**5. Surgical technique and instrumentation**

The rationale of the technique for removing the ERM has not changed since 1972, when Machemer introduced this procedure to vitreoretinal surgery. Machemer used a 23g bent needle to remove the epimacular membrane after 17g pars plana vitrectomy. Despite the continuous evolvement and development of surgical instrumentation, the technique today remains practically the same. First, a three-port pars plana vitrectomy is performed. The ERM is then peeled off with appropriate forceps. Dyes are often used to better visualize the membrane. Sometimes, scissors are necessary for the dissection of highly-adhered membranes. Several surgeons proceed to ILM peeling as a next step in order to minimize ERM recurrence. In most cases, the operation finishes without the need for tamponade and mandatory posture.

In the following paragraphs, the steps of the procedure, as well as the necessary equipment and adjuvants are described in more detail.

#### **5.1. Vitrectomy**

A three-port pars plana vitrectomy is the first step of the procedure, although there are some reports in the literature regarding direct epiretinal membrane peeling without prior vitrectomy [43-44]. A core vitrectomy is performed, followed by posterior vitreous detachment, if this is not already present. This is done either actively with the vitreous cutter, or passively with a flute needle, starting by elevating the posterior hyaloid membrane at the level of the optic disc. Subsequently, the vitrectomy is completed with the cortex removal.

#### *5.1.1. Microincision Vitrectomy Systems, MIVS*

During the past number of years, most surgeons prefer small gauge vitrectomy systems and thus, the procedure is sutureless and atraumatic. The systems that are broadly used for the macula surgery are the 23G and the 25G, while 27G was also recently introduced [45]. The use of either system depends primarily on the surgeon's preference and they do not seem to affect postoperative outcomes [46-49]. However, the wide acceptance of the microincision systems indicates that these outnumber the 20-g system, offering shorter operating times, reduced corneal astigmatism, diminished conjunctival scarring, improved patient comfort and in some cases, earlier visual recovery [50-52]. Although this is true for most vitrectomy applications, it is especially true for macula surgery including ERM peeling.

Small gauge systems are considered to offer better postoperative comfort due to minimal surgical trauma. However, as size goes down, instruments tend to be less stiff, sometimes rendering globe manipulation during surgery difficult. Postoperative leakage from the unsutured entry sites has been correlated to hypotony and endophthalmitis; however, the findings in the literature regarding this are not consistent [48, 50, 53-54]. Moreover, as the small cutter lumen removes smaller vitreous quantities per cut, vitreous removal is relatively slower compared to traditional vitrectomy. Recent advances in vitrectomy systems related to fluidics, cutting rates, instrument design and alloys, have succeeded in compensating for most of these drawbacks and have made microincision vitrectomy systems the preferred platform for most posterior segment surgeons. The introduction of xenon and mercury vapour lights has also helped in overcoming some early problems related to illumination. The bright illumination and low light hazard offered by these light sources, even in very small diameter systems, have helped to broaden the scope of small gauge vitrectomy.

#### *5.1.2. Visualization systems*

In addition, fluorescein angiography (FA) is another adjuvant diagnostic test for ERM. Despite the fact that it is usually not necessary to establish the diagnosis of an ERM, FA can be helpful in assessing the extent of vascular distortion and detect the presence of vascular leakage and macular oedema. ERM associated vascular leakage, when present, is typically irregular, asymmetric and within the area of the ERM. It is also useful to exclude other lesions that may share common clinical findings with ERMs, such as choroidal neovascularization and other

The rationale of the technique for removing the ERM has not changed since 1972, when Machemer introduced this procedure to vitreoretinal surgery. Machemer used a 23g bent needle to remove the epimacular membrane after 17g pars plana vitrectomy. Despite the continuous evolvement and development of surgical instrumentation, the technique today remains practically the same. First, a three-port pars plana vitrectomy is performed. The ERM is then peeled off with appropriate forceps. Dyes are often used to better visualize the membrane. Sometimes, scissors are necessary for the dissection of highly-adhered membranes. Several surgeons proceed to ILM peeling as a next step in order to minimize ERM recurrence. In most cases, the operation finishes without the need for tamponade and mandatory posture. In the following paragraphs, the steps of the procedure, as well as the necessary equipment

A three-port pars plana vitrectomy is the first step of the procedure, although there are some reports in the literature regarding direct epiretinal membrane peeling without prior vitrectomy [43-44]. A core vitrectomy is performed, followed by posterior vitreous detachment, if this is not already present. This is done either actively with the vitreous cutter, or passively with a flute needle, starting by elevating the posterior hyaloid membrane at the level of the optic disc.

