Treatment of Presbyopia through Corneal Surgery
Monovision with LASIK
Monovision by laser is performed by correcting the dominant eye for distance vision and the non-dominant eye for near vision. Due to this, many patients no longer need spectacles and should become accustomed to this new situation. Not all patients can tolerate seeing two different images at the same time, and three-dimensional vision is also reduced. For this reason, it is likely that spectacles will be needed to drive
Using an excimer laser, the cornea is moulded to take on a multifocal shape. This enables near, intermediate and distance vision. The advantage of this treatment is that vision is the same in both eyes, enabling patients to see correctly in three dimensions. The quality of vision which is achieved with this technique is slightly inferior to that achieved with monovision. For this reason, in 20% of cases an optical support is required for reading.
Using the femtosecond laser, small cuts are made in the form of concentric rings in the centre of the cornea to change its shape and create a multifocal optic. The entire procedure is carried out without making a single surgical incision, as the laser acts directly on the corneal stroma. This process only takes a few seconds. In the case of patients with hypermetropia, this technique is possible up to +1.5 dioptres, and can improve near vision.
Conductive keratoplasty (CK):
Conductive keratoplasty is a technique based on radio frequencies. It consists of modifying the curvature of the cornea to make the eye more myopic, thereby improving near vision. During the procedure, the surgeon uses a portable instrument with a small probe for applying the low level radio frequency energy at specific points, forming a circular pattern on the external part of the cornea. This change of the curvature affects the light rays which enter into the eye in such a way that they create a new focus to enable near vision. The corneal tissue is not removed during this procedure. This technique is only used for people with hypermetropia or healthy eyes (emmetropic). It is normally used with the monovision method, leaving the dominant eye corrected for distance and applying CK to the non-dominant eye for near vision. The disadvantage is that this is a reversible process, in other words, the cornea takes on its original shape again, so this technique is not very commonly used.
This treatment is innovative and is based on small lenses or optic implants which are inserted into the cornea to improve the vision. Today they are mainly used to correct near vision. In many cases, the implant of this type of lens is combined with FemtoLasik surgery to eliminate refractive defects such as myopia, hypermetropia and astigmatism at the same time. Attempts are often made to achieve light monovision to improve near vision. Corneal implants do not consume corneal tissue. The risk of this surgery is lower than in the case of intraocular implants, because it is not necessary to go inside the eye. The advantage is that it can be reversed, as the cornea can easily recover its shape and natural function.
Kamra Corneal Inlay:
This is a circular and opaque disc with a thickness of 0.0005 mm and a diameter of 3.8 mm. It has a 1.6 mm hole in the centre which, due to the opening of the diaphragm, creates a field depth to enable clear vision of near objects. Over 8000 small holes found in this disc provide an exchange of nutrients to ensure a the cornea remains healthy. Firstly, a flap is created due to the femtosecond laser. Then LASIK is applied to the middle part of the cornea to correct the refractive defect and a space is created for the Kamra Inlay. This is a type of “bag” which is sufficiently deep to allow for its positioning. Finally, the flap is closed and the disc is fixed in place.
Raindrop Corneal Inlay microlens:
This is a new technique which involves implanting a microlens in the cornea. With a diameter of only 2 mm, a flap is separated from the cornea and this microlens is inserted. Its composition is similar to the properties of the cornea itself. It is inserted into the cornea of the non-dominant eye to create monovision, and near vision is improved in the treated eye because it modifies the shape of the cornea.
This lens is made from a hydrophilic material, which has been used for intraocular lenses for many years. It has a diameter of 3 mm and only 20 microns of thickness. Firstly, a flap must be created with the femtosecond laser. Using special instruments, the lens is implanted in the cornea and then the flap is closed again to fix it in place. It is a reversible process, because if it fails to work correctly it can easily be removed. In this case, the lens has no refraction in its central part but does in the peripheral area, thus helping to provide improved near vision.