Presbyopia

Presbyopia is a refractive defect occurring due to the loss of elasticity of the crystalline lens, the eye’s natural lens, which allows us to focus on items at different distances, known as accommodation. Over the years, the crystalline lens gradually loses it natural elasticity and becomes more rigid, and therefore less flexible. The gradual loss of accommodation generally manifests itself from the age of 40 and evolves over time.

• Difficulty to focus on close items.
• The need to move objects away to see them better.
• The feeling that text is moving and the letters are blurry. Visual fatigue.
• Headache when focusing on items up close for a longer period of time.
• Dry, red eyes, stinging, excess tears and a feeling of grittiness when using your near sight for a longer period of time

This group of symptoms involves visual fatigue.

Presbyopia cannot be prevented because it is linked to the eye's process of ageing. From the age of 40, regular check-ups are important as this condition is age-related and this is when the symptoms normally arise.

Different exercises and nutritional supplements (like lutein) have been recommended to delay the start of presbyopia, but there is no scientific evidence of the efficacy to date.

One way of restoring the eye's physiological accommodation properly would be substituting the crystalline lens content for a transparent elastic gel that fills the capsular bag (Phaco-Ersatz).

With the arrival of ultra-fast lasers (femtosecond lasers), another possibility being considered is the option of performing surgery on the crystalline lens without affecting its transparency, thus restoring its elasticity and accommodative function. 

Presbyopia cannot be cured but there are measures for alleviating focus issues and, therefore, we can talk about correcting the presbyopia.

Optical correction

There are different types of glasses:

• Monofocal: Allows you to see well up close.
• Bifocal lenses: a combination of distance and near vision.
• Occupational lenses: they allow you to see well at an intermediate (computer) distance and near.
• Progressive lenses: the prescription changes gradually to correct distance, intermediate and near vision.

There are also bifocal or multifocal contact lenses, which should be individually adapted to suit each patient.

Surgical correction

None of the surgical methods used until now have been able to restore true accommodation in the dynamic and continually variable sense, to focus on all the distances, just certain ways of repairing it to a greater or lesser extent.

The main techniques used are:

Laser surgery

It involves moulding the cornea, thereby modifying the asphericity by increasing the depth of focus, thus compensating for the loss of crystalline lens accommodation.

Other surgical techniques performed on the cornea include monovision laser surgery (LASIK or similar types). It corrects an eye so you can see well at a distance (dominant eye), another so you can see well up close (non-dominant eye) and can even be used to create different bifocal and multifocal zones of the cornea (PresbyLASIK). The main disadvantage is that these are irreversible procedures.

Intracorneal lens implants

Implantation of thin lenticules in the thickness of the cornea, either by lifting a flap like in LASIK surgery or by creating an interlaminar pocket. These implants can be of refractive type (intracorneal lens), even for a bifocal cornea, or in diaphragm shape without optical power. These procedures are reversible.

Intraocular lens implants

It involves replacing the crystalline lens with a fake lens (bifocal, multifocal or extended range). These lenses are not suitable for all patients, which is why a full pre-operative study must be carried out. In addition, they have certain limitations in terms of visual quality and sometimes feel uncomfortable, particularly at night, although it’s the brain that ultimately chooses the pertinent image at all times and its capacity to adapt may compensate for many of the system's imperfections.

The success of refractive surgery will largely depend on the individualisation of the treatment based on a good diagnosis and correct indication of the surgical technique.