Transzonular TriMoxi injection
Zonules after Trimoxi injection
Source (all): G. Auffarth, MD
Experts discuss the pros and cons of “dropless” cataract surgery
If it’s not broken, why fix it? But when the advantages of the new override the tried and true, we pay attention. The application of an antibiotic/corticosteroid combination into the vitreous body or the anterior chamber after cataract surgery has shown decided advantages for patients in the postoperative period, including warding off infection, inflammatory control, patient convenience, and guaranteed compliance, not to mention appreciably lower costs. Stewart Galloway, MD, Cumberland Eye Care, Crossville, Tennessee, and Francis Mah, MD, director of corneal and external disease and co-director of refractive surgery, Scripps Clinic, La Jolla, California, spoke to EyeWorld about which method they use and why.
A controversial method of administering prophylactic meds after cataract surgery involves the transzonular injection of a triamcinolone/ moxifloxacin combination, TriMoxi (Imprimis Pharmaceuticals, San Diego) into the anterior vitreous, with or without vancomycin (TriMoxiVanc, Imprimis Pharmaceuticals). While some surgeons prefer to avoid any unnecessary manipulation of the zonule fibers due to concerns of preserving their structural integrity and potentially creating new problems in the eye, Dr. Galloway sees this as a misconception. “My own personal approach is almost 100% transzonular. It is very safe and does not damage the zonules. The biggest disadvantage of the approach is that some surgeons might not feel comfortable about going through the zonules, because we are taught in training not to damage the zonules and be wary of going into the vitreous. But, it is very safe once you learn the technique and know how to do it. I don’t see any other disadvantage, whatsoever,” he said.
Dr. Galloway and his colleagues have successfully used TriMoxi for cataract surgery in about 20,000 eyes. His technique involves gently stretching the ciliary sulcus and zonules with viscoelastic and directing the cannula under the iris and above the anterior capsule. The cannula is then advanced through the zonules, which separate but do not break, and into the vitreous. A visual movement or release of the lens capsule sometimes confirms zonular penetration. TriMoxi is injected slowly and at a constant rate.
“The pars plana approach is also very effective and quite prominent in the U.S. The only downside is that there can be some discomfort to the patient. In addition, anatomically we don’t always know the exact location of the pars plana. In some patients, it is more anterior or posterior, and since we are applying a standard, injecting 2.5–3 mm back, finding the pars plana won’t be perfectly precise. It is essentially a blind maneuver, which is why I choose to inject transzonularly. Still, I don’t think there is any huge disadvantage to the pars plana approach, other than making another opening into the eye. With a transzonular approach, you are already in the eye to remove the cataract,” Dr. Galloway said.
All-in-one injected meds are alluring for their practicality, but they also need to live up to a slew of demands. According to Dr. Galloway, a single injection of TriMoxi is not only practical but also far less complicated to do than some might think, and extremely effective in the prevention of inflammation, cystoid macular edema (CME), and endophthalmitis following cataract surgery. Cataract surgeons commonly prescribe both antibiotic and corticosteroid drops for patients to self-administer for days to weeks postoperatively, often including additional non-steroidal anti-inflammatory (NSAID) drops as well. The typical regimen involves antibiotic drops for a week, a steroid taper over a month, and an NSAID drop for 4–6 weeks, with the drop frequency varying from once to four times per day, which can be challenging to elderly patients for a range of reasons.
TriMoxi is a compounded triamcinolone acetonide/moxifloxacin combination of 15 mg/1 mg/ml combined into one stable product. The injection delivers 0.2 ml solution through a 30-gauge cannula into the anterior vitreous, either transzonularly or through the pars plana. He prefers the intravitreal drug effect to drugs given, for instance into the anterior chamber, where an antibiotic may last for only a few hours, while the same drug will have a lasting effect of 12 hours or more in the vitreous. Dr. Galloway said that only a very small percentage of his patients require additional drops after surgery. “Overall, it is around 5% of people who develop some rebound inflammation and need a drop supplement. In my own personal practice, it is closer to the 2% mark, but some others have reported it to be as high as 10%. The difference is that the patient only has to be on one drop postoperatively that he takes a couple of times a day, and within a week or so the inflammation is gone. It is very easy to treat and does not involves weeks of different drops given at different intervals, so it is still better for the patient, even those that break through,” he said.
Postoperative vision varies, mostly because TriMoxi and TriMoxiVanc are opaque and can be unsatisfying for patients and for surgeons who value immediate postoperative visual results as a measure of surgical success. “We are putting a milky substance into the vitreous, so vision on the day of surgery varies tremendously. I’ve seen same-day postoperative patients who have very poor vision and can only count fingers to others who have 20/20. It boils down to whether the TriMoxi is in front of the macula or not. If it is out of the way, they are going to see some floaters, and if it is in the way, they may have poor vision for a few hours. I tell my patients here to expect that this is the tradeoff for getting out of drops. Expect poor vision on the day of surgery, and expect some floaters on the top part of vision typically for 1 to 3 days, after which it will absorb and vision will clear,” Dr. Galloway explained.
