Pearl

Repeatedly grabbing hard membranes (in PVR or PDR) with the ILM forceps can cause enough “microtrauma” to the closing surfaces that they will not work on the ILM anymore.

–If the membrane is infinite (no edge initially), it is the width of the jaws’ tip that determines the area of contact between the forceps and tissue. Once an edge is present, the entire jaw surface can make contact with it.6

–The greater the width of the ILM forceps, the more secure the grip and the less likely that it tears the ILM. However, increasing the width also interferes with the visual feedback the surgeon has over the depth of contact between forceps and ILM.

•The plano-concave contact lens should be scratch-free and fully transparent.

–Using the smallest amount of visco, rather than lots of it, also helps, provided the amount is sufficient not to trap any air bubble under the lens. Still, the nurse should have at hand a tool such as a muscle hook to be able to gently nudge the contact lens if it slides and needs to be re-centered.

•Increase the zoom as much as possible – find a compromise between image size and sharpness.

•Although it is not mandatory to stain the ILM (see Fig. 32.1), it is highly recommended to do so since it has numerous advantages (see Chap. 34).

32.1.2 Opening the ILM

Unlike all other membranes inside the vitreous cavity, the ILM has no free edge to grab: it must be surgically opened before it can be removed. The ILM can be opened in two ways: sharp or blunt.7

32.1.2.1 Sharp Opening: Incision First

Sharp opening of the ILM involves the use of a barbed8 needle (see Sect. 13.2.3.1).

•Place the tip of the hook over the retina at a convenient and safe location9 (see Fig. 32.2) so that the tip barely touches the ILM surface. Avoid all visible blood vessels.

6A thick proliferative membrane does have an edge; in this case the size of the initial grab is determined by the space between the membrane and retina. If the lower jaw of the forceps can be pushed far beneath the membrane, the entire surface of the jaws can be in contact with it.

7Another way of classifying the opening is to distinguish between a one-step (forceps) or two-step (open with one tool and peel using a second) procedure.

8Without the barb, the maneuver is less safe: the tool must be kept and moved while being held perpendicular to the retinal surface. The shaft is at an acute angle to the retinal surface but is moved parallel to it. The barb is needed to incise, hook, and lift the ILM.

9My preference is outside the foveal avascular zone close to, but inside of, the vascular arcade, superotemporal to the fovea in the right and superonasal in the left eye.