Submacular air injection aids tPA haemorrhage displacement

May 20 2015

By Lucy Piper, Senior medwireNews Reporter

Submacular air injection with a microneedle is effective at facilitating the displacement of massive submacular haemorrhages (SMHs) dissolved with tissue plasminogen activator (tPA) in patients with age-related macular degeneration, an interventional case series shows.

“Pneumatic displacement is achieved by a simple fluid–air exchange and postoperative positioning”, explain the researchers. “Because pneumatic displacement works by decreasing the buoyancy of the SMHs without increasing the buoyancy of the air, SMHs readily drift away from the macular area because of their lower buoyancy.”

The team monitored 13 patients, aged an average of 71 years, with massive SMHs secondary to age-related macular degeneration. Surgery involved 25-gauge vitrectomy and submacular injection of tPA 25 µg and 0.4 mL of air delivered through a microneedle with an outer diameter of 50 µm and an inner diameter of 20 µm. The microneedle allows direct and controlled delivery to the submacular area, notes the team, minimising damage to the retina and surgical complications.

Following the procedure, the patients remained in a prone position overnight to help keep the air located around the submacular area allowing a flotation force sufficient to displace the SMHs to be gained.

Total subfoveal blood displacement was achieved in all eyes, and central lesion thickness decreased significantly, from an average of 867 µm before surgery to 379 µm 1 month afterwards.

At the 1-month follow up, vision had improved by more than two lines in 11 eyes, remained the same in one eye and declined by more than two lines in another.

At 3 months, Snellen best-corrected visual acuity had improved from 20/300 at baseline to 20/100 and there was a significant 23-letter improvement in Early Treatment Diabetic Retinopathy Study letter score, from an average of 27 letters to 50 letters.

Lead researcher Kazuaki Kadonosono (Yokohama City University Medical Center, Japan) and colleagues note that the only surgical complications were an intraoperative macular hole in one eye, which was subsequently successfully treated with surgery, and vitreous haemorrhage in another eye that resolved spontaneously.

They comment in Ophthalmology that the advantage of injecting air into the subretinal space rather than the vitreous space is its smaller size, which allows a higher pressure to build that directly pushes the SMH away from the macular area. This teamed with the prone, rather than upright, positioning following surgery facilitates earlier displacement, the researchers explain.

They conclude: “[S]ubmacular injection of air with a microneedle facilitates displacement of clots dissolved with tPA with few complications and results in earlier visual improvement in eyes with massive SMHs secondary to age-related macular degeneration.”

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