RISKS OF TREATMENT OF SIGNIFICANT VITREOUS EYE FLOATERS WITH THE YAG LASER.
There are two decades of combined experience with the laser vitreolysis procedure. It has proven itself to be a low risk procedure and an attractive alternative to 1.) Doing nothing, or 2) Surgical Vitrectomy. As with anything medical and interventional, the laser procedure is not without risk, but the likelihood of vision threatening complications is very, very low.
The only way to have no risk is to do nothing. We believe that for most patients, the potential benefits WELL outweigh the potential risks of the laser procedure – IF the floaters affect the quality of vision and the quality of life.
Here is a listing and explanation of the major real and theoretical risks of using the laser for eye floaters:
1. INACCESSIBLE FLOATERS
Not so much a risk, but still an important consideration. The optics of the treating laser are designed more for use toward the front of the eye and in the central visual axis rather than the periphery of the eye. The further back the floaters are, the treatment increases in difficulty and inefficiency (delivering less energy than desired). The laser energy can be blocked by small pupils, small lens implants, and made more difficult in very nearsighted eyes. Floaters in the periphery of the eye are very difficult to treat and even though we may see them quite clearly, the laser energy may be so diminished that very little happens when the laser is activated. Some of this challenge can be compensated for by a skilled and experienced laser specialist, but not always.
2. INABILITY TO TREAT SOME FLOATERS:
The treatment of eye floaters is highly individualized and dynamic. It impossible to predict exactly how the floaters will behave. That unpredictability is more so in younger patients. There exists the distinct possibility that despite our best, most dedicated and meticulous effort, there may be some residual material that simply cannot be safely treated, or remains inaccessible. Here are some examples:
FLOATER SITUATED TOO CLOSE TO LENS is an example of the vitreous floater located too close to a delicate structure within the eye. The red dotted line demarcates the approximate region safe to treat. In general, the floater must be at least 2 mm away lens. See section #4 “Cataract” below.
FINE MICROSCOPIC EYE FLOATERS are another example of floaters located too close to a delicate structure. In this case, it is the retina. This is a very common situation with younger patients, meaning those younger than about 30 to 35 years of age. You can read more about that HERE.
3. RECURRENCE OF FLOATERS:
The floater material that is directly hit by the laser should be permanently vaporized. That small mass of material should never come back. Immediately adjacent to the laser focal spot, the long collagen molecules may be fractured and broken into small, microscopic, and invisible fragments. We theorize that one of two things may happen to this material: 1. Some of it is liberated into the fluid portion of the eye and flows out with the natural fluid drainage of the eye (trabecular meshwork), and/or 2). The fractured collagen molecules become “sticky” and may regroup or clump up to form a smaller and differently shaped floater. These “reformed” floaters are usually quite treatable with subsequent, follow up laser treatments. Because of this tendency, it is rare to be able to treat someone in just one treatment session. Most people will need a second and 3rd (and sometimes more) treatments to achieve a satisfactory outcome. This expectation of the need for re-treatments is logistically easier for those that live in the Southern California area. Those that travel longer distances may need to allow for longer stays, or leave open the possibility to return at some future date.
UNTREATED SYNERESIS TYPE OF VITREOUS FLOATER. This is a large, diffuse, cloud-like floater that is commonly seen in our practice. They are more gradual in onset, and appear as a large ‘gauze’, haze, or cloud across the vision.
SYNERESIS FLOATER AFTER TREATMENT with re-formation, re-aggregation, and clumping of remaining collagen protein fragments despite an adequate and aggressive first treatment. The aggregated floater most often appears as a ‘fuzzy’ linear strand. Although there is much less material involved, these floaters can still be quite bothersome.
SAME FLOATER AFTER FURTHER TREATMENT may continue with the ‘3-4 steps forward and 1-2 steps back. Continued re-formation of smaller fuzzy linear strand may continue until there is less material, or the remaining material is not bothersome, or no more material reforms. There is no way to predict how many treatments it takes to get to these ‘endpoints’ as it varies from eye to eye.
4. EYE PRESSURE:
Although still quite rare, this is the most common side effect or complication of treatment. We have had several patients that experienced significant elevations of eye pressure within 24 hours of (usually the first) procedure. Now with several patients having experienced this problem, we have a better understanding of the potential pre-existing conditions that might place someone at risk for post-treatment pressure spikes. We believe the broken fragments of vitreous material (microscopic fragments of collagen molecules) will sometimes overwhelm the eye’s own natural drainage system (the trabecular meshwork). It may may take days (or even months) for the eye to clear that material out. We estimate the incidence to be 3-5 episodes per 1000 treatments based on cumulative reported and anecdotal conversations with other providers. There does not appear to be a direct correlation between the amount of treatment (number of shots or total energy used) and the elevation in pressure for the typical patient. There may be some predictive risk factors such as the following:
- pre-existing elevated eye pressures (suggests poor fluid drainage)
- previous cataract surgery (changes the anatomy of the front of the eye)
- large, dense floaters in the front one-third of the eye (there must be enough mass of material available and located closer to the natural drainage pathways)
- aggressive treatment (release more microscopic protein debris)
If a potential patient exhibits some of these or other characteristics we think may put them at higher risk, we may modify the treatment strategy or choose not to treat at all. One modified approach is to treat at much lower energy levels at the first treatment session to assess how the eye responds. We have observed that if the patient does not respond with a pressure elevation after the first treatment, then it is very unlikely they will have a problem with subsequent treatments regardless of how aggressive. There is the possibility that the eye pressure may not come down with treatment which could require long term use of eye pressure medications or possibly the need for further surgery.
