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Are there alternatives for treating floaters?
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Low-dose atropine
The problem with floaters is the shadow they cast on the retina when light is projected on them. Size and location play a role: The bigger the floater and the nearer to the retina, the more intense the shadow and the more intensely the patient is disturbed. Pupil size also plays a role. With a wide pupil, the shadow is not as clear as it is with a narrow pupil. A small dose of 0.01% atropine, one drop every other evening, can dilate the pupil by 1 mm, just enough to weaken the intensity of the shadow and even make it disappear. At this low concentration, we are able to maintain normal pupil dynamics. Dilation will not occur in all lighting conditions: If you project the light onto the eye, the pupil constricts, but you have an increase in pupil size by 1 mm and no drop in visual acuity when the pupil dilates. The drop in accommodation amplitude is only 1 D, which is not a problem in young patients.
In a study we have recently performed in 30 patients, 60% reported significant improvement, 20% moderate improvement and 20% no improvement. We are currently performing a pilot study to select the patients who respond better to the treatment, but at this stage it seems that every patient is potentially a good candidate, and it is at least worth trying.
When a patient comes to see me for floaters and asks for vitrectomy or vitreolysis, I ask him or her to describe their perception of floaters after I have dilated the pupil. Are they still there or have they disappeared? Patients who say they disappeared are good candidates for eye drops. I have the opportunity to offer them all options, but always try atropine first in these cases. It is a good method particularly for young people and for patients who have floaters close to the retina. It is a safe approach, very well tolerated, with no complications.
Hakan Kaymak, MD, is from Internationle Innovative Ophthalmochirurgie GbR, c/o Breyer, Kaymak & Klabe Augenchirurgie, Düsseldorf, Germany. Disclosure: Kaymak reports no relevant financial disclosures.
Femtosecond laser on the horizon
Femtosecond technology may be the next step forward in laser vitreolysis for floaters, overcoming the drawbacks of the YAG laser.
Applications in the femtosecond laser range are very short, three orders of magnitude shorter than picosecond applications and a million times shorter than nanosecond applications. As a result, the average joule output is much lower, but the power distribution is much higher than with YAG laser. Also, the applications are shaped like little needles that can be distributed as an array of spatial and temporal combinations, effectively using the laser as a precision cutting microsurgical knife over a larger 3-D volume, with minimal associated photodisruptive effects. It is a very different action from YAG laser, which is a one-shot explosion that happens quite slowly and creates a lot of photodisruptive effect because of heating.
The femtosecond laser basically works by a mechanism of photoablation, an extreme form of vaporization. It produces plasma, a very special state of matter in which all the electrons in the atoms are stripped away. It is even more intense than an excimer laser, which breaks up bonds between atoms. Plasma is extremely hot but extremely localized.
At the University of Antwerp, with Prof. Marie-José Tassignon, we are currently studying the possibility of using confocal scanning laser ophthalmoscopy, a very good instrument to dynamically visualize floaters, and couple it with the therapeutic laser. We are also working on advanced acousto-optic spatial and temporal light modulation techniques for creating the pattern of laser applications within the vitreous cavity. The acousto-optic modulator is a special device that can change the intensity and position of the laser beam very quickly. This research is still in the early stages, but we see exciting possibilities into this new application of the femtosecond laser.
Frans J. Van de Velde, MD, PhD, is from Schepens Eye Research Institute, Harvard Medical School, Boston. Disclosure: Van de Velde reports he has a patent pending with Marie-José Tassignon on the new development of femtosecond laser technology for floaters.