Examination of Rayner T-flex Toric Intra-Ocular Lens for Spherical and Astigmatic Correction, and Rotational Stability

Background During cataract surgery, an intraocular lens is implanted in the bag. A monofocal lens allows spherical correction only. 15% to 29% of patients with cataracts have more than 1.50 diopters of astigmatism according to current estimations.1 Astigmatic correction can be performed during cataract surgery: the main clear corneal incision can be done at the steep axis, limbal relaxing incisions (LRI) or by opposite clear corneal incision (OCCI) can be performed. These techniques are not fully predictable and stable over time.2 Optimal corneal astigmatic correction can be done by implantation of a toric intra-ocular lens(IOL), with predictable and stable results over time. The toric IOL must be positioned in the correct axis. Rotation of the lens will reduce the astigmatic correction. Approximately one degree of off-axis rotation results in a loss of up to 3.3% of the cylinder power. 3 It is crucial for the intraocular lens to keep its correct axis for optimal astigmatic correction.

A number of toric intraocular lens are approved for implantation such as - Acrysof toric (Alcon), Tecnis toric IOL (Abbott medical), STAAR toric IOL (STAAR surgical company). This study will examine T-flex (Rayner) IOL. The rotational and refractive stability of this IOL has been tested on a relatively small number of patients. 4, 5

Objective Examination of Rayner T-flex Toric IOLs (573T and 623T; Rayner Intraocular Lenses Ltd,East Sussex, United Kingdom) for spherical and astigmatic correction, and rotational stability.

Methods Prospective study on 50 eyes. Patients will be recruited during examination in pre-operative clinic. This examinations include visual acuity, slit-lamp biomicroscopy, applanation tonometry, fundus examination after instillation of tropicamide 0.5% and phenylephrine 10%, IOL calculation with IOLMaster(Zeiss), which also measures corneal astigmatism. After acquiring informed consent, further examinations will be done including corneal topography with Galilei Dual Scheimpflug Analyzer ( Zeimer Ophthalmology), and Tomey keratometer, auto-refractometry and subjective refraction.

Since corneal astigmatism is often binocular, patients with second eye corneal astigmatism, will be offered a toric IOL, even if unsuitable for inclusion in this study. All operations will be done by a senior surgeon, experienced in toric IOL implantations. Rayner T-flex Toric IOLs (573T / 623T; Rayner Intraocular Lenses Ltd,East Sussex, United Kingdom) will be implanted. IOL calculation will be done using Ranyer's online calculator (WWW.TORICIOL.RAYNER.COM).