Focus on the Future
Retina doctors stay fresh on new techniques and technologies to anticipate the industry’s direction.
Retina meetings focus on current trends in our subspecialty. Ideas flow freely in such marketplaces, and intimate gatherings such as the Vit-Buckle Society (VBS) meeting are perfect for discussion about the most cutting-edge and advanced innovations.
As retina specialists, we are excited to bring these new ideas to our clinics and ORs. These innovations have the potential to improve our ability to diagnose and treat our patients, many of whom have lost hope of vision.
The VBS meeting examines the retinal interventions of today and tomorrow by inviting both rising stars and experienced leaders of our field to participate in our annual meeting program. Their presentations shape our notion of retina’s future.
In this installment of VBS Notes, Thomas Berenberg, MD, reviews surgical pearls from Lisa Olmos de Koo, MD, and Ninel Gregori, MD, for implantation of the Argus II Retinal Prosthesis System (Second Sight). A summary by David R.P. Almeida, MD, MBA, PhD, of a talk by Lucia Sobrin, MD, MPH, on the state of genetic testing in retina shows that, although some benefits have already been realized in this blossoming field—screening for RPE65 gene mutations, for example, can help identify diseases mediated by genetic defects—other disease states have not yet benefited from genetic profiling. Ashkan Abbey, MD, in discussing a presentation by Theodore Leng, MD, MS, shows readers how smaller instrumentation elevates surgeons’ abilities to treat complex cases while minimizing invasiveness. By juxtaposing these articles, one can see that some concepts, which may have seemed ripped from the pages of science fiction just some years back, have become a reality.
—Anton Orlin, MD; Aleksandra Rachitskaya, MD; and R.V. Paul Chan, MD
Argus II Implant Pearls
By Thomas Berenberg, MD
Lisa Olmos de Koo, MD, and Ninel Gregori, MD, presented their techniques for implanting the Argus II in a talk entitled “Creating the Bionic Eye—Surgical Pearls for Implanting a Retinal Prosthesis.”
The Argus II Retinal Prosthesis System was approved by the US Food and Drug Administration (FDA) in 2013 and is currently the only FDA-approved retinal prosthesis. In the United States, there are 14 clinical centers implanting the device; in Canada, two sites are implanting the device.
Dr. Olmos de Koo has accumulated a wealth of experience with this surgery from her 4 years as the principal investigator at the University of Southern California site. She now serves as a proctor to others learning this operation, including her residency mentor and copresenter Dr. Gregori. The device works by using images obtained from a camera worn by the patient on a special pair of glasses that sends images wirelessly to a coil embedded on the eye wall, which in turn transmits to the electrode array that rests on the retinal surface. Patients must have a diagnosis of retinitis pigmentosa, have vision of bare light perception or worse, and have previously had useful vision in the eye to qualify for this device.
Dr. Gregori spoke about her experience implanting the device for the first time. She emphasized to members of the audience the importance of learning and maintaining scleral buckling techniques so that they can utilize these skills in the operation. She divided the operation into three phases: the buckling phase, the vitrectomy, and the closure.
Discussion of the surgery began with a pearl: The surgeon should make the conjunctival relaxing incision nasally. The implant sits temporally, and it is important not to disrupt the conjunctiva over the device. Next, the surgery proceeds with rectus muscle isolation, placing the coil under the lateral rectus, placing the metal case superotemporally, and positioning the Watzke sleeve for the encircling band superonasally. The band is sutured with no scleral indentation.
Next, both presenters recommended protecting the $150 000 array with a phaco sleeve during manipulation because it can easily be inadvertently damaged. One of the most important steps is properly positioning the electronics case. Using the nomogram from Second Sight, the case and the tabs of the coil are sutured to the eye. Both presenters emphasized the importance of aligning the device perfectly outside the eye so that, when the time comes for tacking the electrode during the vitrectomy portion of the procedure, the device sits properly on the macula. Both presenters emphasized that the surgeon should take his or her time with this step.
The next phase of the surgery is the vitrectomy, which can be performed with 23- or 25-gauge instrumentation. Use of triamcinolone staining to ensure a thorough vitrectomy is recommended, and careful attention to the superotemporal quadrant around the planned sclerotomy site is essential.
The sclerotomy is then made, 5.2 mm long and perpendicular to the cable. The location of the sclerotomy is based on the axial length of the eye and the nomogram from Second Sight. It is important to make the incision full thickness to avoid stripping the choroid when the array is inserted into the eye. The array is grasped and inserted into the eye with 20-gauge Eckardt forceps. The sclerotomy is then closed carefully, ensuring watertightness.