NORMAL PRODUCTION AND FLOW OF THE AQUEOUS HUMOR IN THE FRONT OF THE EYE. Special cells located at (a.) produce a watery saline and electrolyte solution called aqueous humor. This fluid works its way forward past the lens and through the pupil into the space between the iris and the cornea called the anterior chamber (b.). This fluid flow is shown as (c.). The fluid eventually drains at the “angle” and by the junction of the cornea in the iris. The fluid drained out the structure called the trabecular meshwork. It is the balance of the production of this fluid in the drainage of this fluid which determines the regular pressure of the eye.
THE POSSIBLE EXPLANATION FOR THE CAUSE OF ELEVATED EYE PRESSURES AFTER LASER TREATMENT. Not all patients are at risk for elevated eye pressure after treatment. There appears to be a combination of risk factors involved. This illustration shows a large, dense, syneresis type floater (a.) Located in the front one third of the eye combined with a treatment that releases microscopic protein fragments (b.) Which may find their way into the front part of the eye (c.). If the drainage pathway, the trabecular meshwork is clogged with this microscopic debris, it may decrease outflow of the normal aqueous fluid. This may be the cause of elevated eye pressures in a few of our patients.
SUMMARY OF RISK FACTORS FOR ELEVATED EYE PRESSURE AFTER TREATMENT:
- Baseline high, or high-normal eye pressures
- Previous cataract surgery
- Large, dense, syneresis-cloud floater in the front 1/3 of eye
A cataract is a change in the clarity of the crystalline lens in the eye. There always exists the potential for the creation of a (traumatic) cataract by the laser, but it would essentially take a direct hit (or one of very close proximity) to the lens to do so. There are very few reports of cataract being caused by the laser procedure. If the laser breaks the outer lens capsule, the cataract that develops could be a rapid-onset traumatic cataract and may develop quickly as in days or weeks. A cataract may require surgical treatment. This risk is almost 100% avoidable by staying an adequate distance away from the lens when treating. We are aware of a few cases of cataracts being caused by the YAG laser. In each of these, it was the doctors first attempt in treating floaters or they were very new to the procedure. A good argument for seeing someone who is very experienced and qualified to treat eye floaters.
WE CAN NOT TREAT EYE FLOATERS LOCATED TOO CLOSE TO THE LENS. Legend: (a.) Lens, (b.) Laser energy, (c.) treatment demarcation line, (d.) focus of laser where energy is delivered.
Some floaters located near the lens can sometimes be momentarily moved away from the lens where the laser can be safely fired. This is an advanced technique and not recommended for doctors new to the procedure.
6. RETINA INJURY:
If the laser is aimed and fired directly at the retina, it is possible to directly damage retinal nerve cells. The laser’s focused spot size is approximately 4-8 /1000’s of a millimeter, so the area affected would be quite small, and possibly without any symptoms. We do not believe that even a direct hit to the retina can cause a retinal detachment. We have experienced minor complications to the retina via laser “shock-wave” when we chose to work in close proximity. This has occurred when attempting to get “that one” bothersome floater. It is a judgment call as to whether to fire the laser, and it would never be done in the central part of the vision, only peripheral. The shock wave can cause some temporary edema or swelling of the retinal nerve fiber layer or a small sub-retinal (beneath the retina) hemorrhage. Both conditions are about 0.5mm in size. When these have occurred, most of the time they are without any symptoms. When the patient was aware of anything, they might describe a faint, bluish, after-image seen when they quickly close and squeeze their eyes. This is self-limited and may only last a few weeks to a couple months. There have been a couple of instances where the patient described persistent symptoms, and because of that we have compensated by no longer treating small floaters close to the retina as before. The results of this less aggressive posture have been a near elimination of this problem. We believe it is a better policy overall.
Because many patients come to our office from out of town, we believe it is a good idea to have a local eye care provider that can provide follow up care if needed. For instance, to be able to check your eye pressure, should you experience any unusual symptoms after your procedure and after returning home.
7. RETINAL DETACHMENT:
This is a risk often mention by well-meaning eye doctors unfamiliar with the procedure. There has never been a published or unpublished report of a retinal detachment from this procedure that we are aware of. A theoretical risk. It is much more likely that a person will experience a retinal tear or hole from the original event causing the floaters (posterior vitreous detachment). If fact, your lifetime greatest risk for retinal detachment is when the vitreous is in the process of separating from the back wall. When the vitreous separates completely, then your lifetime risk of retinal detachment drops to its lowest point. The laser does not create traction or tugging on the retina during or after treatment, and so the laser procedure for floaters should not be able to cause a retinal detachment.
SUMMARY OF RISKS OF THE USE OF THE YAG LASER IN THE TREATMENT OF VITREOUS EYE FLOATERS.
No medical intervention or activity is without risk. This is true of even very common procedures such as cataract surgery or LASIK. Even something simple like removing a simple skin tag or mole has the potential for adverse reactions to medications, infection, etc. When discussing risks is not enough just to state the risk, but it is also imperative to describe the relative risk, that is the question “What is the likelihood of that risk having to me?”. Fortunately, in my practice with a combination of experience in the decision-making, we have had a very low incidence of risk to patients undergoing treatment. There’s been no loss of visual acuity or devastating complications. Dr. Johnson could not and would not dedicated his entire professional career to this procedure if it had not shown itself to be acceptably low in risk and high in success for most of the patients undergoing treatment.
The in-person and personalized discussion of risks for any medical procedure is part of the informed consent process and occurs with Dr. Johnson prior to any treatment. We try to present a fair representation of the risks and potential risks of this procedure. Fortunately, virtually all risks listed above can be avoided by the experienced physician being aware of the focus of the laser at all times. Doctor Johnson is one of the most experienced ophthalmologists in this particular procedure with over 3.5 million laser bursts aimed at these sometimes elusive eye floaters. He has enjoyed a very high success rate because of the careful, conscientious, diligent, and unhurried approach to each treatment.