Intravitreal injections are the fastest-growing procedure in ophthalmology and in medicine in general (Video 20-10, Fig 20-17). The most common indications for injections include AMD, diabetic retinopathy, and venous occlusive disease–associated macular edema. The most common injections are anti-angiogenic agents (eg, aflibercept, bevacizumab, and ranibizumab). Other intravitreal injections include steroid preparations, including sustained delivery devices, antimicrobial medications, and many medications used in clinical trials that will likely be approved in the coming years. The number of injections performed in the United States, estimated from Medicare procedure codes, increased from fewer than 3000 per year in 1999 to an estimated 6.5 million in 2016. This number continues to increase as a result of the aging population, new medications becoming available, and an expanding list of indications.
Intravitreal injection of pharmacologic agent.
Courtesy of Stephen J. Kim, MD.
Injections can be accomplished safely 3–4 mm posterior to the limbus. Commonly used methods for anesthesia administration before intravitreal injections include pledgets or cotton-tip applicators soaked with anesthetic and held against the site of injection, application of topical (including viscous) formulations of anesthetic, and subconjunctival lidocaine injection. There is no consensus regarding the optimal method of anesthesia for patient comfort and reduced risk of infection.
Strict aseptic technique, including managing the eyelid to prevent contamination from the margin and lashes, is recommended. The application of povidone-iodine, 5%, to the ocular surface for at least 60–90 seconds prior to injection is widely considered beneficial. Antibiotic eyedrop use before or after injections is controversial and is not recommended in routine procedures, particularly given that repeat topical antibiotic application results in the development of resistant ocular flora.
Figure 20-17 Intravitreal injection. The ocular surface was anesthetized with subconjunctival injection of lidocaine, 2%, in the inferotemporal quadrant. An eyelid speculum was inserted, and povidone-iodine, 5%, applied to the ocular surface. After 2 minutes, povidoneiodine was reapplied over the injection site and—after proper hand placement and no talking—the injection was made approximately 4 mm from the limbus.
(Courtesy of Stephen J. Kim, MD.)
Endophthalmitis remains the most feared complication resulting from an intravitreal injection; the reported incidence ranges from 0.02% to 0.2%. Although respiratory organisms could cause endophthalmitis (via contamination from respiratory droplets), the most common source of infection is presumed to be the patient’s own conjunctiva or eyelids. Therefore, potential mechanisms of infection include direct inoculation of ocular surface bacteria into the vitreous or subsequent entry through a wound track. Multiple studies have reported that Streptococcus viridans, a common component of oral flora, is a more frequent cause of endophthalmitis following intravitreal injections than after other intraocular procedures, presumably from contamination by respiratory droplets. Consequently, attention should be paid to efforts that reduce the risk of respiratory-droplet contamination such as minimizing talking of both the patient and provider and the use of face masks during the procedure. In addition, excessive manipulation of the eyelid margin should be avoided to limit expression of bacteria-laden secretions from the meibomian glands, and aggressive treatment of blepharitis prior to intravitreal injection should be considered for patients with severe disease.
Outbreaks of endophthalmitis from contaminated bevacizumab in the past have prompted periodic review of compounding pharmacy practices and accreditation status to reduce the risk of future outbreaks. To minimize patient risk when bilateral injections are performed, many practitioners have adopted a workflow in which different lot numbers of compounded medications are used for each eye.
Other complications include the development of elevated intraocular pressure following intravitreal injections of anti-VEGF agents, or as a common adverse effect of steroid injections. A complication unique to the dexamethasone sustained-release implant is severe corneal endothelial toxicity if the implant migrates into the anterior chamber. Such migration has been reported to be common in aphakic eyes, but it can also occur in pseudophakic eyes.
Khurana RN, Appa SN, McCannel CA, et al. Dexamethasone implant anterior chamber migration: risk factors, complications, and management strategies. Ophthalmology. 2014;121(1): 67–71.
Kim SJ, Chomsky AS, Sternberg P Jr. Reducing the risk of endophthalmitis after intravitreous injection. JAMA Ophthalmol. 2013;131(5):674–675.
Kim SJ, Toma HS. Antimicrobial resistance and ophthalmic antibiotics: 1-year results of a longitudinal controlled study of patients undergoing intravitreal injections. Arch Ophthalmol. 2011;129(9):1180–1188.
McCannel CA. Meta-analysis of endophthalmitis after intravitreal injection of anti-vascular endothelial growth factor agents: causative organisms and possible prevention strategies. Retina. 2011;31(4):654–661.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.