IOL STUDY

IOLs with rigid unbending haptics are likely to have the most predictable effective lens position and postoperative refraction, according to Albert Galand MD, PhD, Liege, Belgium.

In a study presented at the 26th International Congress of German Ophthalmic Surgeons in Nurnberg this year, Dr Galand reviewed the refractive results achieved with three different types of IOLs. His findings showed that the refractive results fell within a tighter range in eyes with IOLs with rigid closed-loop haptics than in eyes with IOLs with conventional C-loop haptics.

Dr Galand, former head of the Ophthalmology Department at the Hospital of the Université de Liege, Belgium, noted that the effective lens position is the key determinant of the refractive result in eyes that have undergone implantation of an IOL.

However, the effective lens position can be inconsistent from patient to patient when the lens is in the capsular bag. That is because the implanted lens is much smaller than the natural crystalline lens it replaces and because capsular fibrosis and contraction can cause the haptic to bend in such a way as to push the optic forward or backward.

“If the haptic is very soft in the anterior- posterior direction, the optic position, vis-à-vis the equator location, will be rather varying, particularly when the capsule has fibrosed,” he said.

There were three groups of 30 patients in the study. Each group received one of three IOL models, namely, the AcrySof ® SA60AT (Alcon), the Tecnis® ZCB00 (AMO), and the SAV-MultiLink (Swiss Advanced Vision). The AcrySof and Tecnis IOLs are composed of a hydrophobic material and have conventional C-loop haptics. The SAV-MultiLink IOL is composed of a hydrophilic material and has rigid closed- loop haptics. All are uniplanar without vaulting. None of the IOLs in the study had a dioptric power under 20.0 D or more than 25.0 D.

Dr Galand and his associates performed IOL calculations with measurements made with the IOLMaster (Zeiss) and the SRK-T formula with an A-constant 118.6.

One year postoperatively, the spherical equivalent refraction prediction errors, as measured by the Nidek refractometer,  ranged -0.65 D to +1.5 D in the AcrySof group, from -0.6 D to +2.20 D in the Tecnis group and from -1.75 D to -0.05 D in the SAV-MultiLink group. Therefore, the dispersal of prediction errors was 2.15 D and 2.80 D respectively, in the AcrySof and Tecnis group, compared to only 1.70 D in the SAV-MultiLink group

He noted that the difference in dispersal values did not reach statistical significance and should therefore be regarded as a trend.