The retina subspecialty day at the recent American Academy of Ophthalmology (AAO) congress in Chicago (USA) included a full scientific program, bursting with current insights, research and innovation for all things posterior segment. Here, we look at a sample of these informative sessions.
Based on a presentation from Dr. John Thompson on “Anterior Segment Complications of Multiple Intravitreal Injections”.
Intravitreal injections are one of the most common intraocular treatments in ophthalmology. Unfortunately, these injections can sometimes result in significant complications in the anterior segment.
Subconjunctival hemorrhages, with an 11.2% incidence in one study, were thought to be caused by elevated systolic blood pressure and pulse rate; patients on anticoagulants appear to have an increased risk. Corneal abrasions have a lower incidence at 0.15%, according to one study, and can result from an abrasion from the lid speculum; the proparacaine-soaked plunger contacting the cornea; movement of the needle close to the eye, or with self-induced trauma in an anesthetized patient. Dr. Thompson says diabetic patients and those with basement membrane dystrophies are most susceptible.
Corneal or retinal perforation due to sudden patient movement have a low incidence (0.003%) in Dr. Thompson’s experience: “Sudden patient movement is especially problematic in elderly patients with dementia,” he said.
Another complication is hyphema (0.02%, according to Dr. Thompson). This can mimic endophthalmitis and use of anticoagulants is a risk factor. Another condition that can mimic sight-threatening endophthalmitis is noninfectious uveitis – the U.S. Medicare databases lists this at a 0.73% incidence. Of course, endophthalmitis itself also can present with a 0.62% incidence in eyes receiving anti-VEGF treatments. This is compared with 0.10% in the control group. Finally, lens damage can cause acute cataract with an incidence of 0.2% in the MARINA trial and 0% in the ANCHOR trial. Dr. Thompson says this typically involves posterior capsule with focal cataract that progresses rapidly to diffuse lens opacity.
Based on a presentation by Dr. Anat Loewenstein on “What is Actually in the Syringe? Accuracy and Precision of Intravitreal Injections of Anti-VEGF Agents in Real Life”.
While many studies focus on the technical aspects of performing intravitreal injections, Dr. Loewenstein and colleagues recognized that only a few investigate the accuracy of intravitreal drug volume delivery in this common procedure. In fact, several studies have found that the accuracy and reproducibility achieved with typical syringes varies greatly.
The investigators measured volume output of 669 intravitreal injections administered to patients, and calculated the weight before and after expelling the drug. Patients were separated into three groups: Group 1 received prefilled bevacizumab in a 1.0 ml syringe; Group 2 had prefilled ranibizumab in a small volume syringe with low-dead-space plunger design; and Group 3 received aflibercept drawn from a vial by the physician and injected with a 1.0 ml syringe.
They found that volume outputs in all three groups were significantly different from the target of 50 µL – this indicates that the delivered volume outputs are different from what was intended. “Precision was highest in Group 2, indicating that a small-volume plunger design may improve precision,” said Dr. Loewenstein.
Overall, the authors concluded that current practices for intravitreal injections are highly variable – with significant rates of over- and under-delivery, which could be associated with elevated intraocular pressure or undertreatment of patients. “This is the first study to investigate the accuracy and precision of anti-VEGF agents delivered by intravitreal injection to patients, and its finding illustrate the need for a specially designed syringe for this purpose,” finished Dr. Loewenstein.
Based on a presentation by Dr. Narsing A. Rao called, “Three Pearls for Uveitis”.
In an informative session on uveitis, Dr. Rao provided a comprehensive overview of “diagnosis of uveitis entities one should not miss”. Firstly, it’s vital that physicians don’t overlook any infectious etiology. Infectious uveitis can stem from toxoplasmic retinochoroiditis, treponema pallidum (syphilis), tuberculous uveitis and herpetic retinitis (acute retinal necrosis).
Uveitis can also be associated with life-threatening systemic disease, including multiple sclerosis (MS), serious infections, vasculitides, systemic and inflammatory diseases (like Vogt-Koyanagi-Harada (VKH)) and primary intraocular lymphoma. “Among these, first consider entities such as syphilis, VKH, MS and primary intraocular lymphoma,” said Dr. Rao.
While it’s rarely required, Dr. Rao says to perform a vitreous and/or retinochoroidal biopsy if faced with unexplained uveitis etiology. “In patients with compromised immune status and in patients with masquerade entities such as primary vitreoretinal and primary uveal lymphomas, vitreous and rarely retinal and choroidal biopsy may be needed to establish tissue diagnosis for therapeutic interventions,” explained Dr. Rao.
Based on a presentation by Dr. Gaurav K Shah on “Vitrectomy for Diabetic Macular Edema: Why, How and When”.
Diabetic macular edema (DME) is the leading cause of visual impairment in developing nations, and the mainstay for therapy includes intravitreal anti-VEGF agents. However, there is no current standardized approach for the treatment of chronic or recurrent DME, and repeated injection place a heavy burden on the patients, doctors and healthcare system.
In this presentation, Dr. Shah explores pars plana vitrectomy (PPV) for treating DME. A few reasons to consider this procedure include: eyes with vitreous detachment (PVD) develop DME less frequently than eyes with attached hyaloid; the vitreous may harbor inflammatory mediators contributing to DME; and relieving tractional forces may help improve vitreomacular traction, while oxygenation of tissue may favor arteriolar constriction.
Dr. Shah says the internal limiting membrane (ILM) plays a role in the pathology – in fact, a prospective study indicated that IL removal – compared to PVD induction with PPV alone for DME – stabilized visual acuity and improved cystoid macular edema.
So, when should PPV be performed? Some advocate for PPV for patients with persistent DME when the central macular thickness is >250 µm, and for those who have a history of two session of either macular photocoagulation or intravitreal anti-VEGF.
Overall, Dr. Shah concludes: “New studies indicate that PPV may be an appropriate and safe option for DME treatment.”
Editor’s Note: The AAO 2018 annual meeting was held in Chicago, Illinois, USA, on 27-30 October 2018. Reporting for this story also took place at AAO 2018.
