Intraoperative photograph demonstrating the use of the cutter to release the vitreous from the disk neovascularization
A 23-gauge intraocular diathermy is used with low energy to lightly cauterize the edge of the disk neovascularization
Any residual preretinal hemorrhage can then be aspirated using the vitrectomy instrument. Rather than placing the cutter close to the retina and risking potential iatrogenic injury, one can aspirate in the mid-vitreous cavity while directing the infusion cannula toward the area of hemorrhage. The infusion jet stream will then disperse the hemorrhage from the retinal surface.
6.2.2 Approach to Dense Vitreous Hemorrhage
In these situations, a B-scan is imperative preoperatively for surgical planning and in order to ensure that an underlying retinal detachment (RD) is not present. Even with confirmation of no RD, it is important to proceed cautiously as visualization may be limited, and it can be difficult to distinguish hyaloid from retina in some situations. The core vitrectomy, when possible, should be started in the superior half and proceed layer by layer until the location of the retina is confidently confirmed. This is useful in situations where an unforeseen RD is present under the hemorrhage as creating an iatrogenic break in superior retina will be easier for tamponade. Once an opening in the posterior hyaloid has been made and the retina visualized beneath, the cutter should be kept at the edge of the hyaloid and continue to enlarge the opening. Shaving of the inferior vitreous base under scleral depression may be helpful in these cases as much of the blood will have pooled inferiorly by gravity. By shaving down this area, much of the hemorrhage that tends to leach out postoperatively is removed, often allowing for a faster visual recovery postoperatively.
6.3 Surgical Techniques: Approach to Traction Retinal Detachment
TRDs represent some of the most challenging cases in vitreoretinal surgery. The approach that needs to be taken for a successful outcome varies, and no one approach works for all cases. Oftentimes, creativity is essential.
Typically, at least some parts of the hyaloid will be elevated outside the retinal vascular arcades as this is the underlying mechanism leading to the tractional detachment. In this situation, the anterior-posterior traction can be relieved first by incising the elevated posterior hyaloid in the midperiphery then trimming it down toward the edges of the membranes. Once the hyaloid has been trimmed, attention can then be directed toward dissecting the remaining membranes.
Alternatively, it may be helpful to initiate dissection of fibrovascular membranes around the optic nerve and then move outward. Diabetic traction retinal detachment often extends from the optic disk outward and along the retinal vascular arcades. Since the retina is thicker and less fragile near the optic nerve, this is another good option for approaching a TRD.
Although the appearance of the fibrovascular membranes can appear as sheets of contracted tissue detaching the underlying retina, the cross-sectional anatomy usually reveals that the retina is attached to the membranes by focal “pegs” (previous areas of NVE) rather than by broad adhesion to the retina. The most efficient membrane dissection, therefore, first identifies the open areas between the fibrovascular membranes and the retina and, secondly, identifies the adjacent “pegs” which may be detached from the retina with the vitrectomy cutter itself or one of several techniques described below.
6.3.1 Bimanual Techniques: Lighted Pick
Using a forceps in one hand and a lighted pick in the other hand, the hyaloid/membrane can be pulled up in order to identify the underlying pegs (Fig. 6.3). The pick is used to sweep back and forth across these pegs to assist with delamination. The bottom platform of the pick may also be used to apply gentle countertraction simultaneously on the retina as the membrane is being pulled. This enhances visualization of the pegs during dissection. The lighted pick can also be used in conjunction with the vitreous cutter itself to manipulate and cut away fibrovascular membranes while simultaneously creating a safe zone of underlying retina beneath the pick blade.
Intraoperative photograph demonstrating use of the lighted pick in combination with forceps for delamination of membranes from the retina surface
6.3.2 Bimanual Techniques: Chandelier
A chandelier provides excellent diffuse lighting, allowing both hands to be used for membrane dissection (Fig. 6.4). Typically, a forceps is used in one hand to grasp the membrane, while a second instrument may be chosen to assist with delamination and segmentation of the membranes. With the advent of small-gauge vitrectomy instruments, several enhancements have been made to the cutter, including a wider mouth and displacement of the opening toward the tip. These factors allow the cutter to be used almost like a vertical scissor. The neovascular pegs are identified by gently lifting the edge of the membranes with the forceps. The mouth of the cutter can then be used to engage the peg and release the attachment between the membrane and retina. Minimal aspiration is typically necessary, and a low cut rate will often suffice.
Insertion of a 25-gauge chandelier through a self-retaining cannula
Another useful instrument is curved horizontal scissors, particularly when broad areas of fibrosis are present. Using forceps in one hand, the edge of the membrane is lifted. The scissors can be used to perform blunt dissection by placing the tips closed in the space between the retina and membrane and spreading (Fig. 6.5). As the neovascular pegs are identified, these can be directly cut by the scissors with a gentle lifting technique, lowering the risk of iatrogenic breaks related to traction. Scissors can also be used for segmentation by simply tilting the scissors and directly engaging and cutting the membrane. Recently, pneumatic scissors have been introduced which allows the surgeon to use the foot pedal to control the opening and closing of the instrument. This further enhances the stability during membrane dissection, allowing for greater precision and control.
Using a chandelier for illumination, delamination of membranes can be accomplished with forceps and a curved horizontal scissors
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Viscodelamination was originally described by Stenkula and Tornquist in 1983 as a technique for removal of epiretinal membranes . However, McLeod and James were the first to report success with viscodissection in tractional retinal detachments from proliferative diabetic retinopathy . Hubbard and Fortun modified the technique for microincisional vitrectomy and were the first to report use of the viscodelamination instrument which improved access, maneuverability, technical ease, and allowed for surgeon-controlled delivery of the viscoelastic . In this technique, viscoelastic is used to separate the posterior hyaloid and fibrovascular membranes from the subjacent retina. This technique is particularly useful for tractional retinal detachments with broad attachments between the fibrovascular membranes and retina, in combined tractional and rhegmatogenous retinal detachments (Fig. 6.6a), and in cases where there is minimal or no separation of the posterior hyaloid.
(a) Preoperative fundus photograph demonstrating a tractional retinal detachment from proliferative diabetic retinopathy. Note the broad attachments between fibrovascular membrane and retina. (b) Intraoperative fundus photograph demonstrating viscodissection with 25-gauge viscodelaminator instrument. (c) Intraoperative fundus photograph demonstrating the same area following membrane dissection and removal with the vitreous cutter