Face-down Positioning in Macular Hole Surgery: How Important is It?
Thalmon R. Campagnoli, MD • William E. Smiddy, MD
The discovery that surgical treatment improves vision in about 90% of patients with macular hole, a condition previously untreatable, has been one of the most exciting recent advances in vitreoretinal surgery.1 The consensus is that pars plana vitrectomy with removal of the posterior cortical vitreous is necessary, and most agree that internal limiting membrane (ILM) peeling enhances results,2 but there is disagreement about internal gas tamponade and positioning.
The most burdensome aspect of macular hole surgery (MHS) for the patient is face-down positioning—at best, it is a boring way to spend a week or more; at worst, it is painful and may cause or exacerbate other complications.3-6 This is compounded by the demographic that idiopathic macular holes occur mostly in an older, even elderly population. Thus, mitigating or even eliminating this would be welcomed. Additionally, the gas mixture limits air travel and use of certain anesthetic agents. This article will review the rationale for face-down positioning and the evidence for and against it.
RATIONALE FOR TAMPONADE AND POSITIONING
The principal rationale for using an internal tamponade agent is to provide a surface on which bridging cells might migrate to mend the gap of the hole.7 The gas (probably better than a silicone oil8,9) bubble provides that surface; face-down positioning orients it optimally. Additionally, the inherent buoyant force and surface tension probably allow a more effective RPE pump to plaster the margins of the hole and unfurl the raised edges towards closer approximation, effectively minimizing the size of the gap—in this way, less substrate to patch the hole is necessary.
Face-down positioning was adopted from the inception of MHS to mimic procedures that worked to repair rhegmatogenous retinal detachments, and has been time honored as a critical step by most surgeons. Initially, positioning regimens ranged from one to four weeks, and since success rates were so excellent compared to the natural history, there was little reason to question its importance. Not to be overlooked, despite patients' best efforts and intentions, the degree of actual face-down positioning is probably substantially less, on average, than prescribed.10 Probably as a merciful overture to the difficulties incumbent in such regimens, a wide variety of customized positioning protocols have been espoused, generally offering some degree of abatement in the rigor of positioning. These have included not only differences in duration, but certain fractions of days or hours' respite and different degrees of deviation from exactly perpendicular (Table 1).
A related issue is the choice of tamponade agent, which determines the time course of the resolution (and, conversely, size and persistence) of the gas bubble. Two early studies offered evidence for face-down positioning deduced from the “dose response” of gas duration in a study using air11 and another one comparing 5%, 10% and 16% C3F8 gas mixtures.12 Although the setting was different—an adjunctive growth factor and one initial day of face-up positioning was used—the positioning protocol was the same for all patients studied. A small, nonrandomized study found no obvious difference with shorter versus longer acting gas.13 At the same time, although the seminal study of MHS (and its discoverers' follow-up studies) used a shorter-acting gas (SF6),1,14 those authors initially recommended such compulsively face-down positioning (for at least one week) that they didn't even allow the patient to be vertical for the examination on the first postoperative day.
EVIDENCE SUGGESTING POSITIONING MIGHT NOT BE AS NECESSARY
The evidence for considering that compulsive face-down posturing might not be necessary follows from its geometry considerations, empirical studies and imaging studies.
The bubble in a gas-filled eye will bridge the macular hole for quite some time even if the patient is not strictly prone, although the buoyant force and any turbulence from any edge effects might compromise the effect. Parver and Lincoff15 showed that 2 ml of gas (50% vitreous bubble) would tamponade approximately 180° of an arc length, and as little as 0.2 ml (5% bubble) covers 90° of arc. Of course, the geometry of the meniscus of the bubble might reduce those calculations, but it seems unimpeachable that there is a substantial margin for error in positioning for the first few weeks with a 90% bubble, an effect that probably lasts well beyond the time necessary for healing of the hole. The lower efficacy with silicone oil may be due to its lower buoyant force and lower surface tension, which prevents it from contacting the depths of the foveal defect in many cases,16 although many espousing its use paradoxically combine it with less stringent positioning requirements.
