History and concept of vitreoretinal surgery

Fifteen years after his first publication on vitreous removal in a closed system, Machemer wrote, ‘the next step was treatment of the retina itself. It takes an unconventional mind to break major taboos …².’ It was Machemer himself who previously broke with the greatest taboo. When he left Germany to join the Bascom Palmer Eye Institute, vitreous removal was thought of subsequently resulting in phthisis. In Miami, Machemer came across Kasner whose revolutionary clinical work of the 1960s has proved that an eye can also function without the vitreous³. Machemer and Parel developed the vitreous infusion suction cutter (VISC), a 17-gauge instrument which combined suction, cutting, infusion, and illumination properties in one handpiece⁴. For the first time, it was possible to remove vitreous hemorrhage obscuring the optical axis, which otherwise had to be left untreated^5,6. The VISC, however, required a 2.7 mm sclerotomy, and the turbulence the infusion caused at the tip of the vitrectomy port made selective removal of the vitreous difficult. O’Malley and Heintz separated the infusion line from the vitrectomy probe and opened a third sclerotomy for additional instruments, thereby creating the 20-gauge three-port approach which still serves as a standard for vitrectomy almost 40 years later⁷. At the same time, and in collaboration with Oertli instruments (Berneck, Switzerland), Klöti in Zürich developed the ‘Klöti’-stripper for vitreous removal, which is still in daily use in many vitreoretinal services over the world^8,9.

The new and spectacular technique of vitrectomy seemed to offer the solution for all problems in the vitreous cavity². Not only was the optical axis cleared of vitreous opacities, but also the retina itself could now be approached. Epiretinal membranes were removed, and traction was released from the retina¹⁰. In the mid-1970s, however, it gradually became more obvious that the expectations pinned on vitrectomy especially regarding the treatment of complicated forms of retinal detachment could not be fulfilled. At the same time, Scott in Cambridge used silicone oil as a tamponade of otherwise untreatable retinal breaks, a technique initially introduced by Cibis^11–14. As a logical consequence of development, also knowing Machemer’s approach, Haut in Paris combined both techniques, i.e. vitrectomy and silicone oil as an internal tamponade, and the combination of vitreous removal with traction release and silicone oil tamponade has become the method of choice in the treatment of complicated forms of retinal detachment^2,15.

Epidemiologic considerations and terminology

Every year, roughly 600 000 vitrectomies are performed worldwide, most of them in industrialized countries. Numbers are expected to increase further, due to the growing incidence of diabetes mellitus and pseudophakic retinal detachment. The term pars plana vitrectomy refers to the surgical approach and is discussed later.

Fundamental principles, indications, and goals of surgery

Vitreous removal is the main goal of vitrectomy. It clears the optical axis and provides access to the retina. Vitreoretinal traction is released by vitreous removal which therefore should be as complete as possible. Vitreoretinal pathology such as epiretinal membranes can then be approached and removed. Subretinal fluid can be drained via the retinal tear if present or through a drainage retinotomy. Endolaser photocoagulation can be applied, and an appropriate tamponade is filled into the vitreous cavity at the end of the procedure. Indications for vitrectomy are summarized in Box 58.1.

Anesthesia

Vitrectomy can easily be performed under local anesthesia. A peri- or retrobulbar block is sufficient if there is no general obstacle against it, such as claustrophobia.

Anatomical considerations

The ciliary body is composed of two parts: the pars plicata and the pars plana. In the adult eye the pars plicata extends 2.5 mm posteriorly to the iris root and contains approximately 75 ciliary processes that produce aqueous humor. Posterior to the pars plicata, the pars plana extends 4.5 mm temporally and 3 mm nasally.

Sclerotomies for vitreoretinal surgery in adults are ideally located 4 mm posterior to the limbus in phakic eyes and 3.5 mm in pseudophakic or aphakic eyes. This avoids bleeding from the pars plicata as well as damage to the lens and to the retina. In infancy, the ciliary body and the pars plana do not attain adult proportions until age 7 years. Therefore the incision into the pars plana is made at 2.5 mm posterior to the limbus.

Surgical approach

For 20-gauge vitrectomy, a conjunctival incision is performed at the limbus both nasally and temporally (Fig. 58.1). Episcleral vessels are cauterized. A microvitreoretinal (MVR) blade is kept perpendicular to the sclera at 3.5–4 mm distance from the limbus as mentioned above. Care is taken to aim toward the midvitreous cavity to reduce the risk of hitting the lens or damaging the retina. The infusion cannula is typically placed inferotemorally. Therefore, a 7-0 Vicryl suture on a spatulated needle is placed in a mattress fashion at the sclerotomy site. A slip knot is tied and holds the infusion line in place. At the end of vitrectomy, the slip knot is loosened and the same mattress suture is used to close the sclerotomy.

Fig. 58.1 Surgical approach for three-port pars plana vitrectomy.

Care should be taken to ensure that the infusion line enters the vitreous cavity, and not the suprachoroidal space. The infusion cannula must be visualized through the dilated pupil by rotating the eye away from the surgeon while the infusion line is grasped and gently pushed toward the central vitreous cavity. Once the position of the infusion cannula has been confirmed, the infusion is turned on (Fig. 58.2).

Fig. 58.2 The infusion line is turned on after it had been visualized in the vitreous cavity.

Superonasal and superotemporal sclerotomies are placed approximately 120–160° apart to facilitate manipulation within the vitreous cavity and to allow access to the entire retina. Some surgeons use sew-on contact viewing systems; others fixate the eye by passing a suture beneath the recti. Given modern wide-angle viewing systems such as the BIOM and others, however, there is no need to do so, and the eye can be better rotated and manipulated without fixation.

Fundamental principles of vitreous removal

The vitreous is not an easy tissue to operate on. Given the gel-like structure on the one hand and its firm attachment to the retina at least in some retinal areas, special devices and techniques are required to remove the vitreous without damaging the retina. The vitreous can’t be removed either by suction alone or by simple cutting. However, the combination of both techniques enables the surgeon to perform an effective vitrectomy without the risk of visual impairment.