*2.2.3 Patient counselling*

Besides advocating for surgery, it is very important to counsel the patient about the visual potential since despite good anatomical outcomes, in patients with long standing detachments and macular ischemia, functional outcomes may not be very satisfying. The chances of multiple surgeries due to recurrent vitreous cavity bleeds or redetachments due to reproliferations should be explained. Need for subsequent cataract surgery or silicon oil removal surgery should be explained clearly beforehand. Importance of good systemic control should be re-emphasised.

#### **Figure 2.**

*Ultrasound images of a patient with vitreous haemorrhage with subhyaloid haemorrhage with thickened and incomplete hyaloid separation.*

*Vitrectomy in Diabetic Retinopathy DOI: http://dx.doi.org/10.5772/intechopen.101358*

Various studies have shown that a pre-operative intravitreal anti-VEGF injection 3–14 days prior to surgery can help in controlling intra-operative bleeding [7, 8]. Nonetheless, one has to keep in mind that bleeding may occur despite an anti-VEGF injection. Some patients can develop *Crunch syndrome* after anti-VEGF injection. In these cases, TRD worsens due to development of denser fibrotic connections between the retina and overlying tissue, thus making it harder to identify tissue planes. In a retrospective review of TRD following intravitreal bevacizumab, anti-VEGF crunch developed at 5 days or more after initial IVB injection in nearly 80% of cases [9].

## **3. Timing of vitrectomy in diabetic vitreous haemorrhage**

At the time of diabetic retinopathy vitrectomy study (DRVS), vitrectomy was performed in patients who had non-resolving vitreous haemorrhage for more than 12 months. The results of DRVS showed that eyes undergoing early vitrectomy for severe vitreous haemorrhage were more likely to have VA ≥ 20/40 at 2 years and greatest benefit was seen in patients with type 1 diabetes [10]. With the evolution of better surgical techniques and instruments (MIVS), early vitrectomy is more effective in achieving better visual outcomes [11]. Usually, patients with type 1 or type 2 diabetics with VH and no underlying traction, can be observed for 1 month [12]. In the meantime, if haemorrhage improves, visible panretinal photocoagulation (PRP) or intravitreal anti-VEGF injection can be given to allow for neovascularisation to regress. In patients with visually demanding jobs, an early vitrectomy can be performed.

In patients with persistent VH, especially aphakic and pseudophakic patients with posterior capsular defect, there is an increased risk of ghost cell glaucoma and neovascular glaucoma. In these patients, anti-VEGF can be considered prior to surgery and an early vitrectomy is warranted to control IOP.

Vitreous haemorrhage can sometimes develop after panretinal photocoagulation due to contraction of the fibrous component as the vascular component of the fibrovascular membrane regresses or due to posterior vitreous detachment (PVD).

### **4. Surgical technique**

Use of wide-angle non-contact systems would be preferred in diabetic vitrectomy as this would reduce the chances of corneal epithelial defects (since wound healing is delayed in these patients), give a better understanding of vitreous attachments and reduce the chances of iatrogenic breaks.

#### **4.1 Diabetic vitreous haemorrhage**

If the ultrasound does not show any co-existing traction or detachment, pars plana vitrectomy along with panretinal photocoagulation would suffice. Pars plana ports are made using biplanar incisions using 23/25G trocar cannula. After clearing the anterior hyaloids, a thorough core vitrectomy should be performed. Care should be taken while clearing the peripheral vitreous, as it may be difficult to distinguish between retina and blood stained vitreous. In case of dense VH, a burr hole vitrectomy can be performed in the superonasal quadrant until the retina is visualised and then further truncation of cone can performed. If the posterior hyaloid is separated at the disc, then the PVD induction is completed if there are no focal areas of traction. If the posterior hyaloid is not separated completely or not moving freely

or causes a fluttering movement, suspect an underlying FVP. Thus the truncation of cone should be gentle and graded with a watch on underlying retina/FVP/dense vitreoretinal adhesions.

In some cases, PVD separation may not be complete and there may be subhyaloid haemorrhage (SHH). In such cases, an opening can be made in the taut hyaloid overlying the SHH using the cutter or rarely 26G needle to incise the hyaloid if it is very close to retina and the blood can be drained using cutter aspiration or flute.

Once the blood is cleared and underlying retina visualised, PVD can be completed as far anteriorly as safely possible. The aim should be to segment peripheral base of the vitreous from the any posterior hyaloid to prevent reproliferation and rebleeds. It is not mandatory to shave the vitreous base in these cases. One has to be very careful while performing vitreous base shaving in cases of VH, as the peripheral vitreous base would be harbouring the haemorrhage within itself, sometimes difficult to distinguish from the underlying retina. Also, the blood can leach from the uncut vitreous into the fluid filled vitreous cavity and can cause post-operative dispersed haemorrhage.

It is important look for any sites of blood ooze as this can give rise to postoperative rebleeds. Transient lowering of intraocular pressure (IOP) can help to identify the bleeders. Small oozes can be allowed to clot and then trimmed off with cutter, while large bleeders need immediate attention. Clots should not be pulled as they can cause rebleed. Peripheral examination by indentation to look for breaks or sites of bleeding is crucial. A 360° panretinal photocoagulation using endolaser is performed. While performing endolaser, a straight or a curved laser probe can be used. In case a straight endolaser probe is being used, care has to be taken while performing anterior laser to move away from the retina as the curvature of the globe need to be kept in mind to avoid inadvertent retinal touch. Also, exchanging instruments in both hands while performing anterior laser rather than crossing over instruments will help to avoid inadvertent lens touch. A partial or complete fluid air exchange is performed. It is important to ensure that the sclerotomy sites are not leaking and eye is not hypotonous at the end of surgery as these can also lead to dispersed vitreous cavity haemorrhage post-operatively.

In patients with coexisting macular edema or epiretinal membrane, an ERM with ILM peeling after injecting brilliant blue dye should be performed. Anti-VEGF or steroid injection [13] can also be planned at the end of surgery in such cases after partial or complete fluid air-exchange.

#### **4.2 Diabetic retinal detachment**

#### *4.2.1 Understanding the anatomy*

The fibrovascular proliferation (FVP) in a diabetic patient grows along the posterior hyaloid and causes tangential traction leading to pleatlike folds on the retina. As the posterior hyaloid starts separating from the retina, it causes an anteroposterior traction over the retina causing tractional retinal detachment. Thus the PVD creates a cone of vitreous extending from the vitreous base to the posterior pole in diabetic eyes [14]. Thus the goal of surgery would be to initially relieve the anteroposterior traction by truncating the cone and then relieve the tangential traction by dissecting the membranes. Once the detachment becomes long standing, the underlying retina becomes then and atrophic creating breaks, leading to combined retinal detachment. Sometimes, one may also notice subretinal gliotic bands (SRGs) due to long standing CRD. It may not always be possible to identify the breaks preoperatively in CRD. Bullous configuration of detachment, SRG or subretinal bleeds may be indirect indicators of CRD.
