Vitreoretinal Surgery at the AAO
Hello and welcome to Medscape Ophthalmology Insights. I am Dr. Steve Charles, Clinical Professor at Hamilton Eye Institute, The University of Tennessee, Department of Ophthalmology, and Founder of the Charles Retina Institute in Memphis, Tennessee. I am at the American Academy of Ophthalmology (AAO) meeting in Orlando and will be talking to you about the latest developments in vitreoretinal surgery, techniques, and instrumentation.
Advances in Vitrectomy
I will start with vitrectomy -- my pet subject -- and talk to you about some of the advances. We can foresee in the near future, and possibly in the next year, on the Constellation platform a 10,000 cut-per-minute sub-25-gauge surgery. We had a wonderful presentation on retinal subspecialty day by Yusuke Oshima, who presented his 27-gauge surgery techniques and technology. We can all see that these will be used in selected cases, most probably macular surgery. They will be useful in other retinal detachment cases as well. To perform a vitrectomy, we need optimal visualization. Masahito Ohji from Japangave a brilliant talk on the optics of contact-based wide-angle viewing. He combined the contact with wide-angle viewing systems built into the microscope and made the case, which I firmly support, that contact-based viewing both for the periphery as well as for macular surgery provides better axial and lateral resolution, and in the case of peripheral viewing, a farther peripheral view: approximately 10°-15° greater field of view with contact-based wide-angle viewing. This is different from the BIOM [binocular indirect ophthalmomicroscope] and other noncontact viewing systems, so I emphasize the importance, so eloquently expressed by Dr. Ohji, of contact-based macular surgery viewing and wide-angle viewing. This is essential to performing optimal surgery.
OCT Imaging: Making a Better Diagnosis
Surgical technology is of no value if we can't make the diagnosis. OCT [optical coherence tomography] is clearly a huge advance, not just in the field of the medical retina (which I won't address), but in surgical retina as well. Many advancements have been made in OCT. These are real advancements -- not just software enhancements. These are at the acquisition level. Rick Spaide introduced enhanced depth imaging-OCT (EDI-OCT), originally on the SPECTRALIS platform, which allows the choroid to be imaged very nicely. This has more merit in medical retina, but it is something to which we need to pay very close attention. In addition, others are using wavelengths of 1 µm and even 1.1 µm, which are farther into the infrared spectrum and therefore penetrate deeper into the choroid than the shorter wavelengths historically used for OCT. Instead of the spectral domain, as used in the last several years, swept source OCT provides more scans per second and therefore offers the opportunity of less motion blur and finer resolution, adding another layer of detail. I am extremely excited about the future of OCT. It is really core to our diagnostics today.
Intraoperative OCT: Not Ready for Prime Time
What about intraoperative OCT? Will that fit? Clearly, it is not ready for prime time for a lot of reasons. First, it's not real time, so if you are operating at micrometer precision on the retinal surface, peeling off membranes that are tens of micrometers thick, where the outline is not clearly visible and the landmarks are not visible to the OCT machine (so to speak), you have to stop, image, look away at the image, look back at the patient, and go back to work. Therefore, the advantage is not as great as many people are touting it to be. There are very significant display issues. After all, the core image acquisition is the slice, and that slice is oblique to your field of view. When you look at the patient, you are looking en face -- at a frontal view of the retina. That's not a B-scan slice, so even if you rerender these images in a so-called "C-scan reconstruction," it's off axis. How do you render that to the surgeon so that it looks like you would expect it to look when viewing through an operating microscope? There are significant complexity issues around scaling, tracking, and alignment. Put another way: If the image is bigger or smaller than what you are looking at in the fundus or it is positioned somewhere different, that's a problem. Where do you put this display? Do you put it where you look to turn your head to one side? Do you look up, a heads-up display? If you put it in an overlay in the operating microscope's image insertion or augmented reality, then it blocks your actual view of the patient. In short, intraoperative OCT is not ready for prime time, and I'm not sure that it ever will be, except perhaps for special situations such as pediatric cases.
Peeling the Internal Limiting Membrane
Returning to surgical techniques, what about internal limiting membrane (ILM) peeling? Clearly, ILM peeling has been accepted in macular hole surgery, but is it needed in other situations? John Thompson made an excellent case -- which I completely support -- that ILM peeling is required for lamellar macular holes as well as for foveoschisis, especially in myopic patients. He made the point that air or gas is required to restore fovea anatomy and to get the schisis to regress. I have had a very high success rate in these areas, as presented by Dr. Thompson. I emphasize the need for ILM peeling in these other entities, not just in full-thickness macular holes.
