The anaesthesia for the operation is down to personal preference and circumstance, but both general anaesthesia and local anaesthesia are appropriate. In order to minimise conjunctival manipulation, I favour peribulbar anaesthesia before draping (with a top up of sub-Tenon’s anaesthesia if the conjunctiva has been opened). In 23 and 25 gauge where the conjunctiva is not opened, use peribulbar anaesthesia. The patient may be given sedation intravenously under anaesthetic supervision to block out memory of the procedure and to reduce anxiety. This runs the risk however that the patient falls asleep and on awakening may move their head which is potentially problematic if you are starting an internal limiting membrane (ILM) peel or other delicate procedure. In most circumstances, local anaesthesia is satisfactory; however, some patients do not enjoy the experience. Anaesthetic blockade of the relatively large optic nerve is not consistent so that some patients may visualise instrumentation in the eye during surgery especially when it is close to the retina and therefore in focus with only 10 % having total loss of vision (Sugisaka et al. 2007). Most patients find this experience interesting rather than frightening (6 % the latter). General anaesthesia is useful for very prolonged operations, when training surgeons, for young patients or patients with anxiety and those with poor communication.

Patients can be treated as day case without overnight stay, but most surgeons will review the next day although same day review has been described (Desai et al. 2008). Next day review is primarily for measuring the intraocular pressure either high from the gas bubble or low from small incision surgery.

Prepare the eye with dilute povidone-iodine and topical anaesthetic onto the conjunctiva

This is the most commonly performed operation in modern vitreoretinal practice and the second commonest ophthalmic operation in the USA. Variations in technique with different gauge instrumentation will be described later in the chapter. The basic operation is described here with additional manoeuvres explained in the following chapters. In most centres, a three-port approach is used, one sclerotomy for an infusion cannula and two used alternately for a light pipe and a surgical instrument of varying sorts.

For draping and sterility, follow the usual processes. A lid speculum is inserted.

Most cutters work by guillotine action either driven by electric motor or by pneumatic action with a spring return. An electric motor in the hand-piece tends to be bulky; a pneumatic spring return system produces small hand-pieces, but surgery is reliant on a compressed gas cylinder which may run out of pressure in the middle of surgery.

Conventionally, to increase the flow rate of the vitreous (the volume of vitreous extracted per unit of time) through the cutter, slower cut rates (more time for the vitreous to enter the cutter tip), higher vacuums and larger ports (the orifice on the cutter) are required. This will produce large bites of vitreous at each cut. Large bites however allow a larger transfer of forces to the gel and may secondarily cause forces on the retina. Therefore, equipment has been designed to allow smaller bites at higher speed to maintain flow rates of vitreous and to overcome the reduction in gauge of many new instruments. With high-speed cutting, there is not enough time to engage the vitreous. Therefore, higher vacuums are required, but multiple small bites  =  less action on retina. This in turn may lead to less tractional retinal tears. The movement of the vitreous becomes smoother and more predictable allowing cutting closer to the retina. One paper has described less GFAP upregulation, a sign of Muller cell ‘stress’, with high-speed cutters in an animal model (Wallenten et al. 2008).

The position of the port has been moved nearer to the end of the shaft with modern cutters allowing alterations in surgical technique. The efficiency of the cutter depends on the duty cycle D  =  τ/T where τ is the duration that the function is active and T is the period of the function. Modern cutters maintain their duty cycles even at high cut rates, thereby maintaining vitreous flow rates (Magalhaes et al. 2008; Fang et al. 2008; DeBoer et al. 2008). Different settings can be used, but I find proportional vacuum satisfactory although I will reduce the cut rate of some high-speed cutters because their duty cycles are not efficient at the higher settings, for example, reduce from manufacturer’s claimed cut rate of 2,500 to 1,800 rpm.

The natural tendency is for the surgeon to let the instruments drift into the eye during periods of loss of concentration. Remember the maxim ‘if in doubt pull out’. Damage is unlikely from inadvertently removing an instrument from the eye but possible if it goes too far in and contacts the retina. This is especially important when waiting for a change of instrument to be handed by the assistant when the light pipe is still in the eye; therefore, developing the habit of always pulling back on the instrument during any delays in the procedure is recommended.

The light pipe does not need to be pointed at the active instrument; in fact, illumination is often more satisfactory if the light is shone onto the posterior pole of the eye. A beginner’s tendency to want to shine straight onto the instrument tip rotates the light pipe anteriorly bringing the shaft dangerously close to the lens.

