LFT Blog by Dr. Paul I. Singh

16 July 2018

Modern LFT. Does the data stack up?

In recent years, there has no doubt been an increased interest in modern laser floater treatment, LFT. Within the past five years since I began performing the procedure, more and more surgeons are now adopting LFT in their practices. Although the procedure may seem fairly new, surgeons may not realize that the use of a YAG laser to treat symptomatic floaters has been performed for many decades. So, why is this procedure only now starting to gain traction?

Previous studies and publications questioned the efficacy and safety of LFT which in turn, hindered the widespread adoption of YAG lasers for floater treatment. It is important to note that these older studies were performed using YAG laser technology not designed specifically for floater treatment. Indeed, conventional YAG lasers were developed primarily for performing treatments in the anterior chamber, and offered limited visualization beyond the anterior chamber: they were not optimized for visualizing the entire vitreous cavity, let alone the retina. More importantly, by not providing coaxial illumination, efficacy was limited by the laser’s inability to identify many of the symptomatic floaters, such as a Weiss ring, which often reside in the middle to posterior vitreous. This older technology did not provide proper spatial context for the surgeon to decide if the laser could be safely fired, which increased the potential risk for adverse events. With new advancements such as True Coaxial Illumination, TCI™, when firing the laser, the surgeon can now better identify symptomatic floaters while also appreciating the distance between the floater and the retina (spatial context). Conversely, due to the ability of the laser to fire in any slit lamp position, surgeons can now treat floaters closer to the crystalline lens by firing the laser when the slit lamp is in the oblique illumination (off-axis) position. With this, the surgeon can appreciate the distance of the floater from the posterior capsule and also help to provide better contrast by titrating the amount of coaxial illumination. This advancement in visualization is a primary reason for the improved efficacy and safety of LFT.

Many of us were not educated on the physics of the delivery and dispersion of YAG energy in the eye. The relationship between the amount of energy dispersed (convergence zone) and the amount of energy fired from the laser is non- linear (logmar). For instance, at 1 mJ, the size of the convergence zone is approximately 110 microns, yet increasing the energy 10 fold to 10 mJ, increases the convergence zone to 210 microns (less than 50%). This property is what allows surgeons to feel comfortable using energy levels upwards of 6 -7 mJ. It also allows the surgeon to feel comfortable safely treating floaters greater than 2 mm from the lens and retina, due to the small amount of energy dispersion in the vitreous. Using lower energy settings, such as 1-3mJ (typical for YAG capsulotomies), does not allow for vaporization of the opacities. Instead, it only pushes the floaters away.

The recently published paper by Shah and colleagues (JAMA, July 2017) is the first prospective randomized placebo controlled trial evaluating the safety and efficacy of LFT using newer YAG laser technology specifically designed for this procedure. The laser used in this study (Ultra Q Reflex, Ellex) incorporates the advantages of the new coaxial illumination system and a truncated energy beam that increases efficiency of the energy delivery, as compared to the traditional lasers used in previous studies. With this truncated energy beam there is a less wasted energy. As a result, less energy is needed in order to create the plasma breakdown in air. I had the pleasure of meeting Dr. Shah at the American Academy of Ophthalmology (AAO) in New Orleans this past year. We both participated in a roundtable discussion where we addressed many questions around LFT. The group had the opportunity to review the findings of his published data.  There was clear agreement about the impact this study has had on increasing the acceptance of the procedure.

The safety seen in Dr. Shah’s study reflects the advantages of recent advances in YAG laser technology, as compared to that used in previous studies. A fear held by many surgeons is of an increased risk of causing a retinal defect. Not only did this study demonstrate higher subjective symptomatic patient improvement compared to placebo, it also demonstrated no adverse events in the treatment arm. In fact, a retinal defect was seen in the placebo arm. According to the AAO, the definition of vitreolysis is 'severing of vitreous strands and opacities with a laser.' There has been no evidence to date demonstrating laser to the vitreous causes traction on the retina. In fact, in our practice, we have seen the inadvertent release of vitreo-macular traction post vitreolysis when treating floaters in the posterior vitreous. This, to me, is evidence that we are releasing traction rather than causing traction. Although follow-up was only 6 months in the Shah study, if the laser were the cause of a tear, a defect would likely be seen within this 6-month period. Defects occurring years later are more likely to be caused by factors unrelated to 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 since changes from the laser would likely be seen immediately or shortly thereafter. Other adverse events such as anterior chamber and vitreous reaction would also not likely be attributed to the procedure after 6 months.

The placebo controlled design of the Shah study also addresses the question of the 'psychological' effect of the procedure. There was significant difference in patient satisfaction between the placebo and the treatment arm. Therefore, we can conclude that neuroadaption is not the sole reason for improvement in the treatment arm. The results of this study also confirm the rationale for treating patients with floaters, instead of just ignoring them. Clinically, we do tell patients that there is a potential need to perform an additional treatment given that we are severing attachments and breaking them up, in addition to vaporizing them. In routine practice, multiple sessions are common since vaporization occurs in a very small area, and not all the vitreous opacities can always be removed in one session.

As an early adopter of modern LFT technology, I have seen the impact the procedure can have on patient quality of life.  It has been inspiring to see the interest growing every year. Studies such as Dr. Shah’s recent publication are welcomed and needed to address the concerns of safety and efficacy using new modern technology designed for LFT. After meeting with Dr. Shah and other colleagues around the world, we agree that more studies are needed. Studies are ongoing both in the US and internationally utilizing these newer technology and protocols. Our group just presented retrospective data at the AAO with over 1,000+ patients (some patients with 3-4 year follow-up), demonstrating similar safety and efficacy as seen in the Shah study. We are also using pERG and rod functionality pre-and post-laser LFT to address concerns of retinal function post treatment. While there is more to learn, these newer studies have demonstrated that modern LFT is a viable solution to a common and disabling problem for many of our patients.

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