aThe problem with most studies is that vitrectomy was applied as a last resort, not as an early weapon.

experience vision increases then drops with the injections (see Sect. 49.1.2). Furthermore, injections remain a viable option in those relatively few cases when PPV was unsuccessful.

Vitrectomy is able to reduce or cure the macular edema and allow the proper laser treatment to be done intraoperatively.3 Timely removal of the gel is also likely to prevent the severe fibrovascular reaction that occurs in some eyes with CRVO. Once such a TRD occurs, the prognosis is very poor (see below), and PPV is the only remaining option.

58.2Surgical Technique

•Give intravitreal anti-VEGF (or steroid injection) at 3 months, 2 months, and 1 week prior to the planned surgery.

–If proliferative membranes are present or suspected in an eye with VH, give the anti-VEGF injection 2–3 days before surgery.

•Perform a subtotal or total vitrectomy.

–Because this results in an increased oxygen level in the vitrectomized eye, it is advisable to remove as much of the gel as possible.

–PVD is often lacking, and even if it is present, it may be anomalous. In eyes with significant VH, PVD creation is commonly difficult and risky: at certain locations the VR adhesion can be very strong. If the surgeon, assuming that the PVD is complete, proceeds without proper caution, he may cause a retinal tear or even intraoperative RD.

Pearl

In eyes with no or late surgery after CRVO, it is not uncommon for severe fibrovascular proliferation to develop. TRD may ensue, which is difficult to deal with because the retina is often ischemic and thus fragile; separation of the nondetached posterior vitreous is all but impossible.

3 Which is a significant benefit since eyes with CRVO often have nonresorbing VH, making laser treatment impossible or unnecessarily delayed.

•In eyes with proliferative membranes and TRD, consider silicone oil implantation.

–If a retinal vessel loops into vitreous,4 cut the proliferation around it but leave the vessel alone.

•Peel the ILM in the macula (see Sect. 49.2).

–In eyes with BRVO, also peel the ILM over the arteriovenous crossing if the artery lies anteriorly; the fibrous capsule may also have to be cut with a blade or sharp5 needle (sheathotomy).

•Perform laser treatment.6

–If there are many retinal hemorrhages, the laser treatment should be completed when most of the blood has been absorbed.

•If TRD has developed (see Chap. 55), a compromise must be found between doing too much (which may involve removing large parts of the retina if the adherent vitreous is inseparable) and too little (leaving behind much of the vitreous, which later may contract).

4The proliferation slowly drags the retinal vessel above the surface; the vessel has time to adapt since the process is slow. Even when the “loop” is freed from the membrane responsible for the dragging, the vessel will never reinsert into the retina.

5No barb on the needle.

6Grid and in a sector along the occluded vessel in BRVO, panretinal in CRVO.