Talisa E. de Carlo, MD
Vitreoretinal Surgery Fellow
University of Colorado
Drs. Anita Agarwal (West Coast Retina) and Jay Duker (Tufts University) moderated the session on retinal imaging at this year’s Pacific Retina Club meeting. The session started out with a bang with the inspirational Dr. Amani Fawzi (Northwestern University) speaking on her work using OCTA to predict progression of diabetic retinopathy. She credited her research students Situ Chen and Janice Ong in their work defining and auto-quantifying the critical oxygen diffusion distance of non-perfusion >30um as an OCTA marker for ischemic load. Her team looked at ischemia in baseline OCTA images of patients with moderate to severe NPDR and then correlated this with development of DME, NV, VH, and/or treatment for these complications one year later. When looking at non-perfusion on OCTA as a whole there was no difference between the complication and no-complication groups aside from a predilection for males to develop complications more frequently than females. However, when looking more closely at the individual vascular plexi, the middle and deep plexi were predictive of which patients would develop complications. Dr. Fawzi determined a clinically useful cutoff of <28.5% vessel density to help us predict which patients are more or less likely to develop complications.
Dr. Justis Ehlers (Cleveland Clinic) presented on the utility of intraoperative OCT. The technology first emerged from Dr. Cynthia Toth’s (Duke University) handheld OCT, which was then adapted to be microscope-held for better stabilization and eventually microscope-integrated for intraoperative use. Dr. Ehlers reviewed the PIONEER study, which showed a discordance in surgeon detection versus OCT image visualization of residual preretinal membranes. There were residual membranes 15% of the time surgeons thought there were none remaining, and 20% of the time when surgeons believed there was more work to be done the OCT showed no remaining membranes to peel. Intraoperative OCT resulted in valuable added information and the ability to skip staining in 40% of cases. The DISCOVER study further demonstrated the technology was helpful in 60% of surgeries and even altered surgical procedures in 30% of cases. In Dr. Ehlers’ experience, intraoperative OCT was most useful for finding full-thickness breaks and dissection planes in TRDs and for assisting in intraocular biopsies. The technology would benefit from advancements in consistency, the viewing interface, and efficiency of image acquisition, and more work is needed to validate the value of intraoperative OCT to facilitate in future reimbursement.
Dr. David Brown’s (Retina Consultants of Texas) talk was quite literally out of this world, describing novel disease of the choroid and optic nerve of NASA astronauts. While oxygen levels in spaceships are equivalent to those on Earth, the relative high CO2 levels and lack of gravity (resulting in changes to systemic blood flow) could be causing irreversible changes to these astronauts’ eyes. Recently it was discovered that these patients develop an approximate 0.5 diopter hyperopic shift while in space, initially perplexing astronauts as to why their vision was suddenly blurry after going into space and why they needed updated “space glasses.” Fundoscopic examination revealed that the patients’ metamorphopsia and vision loss was explained by choroidal folds, macular and peripapillary pigmentary changes, and papilledema associated with optic nerve sheath distention that weren’t present prior to their space expeditions. This lead to a study using a Heidelberg OCT that was brought on the NASA spaceship to image the astronauts’ optic nerves and maculas. Dr. Brown showed concerning before and after OCT images that showed that 100% of eyes demonstrated prelaminar optic nerve edema and choroidal thickening with folds after even a couple weeks in space. These changes improved to some degree (but not fully!) after returning to Earth, and it seemed cumulative based on the number of space expeditions and longevity in space. He noted that eyes with larger cup-to-disc ratios were affected less by papilledema, and surmised that likely the ophthalmologic changes were due to a combination of orbital venous congestion, hypercapnia, and elevated CSF.
Dr. Bailey Freund (Vitreous Retina Macula Consultants of New York) introduced the audience to high resolution OCT, which sports an incredible 3 um axial resolution. With this technology an amazing six distinct outer retinal bands can be detected and the retinal blood vessels and their connections were more readily visualized. He showed stunning images of multiple diseases where the high resolution OCT was superior at visualizing the retinal and choroidal anatomy. Dr. Freund demonstrated that this technology could be helpful for more accurately grading images such as differentiating iRORA and cRORA lesions. Unfortunately, you just had to be there to really appreciate the beauty of these images – see you in person at the next Pacific Retina Club meeting?
Finally, no imaging session is complete without an update from Dr. Richard Spaide (Vitreous Retina Macula Consultants of New York) on his newest application of OCT. In this session he focused on a novel way to visualize the vitreous using OCT. The vitreous is typically difficult to image using OCT unless one turns up the brightness significantly on the device, at which point the view to the retina and choroid is washed out. Dr. Spaide used the Heidelberg Spectralis to average four A-scans with a defocus into the vitreous cavity, averaged 100 B-scans, and performed volume-rendering to develop incredible 3-D images of the vitreous, retina, and choroid. In this way he was able to show that the vitreous contains hyporeflective liquid troughs surrounded by hyperreflective vitreous condensation. He evaluated eyes with early PVDs, noting that a hole or rip in the hyaloid face seems to allows vitreous fluid to egress between the hyaloid and retina. He also proposed that perhaps the function of the premacular bursa was to minimize traction to the fovea during eye movement by directing the force away from the macula. Finally, Dr. Spaide is always looking forward and beyond, and is working on AI to decrease image noise and machine learning segmentation of his vitreous OCT renderings.