The climax of the surgery is the tacking. Dr. Olmos de Koo showed a video in which the tack is engaged through a hole in the array, which is pulled over the retina. When properly positioned, the edge of the implant overlaps the margin of the optic nerve, and the electrodes sit on top of the macula. The surgeon should avoid scratching the retinal surface while positioning the device over the macula.
Dr. Gregori showed the audience a video from the first case performed at the Bascom Palmer Eye Institute in which she utilized a novel bimanual technique with chandelier illumination, using Eckardt forceps in one hand and the tack in the other, to position the implant over the macula and safely tack it in place. Dr. Gregori and her colleagues recently published this technique in Retina.1
Once the array is in position, the intraocular pressure is raised to 60 mm Hg to 80 mm Hg, and the device is tacked into place. Drs. Olmos de Koo and Gregori offered another pearl at this point: Take time hovering with the tack to make sure that it is oriented exactly anteroposteriorly before penetrating the posterior ocular coats.
Questions from the audience included queries on the type of anesthesia (answer: general) and most common intraoperative complication (answer: choroidal detachment during insertion of the array through the sclerotomy). Dr. Olmos de Koo recommended making sure the sclerotomy is larger than 5 mm to avoid choroidal detachment.
The final phase of the surgery is covering the device suture tabs and the sclerotomy with Tutoplast material (IOP Ophthalmics) or donor cornea (due to its transparency) to avoid postoperative suture erosion and endophthalmitis. All sclerotomies are then sutured. Overall, the case takes around 4 hours, and, according to the presenters, is “like a marathon with a sprint in the middle!”
The presentation concluded with videos demonstrating patients with the device being able to walk independently.
Thomas Berenberg, MD, is a second-year vitreoretinal fellow at Weill Cornell Medical College in New York. Dr. Berenberg may be reached at firstname.lastname@example.org.
1. Gregori NZ, Davis JL, Rizzo R. Bimanual technique for retinal tacking of an epiretinal prothesis [published online ahead of print December 1, 2015]. Retina.
Genetics in Retina
By David R.P. Almeida, MD, MBA, PhD
It was an honor to attend VBS VICE as a travel grant award recipient. In a presentation on genetic testing in retina practice, Lucia Sobrin, MD, MPH, illustrated the utility of genetic testing in the modern retina clinic.
Dr. Sobrin reviewed recommendations from the American Academy of Ophthalmology (AAO) regarding genetic testing and emphasized the benefits of offering genetic testing to patients at risk for Mendelian disorders. Mendelian disorders, such as Von Hippel-Lindau disease and Stargardt disease, are usually caused by variation in a single gene without any environmental influence. Mutations for retinal degenerations such as retinitis pigmentosa can be identified with whole-exome sequencing; however, there are significant data to mine to properly ascertain the plausibility of disease-causing nature for any identified mutations. For whole-exome sequencing, Dr. Sobrin reminded us, identifying a laboratory that reliably interprets findings is of paramount importance.
The ability to identify Mendelian genes is helpful for confirming diagnoses, facilitating access to treatment, and initiating genetic counseling. Finding a gene and confirming a diagnosis may allow a patient to participate in a clinical trial. Dr. Sobrin illustrated this point via the example of a pediatric patient with Leber congenital amaurosis caused by mutation of the RPE65 gene. Gene therapy as a method of treatment for RPE65 mutations has garnered widespread attention as a viable therapeutic target in clinical trials.
Genetic testing usually requires prior authorization from the patient’s insurance carrier, based on a statement from the physician of how this will affect disease management. Single-gene tests cost several hundred dollars; whole-exome sequencing costs close to $2500. Dr. Sobrin said that, according to experience at the Massachusetts Eye and Ear Infirmary, causative mutations are found in approximately 55% of tests. Patients should be made aware that genetic testing is a lengthy process and that they commonly have to wait 6 to 12 months for results.
Dr. Sobrin warned the audience against routine use of genetic testing in age-related macular degeneration (AMD). Genetic testing results in only a 10% to 35% increased accuracy of predicting which patients will develop disease compared with macula examination alone. Moreover, there is no proven clinical benefit from identifying these patients via genetic testing, she said.
