Computer Technology in Laser Eye

¶ … Computer Technology in Laser Eye Surgery

Laser eye surgery was first approved by the Food and Drug Administration in October 1995.

Since that time, the procedures have evolved to help a variety of people overcome several different eye disorders. This paper overviews the use of computer technology in laser eye surgery, as I feel this is still an emerging technology that will continue to grow and eventually be customized to assist patients with all eye disorders, making glasses and contact lenses someday obsolete. The procedures used for the surgery are so precise that they could not be effectively completed by the human hand, and therefore are guided through the use of computer technology. It is estimated that more than 150 million Americans wear corrective lenses, for refractive errors, making this technology of vital importance to a large segment of the population.

To better understand how computer technology is used in laser eye surgery, this paper will overview the history leading up to the development of laser eye surgery. The two primary types of laser eye surgery in use today will be discussed. Lastly, how computers assist eye surgeons in the performance of laser eye surgery will be reviewed.

Laser Eye Surgery History:

The interest in laser eye surgery is not a modern concern. For nearly a century, ophthalmologists have considered the possibilities of refractive surgery. In 1898, a Dutch professor of Ophthalmology established the basic principles of radial keratotomy. By the 1930s, the Japanese were working with corneal incisions, placed in the endothelial and epithelial surface. However, many patients suffered from late corneal decompensation, following the procedure.

It wasn't until 1974, when Russian eye surgeon, Svyatoslav Nikolayevich Fyodorov developed radial keratotomy, an eye microsurgery to correct myopia by using precise incisions near the cornea of the eye. Tens of thousands of patients received this treatment, both in Russia and around the world.

His discovery came when treating a boy who had broken his glasses and suffered corneal lacerations. Upon recovery, Fyodorov discovered that the boy's vision was significantly less myopic. This spurred his research into developing a treatment that would provide more predictable results than in the past.

It would be this system that Dr. Leo Bores would bring back to the United States.

While visiting the Soviet Union, Bores came across Fyodorov's radial keratotomy technology and brought it back to the United States. Since that time, more than 2 million patients have received radial keratotomy surgery, in the United States alone.

However, there were limitations to the surgery that prompted continued research. This continued research led to the development of the use of lasers for what would become LASIK and photorefractive keratectomy (PRK) surgeries.

Laser-Assisted in Situ Keratomileusis (LASIK) and Photorefractive Keratectomy Surgeries (PRK):

The first PRK patient was in Germany, in 1988. By November 1994, more than 1 million PRK surgeries had been performed, in more than forty countries around the globe. PRK reshapes the cornea of the eye, to improve a patient's vision. A local anesthetic is applied to the eye and a laser is utilized to sculpt the cornea. This reshaping helps the cornea focus light properly on the retina, eliminating blurry vision from either nearsightedness (myopia) or farsightedness (hyperopia).

Laser-assisted in situ keratomileusis (more commonly known as LASIK) eye surgery was developed in the early 1990s. Ophthalmologists combined keratomileusis, which is the removal of the cornea, so it can be frozen and reshaped before being replaced, with the use of PRK surgery. During LASIK surgery, a hinged flap is cut into the outer corneal tissue. This flap is then lifted out of the way, so that the excimer laser can reshape the tissue underneath. The excimer laser is an ultraviolet chemical laser.

During the procedure, the underlying tissue is reshaped. This improves the ability of the eye to focus light. This corrects blurry vision and reduces a patient's dependency on corrective lenses, including contact lenses and eyeglasses. Because the cornea flap features natural adhesive properties, there is no need for stitches. LASIK is used to correct farsightedness (hyperopia), nearsightedness (myopia), and astigmatism.

Neither of these two methods of laser-based eye surgeries could be accomplished without the use of computers.

Computer Technology and Laser Eye Surgeries:

Where eye surgery used to be performed solely by hand, left to the skill and steadiness of the surgeon, today's laser eye surgery is dependent on computer technology. The excimer laser is precisely controlled by a computer, during refractive surgery. Only a tiny amount of corneal tissue is removed with each pulse of the laser. This amount is so small, it is approximately 1/500th of the thickness of a human hair.

This precise control is needed no matter what the configuration of the laser.

Early excimer lasers use a beam which is approximately 6 mm in diameter. These first- and second-generation lasers feature an aperture that can control the amount of laser that the eye is exposed to, during each pulse. Newer excimer lasers now feature a single beam that is split into multiple smaller beams. These smaller beams rotate around the area for treatment. Bausch and Lomb's analogy for this type of configuration is comparing it to a shower head, where a single stream of water is divided into many smaller streams.

More recently developed excimer lasers use a narrow beam, only about 2 mm wide as opposed to 6 mm wide. Deemed a 'flying spot laser', the laser makes contact with the eye at incredibly high speed. It operates in a pattern that ensures debris is cleared in a specific areas before it returns to that same area. Although a broad area of the cornea is covered by the laser, radial keratotomy procedures penetrate much further than with laser-based eye surgeries. In addition, unlike the broad beam with an opening and closing aperture to control the amount of the beam that is exposed to the eye at each pulse, the flying spot beam is exposed in its entirety to the cornea with each pulse. For this reason, it is surmised that this results in a corneal shape that is much smoother, while also increasing the efficacy and accuracy of the surgery.

Despite this advancement, research continues for even more accurate and effective laser alternatives.

The most recent development in excimer laser finds lasers that have both a 2 mm and a 1 mm beam. The combination of these beam diameters is unique. In addition, this latest generation of excimer lasers amongst the fastest times for laser vision correction treatment that are available in the United States.

Whichever generation of laser is utilized, precision is the key to patient success and this precision cannot be accomplished with solely human hands.

As noted, the laser utilized in laser eye surgery is precise. It takes minute bits of material from the cornea, with each pulse. The beams are also lightning fast. Once a corneal flap is cut, for LASIK surgery, the laser treatment only lasts between 30 and 90 seconds.

It is this infinitesimal amount of material that needs to be removed, while the laser runs at incredibly fast speeds, that means this is not a job for solely human hands.

The laser is controlled by computer technology. Not only does this computer technology instruct the laser in things such as the flying spot laser and ensuring it does not come back to a spot until the debris is cleared. It is the computer technology that controls the depth of the laser. Without computer technology, human surgeons would have to trust their reaction times to control and adjust a very powerful laser beam. While no human reaction times are that quick, luckily computer technology is there to assist. When comparing radial keratotomy to LASIK or PRK, one can see the benefits of the computer controlled systems. The handheld knife cuts made in radial keratotomy can only treat low degrees of astigmatism and myopia. However, with the guidance of a computer, the accuracy of LASIK and PRK can be used to correct higher degrees of both conditions and hyperopia as well.

As one of the most sensitive organs, the precision only offered through computerized control is needed to provide the improvement in vision that typically begins to be noticed in only a few short days following the surgery.

In 2006, the University of Rochester Nomogram, a new software, was developed to analyze a the shape of a patient's cornea, during LASIK surgery. As each person's eyes are unique, this new technology allows the surgery to be customized to each patient's specific cornea anomalies. These eye imperfections sometimes cause patients to still experience slight farsightedness or nearsightedness, even after having laser eye surgery. The Nomogram system now yields better results, bringing the number of patients who are still slightly farsighted down from 20% to 2%, with this computer-corrected system.

Conclusion: