Working With and Under Air

Pearl

The intravitreal fluid adheres to the retina, however weakly: trickling down takes time. Think about your coffee mug after you drank all your coffee; within seconds, a small pool of coffee starts to become visible at the bottom of the mug.

31.1.2Detached Retina (Retinal Reattachment via Draining Through a Retinal Break)3

This may be a rather frustrating maneuver for the inexperienced surgeon.

•Mark the central edge of all retinal breaks4 so that they remain visible in an airfilled eye.

–The retinal break, so conspicuous under fluid, is likely to “disappear” under air.

•Turn the eye so that the central-most retinal break is at the deepest possible point of the eye.

•Insert the flute needle. Position your hand firmly, holding securely the tip of the flute needle just above the break.

–Lift your finger off the silicone chamber only when the flute needle’s tip is in position.

–Occasionally, the subretinal fluid will drain even without employing air.

•Switch to air. The air pushes the subretinal fluid posteriorly, toward the flute needle’s opening.

–Unless the RD is old, the fluid is not viscous: the fluid column readily enters the flute needle as long as the column is not interrupted.

Q&A

Q How do you drain a subretinal fluid that is very viscous?

AToo viscous a fluid will either not enter the flute needle at all or it will rapidly obstruct it. (Naturally, the smaller the gauge, the greater the chance that this occurs.) The surgeon either asks the nurse to repeatedly flush the silicone chamber and the needle itself, or, preferably, choose active suction. The latter may be possible with the flute needle (see Fig. 36.2) or the probe. The port may need to be “dipped” into the subretinal space to avoid catching the retina (see Sect. 25.2.6).

3Additional details and a summary are provided in Table 35.3.

4Except if they are in a cluster and at equidistance from the ora serrata; here a single mark is sufficient.

•A highly mobile retina can easily be caught in the port as the surgeon’s finger is lifted off the flute needle’s chamber.

–Carefully push the tip of the needle into the subretinal space through the break. This maneuver risks injuring the choroid, but it greatly reduces the chance of retinal incarceration.

–Alternatively, inject PFCL to keep the retina immobile. This, however, introduces its own issues if air is used: the PFCL evaporates, and tiny droplets collect on the IOL (see Sect. 31.2).

•With the air entering and the subretinal fluid escaping the eye, the surgeon has a good chance of achieving a complete drainage. The capillary effect assures that the fluid will keep streaming even if the retinal break is not at the deepest point of the eye, as long as the fluid column is not interrupted – which is the beginner’s most difficult task to achieve.

Pearl

A F-A-X can also serve as an air-test. If no membranes are left on the retinal surface, no significant subretinal membrane is present, and the retina is not shortened, the retina will be attached but not stretched when the drainage is complete, and its surface will be smooth.

–Initially, the air forms small bubbles as it enters the vitreous cavity (see Fig. 31.1), and it takes a few seconds, sometimes longer, for the bubbles to coalesce. Until this happens, the view is completely lost; if indeed the surgeon holds the flute needle absolutely steady, drainage continues.

–Conversely, once the fluid column is broken, the air pushes the central edge of the retinal break onto the RPE, and the subretinal fluid is trapped centrally.

•In cases of residual subretinal fluid you have the following options.

–Redetach the retina (acceptable though not ideal), and repeat the entire process.

Fig. 31.1 Multiple air bubbles during F-A-X. It is rare that the incoming air immediately forms a single, large bubble. View of the posterior retina is lost until these small bubbles coalesce. See the text for more details

–Inject a small amount of PFCL and turn the eye so that you push the subretinal fluid toward the break, then try to complete the drainage.

–Make a small central retinotomy and drain through it. This is not advisable since it represents a risk factor for PVR.

–If only a small amount of subretinal fluid remains and silicone oil is not used, leave the fluid behind and the RPE will pump it out it within days.5 If the RD was macula on, keep the fluid out of the submacular space (steamroller effect, see Sect. 54.6.3.1).

–Leaving a larger amount of subretinal fluid behind is unacceptable. If silicone oil is used as the intraocular tamponade, you cannot achieve a 100% fill. If gas is used and the border of the detachment is close to the fovea, a macular fold may be caused.6

•Drain all the subretinal fluid first, before collecting the BSS in front of the disc; otherwise the incoming air may push the remaining subretinal fluid into the submacular space.

Q&A

Q Is it always possible to drain all the subretinal fluid?

A No. If the surgeon does not use PFCL and the break is very peripheral, some fluid will be retained subretinally. A very viscous fluid may form a difficult-to-remove film on the retinal back surface. Especially after SB surgery, a small fluid pocket may be retained for months under the fovea (see Fig. 54.11).

•Whether all the intravitreal BSS needs to be collected depends on whether silicone oil or gas tamponade is to be used (see above).

31.2Working in the Air-Filled Eye

Accept that visibility will be poorer under air than under any type of fluid.

•The BIOM’s front lens in a phakic or pseudophakic patient must be adjusted higher (see Table 16.5).

•Retinal tears of small size tend to “disappear,” unless marked by diathermy (see Sect. 54.5.2.3).

•Condensation may occur on the surface of the IOL in the area of the posterior capsulectomy.

5Unless the fluid is very viscous – try to remove such viscous fluid completely (see below).

6A real disaster if it is through the fovea. If a fold develops, the retina must be redetached to deal with it – easy if the fold is discovered intraoperatively. However, if the retina reattaches and the fold is noticed only weeks postoperatively, even a successful anatomic result (no small feat by itself) may not bring functional improvement.