2. Do not be complacent when performing the internal search. Identification of potential problems in the retinal periphery is one of the key steps to lower your complication rate. Make sure that you visualize the entire retinal periphery 360° up to the ora serrata. Move your scleral depressor constantly when inspecting the vitreous base. This is a dynamic procedure. This way you will identify breaks opening up during your indentation that you may miss if the indentation is too ‘static’.

9. Laser photocoagulation of peripheral breaks

If the break is so peripheral that you need a scleral depressor to see it, you must now either insert a chandelier light in order to have a free hand for the scleral depressor, or you use a combined laser with optical fibre (see instruments) or indent the eye with your light pipe. Surround the break with one to three rows of laser burns (e.g. using the 532-nm diode laser OcuLight GL Company Iridex, we use the laser parameters: power 150 mW; duration, 200 ms; interval, 300 ms).

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Iatrogenic break: When a small break is located within the vascular arcades, a laser treatment is not necessary as the pigment epithelium in the central area has sufficient pumping function so that no detachment occurs. If the break is large, however, we recommend lasering the break with one row of laser burns. Even if you create a peripheral break, this is not a problem as long as you also recognize the break. Surround the tear with three rows of laser burns, and perform a gas tamponade.

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Laser therapy

1. A laser treatment can be carried out in a water-filled (BSS-filled), silicone oil–filled and PFCL-filled eye. In an air-filled eye, it is difficult to laser due to a poor visibility.

2. It is easiest to laser breaks under heavy liquid, as you have a good apposition of retina and retinal pigment epithelium. One of the disadvantages of this technique is that the margins of the break are more difficult to see. Mark the location of breaks with endodiathermy or laser spots before covering it with heavy liquid. This way it is easy to identify them under heavy liquid.

3. Beware of the ‘continuous’ function of the laser. You can easily overtreat. This may result in mini-explosions, choroidal haemorrhage, retinal breaks or predispose to postoperative tears. Pigmentation increases towards the periphery. Less energy is needed for peripheral laser spots.

4. The further you move the laser probe away from the retina, the larger the resulting spot size on the retina (and the more energy you need to create a burn). This can be quite useful if you want to treat larger areas as the resulting burns have softer edges and do not cut the retina like a knife.

5. Use 360° prophylactic laser with caution. It may not be necessary, may result in anterior segment ischemia and will make it very difficult to identify small breaks in cases of postoperative retinal detachments.

10. Cryotherapy of peripheral break

The cryotherapy of a peripheral break is a good alternative to laser photocoagulation, in particular in phakic eye where endolaser of breaks in the retinal periphery without touching the lens is challenging. You indent the retina with the cryo-probe and hold the light pipe in the other hand. Cryotherapy should be applied sparingly, preferably with one cryo-effect in the middle of the break in order to reduce the risk for PVR.

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Cryotherapy: When performing cryotherapy for retinal breaks, a lot less cryo is needed if the vitreous cavity is filled with air.

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Cyclocryotherapy: When we perform cryotherapy of the ciliary body, we treat three quadrants (the superonasal quadrant remains untreated). The cryo-probe is applied approximately 2–3 mm posterior to the limbus so that the freezing effect reaches the limbus. We apply 3–4 freezings per quadrant; duration: 50 s. The cryotherapy of the retina for ischemic retinopathy should, if possible, be performed with an indirect ophthalmoscope. You can freeze until a strong white colouring occurs. In the absence of a good field of vision, we freeze for 10 s.

11. Intraoperative tamponade

Intraoperative tamponades have several indications. A fluid/air (fluid against air) exchange may be necessary before injecting a dye (e.g. Brilliant Blue G). Further, a

fluid/air exchange is an important step in detachment surgery. A PFCL (heavy liquid) tamponade is important in detachment surgery to attach the retina. PFCL must always be completely removed because it damages the retina.

Air tamponade (exchange of water against air)

To perform an air tamponade, you hold the fluid needle in front of the optic disc of the water-filled (BSS-filled) eye. The scrub nurse switches from water to air. The air streams anteriorly in the eye, and the water is aspirated by holding the tip of the fluid needle in the water. During air insufflation, the visibility worsens, as air has a different refractive index to water. This problem can be solved by turning the front lens of the BIOM with the focus wheel up a little bit until the image is sharp. After a while, you recognize a water level at the posterior pole. You continue to hold the fluid needle in front of the optic disc and aspirate the remaining water. If in doubt, it is better to leave a little water at the posterior pole than to risk a retinal or optic disc touch.

Water tamponade (exchange of air against water)

Hold the fluid needle directly behind the IOL. Then the scrub nurse switches from air to water, and the eye fills up quickly with water. If small air bubbles remain at the end behind the IOL, then there is still (anterior) vitreous behind the IOL. If you plan to perform now macular surgery, you have to remove these irritating air bubbles. In order to do so, perform an anterior vitrectomy.

