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Pneumatic retinopexy (PR) is a minimally invasive technique for the repair of rhegmatogenous retinal detachment (RRD). It is composed of intravitreal gas injection, either cryopexy or laser, and postoperative positioning.
ADVANTAGES OF PR
Given an optimal clinical scenario, PR has several advantages over primary pars plana vitrectomy (PPV) and/or scleral buckle (SB) for the repair of an RRD. Pneumatic retinopexy is usually performed in the office or as a brief procedure in an outpatient surgical facility. In a multicentre trial reported by Tornambe,1 the average number of hospital days including reoperations was 0.6 for the PR group and 2.7 for the SB group. The physician spends less time waiting for availability of the operating room, performing the procedure, and performing postoperative hospital rounds. It should be noted, however, that since this publication in 1989, the majority of procedures, including PR, primary PPV, and SB, are now performed in an outpatient setting.
With PR, the patient generally experiences less pain, and there is a quicker recovery in the more comfortable home setting. There is also a significant economic advantage to the patient and the insurer in terms of cost savings by avoiding the operating room, anaesthesia, and hospital expenses. It is estimated that the cost of PR is between 25% and 50% that of SB including re-operations.2
Pneumatic retinopexy is a technically easy procedure. There are very few significant intraoperative complications. When they do occur, it generally involves improper location of the injected air or gas, generally into the subconjunctival or subretinal space—in only 0–10% and 0–4% of cases.1–7 New and/or missed retinal breaks are created in 7–33% of cases.1–10
There are more significant risks associated with primary PPV and SB procedures. Primary PPV surgery has a much higher incidence of lens injury/cataract (3%) and other anterior segment complications such as intraocular lens (IOL) subluxation, iris capture, and flat anterior chamber.11,12 Scleral buckle procedures are associated with significant risks primarily due to inadvertent scleral perforation (5%) or during drainage of subretinal fluid.3,13–15 Subretinal haemorrhage (3.0–4.5%), retinal incarceration (2.2–3.0%), retinal breaks (0.54–4.0%), and vitreous loss (0.36–3.0%) are all significant risks associated with drainage sites.3,13–15 Postoperative diplopia is ubiquitous with SB procedures, being reported in up to 20–50% of cases.16,17
Postoperative complications of PR are rare with the exception of new and/or missed retinal breaks. Epiretinal membrane (ERM), cystoid macular oedema (CMO), macular hole (MH), and proliferative vitreoretinopathy (PVR) rates are all less than or equal to published risk rates for SB and PPV (Table 1).1–10,1617
Functional visual results of the three techniques are an area of significant controversy. It is well recognised that PR and primary PPV both avoid the significant induced myopia associated with SBs. The induced changes in refractive error can, in some cases, produce significant anisometropia requiring contact lens use or even refractive surgery. A large multicentre trial comparing SB and PR found a significant visual benefit with PR. For eyes with preoperative macular detachment of less than 2 weeks’ duration, the percentage of patients achieving 20/50 or better best corrected visual acuity was 80% for PR and 56% for SB.1 Two retrospective, comparative series by Han9 and McAllister,18 however, found no statistically significant difference in visual outcomes between the two procedures. Similar data for primary PPV are unavailable for a meaningful comparison; however, the positive impact of the clearance of vitreous floaters and debris cannot be underestimated.
DISADVANTAGES OF PR
Anatomical success is the key issue regarding surgical techniques for the repair of RRD. The cumulative initial success rate for the surveyed papers was 75.5%, with a final overall success of 97.4%. This is lower than reported rates for PPV (85%) and SB (1440 of 1630 cases, 88%).19–21 The case selection for PR typically involves simple anatomy so matching for similar cases done with PR or SB might uncover a larger disparity in success rates. A prospective, randomised, multicentre trial comparing PR with SB found a lower primary success rate with PR (73%) versus SB (82%), but a similar final success rate of 99% versus 98% respectively.1 A retrospective comparative series by McAllister18 found a higher success rate for SB (96%) compared to PR (71%). However, when aphakic and pseudophakic eyes with open posterior capsule were excluded, the success rate for PR improved to 81%.18 A similar study by Han9 found a higher anatomical success rate for SB (84% versus 62%) but an equal final success rate of 98%. The data support the fact that for RRD, SB, and primary PPV offer superior initial success rates, yet equivalent final anatomical success rates.
