opposite edges which displace the lens along the optical axis when an inward transverse force is applied to the haptic loops at the outer ends of the struts (the components transferring the movement of the contact points to the device), and it springs back when the force is reduced. It is implanted in the eye's lens capsule, where the contractions of the ciliary body which would focus the eye with the natural lens are used to focus the implant. The intraocular lenses used in correcting astigmatism have different curvature on two orthogonal axes, as on the surface of a torus, and are called toric lenses. The STAAR Surgical Intraocular Lens was the first such lens developed in the United States and it may correct up to 3.5 diopters. A different model of toric lenses was created by Alcon and may correct up to 3 diopters of astigmatism. To achieve the most benefit from a toric lens, the surgeon must place the lens with the axes of curvature to suit the patient's astigmatism. Intraoperative wavefront analysis, can be used to assist the surgeon in toric lens placement and minimize astigmatic errors. Monofocal intraocular lenses provide accurately focused vision at one distance only: far, intermediate, or near. Patients who are fitted with these lenses may need to wear eyeglasses or contact lenses for reading or using a computer. These lenses usually have uniform spherical curvature. Cataract surgery may be performed to correct vision problems in both eyes, and in these cases, if both eyes are suitable, patients are usually advised to consider monovision. This procedure involves inserting in one eye an intraocular lens that provides near vision and in the other eye an IOL that provides distance vision. Although most patients can adjust to having implanted monofocal lenses with differing focal length, some cannot compensate and may experience blurred vision at both near and far distances. An IOL optimised for distance vision may be combined with an IOL that optimises intermediate vision instead of near vision as a variation of monovision. The first aspheric IOLs were developed in 2004. They provide better contrast sensitivity by having their periphery flatter than the middle of the lens. The effectiveness of aspheric IOLs depends on a range of conditions, and they may not always provide significant benefit. Some IOLs provide ultraviolet and high energy blue light absorbption. The natural crystalline lens of the eye filters