Article

Challenges of Reintervention in Vitrectomized Eyes

Techniques and strategies for reoperation.

Much has been written about surgical techniques in vitreoretinal surgery, especially with the advent of minimally invasive vitreoretinal surgery (MIVS) techniques and their attendant instrumentation. However, little has been said about the special considerations and challenges involved in reoperating on previously vitrectomized eyes. This article will address some of the management strategies and surgical techniques applicable to reintervention based on the authors’ own clinical experience and drawing from the scant relevant literature.

SCLEROTOMY AND CONJUNCTIVA

Three-port transconjunctival sclerotomy is the most basic, but important, approach of pars plana vitrectomy (PPV). MIVS has drawn some measure of its popularity from enabling sutureless sclerotomies.1,2 While many sclerotomies do still require sutures, this number is falling with even smaller gauge, additional techniques, and more experience.3-8 However, prior incisions alter the local elasticity of scleral tissue, rendering them less likely to seal. Thus, in reinterventions, the nonvirgin sclera seems to be less occlusive and more frequently requires sutures. Anticipating this need, the vitreoretinal surgeon should be aware of where previous sclerotomies were placed and be prepared to shift the placement of new sclerotomies to avoid obviously thinned, spent locations. Sometimes, placing the infusion cannula inferonasally can avoid atrophic sclera in the usual, high-traffic, temporal meridional location.

The sclera does not innately heal; its integrity depends more upon enveloping fibrosis. With 20-g vitrectomy, it was common to reuse the original locations, especially following recent surgery, but this practice is not well advised for MIVS. The transconjunctival, small-incision sclerotomy seems to seal more rapidly than 20-g incisions, as OCT and ultrasound studies have demonstrated,9-10 but the tissues are still notoriously compromised for subsequent sclerotomy placement.

An ancillary observation is that, like with 20-g sclerotomy sites, the conjunctiva is commonly stuck down at the MIVS sclerotomy site, probably as a wound-healing response, perhaps stimulated by a temporary postoperative leak. Such adhesions might require additional attention if a peritomy is being performed (as in subsequent scleral buckling) to avoid buttonholes or conjunctival foreshortening. Also, maximizing the vitality of the conjunctiva is important as complex eyes not uncommonly come to need glaucoma surgery; healthy, mobile conjunctiva optimizes the lifespan and effectiveness of any such future or concurrent interventions.

CLARITY OF THE SURGICAL FIELD OF VISION

Another principle common to all vitreoretinal surgery is maximizing visualization of the posterior pole, both for assessment and treatment. This principle is more common in reintervention. Assessing the extent of reproliferating preretinal membranes and areas of intrinsic retinal tightness and identifying retinal breaks are vital surgical objectives that might be compromised by poor visualization due to media opacities. A general principle is that the chances for success diminishes with each succeeding operation; hence, maximizing surgical opportunities at each earlier surgery is critical to optimal outcomes.

Not uncommonly, there is corneal haze due to endothelial compromise, elevated intraocular pressure, band keratopathy, or blood staining. The pupil is commonly smaller due to posterior synechia, pupillary membrane formation, or even retropupillary proliferation. The phakic eye frequently develops more lens opacity by the time a reoperation is undertaken, while the pseudophakic eye is a ready surface for all varieties of reproliferating cells, red blood cell dusting, and lens artifact, such as with silicone oil. MIVS may pose more challenges in contending with these issues as probe flexibility makes accessing the anterior chamber more difficult. The vitreous cavity may include opacities from flare or hemorrhage but poses no particularly different challenges in removal in a reintervention.

Debriding edematous corneal epithelium is a mainstay maneuver, but it carries with it the risk of inciting a persistent epithelial defect, particularly in the diabetic eye. Hence, trying to make a smaller area of induced epithelial defect can avoid some of the later complications; the limbal stem cell zone in particular should be preserved as much as possible. More severe opacities might require the use of a temporary keratoprosthesis11-13 and penetrating keratoplasty. Corneal graft survival and final visual acuity in this setting are often poor.

Cataract formation or acceleration is an inevitable consequence of vitreoretinal surgery. While the mechanisms are incompletely understood,14 even in the short term, lens opacities can be an impediment to the vitreoretinal surgeon’s visualization. Both of these considerations should prompt a lower threshold for performing lensectomy concurrently with vitrectomy. Usually if lensectomy is necessary, the posterior-segment objectives are sufficiently in jeopardy that intraocular lens (IOL) implantation is best deferred for a later time when there is more stability and to avoid providing a surface for subsequent reproliferation. However, unless there is florid anterior proliferative vitreoretinopathy (PVR), the lensectomy can usually be performed in such a way as to preserve peripheral anterior capsule to enable subsequent sulcus posterior chamber IOL implantation.15

Similarly, an IOL can harbor media opacities, so in eyes with advanced vitreoretinal disease, IOL explantation should be a consideration. If the pupil has synechia, these should be lysed; not uncommonly, this issue is commensurate with a small pupil, so iris hooks may be invaluable to facilitate a view posteriorly. However, with iris hooks, the corneal tracks may provide an outlet for air in the anterior chamber during infusion of silicone oil. This can eliminate the relative anterior-chamber air lock and allow prolapse of silicone oil into the anterior chamber, where it compounds corneal and glaucoma tendencies postoperatively. Pupillary membranes may be extremely dense, and the MIVS cutter might either be ineffective to excise or be too flimsy to reach these targets. In such cases, forceps or shredding of the membranes may facilitate their removal. Liberal use of viscoelastic in the anterior chamber should be considered when manipulating or removing anterior-segment structures.