Insert the light pipe only far enough to provide illumination, minimising the presentation of the bare fibre optic into the view. This avoids glare especially with tapered fibre-optic tips.

Note: Avoid light toxicity by removing the light pipe periodically or at least by pointing the illumination away from the macula. Experimentally, the likelihood of toxicity increases severely after 13 min. Ten minutes is a rough amount of maximal exposure of the retina during surgery after which illumination of the retina should cease for a period of 30 s.

Note: Occasionally, the tapered light tip (fibre optic protruding from end of sheath) will cause glare, for example, when the eye is air filled. In this case, cut the protruding end of the fibre optic off with scissors to minimise the exposed fibre optic.

These are used with the intention of preventing peroperative hypotony. They are unreliable devices which often disinsert (if you lose one, first check in the superior conjunctival fornix), and it is better to use self-sealing sclerotomies for fluid control or self-sealing trochars as in 23 and 25 G. There are some bullous superior retinal detachments in which the retina could easily incarcerate where plugs must be used. In these cases, it is useful to insert a small quantity of heavy liquid into the vitreous cavity to stabilise the retina and keep it away from the sclerotomies. If peroperative hypotony occurs, use plugs. Otherwise, rely on small tight sclerotomies or well-designed trochars. It is important that the vitreous has been removed around the incision to avoid vitreous incarceration which in RRD patients can encourage retinal incarceration. In patients with flat retinae and those with RRD away from the sclerotomies or shallow RRD, plugs are not always necessary. As long as the infusion fluid pressure (as controlled usually by the infusion bottle height) is high enough, the potential for fluid entry into the eye is greater than its egress and the IOP will be maintained. In practice with trochars without valves, you can leave one trochar free flowing but will need to block the other one with an instrument or a plug.

This is one of the most crucial parts of the vitrectomy and will be required in almost all patients. The IVS makes this part much more attainable but still requires some development of technique. The aim is to see the entire retina not directly visible, that is, up to the ora serrata. In rhegmatogenous retinal detachment, the search is for the detection of pre-existing breaks, and so the procedure is performed early in the operation. In all other conditions, the search is performed at the end of the operation to check if a retinal break has been created during a manoeuvre, for example, tearing the retina during surgical peeling of the posterior hyaloid membrane. The search gives the opportunity to fix the mistake whilst still in the eye. Never ignore a problem. In vitreous surgery, the surgeon will not get away with it. Always ‘check and treat’ if a problem has been created. It does not feel good to have a straightforward macular procedure return with a detached retina 2 weeks later.

Again a systematic approach should be followed. For the nasal side, insert a squint hook under the conjunctiva and Tenon’s layer through the superonasal incision (if the conjunctiva has not been opened, see the technique described later in the chapter for small gauge surgery). Pass the hook around the eye up under the inferior rectus and pull anteriorly to commence indentation at 6 o’clock and at the ora serrata. For the temporal side in most patients, you can indent on the surface of the conjunctiva. Apply gentle pressure in towards the centre of the eye to produce a ridge that can be seen internally with the IVS. This brings the peripheral retina into view. Observe the retina on the ridge whilst moving the hook posteriorly and watch for any abnormalities whilst moving around the clock hours of the eye. Movements should be gentle and smooth. Inspect the retina during the movement of the ridge from the ora serrata to just posterior to the equator. Most breaks appear at the posterior border of the vitreous base, but some may be more posterior, for example, retinal scrapes from instruments or operculated holes. Be wary of anatomical variations; in some patients, the posterior attachment of the vitreous is abnormally far back, for example, some myopes. As the retina moves dynamically, there is a good chance to spot a problem. Work up to 12 o’clock and then examine the other side of the eye. Overlap at 12 and 6 o’clock to make sure the entire retina has been seen.

This is applied via a fibre optic internally during the PPV for retinopexy or for retinal ablation in diabetes (Peyman et al. 1981). Argon lasers (514-nm wavelength), double frequency YAG lasers (532 nm), dye lasers (577–630 nm), diode-pumped solid state lasers (532 nm) and diode lasers are available. Argon provides wavelengths in the blue and green spectra but has been recently superseded by others such as double frequency YAG laser (producing a 532-nm wavelength from a YAG tube, normally 1,064 nm), partly because manufacturers can produce smaller more portable equipment of higher reliability. In the green spectrum, a thermal burn is produced in the retina, easily identified by a whitening of the retina. It is therefore easy to adjust the dosage to produce the minimum burn necessary for adhesion of the retina without damaging superficial retinal nerve fibres causing further visual loss. Yellow lasers (561 nm) are available which may have advantages around the macula because of reduced absorption by Xanthophyll. Diode lasers are available which produce a wavelength of 810 nm (infrared); these burn deep into the retina and choroid without a visible burn on the retina until a large burn has occurred in the choroid. Care must be taken when using diode lasers that choroidal ischaemia is not created.