Overall, a one-shot surgical prophylaxis regimen gives patients and physicians significant peace of mind. In addition, TriMoxi saves the patient between $300 and $500 on postoperative drops. “There is a substantial savings to the patients using TriMoxi. It actually costs the surgery center about $20 for Trimoxi and $25 for TriMoxiVanc. We also save a significant amount of time counseling patients about drops, in phone calls from pharmacies, for substitutions, and so on. On the service side, we save valuable time and energy,” he said.
According to Dr. Mah, injecting postoperative meds is a smart, proactive move toward taking the responsibility out of the patient’s hands and into his own. “I think there are several reasons that surgeons are reacting negatively toward drops today, and trying to take that responsibility from the patient. One big reason is compliance. You have no idea what the patient is doing, if he has picked up the medication(s), picked up the prescribed medication(s), if he is applying it correctly, or has the help he needs to take the meds. These unknowns strongly influence surgical outcomes, and the surgeon should have more control here,” Dr. Mah said. In addition, “efficacy is another reason to consider new drug delivery methods like the Imprimis or Dextenza [Ocular Therapeutix, Bedford, Massachusetts] or other types of ‘dropless’ cataract surgery such as compounded dexamethasone-moxifloxacin [Ocular Science, Manhattan Beach, California] which is what I have actually been using. I apply meds intracamerally. There is voluminous medical literature supporting the intracameral method of prophylaxis including prospective clinical trials. It brings into question the topical method of prophylaxis, where the efficacy of these medications is out of our hands. Why not use something that can be more efficacious and takes outcomes issues away from the patient?” he said.
Dr. Mah opts for an intracameral approach to apply postoperative prophylactic meds, choosing to avoid the transzonular and pars plana approaches. Although TriMoxi and TriMoxiVanc offer the all-in-one approach, there are a few reasons he prefers not to use it. “Firstly, I am in favor of avoiding intraocular vancomycin until the incidence and association of vancomycin with hemorrhagic occlusive retinal vasculitis (HORV) is elucidated and debunked. As for triamcinolone, it is only usable in the vitreous, which I do not feel is necessary. It has a long half-life, which can be a big problem in steroid responders. Also, as a suspension, triamcinolone leaves vision blurry for at least a day or two, or longer, even if everything else goes perfectly. I prefer to assess my patient’s vision right after surgery, and patients appreciate immediate improved vision,” he said. Dr. Mah also noted that not all patients can afford to have poor vision for days after surgery.
Dr. Mah explained that knowing the effective lens position immediately following surgery was a key factor in managing premium patients (i.e., those primarily electing to have surgery with largely non-reimbursable products). He thinks that manipulating the zonules by injecting something transzonularly can potentially affect the effective lens position and the determination of the best possible postrefractive outcomes. He elucidated that putting something into the anterior vitreous has anecdotally affected the potential space between the posterior capsule and anterior hyaloid face, altering the desired refractive outcome by causing a myopic result of several Crystalens (Bausch + Lomb, Bridgewater, New Jersey) or Trulign (Bausch + Lomb) cases, where the posterior capsule was pushed forward due to medication placed transzonularly into the potential space, pushing the implant lens forward.
“My choice is moxifloxacin with dexamethasone (Ocular Science), which I inject directly into the anterior chamber after cataract surgery. The combination consists of 0.5% moxifloxacin and 0.1% dexamethasone, giving 0.15 cg of this mix. What gets into the eye would be approximately 750 micrograms of the moxifloxacin and 150 micrograms of the dexamethasone. After I’ve taken the cataract out, I check my incisions like I normally would to make sure the incisions are water-tight. Then I use a 1cc syringe and an AC cannula (27 or 30 gauge) through the paracentseis site, and go right underneath the anterior capsule and inject,” he said.
According to Dr. Mah, dexamethasone is a preferable choice over triamcinolone due to its shorter half-life of 7 to 8 days, voluminous data of use in ophthalmology compared to all other steroids, and clarity of the preparation. As most cataract patients would not require steroids after surgery for any longer than 2 weeks, dexamethasone would very likely be sufficient coverage. A huge advantage is that compared to the murkiness of triamcinolone that obscures early postoperative vision and requires transzonular or pars plana application, dexamethasone is clear and can be left in the anterior chamber without concern—even in glaucoma patients. When he was at the University of Pittsburgh, Dr. Mah’s colleagues published a paper with higher amounts of intracameral dexamethasone in glaucoma patients being safe and effective following routine cataract surgery.
Dr. Mah thinks that anterior segment surgeons who do not normally deal closely with the vitreous might feel uncomfortable and avoid vitreous manipulations if possible. Surgeons unaccustomed to working beyond the anterior segment might feel uncomfortable trying to perform a transzonular or pars plana drug delivery approach, which may invalidate TriMoxi from their list of options, while intracameral application would be more attractive to them. “Injecting into the anterior capsule is not challenging for anterior segment surgeons. That’s just my own assessment. Obviously there are surgeons out there successfully using TriMoxi and other formulations using vitreous approaches which is great, but for me, I just don’t feel as comfortable and I’m glad I don’t have to learn a new technique or disturb the zonules or vitreous,” Dr. Mah said.
Editors’ note: Dr. Galloway has financial interests with Imprimis Pharmaceuticals. Dr. Mah has financial interests with Bausch + Lomb (Bridgewater, New Jersey), Novartis (Basel, Switzerland), Ocular Science (Manhattan Beach, California), and PolyActiva (Melbourne, Australia).