with a pre-existing missed hole in the retina, as very seldom is the intact retina torn during silicone oil injection (Stappler et al. 2010).

It is the consequence of insufficiently released or newly developed tractions. Silicone oil may migrate under the retina during the instillation at the end of surgery due to an insufficient release of the tractions or, postoperatively, if a massive postoperative contraction of the retina occurs. As the retina is again under tension due to the epiretinal or subretinal proliferation, eventual retinal tears reopen and enlarge, thus causing subretinal migration of the oil because the interfacial tension of the bubble is reduced.

The key point is to mobilise the retina. The use of vital staining helps in removing the epiretinal membrane as much as possible. If subretinal proliferation is highlighted, either a small central retinotomy must be performed to remove solitary and clearly visible strands or a large circumferential retinotomy is necessary, in order to inspect the outer side of the retina and to remove multiple network and sheets. The injection of silicone oil after a fluid air exchange helps in flattening the retina.

Oil evacuation can be performed by using different techniques depending on its amount. With a small bubble, PFCL can be injected onto the disc, and the oil removed with a flute needle through an open tear or a small drainage retinotomy: in this case, an air filling can be still indicated.

If a large amount of oil under the retina is present, a persistent retinal detachment is evident after the removal. Evacuation of subretinal silicone oil should not be started until all tractions have been removed as remaining epiretinal membranes are easier to remove with the retina stretched by the underlying bubble. After the surgeon has ensured that the retina is no longer withheld, he has to perform a long peripheral retinotomy and inject PFCL on the disc so that the trapped silicone oil will escape from the back to the vitreous cavity. Then he has to aspire the oil with the pump, perform endolaser, a PFCL/air exchange and finally a new silicone oil filling.

The oil does not float; therefore, it cannot be removed passively and must be actively aspirated by an 18-gauge cannula. A metal cannula is recommended because plastic or silicone causes the oil to stick to the tip of the cannula.

It may be better to use conventional oil, the properties of which are well established and the results predictable.

8.4.10 Removal of Subretinal Bands

In severe PVR, subretinal bands may prevent reattachment of the retina. The bands are usually attached to the choroid in the periphery and may have subretinal attachments along their course. These attachments will usually break when the band is pulled.

To remove, make a retinotomy adjacent to the band to allow you to grasp the band with forceps. There are two methods:

Unimanual: It is not safe to pull the band towards the sclerotomies because the band will put pressure on the rim of the sclerotomy and cause it to enlarge. In addition, these bands can be long, and you will run out of space in the eye to pull it. Instead, roll the forceps in your fingers as if rolling spaghetti on a fork to gradually roll up the band without any displacement of the position of the forceps tips.

Bimanual: Insert a chandelier system to provide illumination. Make a retinotomy. Use two pairs of forceps one in each hand. Grasp the membrane at the retinotomy with a pair of forceps and pull a short distance; then regrasp the membrane at the retinotomy site with the other forceps and pull a short distance. Repeat the ‘hand over hand’ approach until the adhesions break and the band has been removed.

Note: Always keep retinotomies as superiorly placed in the eye as possible to allow tamponade postoperatively.

Stanislao Rizzo and Federica Genovesi Ebert,

Ophthalmology Unit, Pisa, Italy

8.4.9.2 Heavy Oils

These may be used to treat inferior retinectomy or inferior retinal breaks. The oils currently available are not very dense, and so their effect on inferior PVR is poor. In addition, PVR occurs in the superior retina in the postoperative period often exacerbating the problem. Extraction of the oil is more difficult than routine silicone oil because the heavy oil:

•May separate into its components

•Has a tendency to stick to the retina

Fig. 8.39 A persistent RRD under oil with shallow SRF and subretinal bands; this will be difficult to fix because the extensive inferior laser will force a very posterior retinectomy. In addition, the subretinal fibrosis will not be easy to remove from under the retina

8.4.11 Adjunctive Therapies

Adjunctive therapies such as daunomycin and a combination of heparin and 5-fluorouracil have been investigated to try to reduce redetachment rates but without success in patients with established PVR (Wiedemann et al. 1998; Charteris et al. 2004; Stern et al. 1983; Blumenkranz et al. 1984). The latter was found to be effective in reducing the risk of developing PVR in patients with retinal detachment with a high risk of PVR, but reoperation rates were unaffected (Asaria et al. 2001). Others have suggested washing out any RPE cells in the vitreous cavity after retinopexy to try to reduce the postoperative risk of PVR (Vidaurri-Leal et al. 1984).

