Pits & Pearls No. 17

PVD and dye

1. We recommend beginners to stain the vitreous at the beginning of vitrectomy for the first 10–20 vitrectomies. The vitreous is much easier to recognize and vitrectomy and especially the induction of a posterior vitreous detachment become considerably easier.

2. To stain the posterior vitreous face with triamcinolone: Perform a core vitrectomy and a peripheral vitrectomy in front of your ports. Induce the cannula into the mid-vitreous (be careful not to inject peripherally, or you will inject in to the vitreous base and exert traction). Inject a small amount of triamcinolone that will drop down onto the posterior pole. This will very nicely stain the bursa praemacularis of the vitreous. Do not inject too much triamcinolone for vitreous staining. It will only obscure your view and will be cumbersome to remove later on during the surgery. Few drops are sufficient for staining the posterior vitreous.

3. Once the bursa praemacularis is stained with triamcinolone, try to engage the posterior vitreous face at the optic disc. Try to cut a small break in the posterior vitreous face nasal to the disc, then ‘pick up’ the posterior vitreous phase with the cutter and suction only. Pull anterior towards the lens. Try to keep an eye on the advancing posterior vitreous face in the midperiphery. This looks like a tidal wave. It is where breaks will develop during induction of a PVD.

Pits & Pearls No 18

PVD and myopic eyes: Beware of highly myopic eyes. They often have a ‘vitreoschisis’. You may think that there is a complete PVD, yet, there only is a vitreoschisis with the posterior vitreous face still attached to the retina. In the case of doubt, stain with triamcinolone. The remnant vitreous face will appear as a thin membrane-like structure on the retina. Sometimes you can peel it off with the forceps; sometimes you have to use the fluid needle to brush it of the retina.

Pits & Pearls No. 19

Difficult PVD: If you are not able to induce a PVD, try the following: (1) increase the vacuum to 600 mmHg and try again, (2) stain the vitreous with trypan blue or triamcinolone and try again, (3) insert a 90D lens and mobilize the central vitreous or even better, the posterior hyaloid membrane with an Eckardt forceps. If you have mobilized a larger piece or created a hole, try to aspirate this part with a vitreous cutter and provoke a PVD.

Fig. 4.8 Drawing of the anatomical relationships in the anterior eye (Hogan et al. 1971). (1) ora serrata (termination of the retina), (2) insertion of vitreous base stretches 4 mm posteriorly over the retina and 2 mm anteriorly over the ciliary body, (3) posterior hyaloid, (4) anterior hyaloid,

(5)hyaloid fossa and Berger space

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6. Trimming of vitreous base

After successful PVD, continue with trimming of the vitreous base (Fig. 4.8). We usually use a 120D or comparable wide-angle lens. Regarding the settings of the vitrectomy machine, decrease the vacuum and increase the cutting frequency the closer you work with the vitrector at the retina (Table 4.2).

When performing vitrectomy, hold the instruments almost vertically towards the orbital apex. Make calm and slow movements, in contrast to irrigation/aspiration during phaco. Another important difference is that you hardly move the irrigation handpiece during phaco, but the light pipe in PPV is in constant motion. Light pipe and vitreous cutter move simultaneously, the light pipe illuminating the path of the vitreous cutter. You point the beam of the light pipe to the tip of the vitreous cutter. The vitreous is often difficult to detect. You recognize the vitreous best in the light cone. Move both instruments in a half circle in the vitreous cavity as if peeling an onion from inside to outside. In pseudophakic eyes, the nasal vitreous is cut with the vitrector from the temporal trocar and the temporal vitreous is removed from the nasal trocar.

One should always remember that the eye is a sphere. This means that you have little space behind the lens but plenty of room in the middle of the eye. Coming closer to the posterior pole, you can estimate the vicinity to the retina by looking at the shadow of the vitreous cutter. Be aware: The retina forgives no mistakes, and retinal breaks are easily made. Be cautious, if you come close to the retina with the vitreous cutter.

In phakic eyes, you can cross the midline only when working at the posterior pole to mid-periphery. To reach the vitreous base, you are not allowed to cross the midline. The vitreous base can be removed from the opposite site by indenting the vitreous base or from the same side with the ‘backhand’ and wide-angle viewing systems.

