Ординатура / Офтальмология / Английские материалы / Retinal and Vitreoretinal Diseases and Surgery_Boyd, Cortez, Sabates_2010

Surgical Steps of Complete

Vitrectomy

(Author's Note: Variations in surgical technique exist; the authors simply describe here their own technique without

Figure 10 A-B: Cellophane maculopathy. (A and B). Different areas of a macula with fine wrinkling of its surface. The negative staining with indocyanine green shows the presence of cells and perhaps a fine, invisible membrane on the ILM; use of TA, however, enhances fold detection. In the right lower corner of Fig. 10B, the bent MVR blade used to incise and peel the ILM can be ascertained.

the intention of claiming its superiority over other techniques).

•Remove the central vitreous.

•Inject a minimal amount (0.1 ml) of filtered TA to verify the presence and geography of the PHF.

•Lift the undetached PHF with aspiration using the vitrectomy probe or engage and lift it with a bent microvitreoretinal (MVR) blade. Do not carry detachment of the PHF too far to the periphery as it risks retinal break formation with subsequent development of retinal detachment.

•Remove the remaining vitreous.

For the surgical steps of ILM removal, see the section on macular hole (below).

Prognosis: Usually excellent, unless severe macular edema has developed and the treatment has been delayed for too long.

Epimacular Proliferation (EMP,

Macular Pucker)

(Author'sNote: The term “macular pucker” implies that the full thickness of the tissue is involved; the term “epimacular proliferation” refers to the underlying cause of the condition. In clinical practice, the two terms are used interchangeably as one refers to the cause and the other to the effect). An asymptomatic EMP is detectable upon careful examination in over 6% of persons over the age of 50 years; an estimated 15% of the cases ultimately become symptomatic.

The condition is characterized by proliferative cells forming a visible membrane on the ILM (Figure 11), causing full-thickness macular effects; inner folding, vascular distortion, leakage, macular edema, and cystic changes are characteristic consequences. The membrane may have a discernible edge or it may gradually “disappear” from recognition at its border. The visual complaint may arise from the distortion of the macula or from the opaque nature of the membrane itself.

Treatment: Removal of the vitreous, the epimacular proliferation, and, preferably, the ILM. (Author's Note: Some surgeons prefer removal only the vitreous directly in front of the macula, leaving most of the vitreous in situ (“minimal” or “core” vitrectomy). Yet another, small group of surgeons advocate removal of the EMP without performing any vitrectomy “non-vitrectomizing vitrectomy”). Peeling of the ILM is not an essential step for the removal of the EMP, but it is helpful for two purposes: making certain that no part of the EMP is left behind; and to virtually eliminate the risk of reproliferation, which is otherwise expected in 5-10% of the cases. During removal of the EMP, the surgeon must keep in mind that the membrane may have several layers, and failure to start with the outmost layer can extend the procedure’s time, risking photic maculopathy. Finally, the surgeon should not be hasty even when the membrane gives easily: it may have strong connections to the retina in unexpected areas, risking harm to critical macular tissue. (Author's Note: The fovea is identical to what is called in American football the “red zone”).

Surgical Steps of EMP Removal

(Author's Note: Variations in surgical technique exist; the authors simply describe here their own technique without the intention of claiming its superiority over other techniques).

•Remove the entire (core) vitreous (see above).

•Consider staining the EMP if its anatomy is unclear – although rarely necessary, staining does have tangible benefits, especially for less experiences surgeons. A commonly used stain is trypan blue. (Author's Note:

Alternatively, stain the ILM with indocyanine green (ICG) to show areas of no staining, which is caused by the presence of the EMP).

•Carefully examine the characteristics of the membrane: thickness, size, vascularization, adherence etc.

•Design your removal tactics, deciding whether:

•You want to use a centripetal (towards the center) or centrifugal (starting in the center) technique of advancement, or a combination of the two (Figure 12);

•You want to find an edge first to use direct-grabbing with forceps;

•You want to create an edge (for which the Tano membrane scraper may be useful) first;

•You prefer one type of forceps over another.

