similarly high rotation outcomes prompted some innovative ideas, like trying to increase capsular tension with a capsular tension ring.

The ring fits through the plate-haptic IOL and lends it the right amount of tension, reduces folds and symmetrical capsule stretching and allows good IOL centration. It also promoted the search for new IOL designs to reduce rotation.

In a paper to be published in the Journal Cataract Refractive Surgery in 2003, Dr Dick shows the relationship between the capsular bag diameter and the axial length and the shrinking process which occurs as early as one to three days after surgery and continues over six months.

Other studies have also concluded that z-haptic IOLs rotate less than c-haptic IOLs implanted in the capsular bag. Sulcus implantation has been shown to be more stable than the capsular bag implantation.

Dr Dick presented an overview of several studies involving toric IOLs. Rotation was noted in 16% of z-haptic silicone lenses (Dick); 23% of three-piece c-haptic PMMA IOLs (Gerten); 32% in c-haptic silicone IOLs (Dick); 41% in three-piece c-haptic PMMA IOLs (Patel); and 67% in plate-haptic silicone IOLs (Patel).

The future will see more lens combination surgeries, light-induced adjustments of optics, and intraoperative freezing of the capsular bag, all of which will contribute to better lens fixation, lower astigmatisms and improved visual acuity.

Burkhard Dick MD
Johannes Gutenberg-University, Mainz, Germany
Email: bdick@mail.uni-mainz.de

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