There has been significant debate regarding the pharmacogenetics of nutritional supplements, Dr. Sobrin said. The debate has concerned differing interpretations of the data from the AREDS. Some researchers have argued that genotype made a difference in therapeutic response after supplement use in these studies; others have concluded that genotype made no difference in response. Based on the five articles published to date on this matter, Dr. Sobrin said, any effect of genotype, if present, is likely clinically insignificant, as it has not been replicated by independent studies. Moreover, none of these pharmacogenetic studies has been performed prospectively, therefore failing to meet the standard the AAO sets to justify genetic testing for a complex disease like AMD.
David R.P. Almeida, MD, MBA, PhD, is a vitreoretinal surgeon at VitreoRetinal Surgery, PA, in Minneapolis. Dr. Almeida may be reached at email@example.com.
The Case for 27-Gauge Instrumentation
By Ashkan Abbey, MD
Theodore Leng, MD, MS, began his presentation with a discussion on the potential advantages of performing surgery with 25-gauge instruments, previously the smallest gauge available. Such advantages included faster healing of smaller incisions, reduced postoperative inflammation, minimized wound leaks and postoperative hypotony, and reduced rates of infection. He then shared his experiences with 27-gauge vitrectomy instrumentation, noting that disadvantages associated with this gauge include potentially increased vitrectomy time, reduced instrument rigidity resulting in decreased stabilization of the eye, fewer instrument options (such as lighted laser probes), and the inability to efficiently remove dense lens fragments or silicone oil from the eye.
Dr. Leng said he appreciated the functionality of 25-gauge instrumentation, namely that the mouth of a 25-gauge vitrector is located close to the tip of the instrument, which allows for easier dissection of membranes. He pointed out that the most significant advantage of the 27-gauge system is that the vitrector and other instruments are even smaller, which could make complicated cases much easier to perform. Additionally, many 25-gauge instruments are now available in 27-gauge, providing greater options to the surgeon.
Dr. Leng presented an interesting set of videos demonstrating procedures that used 27-gauge instrumentation. During the video segment, he provided guidelines for improving the operating experience with this new technology. Speaking to the reduced ability to stabilize the eye during 27-gauge vitrectomy, Dr. Leng recommended placing the cannulas along the horizontal meridian at 3 o’clock and 9 o’clock (rather than at 10 o’clock and 2 o’clock). According to him, this placement allows better control when using the more malleable 27-gauge instruments. To maximize efficiency during vitrectomy, he recommended following the edge of the peripheral vitreous with the mouth of the vitrector facing the vitreous skirt.
Dr. Leng presented two complicated cases. The first was a patient with pathologic myopia and a history of previous macular hole repair whose retina redetached, resulting in a combined rhegmatogenous retinal detachment and macular hole. Dr. Leng used 27-gauge end-grasping forceps to peel the premacular membranes and relieve the traction in the center of the posterior pole. He then injected perfluorocarbon liquid to stabilize the macula. Using 27-gauge Maxgrip forceps, he peeled the peripheral preretinal membranes. This case demonstrated the utility of the various types of 27-gauge forceps for efficient peeling of preretinal membranes. Dr. Leng used silicone oil in this case and injected the oil through the 27-gauge cannula without difficulty.
Dr. Leng’s second complicated case demonstrated the use of the 27-gauge vitrector in the dissection of complex membranes. He noted that the smaller mouth at the tip of the vitrector allowed for safer membrane dissection with lower risk of iatrogenic tears.
During the discussion, Maria Berrocal, MD, advocated peeling diabetic membranes using the suction setting of the 27-gauge vitrector. She emphasized that any time the resistance became great enough to cause a retinal break, the vitrector would release the membrane, avoiding this potential complication. Audina Berrocal, MD, agreed, and cautioned that some of the 27-gauge instruments are more fragile and can break inside the eye during more challenging cases.
A DEFINITE PLACE FOR 27-GAUGE INSTRUMENTATION
Dr. Leng said he believes that most cases done with 25-gauge vitrectomy can also be performed using 27-gauge instruments. He found the greatest utility of 27-gauge vitrectomy in more complicated cases requiring extensive dissection of membranes. The 27-gauge platform for vitrectomy is an exciting new addition to our surgical armamentarium that will continue to evolve to meet the needs of the modern retinal surgeon. n
Ashkan Abbey, MD, is a surgical and medical retina specialist at Texas Retina Associates in Dallas. Dr. Abbey may be reached at firstname.lastname@example.org.