Rotational Stability, Decentration And Tilt Of A New Hydrophobic Acrylic Intraocular Lens Platform

The purpose of this study was to investigate the rotational stability of a new hydrophobic, monofocal, acrylic one-piece intraocular lens (IOL) with a modified, 5° angulated C-loop (Nanex NC1-SP; HOYA Surgical Optics, Chromos, Singapore).

This single-center, prospective, randomized clinical trial was performed at the Department of Ophthalmology at the Vienna General Hospital, Medical University of Vienna, Austria. 

Inclusion criteria were age-related cataract and pupil diameter >6.5mm in mydriasis. Exclusion criteria were pseudoexfoliation syndrome, uncontrolled ocular disease, preceding ocular surgery or trauma, corneal abnormalities and history of uveitis. Cataract surgery with implantation of a Nanex IOL on a randomized implantation axis was performed.  At the end of surgery (EoS), a baseline image for rotational stability evaluation was obtained and compared to retroillumination images taken at 1 hour, 1 week, 1 month and 6 months after surgery. Axis alignment was assessed using non-movable landmarks on the sclera and the optic/haptic junctions of the IOL. The main outcome was absolute rotation from EoS to 6 months postoperatively.

A total of 130 eyes of 68 patients with age-related cataract were included. A mean age of 72 ± 6.5 years and mean axial length of 23.25mm ± 0.72mm was observed. Of all included eyes, 122 eyes were available for analysis of rotational stability. Median IOL rotation of all eyes from EoS to 6 months after surgery was 1.9° [ 0.1;37.5°]. Ten eyes (9,71%) rotated more than 5°, two eyes (1.94%) more than 10°. IOL rotation did not correlate with axial eye length (Spearman’s r= -0.042, p=0.46), crystalline lens thickness (Spearman r=0.134; p=0.19) and crystalline lens equatorial diameter (Spearman r=0.101; p=0.325). IOL rotation correlated weakly but significantly with anterior fibrosis severity from 1w to 1m (Spearman r=0.321; p=0.002).

The investigated IOL Nanex presented good rotational stability. Nevertheless, anterior capsule fibrosis development led to a higher tendency of IOL rotation after 1 week. Rotational stability is dependent on various factors, including IOL overall diameter, anterior capsule fibrosis, design and surface texture of the IOL. Surprisingly, crystalline lens, capsular bag diameter and lens thickness had no impact on rotational stability. Rotation after more than 1 week after surgery is infrequent and might be explained by anterior capsule fibrosis and therewith twisted IOLs rather than rotation of the IOL.