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Examining how utilizing an intravitreal transzonular injection can help patient compliance.
Take-home: Examining how utilizing an intravitreal transzonular injection can help patient compliance.
Reviewed by M. Stewart Galloway, MD
Crossville, TN-Intravitreal transzonular antiobiotic/steroid combination concurrent with cataract surgery can provide a “significant benefit with minimum risk,” said M. Stewart Galloway, MD, Cumberland Eye Care, Crossville, TN.
Trimoxi (intravitreal triamcinolone/moxifloxacin, Imprimis Pharmaceuticals) following phacoemulsification with IOL implantation “is able to prevent postoperative inflammation, cystoid macular edema (CME), and endophthalmitis,” said Dr. Galloway, Cumberland Eye Care (Tenn.).
It is common practice to deliver antibiotics topically, but with Trimoxi, the delivery is transzonular. Trimoxi is compounded, preservative-free triamcinolone acetonide and moxifloxacin delivered 15 mg/1mg/ml, with 0.2 ml injected transzonularly into the anterior vitreous, Dr. Galloway said, resulting in a total drug delivery of 3 mg triamcinolone and 0.2 mg of moxifloxacin.
“After the lens implant is in place, and prior to removing viscoelastic, you pass a cannula through the incision, over the anterior capsule, underneath the iris, and then penetrate the zonules into the anterior vitreous so the drug is delivered into the vitreous itself,” Dr. Galloway said.
Unlike intracameral injections, which go into the anterior chamber, Trimoxi is designed to be delivered to the posterior chamber, directly into the vitreous, he said.
In his retrospective chart review of 2,300 consecutive eyes that underwent phaco/IOL implantation with the use of Trimoxi instead of topical antibiotic/steroids postoperatively, not one eye has developed endophthalmitis.
“There have been more than 14,000 eyes injected with Trimoxi-not all at our center, of course-and while we can’t say we have a zero rate of endophthalmitis, we can say it’s zero thus far,” he said.
Dr. Galloway said he believes the reason Trimoxi has yet to result in a single case of endophthalmitis is because when bacteria do enter the eye, it colonized in the vitreous.
“It’s a nutrient-rich place, and that’s where the bacteria grow and cause the problems,” he said. “We put the antibiotic where the bacteria want to grow. We’re not putting drops on the cornea and hoping they diffuse into the eye, we're not delivering them intracamerally and hoping some of it gets through to the vitreous.”
He noted that a problem with intracameral injections is that “the drug is washed out of the eye in a fairly short time frame,” he said.
In rabbit eyes, conversely, “the moxifloxacin stays at therapeutic concentrations for at least eight hours. The anti-inflammatory portion is detectable there for months afterwards.”
In Dr. Galloway’s study, all patients were seen day of surgery (4-7 hours postoperatively). All patients were then seen between 3 and 4 weeks postoperatively, and then again at 6 months.
Of the original 2,300 patients, only 10 were lost to follow-up. The average age was 73 years (ranging from 34 to 95 years old). Almost one-fifth of the eyes/patients had diabetes, and 5% presented with epiretinal membrane (ERM).
Dr. Galloway said 19% of the patients received supplemental topical nonsteroidal anti-inflammatory drugs (NSAIDs) because of diabetes, ERM, or premium IOL implantation.
The rate of breakthrough inflammation requiring the addition of topical steroids during the postop period was 2% but was “slightly higher at 3.5% in those with ERM, and 6.3% in those who developed CME,” Dr. Galloway said. Mean intraocular pressure fell from 21.1 mm Hg on day of surgery to 14.1 mm Hg at weeks 3-4 postop, he added.
The overall CME rate in the study was 1.4% (see Figure 1). The rate of CME in the diabetic subgroup was slightly higher at 1.9% and not significantly altered with the addition of topical NSAIDs. In the ERM subgroup however, the CME rate was very significantly affected by the topical NSAID, decreasing from 8.5% without to 2.2 % with topical NSAIDs. Dr. Galloway added he now routinely uses NSAIDs only on patients with ERMs and no longer uses them on diabetic patients without pre-existing maculopathy.
With the diabetic patient population, “if there’s no maculopathy, then there’s no reason to treat them differently than someone without diabetes,” he said.
There are some disadvantages to the procedure, he said-primarily that patients experience decreased immediate postop vision and floaters, due to the opaque nature of the drug. There also may be an increased incidence of patients who experience foreign body sensation, “presumably due to a lack of topical anti-inflammatory drugs at the wound itself,” he said.
By not relying on postoperative drops to control potential inflammation, Dr. Galloway said there’s also no issue with patient compliance.
Calling the use of Trimoxi “truly a dropless surgery, there’s decreased patient cost as well, and a decrease in postop care,” he said, explaining the lack of postop drops eliminates numerous call backs related to pharmacy and drop regimen.
“There’s enormous potential for this in Third World countries, where follow-up care is less than ideal,” he said.
M. Stewart Galloway, MD
Dr. Galloway is a consultant to Imprimis Pharmaceuticals.