Intravitreal implant: showing promise in DME and vein occlusion

March 1, 2006

Meticulous wound closure is key to success with this implant, as well as patients having realistic expectations about visual acuity outcomes after implantation

Retisert consists of a tiny drug reservoir, designed to deliver sustained levels of fluocinolone acetonide directly to the back of the eye. "The advantages of this therapeutic approach are linear continuous drug delivery, the drug is contained within a nontoxic device, and the device is suitable for sustained delivery of the drug for years," Jaffe said.

In this case, the expected duration of drug release is 2.5 to 3 years.

The Retisert intravitreal implant is constructed of a 1.5 mm core of drug, a silicone/polyvinyl acetate laminated coating, affixed to a PVA suture strut. The device contains 0.59 mg of drug, intended to be released at the rate of 0.5 µg per day, explained Jaffe.

What's the story so far?

Jaffe and colleagues evaluated two fluocinolone acetonide implants, one containing 0.59 mg, like the commercially available Retisert, and another containing 2.1 mg, to treat uveitis during an individual investigator (IND) trial in 36 eyes of 32 patients who had severe non-infectious uveitis with posterior segment involvement that was refractory to standard therapy. The average follow-up in this group was two years.

"Both implants had potent anti-inflammatory effects. Whereas these patients had 2.5 recurrences of uveitis per eye annually, postoperatively there were no recurrences at two years and only two recurrences at 29 months to three years," Jaffe reported.

Most patients had stabilized or improved visual acuity and very few eyes lost vision. Reported side effects were cataract development and increased IOP; 16.7% required antiglaucoma medications before implantation of the device and 46.7% required medications after implantation. Almost 20% required a filtering surgery post-implantation.

And the next step?

The Retisert implant is now being tested as a treatment for DME and as salvage therapy in patients with vein occlusion. It appears promising in both cases.

In the DME multicentre, controlled, randomized trial, 180 patients were enrolled to receive either a 0.59 mg implant or standard care that consisted of repeated applications of laser or observation. The two-year results have thus far demonstrated a beneficial effect of the implant on visual acuity. A three-line or greater increase in vision occurred in 27.6% of patients who received the implant compared with 8.7% of those who received standard care, Jaffe reported, whilst a three-line or greater decrease in visual acuity occurred in 15.7% of those who received the implant and in 13.0% of those who received standard care. Fifty-eight percent of those who received the implant had complete resolution of macular oedema, compared with 30% of those who received standard care.