Endoscopic vitrectomy provides direct visualization of the posterior segment with a directional camera, allowing surgeons to bypass compromised anterior segments, opacified corneas, and media opacities. Additionally, the ability to direct the visualization from the pars plana allows surgeons a method to visualize the anterior retina, ciliary body, and posterior iris surface in their natural anatomic configuration. New techniques are continually being described that demonstrate how endoscopic vitrectomy is beneficial to the retinal surgeon. In this article, we review our most common uses for endoscopic vitrectomy: infectious endophthalmitis, hypotony from anterior proliferative vitreoretinopathy, and surgical management of patients with a compromised cornea.

Video 1. Multiple retinal repair techniques done under endoscopic visualization.

Endoscopic Vitrectomy Overview from Pentavision on Vimeo.

INFECTIOUS ENDOPHTHALMITIS

Postprocedure endophthalmitis is for any ocular surgeon a dreaded complication and vitrectomy may be required in advanced cases. Patients with severe endophthalmitis often present a compromised view to the posterior segment from a combination of corneal edema, hypopyon, and fibrin plaques.¹

Endoscopic vitrectomy can improve the surgeon’s view. Insertion of an endoscope through the pars plana can verify the location of the vitreous cutter and its relationship to critical intraocular tissues. The dense vitreous debris associated with endophthalmitis can then be safely debulked, allowing visualization of the retina with the endoscope. Surgeons initially note an oversaturated white image from the endoscope upon entering the pars plana due to the glare and reflections from white inflammatory debris. Maintaining the vitreous cutter in a safe and stable position allows for a pocket of visualization that can be exploited to safely maneuver closer to the retina until retinal visualization is achieved. Then, following the retinal plane, the surgeon can work anteriorly to posteriorly to perform a thorough core vitrectomy with peripheral vitreous removal that would not be possible with transpupillary visualization.

When visualization to the retinal surface is achieved, the opportunity arises to address additional retinal pathology such as preretinal membranous adhesions, which can be debulked or removed with the direct visualization the endoscope provides. In some cases, retinal detachments may be present as well. These can be addressed using standard retinal detachment repair techniques, with endolaser applied either with the endoscope or with an independent laser. A lighted laser probe can be helpful in these case.

In our experience, patients with severe endophthalmitis often also have significant inflammatory and infectious material posterior to the iris. Removal with the vitreous cutter or intraocular forceps is safest with endoscopic visualization and may aid in the patient’s recovery.

Video 2. A case of treated fungal endophthalmitis with development of proliferative vitreoretinopathy retinal detachment. Despite clear media, the endoscope was used to inspect the anterior ciliary body. With endoscopic vitrectomy, this significant inflammatory debris was identified and removed.

Endoscopic Vitrectomy: Fungal Endophthalmitis from Pentavision on Vimeo.

HYPOTONY FROM ANTERIOR PROLIFERATIVE VITREORETINOPATHY

After retinal detachment repair, some patients will develop anterior proliferative vitreoretinopathy (PVR), requiring additional surgery. In some cases, PVR can develop overlying the ciliary body, resulting in chronic hypotony and eventually phthisis bulbi.² In many of these cases, anterior PVR is not accompanied by peripheral retinal detachment. Visualization of the ciliary body is challenging with standard transpupillary visualization techniques. In patients with anterior PVR, corneal edema and other anterior segment abnormalities often further compromise the view. In addition, scleral depression, which can bring the peripheral retina into view, does not allow the surgeon to appreciate the “true” anatomy, which can only be seen if the tissues are left in their natural position. Endoscopic visualization can achieve a clear view to these anterior membranes. Removal can then be done under direct visualization with a combination of the vitrector, intraocular forceps, and intraocular scissors.³ In general, we attempt to remove a minimum of 180° of the anterior scar tissue, taking care to avoid iatrogenic injury to the ciliary body. Endocautery is kept readily available, as the removal of anterior PVR can result in hemorrhages due to strong attachments to the underlying tissue.

In some patients, removal can be associated with a definitive improvement in IOP. Other patients may see no improvement, presumably due to the underlying atrophy of the ciliary processes.³ In our series, only a few patients had visual improvement associated with the increased IOP. Despite these limitations, we believe this technique is a potentially globe-saving surgery in patients who otherwise have limited options.

