What types of intraocular lenses implants are there to treat presbyopia?
The crystalline lens is the eye's natural lens which enables us to focus the image both at distance (>20 feet) as well as close up (approximately 20-30cm).
From our 30s onward, the crystalline lens loses its elasticity and capacity to focus, initally affecting our near vision. This phenomenon is known as presbyopia or tired eyes. Later on, the crystalline lens will experience further changes affecting its transparency, thereby developing a cataract.
Currently, the only option for correcting these changes is crystalline lens surgery with an intraocular lens implant (IOL). There are various types of intraocular lenses: monofocal (enabling the patient to see at one single distance, generally far) and multifocal (enabling the patient to see at various distances).
While monofocal lenses have optimum optical quality as they focus all the light reaching them at one focal point (far), their disadvantage is that glasses are required to read (near vision) and to use the computer (intermediate vision) in the majority of cases.
Multifocal lenses enable patients to be less reliant on using glasses (they are not completely free from using them nor do they have perfect vision) at practically all distances, despite greater optical quality (the light divides into the various focuses of the lens).
These lenses are indicated for patients with established presbyopia (people over the age of 50) who want to stop wearing glasses or contact lenses, and who cannot have corneal refractive laser surgery.
Crystalline lens surgery for refractive purposes would be another option for patients with high or very high myopia (+15D), who cannot undergo any other type of refractive surgery, be it with laser or a precrystalline intraocular lens.
The surgery basically involves performing cataract surgery, without there being any cataracts. To do so, the crystalline lens is aspirated from its capsule and the appropriate intraocular lens (according to a preoperative study) is put in its place.
This is performed by making an incision or small cut, approximately 2mm in size, so surgical sutures are not usually required.
Surgery is normally performed under local anaesthesia, either around the eye (peribulbar or retrobulbar) or with drops (topical). This is why it is important not to move during the procedure, which usually lasts 15-20 minutes. One eye is operated on at a time, with a week's difference between each one.
Before being offered a multifocal IOL, it's important to be aware of the limitations of these lenses:
The brain requires a learning period (neuroadaptation) to be able to see at a distance without glasses. This period varies from patient to patient and may last from a few weeks to a few months.
The patient may see halos or rings around lights at night. This is because lenses have circles in their optics which provide vision at all distances but reflect light in the shape of halos.
Usually, this phenomenon is not very important and/or goes away after a few weeks or remains but is not bothersome. However, it is important to know that it may not be the best option for professional drivers who are on the road a lot at night.
It is important to remember that these lenses allow us to stop wearing glasses for practically everything, but our vision won't be perfect. In certain conditions, especially to see in dim light and small letters, reading glasses may be needed.
At our Centre, we use a range of multifocal lens models. We choose the most appropriate for each of our patients in a bespoke way, thereby providing them with satisfactory results overall.
The intrinsic risks of this surgery are similar to those of cataract surgery, mainly:
Lastly, please remember that not all patients are good candidates for a multifocal IOL. A monofocal IOL would be recommended for patients with eye conditions (dry eye, glaucoma, macular degneration, keratoconus...) to prevent the patient being unsatisfied with the results.
Frequently asked questions
No. Currently, there is no option that provides "perfect" vision at all distances. Multifocal lenses lead to less reliance on the use of glasses at practically all distances. However, their limitations must be taken into account.
No. What might happen is that a so-called "secondary cataract" could appear. This is no more than the growth of epithelial cells of the crystalline lens which spread to the posterior capsule of the crystalline lens (the "bag" where we place the IOL so that it stays inside the eye), causing blurred vision as if it were fog. In the case of multifocal lenses, if a secondary cataract appears, it usually affects the vision first. The solution is simple: painless, laser treatment, which "cleans" the lens and restores the previous vision.