What about ILM peeling in epimacular membrane surgery or so-called "macular pucker" (an outdated term)? It is clear that it reduces recurrences because it takes away all the cells that are on the retinal surface, and it eliminates the adherence sites on which these modified astrocytes proliferate in the recurrence setting. It also immediately gets rid of metamorphopsia as evidenced by the disappearance of stria on the table. Kirk Packo emphasized these points in his eloquent presentation at the great debate at the Academy today. Earlier in the week, we heard a presentation by Stanley Chang that would dispute this issue. However, his data were based largely on microperimetry and a relatively short-term follow-up; I don't think they take away from the point that ILM peeling is advantageous in all cases of epimacular membrane surgery.
Staining the ILM
How can you peel the ILM if you can't see it? ILM staining is crucial. However, indocyanine green (ICG), which has been used by many surgeons for years, is toxic. There are numerous reports in the literature of its toxicity, I have seen many of these cases in the office. Christos Haritoglou from Germany made an eloquent presentation on the use of Brilliant Blue, which is the only safe stain. Other work from South America has validated this as well. In short, Brilliant Blue is the optimal stain for ILM. It has to be prepared by a compounding pharmacy, but so does bevacizumab (Avastin®; Genentech, Inc.; South San Francisco, California) and many other compounds that we use. We are all more aware now because of some of the problems with bevacizumab, of the need to qualify your compounding pharmacy and to be careful about safety issues. In short, I see a transitioning away from the unsafe toxic ICG to Brilliant Blue and using this in every case of vitreomacular traction syndrome, vitreomacular adhesion, macular hole, and foveoschisis.
Vitrectomy vs Scleral Buckling: The Great Debate
Today, I participated in a great debate with Allen Ho about vitrectomy vs scleral buckling for retinal detachment. Briefly, I made the point that cataract progression and nuclear sclerotic cataract progression, not de novo cataract, is what occurs with vitrectomy. That is the only vitrectomy-specific complication, whereas with the scleral buckle to repair retinal detachment (even though we have done them for 75 years or more) can induce, if there is an encircling element, 2.75 diopters of myopia and strabismus. At least 75% of the patients have limited ductions and 20% have clinical strabismus. It's a much more painful, inflamed eye. Extrusion, infection, and intrusion of implants occur at rates up to 9%, as reported by Schwartz. In short, I am a big advocate, as is Dr. D'Amico who presented today, for transitioning away from scleral buckles for repair of retinal detachment to vitrectomy in most cases.
Unimpressed With Microplasmin
What about microplasmin? There has been a lot of hype about microplasmin. Clearly, it is something that needed to be studied. However, there was only a 27% success rate in vitreomacular adhesion and a 10% success rate with the placebo (just injecting balanced salt). There was a 40.6% success rate in stage II macular holes. I am simply unimpressed with microplasmin. It has not been approved by the US Food and Drug Administration. We don't know what the price will be. I can't imagine that it is going to be inexpensive with the price of biopharma in every other arena, and I simply don't understand where this fits. Maybe for the patient who is very ill and who has vitreomacular adhesion, it makes sense, or for a patient on chemotherapy, but again I think this has been overhyped. Not that it's dangerous, it's just that it is minimally effective. Unfortunately, it doesn't create a posterior vitreous detachment in most cases -- it only worked 13.4% of the time. Therefore, it won't work for these complex so-called "round hole" young patients, myopic patients with dialysis, or round hole retinal detachments, although it would be a great boon if it did. Nor will it work for diabetic tractional detachments or epiretinal membranes. In short, I am unimpressed with microplasmin even though it's safe.
Lastly, I would like to speak about adaptive optics, a somewhat complex subject to understand. Basically, what happens is that a probeam is sent into the eye. That probeam is then detected by a Roland Shack Hartmann interferometer, which then allows them to create the inverse transform to compensate for every optical aberration in the cornea and the lens of that particular eye, in real time. That allows you to image the cones, and I think that we will learn from looking at the cone mosaic using adaptive optics technology. We will learn to correlate with microperimetry with OCT and autofluorescence and the other imaging domains as well as electrophysiologic and psychophysical domains to gain a greater understanding of what affects vision and reading speeds. We won't have this singularity around Snellen visions or ETDRS [Early Treatment Diabetic Retinopathy Study] visions, and we will learn more about function in the perimacular region and what drives that in response to various technologies.
It has been a very exciting meeting. We heard a lot of new things from the biopharma side as well: a lot of advances in surgery -- some things that are not ready for prime time but that we hope will improve as the years go by. Thank you for joining us today. I hope you found this information useful. This is Steve Charles for Medscape Ophthalmology Insights.
Medscape Ophthalmology © 2011
Cite this: Steve T. Charles. Advances in Vitreoretinal Surgery - Medscape - Nov 02, 2011.