What is it?
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 more changes affecting its transparency, thereby developing a cataract.
Currently, the only option for correcting these changes is crystalline 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.
What does the treatment involve?
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, therefore 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's important not to move during the procedure, which usually lasts 15-20 minutes. One eye is operated at a time, with a week's difference between each one.
Before being offered a multifocal IOL, it's important to realise 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 patiend 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.
This phenomenon usually is not very important and/or goes away after a few weeks or remains but isn't 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, it's possible that reading glasses will be needed.
At our Centre, we use a variety of multifocal lens models. We choose the most appropriate for each of our patients in a bespoke way, which provides our patients with satisfactory results overall.
The intrinsic risks of this surgery are similar to those of cataract surgery, mainly:
- Intraocular infection: The risk is low as it is a clean surgery without practically any complications in the hands of an expert. Our intra- and post-opertive antibiotic protocol reduces this risk even further.
- Haematoma or hemorrhage in the eye: It is usually due to the prick from the anaesthesia. It is not significant and goes way after a few days.
- Refractive defect (“some prescription remains”): In these cases, it may not affect the result and the vision may be excellent (which is most common); it affects the vision in one eye concerning distance (e.g. far away) but it helps for another distance (e.g. near), however the patient is satisfied; it affects the vision significantly and the patient is unhappy (very uncommon). In the latter case, the options have to be reviewed in a personalised way.
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.
Professionals who perform this treatment
Frequently asked questions
I get a multifocal lens implant, will I be able to see perfectly without glasses?
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.
Could I get a cataract if I get a crystalline lens operation for refractive purposes?
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 spreads 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.