Fig. 8.32 If there is a point of adhesion inferiorly, for example, an old retinopexy scar, the retinectomy should be taken posterior to the scar to relieve the shortened retina as indicated by the arrows. Failure to do so causes persistent elevation of the retina between the scar and the optic disc postoperatively

Fig. 8.33 After the circumferential retinotomy, a fold of retina under the optic nerve head indicates circumferential shortening of the retina, thick arrows. This can be relieved by a small radial retinotomy at (a) and a longer retinotomy at (b) to create a petaloid shape to the inferior retina

Note: It may be useful to use a chandelier light pipe so that the peripheral retina can be removed with the cutter whilst indenting the eye with a squint hook in the other hand. There is a risk of cutting the choroid and causing bleeding if the retina is not removed under direct observation.

Once completed, insert oil through the infusion line and flatten the retina.

8.4.4Radial Retinotomy

Sometimes, there will be circumferential shortening of the retina, seen as folding of the retina inferior to the disc, perhaps passing through the macula horizontally. You will now need to perform a radial retinotomy. This is best performed between the inferotemporal arcade and the inferonasal arcade (this avoids the major retinal blood vessels and avoids cutting across too many retinal nerve fibres) passing up towards the disc and may even reach almost as far as the disc, depending on the shortening that is present. This allows the retina to open out like the petal of a flower and reduces the chances of any folds. Sometimes, a small radial retinotomy will be needed at the temporal upper end of the retinectomy.

8.4.5Silicone Oil Injection

Fig. 8.34 This patient presented with CA12 CP12 PVR and has had a large retinectomy with two radial cuts (arrows) to open out the retina as seen in this early postoperative image

Now, continue to flatten the retina whilst injecting oil and aspirating aqueous fluid from the inferior margin of the retinectomy. Take care not to engage the retinectomy in the fluid needle by increasing the pressure only slightly in the eye and then aspirating. Do not inflate the silicone continuously, as there is a lag time for the silicone to enter the eye (because of its viscosity) which may not be anticipated during aspiration of the fluid, thereby risking incarceration of the retina into the flute needle end. If this eventuality occurs, remove your light pipe so that some oil comes out through the sclerotomy, and

Fig. 8.35 When incising for a radial retinotomy, use the direction of the arrows to minimise the number of nerve fibres cut during the retinotomy thereby reducing visual field loss

this will usually be enough to release the pressure; by pressing the bulb of a finger into the flute needle, or using a back-flush flute, the retina will extrude. If in a severe case, this is not possible, disconnect the flute needle from the shaft, and attach a syringe to the end of the fluid needle to eject the retina.

Surgical Pearl

The use of perfluorocarbon liquids (PFCL) can provide a false sense of security concerning the adequate relief of traction during PVR surgery. The high specific gravity of PFCL will give the appearance of complete reattachment even in the presence of residual traction. This residual traction may be appreciated by carefully observing the intensity of laser burns at the edge of retinal breaks and retinectomies. A decrease in the intensity of laser burns may signify subtle subretinal fluid due to residual traction. However, if the laser burns are too intense to begin with, this phenomenon may not be apparent. If residual traction is detected, it must be relieved by further dissection or relaxation. It is important that any retinectomy be posterior to the vitreous base and that the retinectomy extend through the vitreous base to the ora serrata at its circumferential margins. An adequate retinectomy should extend circumferentially into uninvolved or ‘normal’ retina for at least 1 clock hour beyond the apparent traction. Circumferential retinectomies should have one posterior radial relaxation for every 3 clock hours of extent. When it comes to retinectomies, bigger is better.

George A Williams, Professor and Chair, Department of Ophthalmology Oakland University William Beaumont School of Medicine, Royal Oak, Michigan, USA

8.4.6 Applying Laser

Having flattened the retina, apply three rows of laser to the posterior edge of the retinectomy and around any radial retinectomy. In an aphakic or pseudophakic eye, it should be possible to laser close to the ora serrata at the upper ends of the retinectomy. Sometimes, there is a need to indent the ends of the retinectomy from the outside through the sclera with the light pipe (see Chap. 6). This will transilluminate the retina and allow visualisation of the edge of the retinectomy and where the ora serrata is to apply laser. The laser burns are not seen whilst being applied, and the surgeon must keep a mental note of which part of the retina has already been treated.

In a phakic eye, however, this may not be possible without touching the back of the lens and damaging the lens, and, therefore, it is recommended that two or three cryotherapy burns are applied to the top edge of the retinectomy,

thereby sealing the top edge. Cryotherapy allows indentation whilst visualising from the inside, and applying only a few burns minimises any reactivation of the PVR process.

Note: At the end of the silicone oil insertion, on closing the eye, keep the eye relatively soft, 10 mmHg.

A hard eye indicates an overfill causing raised intraocular pressure postoperatively. Remove some silicone oil in the immediate 1–2-week postoperative period.

Now that the retinectomy has been created, leave the eye for another 3–6 months, to allow the retinectomy to seal and to allow any reactivation of the PVR to cease.

