Pneumatic Retinopexy

Pneumatic retinopexy (PR) is an office-based nonincisional procedure that has become a well-accepted alternative to scleral buckling and vitrectomy for the repair of selected cases of rhegmatogenous retinal detachment, as depicted in the images below. ^{[1, 2]}

Pneumatic retinopexy is a 2-step procedure. In the first step, an expanding gas bubble is injected into the vitreous cavity and the patient is positioned so that the bubble closes the retinal break, permitting resorption of subretinal fluid. The second step entails induction of a chorioretinal adhesion around all retinal breaks with cryopexy, laser, or both. ^{[3, 4, 5]}

The main advantage of pneumatic retinopexy over scleral buckling is the minimization of complications such as inadvertent scleral perforation by scleral sutures, postoperative refractive error changes, strabismus, and potential complications associated with the drainage of subretinal fluid.

The initial success rate of pneumatic retinopexy is lower than that of scleral buckling, but the final anatomic and functional results are comparable. The lower initial success rate is due to a higher frequency of new retinal breaks and missed retinal breaks. ^[6]

However, an initial failure of pneumatic retinopexy does not affect the final visual outcome. ^{[7, 8, 9, 10, 11, 12, 13]} In a comparative trial of eyes with rhegmatogenous retinal detachment involving the macula for 14 or fewer days, the visual outcomes following pneumatic retinopexy were statistically better than those following scleral buckling. ^[14] A 2019 randomized controlled trial demonstrated that eyes treated with a pneumatic retinopexy achieved better visual acuity, less vertical metamorphopsia, and less morbidity than eyes that underwent pars plana vitrectomy. ^[15] Studies have shown that, if pneumatic retinopexy were more popular, significant cost savings may be achieved. ^{[16, 17]}

Unintentional retinal displacement following retinal re-attachment has been described. Not all patients with a rhegmatogenous retinal detachment are good candidates for pneumatic retinopexy (PR). Case selection is the most important determinant of success.

In general, the best candidates for pneumatic retinopexy are those who have a single retinal break or group of retinal breaks that are not larger than 1 clock hour (30°) and that are located in the superior 8 clock hours of the globe. Furthermore, the patient must have the ability to maintain a proper head position for at least 16 hours per day for 5 days or more.

Patients with a retinal detachment not satisfying these criteria are expected to have much poorer responses to pneumatic retinopexy than those who do. Predictors of treatment failure for pneumatic retinopexy include eyes with a vitreous hemorrhage, a retinal detachment extending more than 4.5 clock hours, pseudophakia, proliferative vitreoretinopathy, visible vitreous traction on a tear, and/or a retinal break greater than 1 clock hour. ^{[16, 18, 19]}

A 2015 report highlighted the value of rescue pneumatic retinopexy in patients with failed primary scleral buckle or vitrectomy for retinal detachment. ^[20]

The PIVOT was a single center, randomized clinical trial that compared the outcomes of primary PR in 77 eyes versus primary pars plana vitrectomy (PPV) in 73 eyes with primary RRD. The single operation anatomic success rate was significantly better in PPV (93.2%) compared with PR (80.8%). The final anatomic success rate was similar in both groups (98.7% and 98.6%, respectively). However, the visual acuity outcomes with PR were superior to those obtained with PPV. The ETDRS best corrected VA was better at 3, 6, and 12 months of follow-up. The mean best corrected VA at 12 months was 79.9 letters in the PR group compared with 75 letters in the PPV group. In addition, the proportion of eyes achieving  ≥ 20/40 was 90.3% compared with 75.3% in the PPV group. ^[21]  Furthermore, the PIVOT trial showed that patients with eyes that underwent PR scored higher in mental health and vision-related functioning scores than patients with eyes subjected to PPV during the first 6 months following the respective procedure. ^{[22, 23]}

Unintentional retinal displacement following retinal re-attachment has been described. This retinal displacement may account for the post-operative vertical metamorphopsia experienced by some patients. In the PIVOT trial, FAF images were used to demonstrate that the retinal displacement induced by PR compared with those induced by PPV was significantly less. ^[24]  Vertical metamorphopsia scores were also superior in the eyes treated with PR compared with those treated with PPV in the PIVOT trial. ^[21]

Presence of retinal breaks within the lowest 4 clock hours of the inferior quadrants

For an average eye, 0.3 mL of gas covers 90° of the retinal surface in an emmetropic eye. In contrast, 1.6 mL of intraocular gas is necessary to cover 150° of the retinal surface. ^{[4, 5]} Thus, even after full expansion of a 0.3-mL bubble of pure perfluoropropane (C₃ F₈) to 1.2 mL, the inferior retina will not be covered by the gas bubble unless the patient assumes an extreme head position.

