YAG laser vitreolysis improves symptomatic vitreous floaters

Inder Paul Singh, MD

Many surgical procedures in eye care have historically undergone advances in technology and changes in protocol that have improved safety and efficacy and have often expanded indications. This has been the case for procedures such as modern cataract surgery and pars plana vitrectomy. Laser floater removal, or vitreolysis, has also undergone this same transformation. Surgeons who have been performing modern laser floater removal have seen the positive impact on patients’ quality of life while experiencing a high safety profile. Unfortunately, there has been significant pushback from colleagues regarding safety and efficacy due to the lack of peer-reviewed papers in the literature demonstrating what has been observed clinically.

The recently published paper by Shah and colleagues is one of the first randomized placebo-controlled trials evaluating the safety and efficacy of laser floater removal using newer technology specifically designed for this procedure. Historical studies, often quoted by those opposing this procedure, were using technology not optimized for visualizing the entire vitreous chamber. Therefore, the laser slit lamp did not provide the surgeon with the ability to identify many of the symptomatic floaters in the posterior vitreous, as well as provide sufficient spatial context for the surgeon to safely decide if the laser should be fired. With the advancement in the illumination system, providing coaxial illumination while firing the laser, the surgeon can now appreciate the distance the floater is from the retina. Conversely, being able to fire the laser using oblique illumination (off axis), the surgeon can appreciate the distance from the posterior capsule as well.

This illumination advancement is a primary reason for the high safety and efficacy seen in the study and is a crucial advancement in technology compared with technology used in previous studies. There is still no doubt a risk of hitting the lens or retina with the laser. It is important for surgeons to realize that with any procedure or surgical tool, damage can occur if not used correctly. Damage can occur to structures in the eye with a phaco needle if standardized techniques are not used, and the same can be said for vitrectomy; if too close to the lens or retina, severe damage can occur. There are now standardized guidelines for laser floater removal to ensure a high safety profile.

In training, many of us were not taught the physics behind the delivery and dispersion of YAG energy in the eye. There is a non-linear relationship between the amount of energy dispersed (convergence zone) and the amount of energy fired from the laser, For instance, at 1 mJ, the size of the convergence zone is approximately 110 µm, yet increasing the energy 10-fold to 10 mJ increases the convergence zone to 210 µm (less than 50%). This is an important property because it allows surgeons to feel comfortable using energy levels upward of 6 mJ to 7 mJ, such as in this study. This property also allows surgeons to feel comfortable safely treating floaters greater than 2 mm from the lens and retina by understanding the amount of dispersion occurring in the vitreous. Using lower energy settings, such as 1 mJ to 3 mJ, like in many of the previous studies, does not allow for vaporization of the opacities and will often push the floaters away. The laser used in this study also has a truncated energy beam that increases efficiency of the energy delivery as compared with the traditional lasers used in previous studies. In other words, much less energy is needed in order to create the plasma breakdown in air.

This study also demonstrated no retinal adverse events in the treatment arm; in fact, a retinal defect was seen in the placebo arm. This is an important point because the cause of retinal defects is often from vitreous traction. According to the American Academy of Ophthalmology, the definition of vitreolysis is “severing of vitreous strands and opacities with a laser.” There is no evidence that the treatment using a laser is causing traction on the retina. In our practice, we have seen inadvertent release of vitreomacular traction after vitreolysis when treating floaters in the posterior vitreous. This, to me, is clinical evidence that we are releasing traction rather than causing traction. In this study, the follow-up was 6 months, and many would agree, if the laser were the cause of a tear, one would likely have seen the defect within the 6 months. Defects occurring years later are more likely to be caused by factors unrelated to the treatment. There have been no reports of increasing cataract formation after vitreolysis if the lens was not directly hit at the time of the procedure. If the lens was not hit at the time of the procedure, a follow-up of greater than 6 months would not likely add much information because changes from the laser would likely be seen immediately or shortly thereafter. Other adverse events such anterior chamber and vitreous reaction would also not likely be attributed to the laser after 6 months.

Some skeptics point to a psychological or adaptive component to floaters. Doctors may say the laser did not have an effect, but rather there was a placebo effect or neuroadaptation. This study addresses that issue; there was a significant difference in patient satisfaction between the placebo arm and the treatment arm. This study also confirms the rationale for treating patients with floaters instead of ignoring them. Clinically, we do tell patients there is a potential need to perform an additional treatment because although we are vaporizing the opacities in a small area we are also breaking them up at the same time. Therefore, there are a few remnants that patient might notice postoperatively. This study showed significant subjective improvement in the treatment arm, but there were some who still noticed symptoms. This study was not designed for a follow-up treatment session. It is important for doctors to realize that multiple sessions are common; the plasma or vaporization is occurring in such a small area, thus it is not able to always vaporize the entire floater in one session.

This study was designed to treat Weiss rings. Clinically amorphous clouds and other types of floaters are typically treated as well. The impact on quality of vision can be variable depending on the type of floater, and therefore the postoperative effect on patient satisfaction and improvement in daily functioning can be variable. This is why the placebo-controlled nature of the study was important, but it also demonstrates the need for studies including other types of floaters.

In short, this was a much-needed study to address the basic concerns of safety and efficacy using new modern technology designed for laser floater removal. There are a number of studies ongoing both in the U.S. and internationally that will be coming out in the near future using newer technology and protocols. In fact, we are set to submit a retrospective study with more than 1,000 patients, some having 3 to 4 years of follow-up, demonstrating similar safety and efficacy as seen in this study. There are studies using pattern electroretinogram and rod functionality testing before and after laser floater removal addressing concerns of retinal function after treatment. There is no doubt more work is needed, but with this study, laser floater treatment has been shown to be a viable option for certain patients with disabling floaters.