TREATMENT EXPECTATIONS:
EXAMPLE 1, A SIMPLE WEISS RING FLOATER
We have created a model to better understand how the YAG laser interacts with the collagen of the vitreous fluid. We use cooked noodles on a cross-section cartoon of the eye.
The normally clear vitreous fluid is 99.9% water with the remaining material mostly collagen. Collagen is a non-cellular, long-stranded, polymer structure. It is normally dispersed throughout the vitreous, and it is invisible.
fig.1 This first image shows a cross-section of the eye with multiple random oriented strands of cooked, soft noodles which are meant to represent the long stranded collagen fibers in the viscous vitreous fluid.
Around the optic nerve head is a particular thickening that may become obvious when it pulls away and separates which is typical of a posterior vitreous detachment (PVD). There is a naturally occurring outer thickened layer of the vitreous shown here as a shiny and reflective food wrap sheet. It is the material that is adherent to the retina and often collapses into semi-transparent fold or wrinkled sheets after the collapse of the vitreous and separation.
fig.2 This illustration represents a posterior vitreous detachment. The thickened group in the center of the eye is known as a Weiss ring. this is one of the simplest and most classic type of floaters.
The Weiss ring type of floater is our favorite type of floater to treat. They are usually easily seen, they correlate very well with the patient’s description of the moving shadows and they are typically tethered fairly stably in the central part of the eye.
fig.3 This illustration shows what the eye may look like after even one treatment with the YAG laser. there may be some residual small bits of debris, but an 80-95% improvement would not be unusual in this circumstance.
fig.4 This chart may seem complicated at first, but it illustrates a number of important points and concepts. On the left-hand vertical axis is the subjective scale that represents how much the floaters bother the patient. Generally, for someone to seek our care, they will usually be quite bothered by the floaters and score high on that scale. The red dot on that vertical scale represents where they are prior to any treatment. The first treatment may drop them down on the scale with perhaps a 60 to 70% improvement. The blue line represents some theoretical line of satisfaction wherein they claim they will be satisfied with results below that line. In the case of the treatment for a Weiss ring, the first or second treatment will often achieve the desired effect. The treatment for Weiss rings tend to be stable and remain in a satisfactory range after treatment.
TREATMENT EXPECTATIONS:
EXAMPLE 2, MORE COMPLEX
This next example illustrates a much more complex situation with a mixture of various types of vitreous thickening and densities. There may be a mixture of strands, and dense clouds, and thicker fibrous material.
fig.5 This is a much more complex vitreous degenerative condition. This massive amount of degeneration will require more treatment.
fig.6 As we progress with the laser treatment, there is further vaporization and evaporation of collagen material as well as microscopic fragmentation of the collagen strands. These microscopic fragments are too small to cast a shadow and go into solution.
fig. 7With even further treatment, there is significant improvement in the appearance and further fragmentation of the collagen. If we could stabilize and freeze the results here, the patient would be quite pleased.
These small residual fragments of collagen have the opportunity to do one of two things: 1) Now that they are liberated from the original tangled mass of vitreous condensation, they can break free and work their way into the eye’s own drainage system. There is a naturally occurring recirculating pump and drainage of fluid in the front part of the eye. It occurs where the cornea meets the iris which drains fluid (trabecular meshwork). The small fragments of collagen may find their way into the eyes drainage system and exit the eye as a secondary manner. 2) Unfortunately, some of this fragmented collagen has a strong attraction towards itself and may re-form. The reformed clumps typically form as long, soft and fuzzy strands as illustrated here.
fig.8 This long, winding strand is typical of the re-formed or regressed formation of floaters after treatment. Overall, there is less material present and the patient may describe 40 to 60% improvement, but that residual strand may be quite bothersome and overall intolerable suggesting that more treatment is warranted and indicated.
The situation described above is not that unusual and is in fact quite common when there is a large, three-dimensional, cloud-like floater mass to begin with. This regression of treatment is not a treatment failure, but a not-uncommon treatment challenge. Typically, these long fuzzy strands are quite treatable even though a bit resistant to the laser energy. Further treatments are usually necessary to break it down and reduce the mass and volume of the residual floater material. This may take to or three or sometimes more treatments to get to the desired effect.
fig. 9 This graph is more complex and shadows a more jagged treatment progression. The first treatment may show a significant improvement, but over the ensuing 24 hours there is a regression perhaps of 20 to 40%. I have described this as a "journey of 3 to 4 steps forward and then 1 to 2 steps backwards". In this example the second treatment continues the noticeable improvement with some backsliding 20 to 40% again.
We think it is important and beneficial to understand these concepts prior to treatment as it is all about setting appropriate expectations for the patient. If our patients have these large, three-dimensional, thick masses of floaters we want them to understand that it will take more than 1 to 2 treatments to get a stable improvement. It is better to describe this in advance as it better prepares the patient for the treatment series.
What happens to the vaporized collagen? It is converted directly to gas bubbles. You can see the bubbles float away in the videos. They go to the roof of the eye (seen here using a mirrored lens way out in the periphery of the retina). Here is one larger bubble and approximately 60-80 very small micro-bubbles. They will only last about 10-30 minutes where they will dissolve into the surrounding fluid.
So what can you expect for a treatment or treatment series. The answer is that it is very difficult to know in advance of the initial consultation and evaluation with Dr. Johnson. It is often difficult to know after the evaluation or even after the first treatment. Each eye is different and each eye behaves and responds differently. Some floater types are more likely to regress or reform than others. It is one of the weaknesses of the laser procedure, this difficulty in predicting its behavior. We strongly believe it is better to educate and prepare the potential patient prior to treatment rather than proffer excuses and explanations after their 1st or 2nd treatment. We look forward to your thoughts and comments.
Do pre-existing retinal tears make the laser treatment of floaters more risky?
As long as the previous retinal tear has been stabilized (either spontaneous healing or more likely “spot welding” with and argon laser) and have been stable for a few months, then I can treat. The laser and its immediate or delayed effects do not increase traction on the retina and laser for floaters does not increase the risk of retinal detachment. Most of the time in mature adults, the bad floaters (and likely in your case, retinal tears and holes) are usually caused by a posterior vitreous detachment whereby the vitreous has separated from the retina. That is a one-time event. After a posterior vitreous detachment, the risk of retinal tears IS MUCH LOWER than before. – Dr. Johnson