PFCL tamponade (exchange of fluid against PFCL)

Inject PFCL preferably in a fluid-filled eye and not in an air-filled eye. The PFCL must be injected slowly. PFCL injected too quickly can induce retinal damage. PFCL should never be injected in direction of the macula. You start with the injection nasal to the optic disc and then move the cannula slowly towards the lens leaving the tip of the cannula in the PFCL bubble. Leaving the tip of the cannula in the big bubble prevents the formation of small PFCL bubbles (fish eggs).

When injecting PFCL, simultaneously decompress the globe with a fluid needle. Alternatively, you can use a dual-bore cannula (Fig. 2.25) which allows simultaneous injection and decompression.

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Try to inject one bubble only. Start very slowly, and then always keep the tip of your cannula in touch with the bubble. This avoids splitting the stream into multiple bubbles, which can then displace into the subretinal space.

Removal of PFCL

Hold the fluid needle in front of the optic disc and aspirate the complete PFCL bubble. If a small bubble remains and you do not succeed with the fluid needle, then do not insist but aspirate the residual bubble with a silicone-tip fluid needle in order not to damage the retina or the optic disc.

12. Postoperative tamponade

Important: The performance of a tamponade depends very much if you use a trocar system with valves or without valves. This is especially important for a silicone oil tamponade. If you use a trocar system with valves and inject too much silicone oil, you can create a dangerous excess pressure that can lead to the occlusion of the central retinal artery. In case of water or gas, you can easily release excess pressure with the fluid needle. This is not possible with silicone oil. You must therefore learn to control a possible hypertension. DORC’s trocar system has the advantage that the valve can be removed in case of high intraocular pressure (Fig. 5.2). This is not possible for other manufacturers (Alcon (Fig. 2.3b), Oertli, Geuder). Alcon includes a metal cannula in the trocar valve pack, which is inserted into the valve trocar in order to release excess pressure. An intraocular hypertension cannot arise with a trocar system without valves (Fig. 2.4). Here you must deal with a possible hypotension.

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Anterior segment and tamponade

1. Make sure that all potential anterior segment problems are addressed before starting a fluid/air exchange. The air bubble will push the iris-lens diaphragm forward, making any manipulations in the anterior chamber extremely difficult. In addition, fluid injected into the anterior chamber will enter the posterior segment and displace the tamponade, potentially causing an ‘underfill’.

2. In cases of large defects within the zonules or the lens capsule, inject miochol and an air bubble into the anterior chamber before fluid–air exchange. This prevents the iris-lens diaphragm from moving forward and avoids iris capture or displacement of the gas tamponade into the anterior chamber. With modern viewing systems and air in the anterior chamber, there usually is a sufficient view of the posterior pole to perform a safe fluid–air exchange.

Air tamponade (exchange of water against air)

Remark: An air tamponade has several indications: (1) Air in the vitreous cavity presses against the edges of the sclerotomy incision and thereby stabilizes the sclerotomies, which results in a reduced postoperative hypotony. (2) Reduces postoperative bleeding (favourable for diabetic eyes) (3) tamponade for macular holes.

(4) reduces the risk of an endophthalmitis.

Gas tamponade (exchange of air against gas)

After the fluid/air exchange, you can swing out the BIOM, activate the inverter, and switch on the light of the microscope. The surgical nurse attaches a 50-ml syringe with diluted gas to the three-way tap and injects the gas (about 45 ml) into the vitreous cavity (Fig. 4.9a, b). Instruct the scrub nurse to stop injecting immediately if he or she feels an increasing resistance to injection. To avoid an increased pressure in the eye, you must simultaneously decompress the eye. This can be achieved by holding the fluid needle behind the lens and leaving the side opening

Fig. 4.10 (continued)

Diagram 4.3 Diagram of the location of liquids at an air/silicone oil exchange

We use a silicone oil 23-gauge plastic cannula (Med One, DORC) which fits into a 23-gauge trocar. The oil falls from the anterior onto the posterior pole, i.e. the eye is filled from the back to the front with oil. At the same time, you must drain the air with a fluid needle from a trocar. When the last bubble disappears behind the lens (Fig. 4.10c), stop the infusion of air and remove the residual air bubble. Then inject so much silicone oil until the globe is hypotill normotensive. During this procedure, check for a positive venous pulse.

The sclerotomies should be sutured because otherwise silicone oil can flow under the conjunctiva. In aphakia, one needs an Ando-iridectomy: Before you inject the oil, cut a break with the vitreous cutter (low cut rate: about 200 cuts/min) in the peripheral iris at 6 o’clock (conventional oils) or 12 0´clock (heavy oils).

The Diagram 4.3 shows the location of the fluids in the vitreous chamber during an air/silicone oil exchange. Air is lighter than silicone oil. During surgery, the silicone oil is injected into the air-filled vitreous cavity. Depending on the amount of injected oil, more or less water will be localized at the inferior pole after surgery.

Exchange of PFCL against silicone oil (light and heavy)

Exchange of PFCL to silicone oil is a common procedure. Remove the infusion line, fasten it to the silicone oil–filled syringe and reattach the infusion line to the infusion trocar. Inject the silicone oil with active injection modus into the vitreous