An endoscope can improve outcomes in cases in which the view through the traditional operating microscope is known to be compromised preoperatively, and is a good backup if a problem makes visualization difficult intraoperatively.
Take-home message: An endoscope can improve outcomes in cases in which the view through the traditional operating microscope is known to be compromised preoperatively, and is a good backup if a problem makes visualization difficult intraoperatively.
By David Liao, MD, PhD, Special to Ophthalmology Times
Dr. LiaoProper visualization of pathology is the key to successful vitreoretinal surgery. As a result, I frequently make use of the endoscope (Beaver-Visitec, Endo Optiks, Inc.) in cases where the view through the traditional operating microscope is known to be compromised preoperatively or degrades intraoperatively. Having the endoscope available gives me confidence that I can identify and treat the underlying retinal pathology in practically every case.
The most common situation in which I use the endoscope is when coexisting anterior segment pathology precludes a view of the posterior pole. Often, these are cases of long-standing retinal detachment or trauma that have resulted in significant cornea or lenticular opacities. At times, I also use the endoscope to locate and remove anteriorly situated retained lens fragments and for membrane peeling in cases of anterior loop proliferative vitreoretinopathy.
Rarely, a routine case can start out with a clear view but end with a substantially worse view. An uncooperative pupil or misbehaving IOL can make good visualization difficult. During these times, having the endoscope as a backup can offer a distinct surgical advantage in terms of safety and presumably outcomes.
(Figure 1) Malpositioned single-piece PMMA lens in the sulcus with optic capture. The outlines of the haptics are visible due to iris chafing (black arrows). Residual keratic precipitates are visible on the endothelium and lens surface. (Image courtesy of David Liao, MD, PhD)
In complex cases, the normal anatomical landmarks can be distorted. At the start of the case, the view through the endoscope may therefore be disorienting. It is important to first maintain proper image orientation. Retinal surgeons are accustomed to a more or less static, en face view of the posterior pole through the microscope. The endoscope allows the surgeon the view the retina from a shorter distance and at various angles. Keep in mind that while holding the endoscope probe, the small rotational movements can dramatically alter image orientation on the viewing screen.
Therefore, orienting the scope before entering the eye and maintaining that orientation during the case allows safe manipulation of instruments within the vitreous cavity. I find that getting my bearings with the help of an illuminator through the opposite port or an additional chandelier light is helpful. In addition, staining the vitreous with triamcinolone or membranes with indocyanine green can be helpful due to the lack of stereopsis with endoscopy.
Recently, a 72-year old female presented with a single piece PMMA lens that had been placed in the sulcus during complicated cataract surgery 3 years earlier. (Figure 1). There was optic capture, with the malposition resulting in a low grade iritis. The patient also had a significant macular pucker.
After treating the inflammation topically, I thought removing the lens would be a simple case of dialing it into the anterior chamber. I did not anticipate using the endoscope. The lens mobilized easily at first. However, after completing the rotation, I noticed that the inferior haptic had fractured and remained hidden behind the iris. Leaving it in place might have been acceptable but also might have resulted in further uveitis. Using the endoscope, I was able to visualize it behind the iris, grasp it with forceps, and deliver it through a sclerotomy fairly easily.
My first experience with endoscope probes were with the 20-gauge variety. These provided excellent resolution at 17,000 pixels as well as a wide, 140° field of view. Afterward, I transitioned to mostly 23-gauge cases, which were more technically challenging as the smaller probes had a 6,000 pixel resolution and a 90° field of view. The newer 23-gauge probes will increase resolution to 10,000 pixels and field of view to 125°.
I expect that ongoing advances in probe technology will make endoscopy even simpler and practical to use.
David Liao, MD, PhD
Dr. Liao is in practice at Retina Vitreous Associates Medical Group.