Most patients cannot tolerate the 90° neck flexion or hyperextension position required for proper gas tamponade of retinal breaks in the inferior quadrants. ^{[4, 25]} Even though some reports showed the successful repair of selected cases of retinal detachments along the inferior 4 clock hours (4 to 8 o’clock), ^[26] pneumatic retinopexy (PR) usually fails to repair such detachments.

Presence of proliferative vitreoretinopathy grade C or D

A retinal detachment with substantial proliferative vitreoretinopathy (PVR) that exerts considerable retinal traction is not a good candidate for pneumatic retinopexy. For an optimal outcome, the basic criteria for pneumatic retinopexy require the absence of PVR grade C or D. However, a successful outcome with pneumatic retinopexy has been reported for retinal detachments with limited grade C PVR. ^[4]

Noncompliance with required head positioning

Retinal breaks outside the 11 to 1 clock hours in the superior quadrants require more extreme head tilt positioning following pneumatic retinopexy. This may be difficult for patients with certain physical disabilities, neck and back problems, or mental incompetence. ^[4]

Severe glaucoma

With the exception of advanced glaucoma, most eyes with concomitant retinal detachment and glaucoma can be safely managed with pneumatic retinopexy, as long as the intraocular pressure is closely monitored and corrective measures taken, if necessary. ^[4]

Hazy media

Ocular opacities such as vitreous hemorrhage or a dense cataract may impede the identification of all retinal breaks, lowering the success likelihood of pneumatic retinopexy. Certain aphakic and pseudophakic eyes with multiple small peripheral retinal breaks in the presence of cloudy peripheral lens capsule are also poor candidates for pneumatic retinopexy. ^[4]

Most patients undergo pneumatic retinopexy under subconjunctival anesthesia supplemented by topical drops.

When cryotherapy is being considered, retrobulbar anesthesia allows comfortable scleral depression, permits cryotherapy to any quadrant, and prevents a vagal response that may occur if the intraocular pressure is temporarily raised to a high level.

In the rare instance that general anesthesia is used, the surgeon must remind the anesthesiologist to avoid nitrous oxide in order to prevent postoperative shrinkage of the intraocular gas bubble. ^{[4, 5]}

Equipment used for pneumatic retinopexy includes the following:

• Cyclopentolate 1% and phenylephrine 2.5% drops to dilate the pupil

• Topical anesthesia drops

• A lid speculum

• Povidone-iodine solution drops, 5%

• Millipore filter, 0.22 µm

• Syringe, 1 mL

• Needle, 27 or 30 gauge

• C₃ F₈ or sulfur hexafluoride (SF₆)

• Cotton-tipped applicators

• Indirect ophthalmoscope

• Laser and/or cryotherapy

Following the gas injection, the patient’s head is immediately positioned so that the gas bubble is opposed directly to the break. If the retinal detachment does not involve the macula but threatens it, the steamroller technique should be seriously considered to prevent subretinal fluid displacement into the macula.

Steamroller technique

In the steamroller technique, the patient’s head is initially turned to a face-down position, as depicted in the first image below. Over 10-15 minutes, the position is gradually changed until the retinal break is uppermost, as depicted in the second image below, causing the bubble to roll toward the retinal break, pushing the subretinal fluid away from the macula and back into the vitreous cavity through the retinal break, flattening the retina. See the third image below.

One of the theoretical disadvantages of the steamroller technique is the potential for proliferative vitreoretinopathy development. Since the subretinal fluid is displaced back into the vitreous cavity during this maneuver, retinal pigment epithelium (RPE) cells within the subretinal fluid might gain access to the retinal surface.

