The very first human laser treatment to correct for spectacle error (LASIK) was done back in 1990. LASIK is the most widely used technique to correct for spectacle errors due to its safety and accuracy.
The treatment is done using an excimer laser. This laser uses a very short wavelength of light to photoablate the cornea. The laser effect is a chemical effect that breaks the chemical bonds between compounds, vaporizing the tissue with a minimal heating effect. In this manner the shape of the cornea is changed, much like you would reshape a spectacle lens. The corneal tissue is not burned at all. The laser does use gases to function, and these can sometimes be smelled during the procedure.
Despite the fact that the laser treatment usually takes only a few seconds, some eye movements are inevitable. The patient will lie down on a bed and fixate on a central blinking green light. The laser very accurately compensates for any eye movements in two ways. During the routine scans done before the surgery, an infrared camera takes an image of the iris (colored structure behind the cornea) of the eye and this is transferred to the laser via a computer. During the procedure the laser compensates for any eye movement within a few microseconds. When you lie down the eye also rotates, and this is also compensated for by the laser system.
The software and treatment planning have also improved immensely in the past 25 years. In the beginning only the spectacle error was treated. This resulted in all patients with the same spectacle error receiving the same treatment. At present we can perform customized treatment for each and every patient. This is done in two ways. The front of the eye and its contact with air is the most important surface that allows sharp vision. This surface is not always regular and causes poor vision, but this can be treated with a topographical laser treatment. Sometimes the aberrations that limit sharp vision originates from within the eye. With wavefront-guided treatment all the aberrations originating from the eye are treated, with the result that all the light entering the eye is focused sharply at the back of the eye.
All these new developments not only increased the accuracy of laser treatment, but also the safety. The biggest side-effect after laser eye treatment is transient dryness. This is easily treated with lubricating eye drops and usually resolves spontaneously after a few weeks. The accuracy of the newest laser systems results in achieving the desired outcome in more than ninety percent of treatments. That translates to more than ninety percent of patients achieving the same or better vision than what could be achieved with spectacles. It is also important to note that laser treatment can be repeated if the desired outcome has not been met, and this will be done free of charge. Another misconception is that contact lenses cannot be used after you had laser treatment.
Millions of people use contact lenses daily to correct their vision, considering it extremely safe to do so. It is however noteworthy that despite contact lenses being very effective and safe, there is still a one percent chance of losing your vision for every year that you use contact lenses. This is mostly due to infections and corneal infiltrations. Compared to this risk with contact lenses, the risk of complications in laser eye surgery is only one percent, and this risk is once off during the procedure.