Surgical Pearl of Wisdom

Retinal detachment is a blinding condition that requires prompt surgery in order to have the best possible results and preserve as much vision as possible. Proliferative vitreoretinopathy is the main cause of retinal detachment surgery failure. It manifests usually in the lower retina in the form of epiretinal or subretinal membranes exerting a great amount of traction on the retina, thus preventing it from flattening. The goal of surgery in such cases is to remove all membranes from the retina in order to release all traction. However, there are cases that the only way to totally relieve traction is to remove part of the lower retina performing a retinectomy. In those eyes, one of the main complications after surgery is hypotony. This is the result of the large area of retinal pigment epithelium that remains exposed after retinectomy. The retinal pigment epithelium pump drains the vitreous cavity in such a degree that may lead to permanent hypotony and even phthisis bulbi.

I had a severe case of proliferative vitreoretinopathy that required 180o lower retinectomy. However, that day there was a malfunction of both laser machines, as it usually happens when something new is about to be born, making laser photocoagulation impossible to perform. I was obliged to apply cryotherapy along the margin of the retinectomy and consequently to a large area of the exposed retinal pigment epithelium. Fearing for the worst, I followed up the patient closely after surgery. To my surprise, the patient not only did extremely well with a flat retina, reasonable visual acuity and no recurrence of proliferative vitreoretinopathy but also developed high intraocular pressure that required control with antiglaucoma medication. At that moment, it struck me that maybe it was the cryotherapy that destroyed the exposed retinal pigment epithelium and prevented the overdrainage of the vitreous cavity by its pump.

So, in my following two cases of retinectomy for inferior proliferative vitreoretinopathy, after laser

photocoagulation to the margin of the retinectomy, I applied a few spots of cryotherapy to the exposed retinal pigment epithelium. Postoperatively, both eyes maintained normal intraocular pressure that remained after the removal of the silicone oil. I believe this may be an interesting way to control postoperative hypotony after surgery involving retinectomy. I am currently fine-tuning this method in order to achieve the best results (e.g. how many spots of cryo, what area of retinal pigment epithelium to cover)

Vlassis Grigoropolis, 2nd Ophthalmology Department, Henry Dunant Hospital, Athens, Greece

Surgical Pearl of Wisdom

Proliferative vitreoretinopathy is often the cause of recurrent retinal detachment. Epiretinal membranes but also retinal fibrosis may cause contraction of the retina and curling of retinal tears.

When inferior detachments recur under silicone oil (regular lighter than water oil), it may help to remove all epiretinal tissue again and to leave retinectomies without any laser. Without laser anchoring the retina, intraretinal fibrosis contraction of the retinectomy edge results in curling and not anterior contraction over the lasered area. This allows gentle posterior slippage of the retina instead of retinal redetachment. Again, regular silicone oil is left as tamponade.

Two months after retinectomy without laser, slit lamp laser can be performed at the retinectomy edges, curls or not. The retina fits comfortably in position. Alternatively, laser at the time of oil removal, in which case you may leave a gas tamponade.

Thus, we may break the vicious circle of recurrent redetachments under oil. Laissez faire: ‘Laissez rouler, laissez slipper.’

Jan C. van Meurs, the Rotterdam Eye Hospital, Rotterdam, the Netherlands

8.4.7 ROSO Plus

Then return to the eye to perform a silicone oil removal. It is recommended to reinspect the retinectomy at this stage, by using a vitrectomy approach at the same operation (removal of oil and vitrectomy procedure, ROSO plus). Once the oil has been removed, inspect the retina to look for any return of retinal detachment. Occasionally, if there is a problem at the edge of the retinectomy, a shallow retinal detachment will

appear which must then be dealt with by further surgery, usually involving gas tamponade if the SRF is superior. If there is SRF inferiorly, there is a six times higher chance of recurrent retinal detachment, and it is recommended to reinsert silicone oil. The inferior retinal detachment can be dealt with by further retinectomy.

Problem areas in the retinectomy include the upper ends where, if the retinectomy was not performed high enough, there may be shortening of the retina in an anteroposterior tangent and elevation of the ends of the retinectomy. You will need to cut the retinectomy further superiorly to overcome the shortening and to get into healthy elastic retina, and then retinopexy the edge of the new cut. Occasionally, a small oneor two-millimetre edge of the retinectomy is elevated allowing fluid to enter the subretinal space; this will be seen as a thicker area of the retinectomy edge, often being pulled posteriorly through the retinopexy scar. These can easily be dealt with by applying further retinopexy posterior to the extension of this part of the retinectomy.

8.4.8Very Severe PVR

(C9–12)

Additional surgical steps: Insert heavy liquids. Stain with trypan blue. Peel PVR membranes. Diathermy blood vessels.

Incise along retinectomy for 350º initially. Remove the redundant anterior retina.

Check for folds, and perform radial cuts in the retina if required.

Insert silicone oil, and cut remaining 10º. Apply laser retinopexy.

Finally, occasionally very severe PVR may be encountered, where there is a closed funnel anteriorly/posteriorly, such as CA12/CP12. There is no option in these eyes but to perform a large retinectomy. Perform a vitrectomy, open out the funnel as far as possible with the heavy liquids placed over the disc and remove any PVR membrane as before. Perform a retinectomy, usually 360°, and often one or two radial retinotomy cuts to allow the retina to open. Thereafter, insert oil on top of the heavy liquids; remove the aqueous layer first, allowing the oil to contact the heavy liquid, which will further open out the retina. Make sure all

Table 8.5 Difficulty rating for surgery for very severe PVR