During the past number of years, most surgeons prefer small gauge vitrectomy systems and thus, the procedure is sutureless and atraumatic. The systems that are broadly used for the macula surgery are the 23G and the 25G, while 27G was also recently introduced [45]. The use of either system depends primarily on the surgeon's preference and they do not seem to affect postoperative outcomes [46-49]. However, the wide acceptance of the microincision systems indicates that these outnumber the 20-g system, offering shorter operating times, reduced corneal astigmatism, diminished conjunctival scarring, improved patient comfort and in some cases, earlier visual recovery [50-52]. Although this is true for most vitrectomy applications, it

Small gauge systems are considered to offer better postoperative comfort due to minimal surgical trauma. However, as size goes down, instruments tend to be less stiff, sometimes

Subsequently, the vitrectomy is completed with the cortex removal.

is especially true for macula surgery including ERM peeling.

vascular diseases of the retina.

120 Advances in Eye Surgery

**5. Surgical technique and instrumentation**

and adjuvants are described in more detail.

*5.1.1. Microincision Vitrectomy Systems, MIVS*

**5.1. Vitrectomy**

Extremely clear visualization of the surgical field represents one of the cornerstones of modern retinal microsurgery. Dealing with fine tissues and transparent membranes, and avoiding damage to sensitive structures, requires a very good stereoscopic view. Several systems have been introduced in surgical practice; below, the most commonly used are reviewed.

#### *5.1.2.1. Contact lenses*

Plano-concave lenses are placed directly on the cornea for posterior segment view. Their primary advantage is the high-resolution image that the surgeon obtains with their application. However, they have an important disadvantage in the form of their instability during surgery. In order to overcome this limitation, ring systems have been designed for sutureless stabili‐ zation on the cornea; at the same time, various ways have been proposed for adjusting them (e. g., on the speculum, at the cannulas etc.). Many surgeons use these lenses either separately or in combination with a non-contact system.

#### *5.1.2.2. Non-contact systems*

The first non-contact optical system for visualizing the posterior segment was presented in 1987, which was the binocular indirect ophthalmomicroscope (BIOM, Oculus, Wetzlar, Germany) [55]. It is the most frequently used wide-angle viewing system for retinal surgery. The BIOM, as all other non-contact systems, is based on indirect ophthalmoscopy, which results in an inverted image. An optical system introduced in the microscope's optical pathway is used for image re-inversion, so that the image viewed by the surgeon has normal orientation. An important feature of the BIOM is the variety of lenses that one can choose from and switch between during surgery, as it comes with a 60 deg., 90 deg. and 120 deg. refraction lens. For example, for macular surgery, a 60 deg. macula lens can be placed for the membrane peeling, while at the end of the procedure, the surgeon can switch to a 120 deg. wide field in order to check for breaks at the periphery. In first BIOM generations, the focus and the inversion of the field were manual; however, most recent BIOMs have incorporated a footswitch for focus adjustment and an automated inverter.

Other non-contact systems include the EIBOS (HS, Moeller-Wedel Optical GmbH, Wedel, Germany), the OFFISS (optic fibre free intravitreal surgery system/OFFISS; Topcon Medical Systems, Oakland, NJ), the OptiFlex (Volk, Mentor, OH), the PWL (PWL; Ocular Instruments, Bellevue, WA) and the Resight 700 (Carl Zeiss Meditec AG, Jena, Germany). Each of them has positive (automatic inverters, adjusted illumination, automatic lens switches, etc.) and negative (adjustable in specific microscopes, unstable coaxiality, etc.) aspects. Eventually, the selection of the particular optical system will depend on the surgeon's experience, comfort and familiarity with the technique and the technology.

#### *5.1.3. Visualization adjuvants*

Vital dyes stain the faint epiretinal membranes and thus improve contrast during surgery. Their utilization has considerably facilitated macular surgery and is considered by many surgeons extremely helpful for both ERM and ILM removal [56]. Trypan Blue (TB) is the most frequently used dye and stains mainly the ERM. Brilliant Blue G (BBG) stains both the ILM and ERM and is preferred when ILM removal is also desired. Other dyes such as indocyanine green (ICG) and infracyanine green (IFCG) primarily stain the ILM and we will not discuss their use in this chapter.