In detachment surgery, the vitreous base must be removed as completely as possible because vitreous traction is causatively responsible for the retinal break and residual vitreous may continue to exert traction on the retina and cause postoperative

new breaks. For surgeries such as macular hole or macular epiretinal membranes, it is not necessary to remove the vitreous base completely because the pathological changes are located here in the macula and not in the retinal periphery. In contrast, working too aggressively in this area may cause more harm by inducing retinal breaks or lens touch. The presence of the natural lens makes working in the area of the vitreous base challenging. Firstly, there is a risk of lens touch, and secondly, access to the vitreous base is more difficult as the lens is in the way, in particular in elderly patients with a thicker lens. Finally, a vitrectomy will induce cataract development in each and every case of phakic patients.

Pits & Pearls

Working in the area of the vitreous base and trimming the vitreous base is another key step to learn if you want to master vitrectomy. Numerous techniques can be used. Our favourite techniques are (US) using a chandelier light and indentation with a scleral depressor and (HH) scleral indentation with a light pipe or working with your ‘backhand’ with the vitreous cutter facing the retina on the side of your vitreous cutter using wide-angle viewing systems. This avoids indentation and is used mainly for trimming the vitreous base during macular surgery.

Pits & Pearls No. 20

Scleral folds or soft globe during vitrectomy: If you view scleral folds during vitrectomy or if the globe is soft, then stop PPV at once. The most likely cause is a dislocated infusion line. Reinsert the infusion line and check if the globe is normotensive and if the scleral folds have vanished.

7. Anterior vitrectomy

As beginner, it is amazing to learn how much vitreous is present in the eye (Fig. 4.8). Even after a thorough peripheral vitrectomy, a lot of vitreous remains behind the lens. This can be noticed intraoperatively when air bubbles are trapped in the vitreous behind the lens capsule. These air bubbles cannot be removed with the fluid needle but only by removing the vitreous behind the lens capsule. An anterior vitrectomy is easy in pseudophakic patients; in phakic patients, it is dangerous because the location of the posterior capsule is difficult to determine. Therefore, injury to the posterior capsule is a common beginner’s mistake. This happens less often when using trocar cannulas, as they limit your movements towards the capsule.

Hold the vitreous cutter behind the intraocular lens and remove the vitreous by moving the vitreous cutter along the edge of the IOL. Hold the aspiration port of the vitreous cutter towards 12 o’clock and then 6 o’clock in order to avoid injuring the posterior capsule.

Pits & Pearls No. 21

Lens touch

1. A lens touch is often caused by the light pipe (focussing the light beam on peripheral vitreous during trimming of the vitreous base) or the endolaser probe when performing peripheral laser on the opposite site. One focusses on the opening of your vitreous cutter but ‘forgets’ the other intraocular instrument. It has to become second nature to hold the second instrument in the correct position without thinking about it.

2. Another common cause of lens touch is pushing the infusion port into the lens during indentation. Avoid by taking extra care in this area and indent pushing the vitreous base towards the centre of the eye, not anteriorly towards the lens.

3. If you notice a lens touch during or at the end of your surgery, clearly mark it in your surgical notes. It is important to know this if you are planning to perform the phaco at a later stage, as this weakens the posterior capsule. We have seen an entire lens dropping onto the posterior pole during hydrodissection; the posterior capsule split at the site of the previous lens touch and the lens dropped posteriorly.

8. Internal search for retinal breaks

At the end of vitrectomy, breaks must be identified and treated accordingly. Inspect the entire peripheral retina with the aid of a scleral depressor. If a break is present, you must remove any residual vitreous adhesions, treat the break with laser -or cryoretinopexy, and a gas tamponade needs to be installed, for example, with 20% SF6. Otherwise, a postoperative retinal detachment occurs.

Pits & Pearls No. 22

Internal search for retinal breaks

1. Perform an internal search in each and every case of vitrectomy, even in low-risk cases. Perform the search at the very end of your procedure, as even minor intraocular manipulations may create breaks in the area of the vitreous base that may not be noticed if you have performed your inspection of the vitreous base beforehand.