Several empiric studies have called into question the necessity for prolonged, compulsive face-down positioning, especially more recently (Table 2). The first to consider the efficacy of MHS without face-down positioning reported substantial anatomic success rates, but possibly not equivalent to contemporaneous series, and also performed simultaneous cataract extraction in most eyes.17 Subsequently, others demonstrated good closure rates with air tamponade only, and only a four-day positioning protocol, although with ILM peeling and many with combined cataract extraction.18 Several other studies have been reported with relaxed or absent positioning regimens—some randomized, controlled trials and some comparative case series—and have been reviewed by Tatham.19
Krohn, in a study involving two comparative, consecutive case series, found similar hole closure rates for three-day and one-week face-down positioning regimens with vitrectomy and gas tamponade but no ILM peeling.20 Tranos demonstrated no differences in functional or anatomic benefit for a 10-day face-down posturing group in comparison to a no-posturing group, using 16% C3F8 as tamponade for both in a prospective trial.21 Guillaubey, in a multicenter randomized controlled trial, stratified for the size of the macular hole, prescribing shorter-acting gas mixtures for smaller holes and longer-acting mixtures for larger holes, but randomized to a seated position vs eight hours per day stringent face-down positioning for five days; all patients were asked not to look up. The success rates were comparable for small holes, but for larger holes were poorer with the less stringent posturing regimen.22 Tadayoni evaluated the results of simply avoiding face-down positioning versus 10 days of at least 90% face down in a multi-centered, randomized controlled trial, but only considered small (≤400 µm) holes and found similar success rates for each.23 Other, nonrandomized studies report closure rates approximating 90% with minimal or no positioning.24-35
An additional question has been raised as to whether simultaneous phacoemulsification cataract extraction, initially advocated by Tornambe, might facilitate results, but this specific factor has not been examined in a controlled fashion.17,18,26,27,30,33
A third line of evidence and rationale comes from studies in which OCT imaging was performed in the early postoperative interval (through a gas bubble), demonstrating apparent anatomic closure in a majority of eyes within a day or two.36-38 These findings corroborate the growing consensus that closure of the hole probably occurs earlier in the postop period than initially presumed, certainly within a week, and even within a day in many cases. One study even used the OCT findings in individual patients to shorten their positioning requirement once closure was observed.36 While this study was uncontrolled, and the correlation between the OCT and functional closure is only assumed, the results are noteworthy and may allow a basis to customize, or at least shorten the positioning requirement.
Even the most ardent proponent of face-down positioning can take solace in the findings of substantial success rates without or even with less stringent positioning. These reports have several implications:
• The patient who is unable or unwilling to pursue postoperative positioning should be encouraged to attempt MHS even if they cannot position more than a few days or at all, since the success rates are still substantial.
• Face-down positioning regimens longer than one week can probably be shortened to a maximum of seven days.
• A shorter-acting gas bubble can be used with some confidence in patients whose circumstances impose limitations by virtue of the need for upcoming air travel in the near term, altitude considerations, or a monocular patient needing more rapid visual rehabilitation.
• Eyes with a better prognosis for various reasons (smaller hole, better visual acuity, shorter duration, absence of other retinal abnormalities) probably have a smaller differential effect (if any) with shorter-acting gas or less stringent positioning, and can even more confidently be recommended for surgery in the face of above constraints.
• The absence of marked differential results probably will prevent any future randomized trials.
• Possibly early postoperative OCT imaging, if made generally feasible, could be an important guide towards minimizing positioning.
Extensive experience has been published offering confidence that stringent face-down positioning is not an absolute requirement to a good result. However, the lack of a 100% success rate will always leave the question of whether a failed case might have been successful if face-down positioning or a longer-lasting bubble had been used. Perhaps it is this mentality that drives most (the author included) to continue to recommend at least some face-down positioning.
As a working protocol, drawing upon historically successful protocols while acknowledging more recent reports, it seems reasonable to ask a patient to be fairly compulsive for the first few postoperative days; patient psychology being what it is, asking for one week might achieve this goal. This protocol might be ratcheted up for larger, reoperated, lower prognosis holes, and might be ratcheted down for better prognosis cases such as small, fresh holes. The duration of the tamponade agent might modulate the need to position but its effect is likely small, except that air might not be enough and oil might not offer optimal physics besides its incumbent need for more surgery. Regardless of protocol, patients and surgeons alike can continue to enjoy the relatively good prognosis of such eyes. RP
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|Thalmon R. Campagnoli, MD, is a visiting fellow at the Bascom Palmer Eye Institute, University of Miami Miller School of Medicine. William E. Smiddy, MD, is a professor of ophthalmology at the Bascom Palmer Eye Institute, University of Miami Miller School of Medicine. Neither author has any financial interests relevant to any products mentioned in this article. Dr. Smiddy can be reached at email@example.com.|