The use of trypan blue for ERM staining has been well-studied and is considered an excellent, non-toxic approach for visualizing the membrane [57-59]. It is usually injected under air in order to avoid lens capsule staining; this will hinder the continuation of the operation due to the deprivation of the view of the posterior segment. Alternatively, heavy TB can be used, which does not demand an air-fluid exchange [60]. The TB is left for one- to three-minutes and is then washed away. The epiretinal membrane and other proliferative tissue are stained and their edges show against the unstained background.

Brilliant Blue G mostly stains the ILM, but the ERM is also stained to some degree [61]. It is preferred when dual staining is necessary, for simultaneous removal of ERM and ILM [62]. It is also injected under air and washed away after a few minutes. It is generally reported to be safe although some concerns about retinal toxicity have been raised [59, 63-64].

Another substance that is quite effective in visualizing ERMs is triamcinolone (TA). TA is not a dye; it forms crystals that are deposited through loosely organized collagen matrices, making visible the vitreous body, but also ERMs and the ILM [65].

#### *5.1.4. Forceps and scissors*

Fine instruments are imperative for handling fine structures such as the epiretinal membranes and the ILM to lessen possible damage to the underlying retinal tissue. Instrument sizes follow the trend of minimizing the size of the vitrectomy ports. Nowadays, forceps, scrapers, scissors and other adjuncts exist in compatibility with 20g, 23g, 25g and 27g PPV systems.

End-grasping forceps are the most commonly used instruments for ERM peeling. Klaus Eckhardt developed the first fine end-grasping forceps in the 90s; these proved to be very effective and are still preferred today. Later, Charles developed conformal forceps, meaning that they have the same radius of curvature as the retina and avoid grasping of the retinal surface by grasping the nerve fibre layer (NFL) during the procedure. Rarely, in high adherence situations, scissors can be used. Horizontal scissors are preferred because of their safer profile compared to vertical scissors. They can be inserted into the potential space between the membrane and the retina, with both blades more efficiently delaminating the ERM from the subjacent tissue.

When the edge of the membrane is not easily grasped by forceps, a Tano diamond dusted membrane scraper (DDMS) can be used. This tool is coated with inert diamond dust that makes traction easier and offers an atraumatic alternative to finding the edge of the membrane due to its soft silicon tip. The Tano DDMS is for some surgeons an indispensable part of macular surgery. Its use is also suggested for ILM removal. However, attempting to create an edge at the ILM with this tool is strongly discouraged due to the damage it can cause to the subjacent tissue [66].

#### **5.2. Removal technique**

Systems, Oakland, NJ), the OptiFlex (Volk, Mentor, OH), the PWL (PWL; Ocular Instruments, Bellevue, WA) and the Resight 700 (Carl Zeiss Meditec AG, Jena, Germany). Each of them has positive (automatic inverters, adjusted illumination, automatic lens switches, etc.) and negative (adjustable in specific microscopes, unstable coaxiality, etc.) aspects. Eventually, the selection of the particular optical system will depend on the surgeon's experience, comfort and

Vital dyes stain the faint epiretinal membranes and thus improve contrast during surgery. Their utilization has considerably facilitated macular surgery and is considered by many surgeons extremely helpful for both ERM and ILM removal [56]. Trypan Blue (TB) is the most frequently used dye and stains mainly the ERM. Brilliant Blue G (BBG) stains both the ILM and ERM and is preferred when ILM removal is also desired. Other dyes such as indocyanine green (ICG) and infracyanine green (IFCG) primarily stain the ILM and we will not discuss

The use of trypan blue for ERM staining has been well-studied and is considered an excellent, non-toxic approach for visualizing the membrane [57-59]. It is usually injected under air in order to avoid lens capsule staining; this will hinder the continuation of the operation due to the deprivation of the view of the posterior segment. Alternatively, heavy TB can be used, which does not demand an air-fluid exchange [60]. The TB is left for one- to three-minutes and is then washed away. The epiretinal membrane and other proliferative tissue are stained and

Brilliant Blue G mostly stains the ILM, but the ERM is also stained to some degree [61]. It is preferred when dual staining is necessary, for simultaneous removal of ERM and ILM [62]. It is also injected under air and washed away after a few minutes. It is generally reported to be

Another substance that is quite effective in visualizing ERMs is triamcinolone (TA). TA is not a dye; it forms crystals that are deposited through loosely organized collagen matrices, making

