Update on imaging the peripheral retina

Since the introduction of the first ophthalmoscope by Charles Babbage in 1847 and the addition of diopter correction to it by Hermann von Helmholtz in 1851, ophthalmic imaging has undergone significant changes. In 1886, William Thomas Jackman and J. D. Webster published their technique of the first-ever successful human fundus photograph in two periodicals. However, it was not until 1926 that Stockholm’s Johan Nordenson and the Zeiss Camera Company were able to market a commercial device for use by practitioners, which became the first modern fundus camera. David Alvis and Harold Novotny performed the first fluorescein angiography (FFA) in 1959, using the Zeiss fundus camera with electronic flash. This development was a huge feat in the world of Ophthalmology. The first noninvasive imaging technique using light waves to obtain cross-sectional images of the retina-optical coherence tomography (OCT) was invented by David Huang et al. only as recently as in 1991. Thus, film photography evolved over time to digital photography catering for ultra-widefield (UWF) imaging, OCT, navigated peripheral OCT, simultaneous UWF FFA and navigated central and peripheral OCT, OCT angiography (OCTA), and three-dimensional (3D) OCT. While the first central images of the retina only allowed us to view a window of 20°, we can now capture a ×10 longer single-scan window of 200° or a montage window of 220°. The aim of this issue is to highlight benefits of new specialized imaging technologies and techniques in various retinal conditions applied by some of the most experienced users, assessing the posterior pole, mid-peripheral and peripheral retina as well as the vitreous and vitreoretinal interface. Professor Stanga’s team at The Retina Clinic London in England focused on the role of widefield (WF) swept-source OCT technology in ophthalmology and highlights its clinical applications. It could be demonstrated that high-quality images obtained by navigated peripheral swept-source (SS)-OCT was successful in assessing various ocular conditions of the peripheral vitreous, vitreoretinal interface, retina, and choroid, enabling visualization of vitreous floaters and opacities, retinal holes and tears, pigmented lesions, peripheral retinal degenerations, vitreoretinal attachments and traction as well as subretinal fluid. 3D OCT scans enhanced the visualization of these abnormalities and improved diagnostic and therapeutic decisions by early detection, precise anatomical measurements, and objective monitoring of disease progression. In addition, this technology served as a valuable tool for patient education, a teaching tool for trainees, and documentation for medico-legal purposes. Dr. Valentin Bravo and colleagues from the Hospital Clinico Universitario de Valladolid in Spain looked into the advantages of WF and UWF imaging with navigated central and peripheral OCT techniques to detect silicone oil emulsification (SOE) which poses a significant concern post vitreoretinal surgery. SOE can lead to various complications if undetected. Enhanced visualization capability enables the early identification of emulsified SO droplets, facilitating a proactive therapeutic approach and mitigating associated adverse events. Dr. Srinivas Sadda’s team from the UCLA Stein Institute in California looked into the advantages of UWF imaging without the need for mydriasis in the assessment of peripheral lesions in diabetic retinopathy (DR). Integration of additional UWF modalities including fluorescein angiography (FA), indocyanine green angiography, pseudocolor imaging, and fundus autofluorescence further enhance our understanding of peripheral retinal lesions. UWF imaging, in particular UWF FA and UWF OCTA, has emerged as valuable tools for assessing retinal and choroidal vascular abnormalities, nonperfusion areas, neovascularization, and microvascular abnormalities, all of which are critical in attributing peripheral retinal lesions to DR and thus offer more accurate management of the disease compared to the traditional fundus photography and dilated fundus examination alone. Detection of predominantly peripheral lesions is associated with a higher risk of DR progression and proliferative DR; hence, the accurate detection is critical in disease management. In their review paper, Dr. Choudhry’s team from the Vitreous Retina Macula Specialists of Toronto Institute in Canada discusses the application of OCT for various conditions in the retinal periphery. In 2019, the International Widefield Imaging Study Group outlined that WF imaging encapsulates a view range of roughly 60°–100°, capturing the retina’s mid-periphery to the posterior boundary of the vortex vein ampulla. UWF imaging involves capturing single images (not montaged) of the retina’s periphery, extending from the anterior edge of the vortex vein ampulla and beyond, resulting in a field of view of 110°–220°. The capabilities of various imaging systems including Heidelberg Spectralis HRA-OCT using a steering technique, the Optos Silverstone, the Zeiss Plex Elite 9000, the Canon Xephilio OCT-S1, and the recently developed 400 KHz SS TowardPi BMizar are discussed. Dr. Guiseppe Querques’ team based at the IRCCS San Raffaele Scientific Institute in Milan looked at the role of OCTA in the evaluation of peripheral ischemia in retinal vein occlusion. In their review paper, they summarized the main literature findings about microvascular changes and clinical applications of OCTA in the context of retinal vein occlusion-induced peripheral ischemia. WF-OCTA represents a promising noninvasive imaging technique for the assessment of peripheral ischemia. There has been a steady worldwide increase in obesity in combination with diabetes over the past decades, a continuous rise of myopia, as well as related and age-related retinal pathologies. Such abnormalities require early detection to prevent vision loss. In addition, it has become even more important in recent years for practitioners to be prepared to objectively monitor, address, and treat peripheral retinal lesions adequately and on time. WF and UWF imaging has therefore become an essential part of everyday clinical care. We trust that you will find this issue as exciting as we do. All contributing authors are leaders in the field, routinely present new findings on these hot topics at international meetings, and publish them. We hope you will enjoy reading this issue.

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