Face Off
COORDINATED BY ABDHISH R. BHAVSAR, MD

Welcome to Face Off, a new Retinal Physician column that will explore controversial topics in the diagnosis and managment of retinal diseases. On each topic, one specialist writes in favor of the treatment or surgery, and another writes in opposition to the treatment or surgery.

In this issue, we address 3 topics: intravitreal triamcinolone injections for retinal vein occlusions with macular edema, intravitreal triamcinolone injections combined with PDT for subfoveal CNV due to AMD, and topical antibiotic prophylaxis in conjunction with intravitreal injections.

Intravitreal triamcinolone injections for retinal vein occlusions with macular edema

Hugo Quiroz-Mercado, MD: Intravitreal triamcinolone should be considered in patients with vein occlusions and macular edema for the following reasons. Edema is caused by extravasation of fluid secondary to persistent arterial flux in an increased resistance of a vein flow. Triamcinolone may decrease vascular damage produced by the thrombus, accelerate thrombus clearance, decrease retinal edema in and out of retinal cells, and stabilize cellular membranes. Because there is a breakdown of the internal retinal barrier, triamcinolone may stabilize and repair this barrier.

OPPOSED

Intravitreal triamcinolone injections combined with PDT for subfoveal CNV due to AMD

IN FAVOR OF

I have several patients with RAP lesions that have resolved with one triamcinolone/PDT treatment and have remained stable with improved vision (one doctor at 20/25!) at 1 year. I now routinely use intravitreal triamcinolone with PDT on all PDT eyes (if there is no history of poorly controlled glaucoma). It is my impression that fewer PDTs are required and that some patients' vision improves. I am also noting PSC cataract at 1 year, which is likely due to the steroid. I have had no cases in which the IOP could not be controlled with drops alone.

George A. Williams, MD: Despite a paucity of data, combination treatment with PDT and intravitreal triamcinolone has become a common therapeutic approach. This suggests that clinicians are seeing a different therapeutic response than they have seen with PDT alone. The reported advantages are visual improvement and a decreased need for retreatment. However, many questions remain.

The risk/benefit ratio of combination therapy has not been established. The recent reports of macular infarction with combination therapy are worrisome. A clinical trial is necessary to answer these questions before this combined therapy can be recommended with confidence.

Topical antibiotic prophylaxis in conjunction with intravitreal injections

Thomas B. Connor, Jr., MD: The goal of any antibiotic prophylaxis is to prevent or minimize infection. Among potential sources for infection are a patient's own flora, including that found in the conjunctiva, lids, and adnexa. However, there are no data demonstrating a benefit of antibiotic prophylaxis for transconjunctival intravitreal injection. Similarly, there are no data demonstrating any benefit of such antibiotic prophylaxis. Until such data are available, our only information comes from surrogate studies of bacterial colony counts from conjunctival swabs. Topical antibiotic use, when combined with topical povidine iodine, reduced bacterial colony counts recovered from conjunctival swabbings. These findings suggest that it is reasonable to use prophylactic antibiotic drops with intravitreal injections, while still appreciating the importance of povidine iodine, aseptic technique, and adequate exposure.

William F. Mieler, MD: The use of a single drop or 2 of prophylactic antibiotic prior to an intravitreal corticosteroid injection is difficult to rationalize as there is really no scientific data to support a benefit. The intravitreal penetration of even the fourth generation fluoroquinolones from a single drop of antibiotic is probably close to zero. In an article to be published in 2005, Hariprasad et al ¹ will show that using topical moxifloxacin q2 hours for 3 days prior to elective vitrectomy surgery did allow for a moderate amount of antibiotic to reach the vitreous. If one was to seriously consider using prophylactic antibiotics prior to an intravitreal injection, the above noted regimen could be employed. Alternatively, a tablet of oral gatifloxacin ² or moxifloxacin the evening prior to an injection and once again on the day of the injection would also make sense. Still the issue of cost-effectiveness would have to be considered ³. Utilization of sterile technique, a lid speculum, and a povidone iodine lid scrub still seem to be most beneficial in limiting the incidence of infection. Similar to preoperative usage of antibiotics, there is no proof that using antibiotics postoperatively offers any benefit.

REFERENCES

1. Hariprasad SM, Blinder KJ, Shah GK, Apte RS, Rosenblatt B, Holekamp NM, Grand MG, Thomas MA, Mieler WF, Chi J, Prince RA. Human aqueous and vitreous penetration pharmacokinetics of topically administered moxifloxacin 0.5% ophthalmic solution. Arch Ophthalmol. (in press)

2. Hariprasad SM, Mieler WF, Holz ER. Vitreous penetration of orally administered gatifloxacin in humans. 2003; 121:345-353. Arch Ophthalmol.

3. Jager RD, Aiello LP, Patel SC, Cunningham ET. Risks of intravitreal injection: A comprehensive review. Retina. 2004;24:676-698.