Fine instruments are imperative for handling fine structures such as the epiretinal membranes and the ILM to lessen possible damage to the underlying retinal tissue. Instrument sizes follow the trend of minimizing the size of the vitrectomy ports. Nowadays, forceps, scrapers, scissors

End-grasping forceps are the most commonly used instruments for ERM peeling. Klaus Eckhardt developed the first fine end-grasping forceps in the 90s; these proved to be very effective and are still preferred today. Later, Charles developed conformal forceps, meaning that they have the same radius of curvature as the retina and avoid grasping of the retinal surface by grasping the nerve fibre layer (NFL) during the procedure. Rarely, in high adherence situations, scissors can be used. Horizontal scissors are preferred because of their safer profile compared to vertical scissors. They can be inserted into the potential space between the

and other adjuncts exist in compatibility with 20g, 23g, 25g and 27g PPV systems.

safe although some concerns about retinal toxicity have been raised [59, 63-64].

familiarity with the technique and the technology.

their edges show against the unstained background.

visible the vitreous body, but also ERMs and the ILM [65].

*5.1.3. Visualization adjuvants*

122 Advances in Eye Surgery

their use in this chapter.

*5.1.4. Forceps and scissors*

Once the vitrectomy is completed, the ERM is inspected for visible edges. Existing edges are visualized much better if dye has been used for ERM staining. Moreover, careful preoperative evaluation using SDOCT can be extremely helpful in this regard by providing information about the 3D configuration of the membrane and the selection of an optimum area for peel initiation. If a pre-existing edge cannot be found, it can be created using a pick or a microvitreoretinal (MVR) blade. The edge is then grasped with the forceps, with the one blade on the anterior surface and the other under the membrane, and a circumscribed flap is created. Then, careful and gentle dissection is started from the periphery to the centre of the membrane (outside-in technique), similar to the capsulorhexis in cataract surgery. Alternatively, the membrane is grasped centrally and peeled away from the centre, always in a circumferential pattern (inside-out technique). Some surgeons consider the inside-out technique safer, because the central retina is thicker and stronger, making it easier for the surgeon to find a tissue plane to begin with.

Since both the picking and the grasping of the membrane can cause damage to the subjacent retinal tissue (tears, bleeding, ischaemia), good visualization and controlled manoeuvres are very important at this stage. Directing the tip tangentially to the retinal surface and engaging the membrane from different directions helps to avoid fragmentation of the tissue sheet and inadvertent tearing of the retina [67].

Charles has proposed an alternative approach for minimizing tissue damage, described as "pinch peeling". In this case, the forceps pinch the membrane without creating an "edge" and grasp it with the two blades on the surface of the membrane. Retinal contact is thus avoided and the risk of retinal damage is minimized [68].

#### *5.2.1. ILM peeling*

Very often, the ILM is peeled off together with the ERM. This can be monitored during ERM peeling by using a dye that stains both the ERM and the ILM, e. g., Membrane Blue Dual® (DORC, Japan). If this is not achieved, the ILM can be removed at a second step. ILM peeling is impossible without the creation of an opening in the inner limiting membrane. If an edge of the ILM has not been created during ERM manipulation and removal, it can be made using a pick or MVR blade, at a location away from the maculo-papillary bundle, frequently along the temporal horizontal raphe. The fine-end forceps are again used to grasp and elevate the membrane and peeling is again performed in a circular motion, extending towards the vascular arcades. The simultaneous removal of the ILM is imperative for some surgeons, but it is not yet clear whether it affects recurrence rates [69-70] or retinal function [71-73].

#### **5.3. Conclusion of surgery**

Following ERM removal, inspection of the peripheral retina follows; if this shows no iatrogenic damage, surgery is completed by trocar removal and sclerotomy closure. If iatrogenic damage is present, breaks in the periphery without subretinal fluid accumulation can be treated by laser retinopexy or cryoretinopexy. The presence of significant amounts of subretinal fluid necessitates internal drainage, retinopexy and gas tamponade.

Although scleral ports in small gauge vitrectomy are designed so that no sutures are necessary, careful inspection of the water tightness of the ports at the conclusion of surgery is mandatory in order to avoid early postoperative hypotony. Gentle massage of the site of scleral incision after trocar removal can improve a relatively leaky incision. Occasionally, the insertion of a small suture may be necessary for a leaky scleral incision.
