Who are Add-On lenses for?
After cataract surgery or refractive lens surgery, a residual refractive error can remain, meaning that the refractive defect cannot be excluded completely. It is not possible to exactly predict the position of the lens in the eye, and if the lens is not perfectly in place it can cause refractive changes. For this reason, when the patient obtains stable refraction after surgery, the ophthalmologist may consider performing an operation with an Add-On lens.
In the case of LASIK surgery, a residual refractive error can also remain. These patients are also candidates for this type of surgery if it is not possible to operate on them again with laser and they have an intraocular lens implanted.
This operation is performed when there is already an artificial lens in the eye, or when surgical removal of the crystalline lens is planned. Also, if it was not already, this new lens can be multifocal to enable vision at all distances.
Add-Ons are implanted in the following cases:
- Correction of residual refraction (myopia, hypermetropia or astigmatism) after cataract or refractive lens surgery.
- Operation in one or two steps in conjunction with the implant of a multifocal lens.
- Strengthening of the capsular intraocular lens as correction of high ametropia.
- Congenital cataract in children.
Where and how are Add-On lenses implanted?
Add-On lenses are placed in the ciliary sulcus (between the iris and the capsular sac). They are made from a flexible material and can bend. For this reason, they are inserted into the eyeball through a minimal corneal incision. When they are inserted into the ciliary sulcus, they are attached securely and do not rotate. A certain distance is also maintained with the capsular sac to ensure there is no contact between the two lenses. They are compatible with all models of intraocular lenses on the market. They can be implanted in a separate procedure or after a primary procedure.
The first option involves inserting the capsular intraocular lens and the Add-On intraocular lens into the eye, during a single operation. This enables correction of high degrees of astigmatism, which could not be corrected with only one lens. If a multifocal system is desired, the intraocular lens which is situated in the capsular sac provides the refractive power for distance whilst the Add-On takes care of the refractive power for near vision, thanks to its diffractive design.
The second option is to implant the Add-On lens when the eye is already pseudophakic (the natural crystalline lens has already been removed and an intraocular lens has been inserted). This can be done at any time, even after the first operation, provided that there is refractive stability. It is an interesting option for patients who want to optimise their visual results with the most modern technology and eliminate dependency on spectacles.
In the past, filters to block blue light were not used. It has been shown that this light can be damaging to the retina. Today, Add-On lenses can be inserted with a yellow filter (which blocks this type of rays) to provide extra protection to retinal tissues.
What are the different types of Add-On lenses?
- Refractive Spherical Monofocal:Spherical monofocal lenses are designed to overcome residual refractive error after a previous intraocular lens implant. They can correct both myopia and hypermetropia. The design of this lens is spherical. They are compatible with practically all capsular intraocular lenses which may have been implanted previously, both standard and Premium.
- Toric Monofocal: Toric monofocal lenses are ideal for rectifying astigmatism which could not be corrected at the time when the intraocular lens was implanted. They can sometimes be of great help to patients who have undergone a keratoplasty (cornea transplant) which has caused residual astigmatism. Many patients with monofocal intraocular lenses implanted can enjoy an improved quality of life and achieve dependency from spectacles for distance.
- Multifocal: Add-On multifocals are diffractive (they have a series of concentric rings which produce different powers of refraction) and enable patients to achieve independence from spectacles for both distant and near vision. They are designed for patients who have been implanted with a monofocal lens to correct distance. The idea is to add an addition of approximately 3 dioptres to enable them to focus up-close.
- Toric Multifocal: This type of lens can correct both residual astigmatism and near vision (creating a multifocal system), to obtain optimum results with a view to ceasing to depend on spectacles and achieving good visual quality. It is a lens that is both toric and diffractive, equipped with the most advanced optic.