The adhesion of the retina from laser has been described as early as 24 h after application (Folk et al. 1989). Use a curved endolaser probe in phakic eyes to avoid the shaft of the laser contacting the lens. The curve can also be used to aid application of laser to the pre-equatorial retina as the tip can be kept more perpendicular to the retinal surface. Straight probes must approach some peripheral retina at an oblique angle risking a scrape of the retina. Standard settings are 200 mW, 0.1 s burn duration and 0.1 s interval between burns on repeat. Continuous burns are used by some surgeons, but this runs the risk of an excessive burn during delays in change of direction of the laser probe. It is hard to keep the rate of movement of your instrument constant over the retina. If the instrument is slowed down, for example, during a change of direction, you will increase the burn in that area. Short, rapid repeated burns avoid this problem (Fig. 2.24).

Increase the intensity of the burns by:

Avoid lasering onto preretinal, retinal or subretinal haemorrhage if possible. Lasering haemorrhage causes a burn in a layer of the retina that is undesirable and may not produce the adhesion between retinal and RPE and choroid that is necessary or the destruction of ischaemic outer retina that is desired.

Always check and recheck the position of the macula if you are applying panretinal photocoagulation (PRP) so that you do not drift into that area. Put a line of laser on the temporal edge of the macula to indicate the posterior extent of PRP in that meridian.

For certain moves which require good depth perception, high magnification, and are not restricted by a reduced visual field of view, a contact lens (e.g. Machemer lens) to negate the refraction to the cornea can be used (Machemer et al. 1972). Disposable lenses are available which can be placed on the cornea with some methyl cellulose to provide ­adherence. For certain difficult macular procedures such as the commencement of internal limiting membrane peel, these can be useful as the membrane can be discriminated from the nerve fibre layer more easily. The field of view is much reduced and the view no longer inverted. Be careful when inserting the instruments; it is a long time before they come into view compared with the IVS. If you are using angled instruments, take care that you know where the heel of the instrument is in the eye. It is possible to touch the retina with it whilst watching the tips of the forceps. In addition, there is a tendency to have the light pipe closer to the retina risking light toxicity.

Stop and examine all elements in the system.

Always close the superior sclerotomies first and the inferior infusion sclerotomy last as this controls the IOP. When utilising gas tamponade, close one sclerotomy, keep the air pump on and attach the syringe with the gas to the three-way cannula, close off the air pump and then exchange the long-acting gas by injecting through the infusion cannula. Inject at least 35 ml of the gas to flush out the air in eyes with 25 mm or less axial length. In eyes bigger than this, the theoretical volume to achieve 97 % saturation of the gas mix in the syringe in the eye is more than 35 ml; therefore, two syringes should be used or use a 100ml syringe.

The volume of gas required to flush the vitreous cavity to achieve 97 % according to the axial length of the eye (Shunmugam et al. 2011).

Close the second sclerotomy. Keep some gas in a syringe (15 ml) to allow a top up of gas if some gas leaks during the disconnection of the infusion at the end of the operation.

Note: With small gauge surgery, remove both the superior trochars and check if they are sealed, then use a 28-gauge needle inserted into the pars plana to vent. This has the advantage that the superior sclerotomies can be checked for leaks whilst the air pump is still available before the exchange of gas. If you wait until after the exchange, there is only 15 ml of gas left in the syringe to sort out a leaking sclerotomy.

Note: Take care with the use of the three-way tap. Do not turn the tap so that the air and the gas syringe are in connection because air will enter the syringe and dilute your injection of gas.

Check the intraocular pressure with your finger tip (using the finger’s Pacinian corpuscles to assess the pressure!) aiming for 10 mmHg (your finger tip is a better pressure sensor in my view than pressing the eye with an instrument).

Always remove the infusion last. If the globe is soft, check for leaks from the sclerotomies, resuture if necessary. To elevate the IOP, add BSS to the anterior chamber via a paracentesis, or, if gas-filled, inject gas through the pars plana using a 30-gauge needle. Check the pressure again.

Full concentration fluorescein dropped onto the conjunctiva will indicate a fluid leak (the leaking fluid dilutes the fluorescein changing its colour from orange to green) and is especially useful when checking small gauge surgery wounds.