SURGERY WITH COMPROMISED CORNEA

Opacities within the cornea can rapidly diminish the usefulness of transpupillary visualization. Retinal surgeons are often referred patients with postoperative complications of anterior segment surgery or ocular trauma patients with extensive anterior segment damage. These patients often have significant corneal edema. The physician typically either waits for the corneal edema to resolve and then go to surgery, or uses a temporary keratoprosthesis followed by a full corneal graft. Endoscopic vitrectomy provides a third option by bypassing an opaque cornea, allowing for a less traumatic — and shorter — procedure.

Cases with retained lens fragments after cataract surgery are examples where endoscopic vitrectomy has been helpful.⁴ These patients often will have substantial corneal edema at presentation. Medical management with aggressive topical steroids and IOP-lowering medications typically suffice to maintain the patient until an improved view can be obtained. In patients with recalcitrant IOP issues despite treatment, utilizing an endoscope can allow for definitive treatment to be performed earlier than would otherwise be possible.

Post-corneal–transplant patients with posterior-segment complications can also benefit from endoscopic vitrectomy. Our group has been referred multiple patients who have had retinal detachments after combined phacoemulsification–Descemet stripping automated endothelial keratoplasty. In traditional settings, the otherwise successful corneal graft would have to be compromised or replaced with a penetrating keratoplasty to repair the retinal detachment. With endoscopic visualization, the existing keratoplasty is preserved and the retinal detachment can successfully be repaired.

GETTING STARTED WITH ENDOSCOPY

Only 2 pieces of equipment are required to begin performing endoscopic vitrectomy: an endoscopy platform and probe. The Endo Optiks E2 endoscope platform (Beaver-Visitec International, Inc.) features a wide array of probes. Options for probes include 19 g, 20 g, and 23 g instruments, with or without integrated laser. Resolution ranges from 6,000 pixels to 17,000 pixels, where large probes offer higher resolution due to their increased diameter.

When first learning to use the endoscope for vitrectomy, it may be beneficial to begin with the 19-g or 20-g endoscope, as these provide higher-resolution images with a wider field of view. As a surgeon becomes more familiar with endoscopic vitrectomy techniques, migrating to the 23-g probe becomes easier. We utilize the 23-g high-resolution (10,000 pixels) probe with laser most frequently, as this can fit through a standard 23-g valved trocar. For challenging cases, or cases where a larger pars plana wound is needed (eg, phacofragmentation), we utilize the 20-g probe for its higher resolution and wider field of view.

Prior to insertion of the endoscope into the eye, it is important to adjust light and focus settings. This is best done by placing the probe close to operating room drapes and having the circulating nurse adjust settings until a sharp image is achieved. Orienting the endoscope such that the cornea is at the top of the display screen prior to insertion through a sclerotomy aids in orientation within the globe. Upon entering the globe, locating the nerve and ciliary processes can orient the surgeon to key landmarks, facilitating safe maneuvering throughout the surgery.

CONCLUSIONS

There are limitations to utilization of an endoscope, such as limited field of view, which requires some adjustment given the familiarity with widefield viewing systems. Additionally, the view is monocular, so the surgeon must utilize other cues, such as focus, size, and light intensity, to compensate.⁵ The free rotation ability of the endoscope probe creates difficulty with orientation, making movements within the eye challenging, especially when first starting out. The combination of these factors creates risk for iatrogenic injury to the retina and results in a steep learning curve. Despite these limitations, endoscopic vitrectomy is a useful addition to the retinal surgeon’s armamentarium. The ability to bypass media opacities and to visualize structures otherwise not visible creates opportunities for unique surgical interventions in complicated surgical situations. RP

REFERENCES

1. Sabti KA, Raizada S. Endoscope-assisted pars plana vitrectomy in severe ocular trauma. Br J Ophthalmol. 2012;96(11):1399-1403.
2. Kim HC, Hayashi A, Shalash A, de Juan E. A model of chronic hypotony in the rabbit. Graefes Arch Clin Exp Ophthalmol. 1998;236(1):69-74.
3. Lee GD, Goldberg RA, Heier JS. Endoscopy-assisted vitrectomy and membrane dissection of anterior proliferative vitreoretinopathy for chronic hypotony after previous retinal detachment repair. Retina. 2016;36(6):1058-1063.
4. Boscher C, Lebuisson DA, Lean JS, Nguyen-Khoa JL. Vitrectomy with endoscopy for management of retained lens fragments and/or posteriorly dislocated intraocular lens. Graefes Arch Clin Exp Ophthalmol. 1998;236(2):115-121.
5. Marra KV, Yonekawa Y, Papakostas TD. Indications and techniques of endoscope assisted vitrectomy. J Ophthalmic Vis Res. 2013;8(3):282-290.