•Carefully lift the membrane, but remember to move your hand in a more-or-less retina-parallel plane to avoid exerting too much anteroposterior traction on the retina but also avoiding “bumping” into the retina by keeping too short a distance from it. (Author's Note: This is why a steady

hand is needed, the surgeon must have a plan (surgical tactics) already established, and have a firm grab of the membrane before actual peeling occurs). Similarly,

Figure 12: Epimacular Membrane (EMM), Radial Peel. The epimacular membrane in macular pucker is often firmly adherent to the fovea, and especially in long standing cases with cystic foveopathy, has the potential to tear the fovea if peeled radially. As shown here, the EMM (E) has been peeled radially across (arrow) the macular area and torn the fovea (F). Unfortunately, this complication cannot be completely anticipated since, unlike in maculorhexis, the fovea cannot be viewed except from the peeled side.

extra caution is warranted when peeling the membrane over cystic areas, to avoid unroofing of a cyst.

•If too strong a vitreoretinal connection is encountered, consider amputating the membrane here with retina-parallel scissors or the vitrectomy probe, rather than force the separation (Figure 13A-C).

•See below for details of ILM removal.

If the epimacular membrane is not too large or thick, an alternate technique is to remove it and the ILM together as a single piece (“en-block resection”).

Prognosis: The final postoperative visual acuity shows an improvement of two or more lines in over 80% of treated eyes, with 25-50% achieving ≥ 20/40 vision. On average, the operated eye can be expected to regain

approximately half of its lost visual acuity. Equally importantly, successful treatment avoids further anatomic and functional deterioration. Thus, with the substantial improvements in the efficacy and safety of macular surface surgery in recent years, earlier intervention may

Figures 13 (A-C): Epimacular Membrane (EMM) (Adherence after Maculorhexis). (A) Occasionally a firm foveal adherence of the EMM will result in non-separation during maculorhexis. The peeled membrane

(E) floating above the fovea (F) can then be reduced by Morris/Witherspoon scissors and meticulously peeled from any side, or amputated (B) just above the fovea with Morris/Witherspoon horizontal scissors (S) held flush with the fovea as shown. (C) Shows the end result of the removed EMM.

reasonably be considered even for eyes with reading vision if cystic foveopathy portends future deterioration (see above) or in the presence of large disparity between the Snellen visual acuity and the MNREAD results.

Macular Hole

A full-thickness defect in the fovea is formed (Figure 14), which usually expands over time, coincident with the development of a surrounding cuff of subretinal fluid. Tangential traction may be present in the form of cortical vitreous and/or minimal fibrosis on the ILM surface (Figure 15). Patients with macular holes of stages 2 through 4 are commonly operated on, but results of surgery for stage 1 (impending) holes are also encouraging even if this indication remains somewhat controversial. (Author's Note: The natural history (i.e., spontaneous closure rate) of this condition is unknown. Despite initial reports of success with adjuvant therapy, it is now rarely employed; rather, surgeons routinely peel the ILM to improve the anatomical and

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functional outcome, and reduce the risk of recurrence.

Treatment: Removal of the vitreous (see above), the epimacular proliferation (see above) if it is present, and, preferably, the ILM, followed by indirect ophthalmoscopic encircling laser prophylaxis (see above) and gas tamponade (see below). (Author's Note: Some surgeons prefer removal only the vitreous directly in front of the macula, leaving most of the vitreous in situ (“minimal” or “core” vitrectomy). Yet another, small group of surgeons advocate removal of the EMP without performing any vitrectomy “nonvitrectomizing vitrectomy”). The rationale to remove not only the hyaloid from above the macular hole but also the ILM is based on the understanding that tangential, in addition to anteroposterior, traction also plays a role in the development of the macular hole.

There are several controversial issues regarding the basic philosophy of surgery, such as:

• The need to routinely make the patient pseudophakic during the same procedure or do the cataract extraction/intraocular lens implantation as a preceding or secondary operation. (Author's Note: When mentioning the patient pseudophakic, we refer to those who already lost most or all of their accommodative power.);

•The need to stain the ILM;

•The type of stain to utilize. (Author's Note: While ICG is ideal to stain the ILM in eyes without a macular hole, it has been reported to cause toxicity in eyes with a macular hole where the dye can easily get under the retina. It is therefore recommended to either utilize another dye (e.g., trypan blue) or plug the macular hole with viscoelastic and limit both the dye’s concentration and its duration in the eye.);

•The need for ILM removal in every vs. only in selected cases;

•The area of ILM removal: restricted to the immediate vicinity of the hole vs. up to the vascular arcades;

•The need to use longer-term gas tamponade vs. only air;

•The need to use silicone oil as a tamponading agent;

•The need to position the patient postoperatively for an extended period vs. only for one or only a few days.

