Dual optic accommodating lens
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Presbyopia still remains the last frontier of refractive surgery.Pseudoaccommodation comprises a group of techniques that can improve near vision on the basis of the use of the cornea or intraocular lenses (IOLs), resulting in an increased depth of field, multifocality or both .Some of these techniques are based on the adequate performance of the ciliary body using part of the physiological accommodative mechanism, but a surgery for the “real” restoration of accommodation has not yet arrived for clinical practice.This fact made these lenses to be almost abandoned in the last few years, but there are currently other AIOL models being used with innovative mechanisms of action and different anatomical support outside the capsular bag that offer encouraging preliminary results that could bring a new potential of application to these types of lenses.In this article, we will update the modern refractive surgeon about the fundamentals and provide updated information about the outcomes of AIOLs by reviewing the concept of accommodation, the different attempts that have been accomplished in the past, their demonstrated published results in human clinical trials, and the future alternatives that may arrive in the near future.When the ciliary muscle constricts, it redistributes its mass like any other muscle and encroaches on the vitreous cavity space, increasing the vitreous cavity pressure, moving the optic forward.
Approximately, 1 mm of movement is equivalent to almost a 2 D power change.
These lenses are known as “positional pseudoaccommodative IOLs”, and their visual results in terms of providing partial or total near visual acuity restoration in the long term have been disappointing.
The aim of this report is to provide an update and a general overview for the anterior segment ophthalmologist regarding the current state of the art AIOLs that have already been the subject of human clinical trials with evidence available by peer reviewed scientific publications.
The aim of this review article is to provide the modern refractive surgeon with updated information about this topic, review the concept of pseudophakic accommodation as well as different attempts that have been made in the past to achieve a real restoration of accommodation via the use of intraocular lenses as evidenced in human clinical trials, and finally, consider future alternatives that may present themselves in the near future.
The change in the refractive power of the eye, when the image of a near object is brought into focus on the retina, is defined as accommodation; such a process must involve an increase in the dioptric power of the system [ It is the difference in refractive power of the eye in the two states of complete relaxation and maximal accommodation.
While corneal procedures for presbyopia are still under a serious debate regarding their long term outcomes and success rate, current surgical options mostly include refractive lens exchange by either monofocal IOLs for monovision or multifocal IOLs.