No go zones
Many vitreoretinal surgeons avoid ‘floater’ surgery because the risks of vitrectomy often seem to outweigh the benefit of removing what are usually thought of as minor visual disturbances. Even laser vitreolysis is suspect, I Paul Singh MD told the 2017 American Society of Cataract and Refractive Surgery Symposium in Los Angeles, USA.
Many surgeons express concern that laser vitreolysis may not be effective, and could produce inflammation or retinal detachment based on a few published cases, said Dr Singh, who heads Eye Centres of Racine and Kenosha, Wisconsin, USA.
“The question I get from colleagues is, ‘is it safe to fire three, four or five mJ of laser energy 300 to 400 times into the eye?’”
In Dr Singh’s experience with more than 1,200 cases, the answer is unequivocally “yes”. Nd:YAG laser vitreolysis using pulse power double or more those typical for posterior capsulotomy not only is safe, it usually is highly effective in relieving patients of visually debilitating floaters.
Floaters often interfere with reading, driving, watching TV and other daily activities, and can be visually disabling, Dr Singh noted. On average, patients would risk more to avoid them, including possible blindness or reduced lifespan, than they would to rid themselves of diabetes or HIV, according to one large study (Am J Ophthalmol. 2011; 152(1): 60-65). While this finding may or may not hold in real life, “we tend to underestimate the impact of floaters on patients’ lives”, Dr Singh said.
1,272 CASES, 10 COMPLICATIONS
Dr Singh presented results from 1,272 consecutive laser vitreolysis cases in 680 patients treated with an Ultra Q Reflex Nd:YAG laser (Ellex), using a Singh MidVitreous lens (Volk) with an adjustable depth of focus extending from the posterior lens surface to the retina. All patients were seen at one month, three months and one year after the procedure, and 146 patients were followed for at least four years. Optical coherence tomography of the macula was performed after the procedure on the first 362 patients. Dr Singh has no financial interest in the lens and is a paid speaker and consultant for Ellex.
An average of 562 laser pulses were fired per treatment session, and a mean 2.4 sessions were required per case. Laser pulse energy ranged from 2.5mJ for treatment close to the phakic lens or retina, up to 12mJ in the mid-vitreous, though most work was done in the 4.0-to-6.0mJ range, Dr Singh said. The laser pulse vaporises target tissue and creates an acoustic shock wave travelling back toward the source, but wave depth does not increase linearly with power, he explained. A 1.0mJ pulse creates a 110-micron shock wave while 10.0mJ increases it to only 220 microns, making 4.0-to-6.0mJ a good compromise of power and precision with a shock wave of about 150 microns. The energy beam is also truncated, which allows for less energy needed to cause a plasma spark. The pulse is also very short, about four nanoseconds, which means energy is dispersed before the next shot is fired and does not build up.
Results were generally best when the floaters were isolated Weiss rings, which required fewer pulses and visits, or large amorphous clouds in the mid-vitreous, Dr Singh said. Small floaters were more difficult to visualise and treat, and patients were generally less satisfied with the results.
Complications included seven intraocular pressure spikes, two phakic lens hits, and one retinal haemorrhage, for a total adverse event rate of 0.8%. Six IOP spike patients resolved with topical drug treatment, with one remaining on treatment. One phakic lens hit later required cataract surgery and the other is under observation. The retinal haemorrhage resolved in three months, with no long-term negative effects. Dr Singh noted that all complications occurred in the first 50 cases, before he understood how to use his laser’s coaxial illumination and off-axis illumination to precisely locate floaters and aim the laser.
High-risk patients also did well, Dr Singh said. Four with a history of uveitis did not worsen, 27 with diabetic retinopathy did not develop macular oedema, and two of four with vitreomacular traction saw their VMT resolve after the procedure. No retinal defects were observed in any patient.
Mohammed Idrees FRCS Edin, of Aldara Hospital and Medical Centre in Riyadh, Saudi Arabia, reported similar results treating 68 patients for floaters with an Nd:YAG laser. Overall, 87% were completely satisfied and another 9% satisfied, with 4% not satisfied. Ten percent required two treatment sessions, and 7% more than two. No loss of best corrected vision or other adverse events were observed, Dr Idrees reported.
“The procedure was safe and painless, effective and minimally invasive, there were no post-laser activity restrictions, and patients were highly satisfied,” Dr Idrees said.
“Use of proper technique and technology is the key for the successful outcome of this amazing laser procedure to relieve the feeling of annoying floaters,” he added. “When you respect the no go zones, then chances of complications are minimal.”
He noted, however, that laser vitreolysis is technically demanding and requires training and practice to aim the laser precisely. He recommended careful patient selection and making sure the pupil is well dilated. If the target is close to the lens, a slight posterior defocus will help avoid hitting the lens.
I Paul Singh: ipsingh@amazingeye.com
Mohammed Idrees: sightsaver88@yahoo.com
