Macular hole surgery (MHS) has emerged as one of the most common indications for vitrectomy. 1 Although it can be highly successful in a number of settings with a variety of technique modifications, some considerations may maximize results. Case selection is important; poorer prognosis cases include those involving larger holes,2 chronic holes,3 reoperations,4 high myopia,5 and association with retinal detachment or trauma.6 The technique component that likely has had the most positive effect on outcomes is peeling of the internal limiting membrane (ILM).7-9 The duration and degree of internal tamponade has also recently been subject to debate. This article surveys these and other considerations that may affect MHS outcomes.
PREOPERATIVE CONSIDERATIONS
Eyes with shorter duration holes, smaller holes, better preoperative vision, and lack of other extenuating circumstances have long been recognized to carry a better prognosis with MHS. Although the surgeon cannot change these factors, preoperative counseling in their presence creates more accurate postoperative expectations and may even factor into the decision for or against surgery. Features now ascertainable by optical coherence tomography (OCT) imaging increasingly influence such evaluations.10-12
Visual acuity, macular hole size, and duration are most likely confounding factors, but the size may be the single most reliable factor. The duration of the hole can be difficult to identify, not only because patients are commonly inaccurate historians in determining unilateral visual loss, but because there may be a variable prodrome or other conditions that confound the actual macular hole occurrence. In general, the prognosis with a macular hole of much more than about a year duration, especially if large, probably does not merit surgical intervention. Recent studies with OCT have demonstrated the size and area of the inner segment/outer segment junction defect to be important determinants of pre- and post-operative visual acuity.10-12 The preoperative visual acuity may also vary based on factors such as intraretinal edema or extent of subretinal fluid, which are possible signs of chronicity and may also influence the visual prognosis.
INTRAOPERATIVE CONSIDERATIONS
In recent years there has been a general trend toward
smaller gauge vitrectomy instrumentation. Although it is
the author's bias to use 20-gauge instrumentation, several
studies have reported equivalent success with both
23- and 25- gauge systems.13,14 A potential limitation of
small gauge instrumentation for MHS, however, is the constricted spectrum of instrument
options to peel the ILM; improved disposable
forceps quality may alleviate
this concern. The author prefers to
initiate ILM peeling with a barbed
20-gauge MVR blade, which does not
have a suitable small-gauge counterpart.
Others have expressed this same
concern (Robert Wendell, personal
communication) and some use one
20- gauge sclerotomy to circumvent
this limitation.
SURGICAL TECHNIQUE
There are two maneuvers for MHS that engender special
consideration: posterior hyaloid separation and ILM peeling.
Unless it is preexisting, posterior hyaloid separation is a
crucial step that must be performed after the core vitrectomy.
It can be deceiving to ascertain posterior hyaloid separation,
as vitreoschisis is probably more widespread than
intuitively suspected.15 The most reliable way of inducing the separation is to use a flexible-tipped extrusion needle
with automated aspiration control to search for and
engage an invisible, residual posterior hyaloid, manifested
by the characteristic “fish-strike sign” (Figure 1A).16 The
posterior hyaloid is engaged and lifted between the temporal
vascular arcades with posterior-to-anterior movements
fairly broadly and contiguously, regrasping and utilizing a
massage-like, teasing motion. Although for some instances
this same technique can be utilized to peel the Weiss ring
off the nerve head, the author finds that using the vitreous
cutter on aspiration mode is more reliable and avoids confusion
of the Weiss ring with other vitreous cortex (Figure
1B). Once the Weiss ring is mobilized, the rest of the
hyaloid usually separates readily into the periphery by aspirating
with the cutter and can be removed in standard
fashion. This technique confirms that the posterior hyaloid
has been completely removed. Excessive movements while
aspirating with the vitreous cutter should be avoided to
minimize retinal break formation.17 Maximal removal of vitreous
allows smother fluid-air exchange later and avoids
unwanted and uncontrollable postoperative peripheral
retinal traction by the bubble postoperatively.
The second key maneuver is to peel the ILM. While substantial closure rates have been reported without ILM peeling,1,2,18-20 it probably increases the success rate,7,8,21 so the author attempts to peel the ILM in all cases. This involves three steps. First, the ILM is incised and one edge is lifted to give a purchase site to dissect it from the retina. The second step involves dissecting (usually with a vitreoretinal pic) the ILM from the surface more broadly, and the third step completes the process with forceps by removing the rest of the ILM from the retinal surface and from the eye. Other instruments are effective for these maneuvers and are preferred by some.7,22
The ILM is incised and an initial edge is lifted by making a short, shallow, continuous, curvilinear, laceration-like movement with a barbed MVR blade through the ILM to develop a rather flat, only slightly elevated, somewhat scrolled edge (Figure 2A). This is generally initiated approximately two disc diameters from the hole, usually superotemporally (right eye) or supernasally (left eye), but may it be adjusted to wherever the ILM sheen seems to be most visible. The MVR blade is convenient for this because of its acute point. The blade is then passed perpendicularly to the original direction to plow up the scrolled edge sufficiently to insinuate a vitreoretinal pick under the ILM. Visualizing the ILM can be challenging, and constant adjustments in the orientation of the endoilluminator help the surgeon monitor the progress. Staining is usually not necessary for standard cases but will be described below.