Pneumatic retinopexy has a lower initial success rate for two major reasons: (1) reopening of the original break; and (2) new and/or missed retinal breaks. Both SB and primary PPV permanently relieve vitreoretinal traction and therefore, retinal tear reopening is a relatively rare phenomenon. With PR, there is no relief of traction so that the laser or cryopexy induced chorioretinal adhesion must be strong enough to overcome this tractional force on the retina. New and/or missed retinal breaks are more commonly encountered with PR than with PPV or SB. One contributing factor for missed breaks may be the extent of retinal examination performed with each technique. All patients undergo extensive retinal examination before any of the three surgical procedures, but SB and primary PPV provide additional examination opportunities. During SB, an examination under anaesthesia with open conjunctival scleral depression is routinely performed, thereby allowing the discovery of previously missed breaks. Pars plana vitrectomy, especially when performed under wide field viewing, allows extensive, high magnification, peripheral examination under anaesthesia. In addition, PPV will remove media opacities such as an opacified posterior capsule, vitreous haemorrhage, or vitreous debris resulting in a superior view of the retinal periphery.
New retinal breaks do occur following PR. It is postulated that a gas bubble within the vitreous cavity creates additional vitreoretinal traction, particularly when the bubble is positioned between the retina and posterior hyaloid face. These breaks may occur in any quadrant, but 76% are located in the superior two thirds of the retina and 52% are located within 3 clock hours of the original causative break. The majority (59%) of new breaks occur during the first postoperative month.1 Prophylactic 360° peripheral barricade laser has been advocated to reduce the risk of new and/or missed retinal breaks. Tornambe2 found a single operation success rate of 55% when focal retinopexy was employed compared to 85% for patients following 360° retinopexy. Presumably this difference was because of a lower number of failures as a result of new and/or missed breaks in the 360° retinopexy group.
CONTROVERSIES ABOUT THE CURRENT USE OF PNEUMATIC RETINOPEXY
Significant controversy surrounds the current use of PR for repair of RRD. Most of this controversy revolves around the issue of case selection. Certainly the ideal clinical scenario for PR is that of a phakic detachment because of a single break or small group of breaks in the superior two thirds of the fundus without additional retinal pathology. Tornambe reported a 97% single operation success rate in this subgroup of patients.2 Scleral buckle and primary PPV probably have similar success rates in this situation; however, the risk profile, patient morbidity, and cost involved favour the use of PR. The success rate for pseudophakic and aphakic detachments is lower presumably as a result of the increased number of small breaks in multiple quadrants and potentially an impaired view of the peripheral retina in pseudophakic eyes. Nevertheless, PR can still be employed successfully in these cases when all the breaks are identified and located preoperatively in a single quadrant. Occasionally, by using a second gas injection or repositioning the patient, detachments with breaks in more than one quadrant can be by addressed by PR.22
The size of the causative retinal break has been another area of concern. Air or gas may be more prone to migrate into the subretinal space through large breaks, and the arc of contact of the bubble may not be broad enough to tamponade the entire break. Reports exist of the successful use of PR for RRDs caused by giant retinal tear (four of five cases, 80%), retinal dialysis (four of four cases, 100%), and other large breaks.23–25 These case series demonstrate that PR can be effective even in cases with large breaks, particularly if they are located superiorly and lack significant vitreoretinal traction. Pneumatic retinopexy has generally been avoided for RRD caused by breaks in the inferior 4 clock hours. Acute, phakic, inferior detachments with single breaks have been managed successfully in two instances by the author (ERH) using a head dangling position. It is evident that although PR has an “ideal” scenario for its chief indication, the technique is more widely applicable in certain select cases for those with multiple breaks, large breaks, and even breaks located in the inferior four clock hours.