Recent years have witnessed a remarkable increase in the indications for intraocular endoscopy. This has been largely driven by the availability of improved endoscopes and probes with major optimizations in size, image resolution and maneuverability.
Today, intraocular endoscopy has become a vital component in the management of several ocular pathologies, including: goniosynechialysis; retained lens fragments; dislocated posterior intraocular lens; transscleral suture fixation; ciliary body photocoagulation; proliferative vitreoretinopathy (PVR); intraocular foreign bodies (IOFBs); retinal detachment repair (especially for undetectable breaks in the peripheral retina); perforating injuries of the globe; post-traumatic endophthalmitis; endogenous; post-cataract and bleb-related endophthalmitis; and retinal assessment in forensic cases.
Intraocular endoscopy is associated with several key benefits. The Endo Optiks® endoscope (Beaver-Visitec, International, Inc.) can bypass opacities in the anterior segment to visualize the posterior segment structures at high magnification and at different angles. Therefore, endoscopy is advantageous in cases of hemorrhage, lenticular opacity, corneal opacity and scarring. In addition, endoscopy provides unique views of anterior structures not feasible with conventional microscopy, such as the sub-iris space and ciliary bodies. Furthermore, the flexibility of the endoscope probe and the ability to visualize posterior segment structures at close range facilitates the diagnosis and treatment of micro lesions in the retina.
A recent review article by Yu-Ping Zou and colleagues from the Department of Ophthalmology at the Guangzhou General Hospital in China, provided a synopsis of the common anatomical features and pathologies observed in the anterior vitreous, as well as the applications and indications of endoscopy-assisted vitrectomy in the anterior vitreous.
The paper, titled “Endoscopy-assisted Vitrectomy in the Anterior Vitreous” was published in the International Journal of Ophthalmology.1
In this paper, Dr. Yu-Ping Zou and co-authors chronicled the evolution and development of the modern intraocular endoscope, from its use in the removal of intraocular foreign bodies by Thorpe in the 1930s, to sulcus localization in sulcus-fixated, sutured, posterior chamber IOL implantation in the 1990s. The intraocular endoscope comprises three main parts: the camera, the xenon illuminating system and an optical laser. Fiber optic cables transmit the intraocular images from the camera and illumination source to an electronic monitor.
The imaging resolution and the field of view (FOV) are determined by the size of the endoscope. For example, a 19-G endoscope produces an image resolution of 17k pixels and a 140° FOV, a 20-G endoscope generates a 10k pixel image and a 110° FOV, and a 23-G endoscope creates a 6K pixel image and a 90° FOV. However, newer, high-resolution 23-G endoscopes can generate up to 10k pixel images and 120° FOVs.
Traditional microscopes versus endoscopes?
The authors summarized the key differences between conventional surgical microscopes and intraocular endoscopes. Traditional microscopes require a clear anterior media to visualize intraocular objects, while endoscopes need to traverse the anterior segment to capture images using their distal tip.
In addition, according to the authors, intraocular endoscopes produce panoramic, unobstructed views of the space between the vitreous base and the anterior segments behind the iris at high magnifications, which cannot be obtained by conventional microscopy.
Furthermore, endoscopes provide a unique intraoperative view from inside the vitreous cavity while traditional microscopes only provide a top-down perspective from outside the patient’s cornea.
However, according to Dr. Igor Kozak, clinical lead at Moorfields Eye Hospital Centre in Abu Dhabi, United Arab Emirates, while endoscopic probes provide an unprecedented view to areas of the eye that are otherwise difficult to visualize, the quality of current visualization is somewhat inferior to standard microscopic view.
“This relates to three qualitative aspects: field of view, intensity of illumination and stereopsis – all of which are limited in endoscopic retinal surgery. The best view is provided by the largest gauge endoscopes which, in turn, are more traumatic to the sclera and conjunctiva, and may be less desired in cases of pediatric vitrectomy. An ideal combination would be to have thinner endoscopes with superior visualization available,” explained Dr. Kozak.
Zooming in on the anterior vitreous: What’s the role of endoscopy-assisted vitrectomy (EV)?
The authors summarized published studies that evaluated clinical outcomes and complications of endoscopy-assisted vitrectomy in a variety of indications.
