Laser eye surgery to reduce or eliminate glasses began in Canada in 1990. The treatment zone size was quite small at that time, and a fairly significant number of people complained of night vision problems (like halos or starbursts appearing around lights). Over the years, the treatment zone size gradually increased, as did the range of prescriptions that could be treated. In the early days, astigmatism and farsightedness was not correctable with the laser. That is no longer true.
There are various tests that are performed to determine your candidacy for laser eye surgery such as wavefront aberrometry and corneal topography maps. When having the LASIK procedure, a flap is created typically using a precise instrument called a Microkeratome.
The Evolution of Laser Technology
Another aspect of the lasers that has changed is the size of the laser beam. Originally, the entire treatment zone diameter was treated with each pulse of the laser. Now, most lasers use a ‘flying spot’ laser that has many advantages over the old broad beam versions. One of the most significant factors is the ability to do customized treatment. By having a small laser beam, it can allow more treatment to be done in certain parts of the cornea than others. It also leaves a smoother surface than the old lasers, increasing the quality of the image focused inside the eye and improving the accuracy of the treatment.
Laser eye surgery relies on various modes of technology to deliver the outstanding results available today. The most important aspect is the laser itself. In the early days of laser eye surgery, the laser had a ‘broad beam’ that covered the entire surface that was being treated all at once. Thankfully, most clinics no longer use this type of laser.
Some lasers, including the Zeiss MEL-80 laser used by BoydVision Centre, are able to leave the cornea in a prolate shape. This means that the focusing power of the centre of the cornea is greater than the periphery. This is a key element in reducing night vision effects (starburst and halos around lights). In fact, some people who suffer night vision problems from treatments down with older lasers are now able to have additional laser treatment done with these new lasers, to improve the quality of their vision.
Laser Eye Surgery Technology
These instruments were quite complicated when LASIK first started, but the Microkeratomes have been refined over the years and have drastically reduced the potential for complications. A microkeratome is a very precise instrument designed to create a thin corneal flap at the beginning of a LASIK procedure. At BoydVision we use the Bausch & Lomb Hansatome microkeratome. We selected this instrument due to it being the gold standard in microkeratomes.
The Hansatome microkeratome creates a corneal flap with virtually no discomfort. There is some pressure sensation for some people while the flap is made (about 15 seconds). The doctor has full control of your eye during the flap making process, so you don’t have to worry about where you are looking. Once the flap is created, the microkeratome is removed from the surface of the eye. The flap remains attached on one side. The doctor gently lifts the flap and performs the laser part of the procedure. The flap is then rolled back into position. The natural forces of the cornea will keep the flap in position. Some care must be taken during the first week or two after surgery with respect to rubbing/hitting the eyes.
BoydVision Centre is proud to use the CRS-Master wavefront analysis unit designed by Carl Zeiss Meditec (the same manufacturer as our laser, the MEL-80) and made in Germany. A wavefront aberrometer measures any imperfections in the focusing of images inside the eye. Most eyes can benefit from a customized laser treatment to increase the quality of focus as light travels from the front of the eye to the retina. Using the wavefront analysis, the information is input into the laser’s computer to produce a custom treatment.
Some wavefront analysers use a fairly low level of resolution. The CRS-Master uses the highest resolution of the wavefront analysers available for use by laser eye surgeons. By recording such a high level of information, any customized treatment using the wavefront map produced by the CRS-Master is as precise as possible. As an added benefit, some people who underwent laser eye surgery using older lasers are able to have additional treatment utilizing the wavefront analysis and improving the quality of vision (especially noticeable at night).
Corneal Topography Mapping:
The cornea is the front ‘window’ of the eye and is responsible for about two-thirds of the eye’s focusing power. Any abnormality in the shape of the cornea will have an impact on the quality of focusing in the eye. Topographical maps of the eye are critical tools to analyze the shape of the cornea. There are a few different ways of assessing the shape of the eye, each method having advantages and disadvantages over the others. As a result, BoydVision Centre chooses to use at least two different methods of determining the topography of the cornea, including the Humphrey ATLAS and the Oculus PENTACAM.
The first is considered best at measuring the front layer of the cornea (useful for ‘topography-based’ laser treatment) and the latter is state-of-the-art technology for measuring the back (posterior) of the cornea. When a scan is done of the cornea, it takes only a few seconds. During this time you will experience no discomfort at all. The only real challenges are to keep your eyes open and looking at the appropriate target. The instruments notify us if there are any imperfections in the scan, at which time we would repeat the scan to ensure the best result.
Once the corneal topographical maps are printed, the examiner will use the information to decide if there are certain types of corneal pathology. The most common problems found using corneal topograhy are keratoconus and pellucid marginal degeneration. Both conditions are degenerative and are usually considered contraindications to laser refractive eye surgery.
In addition to measuring the shape of the cornea, certain corneal topography units are able to measure the thickness of the cornea. When laser surgery is done to reduce or eliminate corrective lenses, a certain amount of corneal tissue must be removed, making it thinner. It is important to maintain a safe level of thickness to keep the structural integrity of the eye intact. At BoydVision, we will also double check the thickness of the cornea using ultrasound – you can never be too safe!