8.4.12 Success Rates

The aim for these cases is to achieve reattached retina with silicone oil removed. Success rates are usually stubbornly low in patients with PVR with single operations approximately 62–65 % (Stolba et al. 1995; Han et al. 1994; Fisher et al. 1988; Cox et al. 1986) or multiple operations 68–84 % (Scott et al. 2003; Han et al. 1994) despite a variety of methods used (Iverson et al. 1990), and even poorer if silicone oil removal is a requirement of success, for example, 51–81 % (Charteris et al. 2004; Lam et al. 2008). Patients who achieve a reattached retina with the one operation have significantly better visual outcomes (Scott et al. 2000), but this is often not achievable. The visual outcome is only a 24–45 % chance of 20/200 vision or better (Scott et al. 2003; Silicone Study Report 2). Patients with anterior PVR have poorer outcomes than those with posterior PVR (Diddie et al. 1996). There is a risk of sight threatening complications in the other eye of

these patients (50 %) which helps justify the surgery in the eye despite poor success rates (Schwartz and Kreiger 1998).

Quiram et al. (2006) have reported a high success rate of 93 % reattached retina with primary retinotomy with a mean of 1.8 operations prior to retinotomy. However, 42 % of the patients in their study did not achieve silicone oil removal despite a mean follow-up of 25 months which was reflected in frequent postoperative silicone oil-induced complications. It is best to remove the oil because of the attendant complications of glaucoma, band keratopathy and central visual loss.

The cause of failure of surgery is usually further PVR formation (Lewis and Aaberg 1991) with reoperations required at 2 months. Using a three-operation approach (planned delayed relieving retinotomy, PDRR) may increase success rates for retinal reattachment without permanent silicone oil insertion in the patients to 89 % and contribute to a high success rate for PVR in general with 85 % reattached retina without silicone oil tamponade for all cases of PVR.

A possible disadvantage of the PDRR method is the delay in attaching some of the retina, thereby delaying the recovery of the neuroretina. If the macula is off after stage one, proceed to stage two early, for example, 2 months. Luckily, the inferior retina lost during retinectomy serves superior visual field which is less used than the inferior visual field.

8.4.13 Postoperative Complications

Cataract

There is a 92 % chance of cataract formation.

Hypotony

This is associated with the presence of anterior PVR. It is claimed that excision of the anterior PVR can help restore

Fig. 8.40 A retinectomy edge is shown. A radial cut has been made because of circumferential shortening of the retina to allow reattachment of the retina without folding through the macula

Fig. 8.41 A subretinal band is seen in this patient tenting up the retina with a concave configuration. No action is required

Fig. 8.42 This patient has not had any specific action taken about inferior PVR, approximately CA2; because no retinal break is present, the normal physiological processes are able to maintain a flat retina. Observation of this retina postoperatively showed that the retinal detachment did not recur and the patient avoided further surgery

the IOP (Lewis and Verdaguer 1996; O’Connell et al. 2000).

Macular Pucker

It occurs in 15 % of eyes with PVR postoperatively (Cox et al. 1995) and can be removed at the time of silicone oil removal.

Cystoid Macular Oedema

This can be common in patients with poor visual recovery after PVR surgery but a flat retina (Benson et al. 2006).

Retinal Distortion and Displacement

The retina after retinectomy is tangentially shorter causing more retinal receptors per area and therefore micropsia. In addition, the retina may not be evenly spread, and, therefore, distortion created. On occasion, the patient who attains better visual acuity for the two previous reasons may not like the disruption of vision in the operated eye and its effect of disruption in the other eye.

Complications of Silicone Oil Use

See Fig. 8.43 and refer to Chap. 2.