Furthermore, they described the common pathologies of the anterior vitreous. They noted that anterior vitreous retraction, prolapse, incarceration or adhesions are characterized by fibrotic changes, neovascularization and traction which could result in retinal breaks or detachment, and that these pathological changes can be clearly and directly visualized using an endoscope. Moreover, in the ciliary sulcus, endoscopy can facilitate complete capsulectomy during vitreolensectomy in cases with uveitis, and in cases with retained lens matter causing chronic uveitis.
The authors then itemized several benefits of using EV during the repair of retinal detachment. For example, it provides better visualization for retinal repair or re-attachment in cases with anterior media opacity, and is a useful tool for identifying undetectable retinal breaks, especially in pseudophakic or aphakic eyes, including cases with complex retinal detachment.
Additionally, endoscopy reduces the probability of retinal tearing or vitreous hemorrhage, especially in cases with IOFBs located in the anterior retina or pre-existing endophthalmitis. In addition, the authors noted other reports that showed that endoscopy can preserve visual acuity in cases which would otherwise require delay of surgery due to hazy media or the non-availability of a donor cornea for simultaneous penetrating keratoplasty.
Regarding the pediatric population, the authors noted that in the very few published studies on clinical outcomes of EV, the evidence suggests that endoscopy provides clear advantages during complex pediatric vitreoretinal surgery. In this context, the common pediatric vitreoretinal pathologies include retinopathy of prematurity, tractional retinal detachment and familial exudative vitreoretinopathy. Furthermore, pediatric eyes have a unique anatomy and physiology, as well as a high risk of aggressive and widespread PVR, especially in cases with traumatic retinal detachment and open globe injuries. Therefore, endoscopy, according to the authors, reduces the risk in these situations, as it can directly guide the surgery with minimal manipulation, thereby reducing the risk of iatrogenic events.
What are the challenge points to remember?
The authors highlighted the possible pitfalls associated with the use of endoscopy assisted vitrectomy, especially by inexperienced users.
The first issue is the indirect viewing of the surgical field on a monitor, which requires training to adapt to precise hand-eye coordination. It is important to note that bimanual surgery is impossible, as only one hand is used to control the endoscope, which can be uncomfortable for first time users.
Furthermore, they highlighted that due to the highly magnified image, endoscopy can provide a false sense of security regarding distance from anatomical structures, heightening the risk of iatrogenic trauma. Therefore, caution should be taken to avoid this by observing the focus of the endoscopic image when close to the tissue. The focus is fixed at 2mm to infinity so the image will blur when closer than 2mm.
In addition, the authors suggested a reduction in illumination intensity when working at high magnifications and short distances and stressed the important of keeping the endoscope’s tip clean to avoid obstruction or blurring of the endoscopic image.
Finally, the authors stressed the importance of extensive training in the successful use of this technique, preferably using an artificial eye, where available.
Final Thoughts
The authors concluded the paper by emphasizing the crucial role of intraocular endoscopy in aiding clear and accurate AV dissection intraoperatively, especially in cases with media opacity, small pupil or iris adhesion. Thus, they noted, it is likely that endoscopy assisted vitrectomy will become an increasingly valuable technique in this field.
In addition, Dr. Kozak highlighted that the trend in vitreoretinal, and ocular surgery in general, is gearing towards 3-D surgery due to excellent visualization and ergonomic reasons.
“As such, intraocular endoscopy has been at the forefront of ergonomics for many years. Currently, there is a wide array of indications and procedures available for intraocular endoscopy. Another application which could be explored more is the collection of intraocular fluid (vitreous) samples in uveitis cases with media opacities,” said Dr. Kozak.
Editor’s Note: Dr. Kozak was generous enough to contribute on this story, but he was not a part of the mentioned study.
Reference:1 Yu Y-Z, Zou Y-P, and Zou X-L. Endoscopy-Assisted Vitrectomy in the Anterior Vitreous. Int J Ophthalmol. 2018; 11(3): 506–511.
“Intraocular endoscopy has been at the forefront of ergonomics for many years. Currently, there is a wide array of indications and procedures available for intraocular endoscopy. Another application which could be explored more is the collection of intraocular fluid (vitreous) samples in uveitis cases with media opacities.”
– Dr. Igor Kozak