Once the edge has been distinctly developed, the pick is used to extend the dissection with gentle side-to-side motions punctuated by shallow posterior-to-anterior lifting motions, successively advancing around the circumference of macular hole. Frequently it is not possible to circumnavigate the hole completely without the ILM-rhexis rupturing, so the dissection may have to be reinitiated in the opposite direction at the initiation point. The characteristic whitening of the underlying retinal surface that occurs within 30 seconds of ILM removal is a good marker for where the ILM has been peeled, as there can be difficulty visualizing the advancing edge of the peel. At some point, ideally after the pick has been used to separate the ILM around the complete circumference, fine forceps are used to remove the specimen or extend any incompletely separated areas. Usually, the entire ILM cannot be widely separated with the pick, but switching to the forceps may be necessary at this or preferably a much earlier stage in some cases. The rhexis should be advanced with the for ceps around the perimeter rather than near the margin of the hole to optimize the peeling. Most commonly, the mobilized ILM remains firmly attached at the internal margins of the macular hole, leaving a funnel-shaped ILM separation. When peeling ILM with the forceps, a continuous rhexis can only be reliably carried out for about 2 clock hours at each grasp or the fragile ILM will fragment, and the progress of the ILM peel becomes more difficult to monitor and complete. Thus, regrasping at the advancing edge of the peeled ILM allows the most efficient removal. The forceps are then used to remove what remains of the ILM from either the funnel-shaped attachment at the hole (pulling centrally to leave the smallest possible remnant) or more peripherally (Figure 2B). Not uncommonly, superficial, petechia-like hemorrhages occur because the ILM inserts directly onto the superficial retinal vessels, which are naked of inner nerve fiber layer. These do not appear to be of any clinical consequence.
A sometimes overlooked step is the inspection of the peripheral retina with indirect ophthalmoscopy for any iatrogenic or previously unrecognized retinal breaks.17 Using a wide-angle viewing system, systematic scleral indentation accomplishes the same goal. The surgery is concluded with a fluid-air exchange. The macular hole commonly seems to get smaller at this stage. This may be due to reapproximation of the hole edges,23 but it may be an illusion due to the minification effect of air exchange.
The differential value of one gas used for tamponade over another is unproven. The earliest reports utilized an SF6 mixture, which gives substantial tamponade for about 1 week and resolves by about 2 weeks.1 Others have advocated the use of longer-acting, C3F8 gas mixtures, which provide substantial internal tamponade for at least 4 weeks and resolve after 8 to 9 weeks.24 One study found better results with longer-acting mixtures.25 Still others have recommended air only25-27 and some, in selected cases, have even recommended that no internal tamponade is necessary.28
POSTOPERATIVE FACTORS
Just as the selection of gas type varies widely, the recommended
postoperative regimen of face-down positioning
varies widely in degree and duration and has not been
specifically proven. While some do not recommend facedown
positioning,29 most would recommend approximately
1 week of face-down positioning, although many
recommend longer positioning, probably based on earlier
series protocols.24 OCT studies performed through air provide
convincing evidence that the macular hole usually
closes within 2 days following surgery, suggesting that long
face-down positioning is unnecessary.M30,31
SPECIAL CIRCUMSTANCES
There are certain special circumstances that augur a
poorer anatomic prognosis and, accordingly, may suggest
the need for some additional considerations, especially
ILM peeling.32-34 These include reoperations (Figure 3),
especially for large holes, eyes with either extremely blonde
fundi or severe underlying RPE depigmentary changes (as
with high myopia), and those with coexisting abnormalities
such as retinal detachment, proliferative diabetic
retinopathy, and myopic traction maculopathy. Trauma,
by virtue of its other associated residual of commotio retinae,
or larger macular hole size may make for a worse
prognosis but, at least for selected case series, results
approximating standard idiopathic macular hole results
have been widely reported.35,36
Although it is not the author's preference to utilize ILM staining routinely,37-40 visibility to ensure more complete ILM removal may be more important in these special cases. Indeed, with certain high myopes, the dye pooling in the hole might be the only way that one can even detect the hole intraoperatively. Indocyanine green (ICG) is the author's preference, but good experience has been reported with trypan-blue,41 brilliant blue,42 and a suspension of triamcinolone acetonide.43 The exposure of the dye to the retina and pooling at the macular hole should be minimized to minimize concerns of retinal toxicity.44-46
Some have considered using silicone oil47,48 or other options49 for “different” cases, but these have not been well proven.50,51 It is widely assumed that silicone oil obviates the need for face-down positioning and, hence, may be suited for patients with neck or back constraints. Its lower surface tension relative to gas, however, may undermine this unproven hypothesis. Because the presumed purpose of ILM removal is to eliminate traction and to stimulate gliosis,52 the author often makes two to four short incisions at the margin of the hole to augment this stimulatory effect for especially large holes, such as are encountered with reoperations.
CONCLUSION
The nuances of macular hole surgery technique are
probably as varied as individual driving techniques. Just as
most driving techniques are successful, most macular hole
surgical techniques are successful. Certain principles
remain, however, that may provide better MHS results and
that should be considered by the vitreoretinal surgeon.
William E. Smiddy, MD, is a Professor of Ophthalmology at the Bascom Palmer Eye Institute, University of Miami Miller School of Medicine. He states that he has no financial relationships to disclose. Dr. Smiddy can be reached at +1 305 326 6172; fax: +1 305 326 6417; or via e-mail at wsmiddy@med.miami.edu.
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