Synchrony dual optic accommodating lens
Presbyopia still remains the last frontier of refractive surgery.
Its surgical management is under constant evolution due to the limitations that exist today with respect to its management, which is probably in relation with the multifactorial basis in which presbyopia is clinically developed in the human.
Helmholtz (1856) proved that accommodation is accomplished by the change of the power of the crystalline lens associated with the active action of the ciliary body.
It is the difference in refractive power of the eye in the two states of complete relaxation and maximal accommodation.
Almost all surgical techniques that have been proposed to date for the surgical correction of presbyopia are based on the acquirement of pseudoaccommodation .
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 .
The elasticity of the capsule is held in check by the normal tension in the zonule so that accommodation consists in the relaxation of the tension in the zonule by the contraction of the ciliary muscle.
This permits the capsule to mold the lens into a more strongly curved system (Table 1).
It can restore near distance vision by different mechanisms: The theory of accommodation is largely based on Helmholz's ideas: the capsule has sufficient elasticity to mold the lens into a more strongly curved system than what is necessary for distance vision.
However, none of them could achieve a complete restoration of accommodation, and multifocal lenses are frequently associated to visual symptoms that may decrease patient satisfaction.
Therefore, presbyopic surgery is one of the most difficult targets that a refractive surgeon will have to deal with today and in the immediate years.
Current non-surgical treatment options include reading spectacles (either mono or varifocal) and contact lenses (either multifocal or monofocal for monovision), but many of these patients, spectacle independent previously, do not easily accept this unavoidable age-related life style change.
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.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.