Possible eye movements can affect the accuracy at the time of surgery. Eye tracking is the process that allows the laser to follow its movements during operation. Prof. Paolo Vinciguerra, Head of the Ophthalmology Centre at the Humanitas Clinical Institute, spoke about this.


What is eye tracking?

When the laser acts on the eye, one of the major concerns of patients is whether they will be able to stand still during surgery. The patient’s collaboration is certainly indispensable but the laser can follow eye movements.

We are used to thinking that the eye only moves from right to left and from top to bottom. Yet, even though the eye seems to be always in axis, it revolves around itself. If you do not have a preliminary diagnostic tool and a laser that can follow eye movements, astigmatism becomes difficult to correct. Precisely for this reason it is necessary to have sophisticated instruments at your disposal.


The technology

The laser acts through light dots that subtract tissue at different points to generate a new shape. It has variable power: it is therefore possible to apply different levels of energy depending on the affected area.

In the central area the cornea is at a precise distance, while in the periphery it is further away; we will therefore have a decrease in energy. In addition, if the eye tends to rotate around its axis, this will lead to an even more inaccurate result. It is essential to have a laser that can compensate for eye movements with variable energy.


The temperature

The energy released by the laser vaporizes the tissue and transforms it into gas. The resulting temperature rise can cause burns. The laser must therefore be able to measure the temperature it is generating on the cornea.

The laser never intervenes twice on the same spot in a short period of time, so that the area concerned has time to cool down. The laser will only return to the area later if necessary. This is a possibility thanks to a camera inserted in the instrument, which, in addition to following eye movements, measures everything that happens in real time.