Lacking a clear answer in the literature to these questions, we simply describe our various methods of ILM removal with brief comments on some other techniques.

ILM Removal Techniques

(Author's Note: ILM peeling” or “ILM maculorhexis” (a term coined by Drs.

Robert Morris and C. Douglas Witherspoon), are commonly used phrases to describe the procedure).

Instrumentation

Forceps

The first issue to determine is whether the surgeon prefers to incise the ILM before grabbing it. The bent MVR blade gives greater control of the depth than the forceps (remember, the ILM is 2-4 μ thick) and allows a more precise initial tearing (Figure 10B).

Next, the surgeon must decide what type of forceps to use. A forceps with a large platform (end-gripping) reduces the risk of shredding the ILM but blocks the surgeon’s direct viewing of the forceps’ action. The Morris/Witherspoon “full-view” forceps has a small platform and an angle as well as a hollowed shaft, allowing ideal visual control of the procedure, but can tear the ILM a little more easily.

Tano Membrane Scraper

Although some surgeon use this instrument to not only create the initial break in the ILM but to actually complete the peeling with it, this a very dangerous procedure since the soft silicone tip of the scraper is coated by diamond crystals that can easily injure the retinal nerve fibers in areas already denuded of the ILM.

Cannula (FILMS® Technique)

(Author's Note: The term FILMS® stands for Fluidic Internal Limiting Membrane Sepa-

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ration, a technique developed by Drs. Robert Morris and C. Douglas Witherspoon).

A specially designed microcannula is inserted under the ILM and viscoelastic is injected to simulate ILM separation, simulating the process found in eyes with a submembranous hemorrhagic macular cyst in Terson syndrome.

Surgical Techniques

The “keyhole” Technique

(Author's Note: The “keyhole” technique is ideally done using the Morris/Witherspoon ILM forceps (Synergetics, St. Louis, MO) because it allows continual visualization of every detail of the peeling).

The initial opening of the ILM is performed using the “pinch technique”.

The forceps is inserted in an oblique, vertical orientation to the retina. With the forceps slightly open, the retinal surface is contacted in an avascular region inside the arcade vessels, at 6’oclock or 12 o’clock. As tissue contact occurs, the forceps jaws are closed and slowly elevated. The stained ILM is seen to rise as the forceps is slowly elevated with the ILM in grasp. If excessive movement of the surrounding retina is seen, the forceps is opened and the maneuver is repeated. An ILM break can easily be seen as the forceps is opened (Figures 16A through C).

TheILMedgethusproducedisthengrasped by gently pushing down on the retina in an adjacent area (i.e., where the ILM “cover” is still preserved) with a slightly opened forceps jaw, causing the ILM edge to lift from the

retina and present itself for grasping (Figures 17A and B). The ILM strip is then gently peeled towards the macular hole, creating a

vertical ILM defect from the starting point almost to the hole (Figures 18 1A through 1C).

The ILM edge is again grasped, and a parafoveal rhexis is performed (Figures 18 2A through 2C). Finally, peripheral ILM maculorhexis is accomplished, and this tissue is also discharged from the eye (Figures 18 3A through 3C). The surgeon must pull the ILM toward, never from, the hole, to avoid enlarging it and causing further damage.

As an alternative, a modified keyholemaculorhexis can be performed, by grasping an edge of the vertical strip peripherally and proceeding circumferentially in a single maculorhexis.

The “Apple-Peel” Technique

The stained ILM is grasped 500-700 microns above or below the fovea, and a thin

strip is peeled radially, almost to the fovea, and released. The exposed edge is then grasped at its midpoint, and a parafoveal strip of ILM is started with a circumferential movement around the fovea. This parafoveal rhexis is continued, releasing and re-grasping as necessary, until the rhexis is approaching a full circle around the fovea. An outward force vector is then intentionally applied so that the ILM strip expands outwardly in a continuous fashion. Re-grasping as necessary, this maneuver is continued until the macular ILM has been removed in a single strip, which is then removed from the eye, avoiding the need for multiple forceps removal and reinsertions (Figure 19).