•If the membrane to be cut is rather far from the retina, straight or curved scissors are fine.

•The blade of the vertical scissors should be as long as possible.21

•There are two very separate actions in play22; the surgeon must never merge the two into one.

–Positioning the blades: carefully select the location where the cut is to be made and place the blade there.23 Make sure that you have firm wrist support (see Sect. 16.2.1).

–When you cut, remember that your fingers must execute two actions simultaneously: hold the scissors blades securely in the same position,24 while your fingers must squeeze the handle.

–With vertical scissors,25 you insert the lower (stationary) blade underneath and the upper (active) blade atop of the membrane that you want to cut. When you squeeze the handle, the upper blade travels downward; you must not make any movement with the lower blade.

Pearl

That the lower blade of the vertical scissors is stationary is not intuitive. The less experienced surgeon, while activating the scissors, tends to lift his hand and thus the forceps. A conscious learning process is needed to strictly keep the lower blade in situ while cutting.

•If possible, avoid making multiple short cuts; try to make each cut as long as possible. This avoids the need for constant blade repositioning with its inherent risk.

13.2.2 Hybrid Instruments

13.2.2.1 The Flute Needle26

The surgeon often uses this simple but extremely useful tool, e.g., to evacuate air or fluid,27 passively, from the vitreous cavity or the subretinal space. Active aspiration is also possible with certain types (see Fig. 36.2).

21The cannula in MIVS limits blade length, unless retractable blades of memory material are used.

22This is equally true for forceps use.

23Remember the carpenter’s primary rule: measure twice before cutting (once). Cutting is a oneway street.

24Unless the membrane moves during cutting, which adds to the complexity of the maneuver.

25Which is by far my preferred type.

26More details about flute needle use are provided under Sects. 25.2.7 and 31.1.2. Always use a back-flush type, which also allows blowing away materials and offers an escape route when you catch retina with the tip (see below). The flute needle is known in many countries as Charles needle, after its inventor. The name is misleading: it is not just a needle but an entire device. The German name (Staubsauger, vacuum cleaner) is more accurate and certainly more descriptive.

27Such as blood (in a previously vitrectomized eye), BSS (during A-F X), PFCL.

Unlike the probe, which has a side opening, the flute needle’s port opens in front of the instrument. This means that the flow generated is primarily anterior to the needle’s shaft.

•The default position for the surgeon is to keep his index finger over the silicone chamber’s aperture to block any flow.

–Lifting the finger results in an outflow since the IOP is higher than the atmospheric one.

•Lift the finger only when you are certain that the cannula’s tip is positioned correctly.

•If the detached retina is very mobile and retina is caught in the tip’s aperture, forcefully press on the silicone chamber so that the fluid contained within pushes the retina away from the tip.

–Since the tip is blunt, such a capture/release, while undesirable, does not cause measurable retinal damage – unless the retina is very fragile.28

–If fluid is drained through a (hopefully preexistent) macular hole, always use a “soft-tip” cannula to avoid damaging the RPE. Otherwise, do not employ the soft-tip version because its internal diameter is smaller and there is more internal friction.29 Drainage may be completely impossible, especially if the subretinal fluid is thick.30

•If the retina needs to be “massaged” under air or PFCL and the scraper is not available, the soft-tip flute needle is an acceptable alternative.

Q&A

Q How safe is it to “massage” the retina?

A A detached but intraoperatively just reattached retina, which is at the moment devoid of the effects of the IPM (see Sect. 26.3.2), is relatively easy to move around with a soft tool, under, for instance, PFCL. What the surgeon must remember, though, is that while manipulating the retina, it is unavoidable that he also puts pressure and shearing on the RPE and choroid (see below, Sect. 13.2.3.2).

13.2.2.2 Retractable Instruments

The external shaft houses the working part of the tool, which is either made of a memory material (e.g., a curved laser probe) or hidden to block the function of the tool until it is needed (permanent magnet). In either case, the surgeon inserts the instrument into the cannula and then pushes an external slide with his index finger. Proportional to this movement, the business end of the tool then appears in the vitreous cavity.

28High myopia, diabetes etc.

29That is, the drainage is slower.

30As a historical note, in the “pre-TA” era the soft-tipped cannula has been used to determine whether the posterior hyaloid is still on the retinal surface (“fish strike” phenomenon).