The human eye functions to provide vision by transmitting and refracting light through a clear outer portion called the cornea, and further focusing the image by way of a lens onto the retina at the back of the eye. The quality of the focused image depends on many factors including the size, shape and length of the eye, and the shape and transparency of the cornea and lens.
When trauma, age, disease or other malady cause an individual's natural crystalline lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is often referred to as a cataract. The treatment for this condition is surgical removal of the natural crystalline lens and implantation of an intraocular lens (IOL).
While early IOLs were made from hard plastic, such as polymethylmethacrylate (PMMA), soft, foldable IOLs made from acrylate based material have become increasingly popular because of the ability to fold or roll these soft lenses and insert them through a smaller incision. Such acrylate based lenses are particularly desirable because they exhibit excellent folding and unfolding characteristics during and upon implantation within the eye. Such acrylate lenses also exhibit desired biocompatibility characteristics.
While typical procedures involve the implantation of only one lens in an eye, there are multiple situations where it is desirable to have a second or two lenses implanted. As one example, dual optic accommodative lenses have been developed to improve the focal range of IOLs. As another example, it may be desirable to, after insertion of a first IOL, implant a second IOL, referred to as piggyback lenses, to improve visual performance.
While such two lens systems can improve visual performance, recent articles have suggested that various types of these lens systems may be susceptible to the development of interlenticular opacification (ILO). Such articles include: Gayton J L, Apple D J, Peng Q, et al., Interlenticular Opacification: A Clinicopathological Correction of a New Complication of Piggyback Posterior Chamber Intraocular Lenses, J. Cataract Refract. Surg., 2000; Eleftheriadis H, Marcantonio J, et al., Interlenticular Opacification in Piggyback AcrySof Intraocular Lenses: Explantation Technique and Laboratory Investigations, Br. J. Ophthalmol. 2001, July 85(7): 830-836; and Werner L., Mamalis N., et al., Interlenticular Opacification: Dual-Optic Versus Piggyback Intraocular Lenses, J. Cataract Refract. Surg. 2006, 32: 655-661. At least one of these articles suggests that acrylate based two lens systems are susceptible to ILO formation.
In view of the above, it would be quite desirable to provide an intraocular lens, particularly a two lens system, that inhibits the formation of ILO that might otherwise occur.