Silicone oil is more commonly an optical impediment for the patient than a barrier for the vitreoretinal surgeon during reoperation. However, microemulsified oil can represent a media opacity that is usually easily dispatched at the onset of the surgery. One of the most problematic features causing media opacity in a reintervention is vitreous hemorrhage. Previously operated tissues are friable and, especially in the diabetic or anticoagulated patient, might bleed profusely. The standard maneuver of elevating infusion pressure, at least temporarily, might permit enough of a respite to allow for the surgical objectives to be accomplished. This possibility, combined with fastidious cautery to induce hemostasis, merits early and constant attention.

REMOVAL OF RESIDUAL VITREOUS

Usually, the primary vitrectomy has involved maximal vitreous removal, and it seems that the vitreous base often consolidates as well. However, sometimes, especially with high myopia or a young patient, there can be residual hyaloidal attachments that cause recurrent or persistent RD in a surprisingly posterior distribution. Being alert to this is important at the assessment stage and requires more extensive relief of such tractional elements. While this possibility can rise in a primary case, it seems more common and even tantamount to achieving success in a reintervention. Triamcinolone acetonide and sclera indentation may aid in detecting and removing residual vitreous.

Recurrent RDs are associated with PVR and are classically associated with cellular elements seeding the residual vitreous base.16,17 Aggressive debridement must be considered in such cases, but if not disproportionate, a more conservative approach might be warranted to avoid induction of hemorrhage or escalated proliferation. Such cases might be good candidates for a scleral buckling procedure to neutralize traction, rather than aggressive vitreous base dissection, especially if the view is suboptimal. This is a common and sometimes difficult intraoperative dilemma for the vitreoretinal surgeon.18,19 These are also putative elements of ciliary body traction-induced hypotony and should be removed when expedient.

MACULAR CONSIDERATIONS

Macular hole surgery has become one of the most successful and gratifying procedures that the vitreoretinal surgeon performs. However, there remains a nagging 5% to 10% of eyes that will fail to respond to primary vitrectomy or will reopen after otherwise successful surgery. The consensus pathogenetic theory is that macular holes occur due to some degree of surface traction — either persistent vitreomacular attachment or ILM seeding by glial or RPE elements. Therefore, at reoperation, it is critical to ensure that the macular anatomy is optimally defined to detect for the removal any such elements. A lower threshold for vitreous ERM or ILM staining techniques is probably warranted. While the authors generally try to avoid such adjuncts (and their possible toxicities) in a primary case, we usually use them in a secondary case to maximize success. Furthermore, opting for longer, rather than shorter, acting gas mixtures is also employed. However, silicone oil is generally avoided even in reoperated macular holes due to its lower surface tension and buoyancy — factors thought to compromise the therapeutic mechanism.

TAMPONADE CONSIDERATIONS

Another conundrum that may be more commonly faced in reintervention is the need for vitreous tamponade. While theoretically, the tamponade is only necessary for the several days, it might take longer for a retinopexy to mature. Hence, most surgeons tend to use longer-acting gas mixtures (or silicone oil) for “tougher” cases, especially with inferior pathology or in patients who are unlikely or unable to optimize positioning. In reinterventions, we are probably more inclined to “round up” and use longer tamponade, rightly or wrongly.20

To some degree, a longer tamponade might allow a longer time for inflammatory factors to recede, but might also place a possible further reoperation into a more psychologically distant point in time. Indeed, the threshold for using silicone oil is generally lower in reintervention for these reasons, as it is the ultimate tamponade agent. In such cases, it is particularly important to minimize the tightness of the retina and consider relaxing retinotomies, as another recurrence may well involve subretinal silicone oil — an especially difficult situation to remedy. Subretinal silicone oil is guaranteed to prevent reattachment, and its high viscosity and colligative properties require a much larger draining retinotomy to remove it from the subretinal space. A longer rigid needle can offer better access and can sometimes reduce the necessary size of a retinotomy, but Poiseuille’s law renders generating sufficient suction adequate for removal challenging. Among the protean considerations in the silicone-filled eye is the entity of perisilicone proliferation, which must be recognized to seek and remove preretinal membrane at the time of silicone oil removal for optimal results.

OPTIMAL TIMING FOR REINTERVENTION

A particularly vexing problem is balancing the urgency to reoperate with the physiologic (and psychological) challenges of early reintervention. The postoperative eye is plagued with media opacities and inflammatory factors, which prime it for more reproliferation. Hence, allowing at least a short period of recovery to allow such factors to subside might enhance outcomes. While this principle has never been proved, it is a widely held practice that allowing the eye to “cool off” may pay dividends. In addition, a few weeks, when possible, might allow ERMs to coalesce (“mature”) to be more readily and completely peeled. Intensified anti-inflammatory regimens (especially topically) might facilitate this maturation as well.

CONCLUSIONS

Reintervention after primary vitrectomy is necessary all too often. While the vitreoretinal surgeon generally extends the same surgical principles to such cases, additional considerations are worthy of attention and may lead to better outcomes. A few of these considerations have been delineated above, but these authors recognize this summary to be an incomplete treatment of the topic, and much is still to be studied in this subset of patients. RP

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