Pearl

A vitrectomy machine should provide some type of audio feedback to the surgeon about a number of characteristics, such as whether the probe is in vitreous or fluid and the actual flow/aspiration level, and confirm any intraoperative change to the machine parameters. The feedback should be moderately conspicuous and its audio level adjustable – the surgeon should also be able to turn it off if he finds it bothersome.

My personal settings for the vitrectomy machine are described in Table 12.2. The software should allow these settings to be programmed into the memory and recalled per user.

12.1.12 Troubleshooting

There are many things that can go wrong with the vitrectomy machine and its accessories; an incomplete list of these and their solution is provided in Table 12.3.

12.2The Microscope

Looking for the ideal microscope, here are a few things to consider:

•Floor-mounted microscopes have the advantage of being mobile and easier to handle if they need to be repaired; they are also less expensive than a ceilingmounted one.

–Conversely, ceiling-mounted microscopes cut down on the clutter in the OR.

•Regardless of the type of mounting, the microscope must remain firm (shakeresistant) when its wheels are locked.

•The microscope should provide an excellent 3D view and have built-in UV and IR filters.

•The view must easily be switchable between coaxial and non-coaxial.25

–It is highly advantageous if slit illumination is also possible (see Sect. 17.2).

•It should have both high and low magnification. The latter is also important because the surgeon may want to see a large field when working externally.26

•All functions, including the speed of the X/Y movement, must be adjustable.

–If the pedal functions are not programmable, at least the buttons should be arranged logically (Fig. 12.3).

mode”), not by function (“if you want to take photos in macro mode, push button A once and button B twice”). Is the user looking for a function or a button?

25Occasionally it is preferable for the reflected light to arrive at the surgeon’s eye at an angle.

26Just think about suturing the iris with a double-armed Prolene suture (STC-6; Ethicon, Livingston, Scotland). The suture is long, the (other) needle easily gets lost, and it is hard to find if the microscope has a small field of view.

*These figures relate to certain machines; different machines require slightly different settings. PVD requires different settings, see Sect. 27.5.1.

aVenturi pump.

bPedal setup: linear (the actual value employed is adjusted according to tissue reaction such as retinal movement).

cPeristaltic pump. The aspiration value set on the machine simply determines the value above which the machine will not increase the vacuum to allow achieving the required flow rate.

dWith either pump.

eThere are advocates of setting the IOP at 50 mmHg. This may be dangerously high in long cases or in eyes with poor circulation (e.g., diabetic ischemia).

fStill, the light should be held as far away from the retina as consistent with sufficient lightning. g≤1,300 cst.

*Related to the machine itself and its major accessories; the list is not a comprehensive one. The cause may also be different with different machines.

aUsed to be a problem with older machines.

bIt can lead to severe iatrogenic complications. This is why the surgeon (not just the machine) should test the probe outside the eye, by looking at the port through the microscope and seeing if the guillotine action is visible. The higher the cutting frequency, the more difficult it is to actually see the motion so the blade’s movement may have to be felt by hand (tactile feedback).

cI am not aware of a commonly accepted terminus technicus. The vitreous appears more structured than normal and has increased resistance to flow.

dShould not happen if a peristaltic pump is used; in reality, it is still possible with older machines. eCommon, not accessory-related reasons include material stuck to the tip (retina was touched with it, blood etc.) or an air bubble that is adherent to it.

fBe very careful; in some older machines the laser will function even when the filter has not been activated; a very unpleasant and dangerous experience for the surgeon and the OR personnel.

•The pedal must satisfy the same criteria as that for the vitrectomy machine (see

Sect. 12.1.8).

•The eyepiece must be highly tiltable to adapt to the surgeon’s comfort (see Sect. 16.7.1).

•It should be easy to mount/intraoperatively add/change various attachments: eyepiece for two assistants + an additional viewing tube, BIOM+SDI, laser filter, and digital video camera. All these must be arranged so that they do not unduly increase the working distance between the eye and the surgeon’s eyepiece.

•The user interface must satisfy the same criteria as that for the vitrectomy machine (see Sect. 12.1.11).

•There should be a digital video camera attached. It has to be of great quality to allow high-definition recording with as large a field as possible (see Sect. 12.4 below).

Regardless of the type of microscope, the surgeon should always keep in mind two inherit characteristics of the operating microscope:

•By increasing the zoom (magnification27), the resolution28 will not increase.29

•Zoom (magnification) and field of view are also inversely proportional.

•During the operation, the surgeon must constantly search for the best compromise between these two opposing pairs of characteristics by adjusting the zoom using the buttons on the pedal.30

27Image size.

28Ability to tell two objects apart.

29See “pixeling” on the computer monitor.

30In theory, if the focus (image sharpness) has been set at high zoom at the beginning of the setup (see Chap. 16), the microscope will keep the focus throughout the entire operation.

•With minor adjustment of the focus,33 equally fine visualization is provided in the gas-filled eye.

Pearl

How easy it is to get used to the BIOM and the numerous advantages it offers is best demonstrated if the surgeon is forced to go back, after having switched to the BIOM many surgeries ago, to a contact lens (see Chap. 13). The surgeon will feel lost as he is not able to see the “big picture” in the vitreous cavity (see Chap. 17).

12.4The Video Camera34 and the Recording of Surgeries

The camera should be digital and of the highest quality. It may require a rather significant initial investment, but as technology advances, a less-than-high-resolution camera will rapidly become outdated.

Q&A

Q Should every operation be recorded?

AYes. If nothing remarkable occurs during the case, the digital recording can easily be erased. This is much preferred to the often-heard exclamation: “What an idiot I was not to record this!” That special moment during the operation may prove “unrepeatable.”

Recording even “routine” surgeries has an additional benefit: The surgeon can periodically set time aside and review them (see Sect. 11.3).

It is also crucial to have a large, high-quality display in the OR so that the surgeon can check whether what he assumes to be recording is indeed visible.35 The nurse must also be able to see the monitor, especially if she is unable to view the operation through the microscope.

For the surgeon, the recording should be of good quality for his own viewing and of excellent quality if he intends to use videofilms for teaching or scientific purposes. Here is a list with a few recommendations:

•Make sure you set up the microscope and the BIOM properly (see Sects. 12.2 and 12.3 above, plus Sects. 16.4 and 16.5).

33Up.

34See Sect. 12.2 above.

35He may be out of focus or outside the field of the camera, or there is too much light reflex.