Yanyali et al (2007) ^[27] prospectively compared the steamroller technique to the basic technique and concluded that both techniques appear to be equally effective and safe in terms of the development of proliferative vitreoretinopathy. Their study was not designed to assess the effectiveness in preventing macular detachment in high-risk eyes. ^[27]

It is recommended to maintain the specified head position for up to 16 hours per day for at least 5 days. ^[5]

After dilating the pupil, 3-5 drops of topical anesthesia are instilled in the eye. Anesthetic is injected subconjunctivally in the quadrant with the retinal break. A lid speculum is inserted, and 3 drops of 5% povidone-iodine solution are instilled and left in place for 5 minutes. Aqueous humor (0.3-0.5 mL) is removed from the anterior chamber via a paracentesis to lower the intraocular pressure. See the images below.

Either 0.3 mL of C₃ F₈ or 0.5 mL of SF₆ is filtered through a Millipore filter (0.22 µm) into a 1-mL syringe with a short (half-inch) 27- or 30-gauge needle. See the image below. Most surgeons perform the gas injection with the patient lying in a supine position. For some eyes, performing the gas injection with the patient in the upright position has certain advantages. For instance, the upright position during gas injection reduces the tendency for gas migration and vitreous prolapse into the anterior chamber in the setting of elevated intraocular pressure, although this technique should be avoided in the presence of a large retinal tear to prevent formation of “fish-egg” bubbles. ^[4]

If the patient is aphakic or pseudophakic, the injection is placed 3 mm posterior to the limbus. If the patient is phakic, the injection is placed 4 mm posterior to the limbus. With the patient in the supine position, the surgeon should usually inject the gas through a superior quadrant of the globe away from the most bullous area of detachment. Point the needle perpendicular to the sclera and downward toward the center of the vitreous cavity. ^{[4, 27]}

After inserting half of the needle into the vitreous cavity, the needle should be partially withdrawn until only 1 mm is still in the eye. A slow injection of gas through the shallowly inserted needle allows continued gas placement into the same single enlarging gas bubble, avoiding the formation of “fish-egg” bubbles. ^[28] The gas should also be injected away from any large retinal break to reduce the risk for subretinal gas migration. ^[4] See the image below.

If multiple bubbles are present, the patient should remain in a position to keep the small bubbles away from a large retinal break for 24 hours. The “fish-egg” bubbles usually coalesce over 12-24 hours. As the needle is withdrawn, a cotton-tipped applicator is placed over the perforation site, and the patient’s head is rotated to prevent gas from escaping through the puncture site.

Afterward, the surgeon must perform indirect ophthalmoscopy to confirm the placement of the gas into the vitreous cavity and to assess the perfusion of the central retinal artery. If the artery remains nonpatent and nonpulsatile 10 minutes after gas injection, a paracentesis is repeated to reduce the risk for ischemic retinal damage. Elevated intraocular pressure is usually not a significant problem after the intraocular injection of less than 0.5 mL of gas. Immediate elevation of intraocular pressure to levels between 30 and 50 mm Hg is common, but pressure returns to normal after 90 minutes.

In certain situations, cryopexy can be omitted and laser may be applied a few days later when the break has flattened.

Tornambe (1997) found a single operation success rate of 55% for focal retinopexy compared to 85% for 360° retinopexy. ^[29]

If all breaks have been closed, the retina usually attaches within 24 hours. ^{[4, 5, 30]}

Pearls for pneumatic retinopexy (PR) include the following:

• Patient selection is key to success.

• Perform paracentesis prior to gas injection.

• Avoid performing pneumatic retinopexy in eyes in which the retinal periphery is not adequately visualized.

• Insert the needle into the vitreous cavity and then retract it so that the tip is just barely in the vitreous cavity. This will allow for a shallow injection. Then, inject slowly. This will reduce the risk for “fish egg” bubbles.

• If “fish egg” bubbles develop, try coalescing them into a single bubble by striking the globe with a finger or a cotton tip applicator.

• If multiple breaks are present over an area equivalent to several clock hours, treat the most superior breaks first.

• Consider prophylactic 360° peripheral laser barricade to reduce the risk for new and/or missed retinal breaks.

• Have a low threshold and high ability to recognize when the procedure has failed and when to move on to scleral buckling and/or vitrectomy.

New or missed breaks and surgical failure

The development of new retinal breaks with a subsequent new retinal detachment following pneumatic retinopexy (PR) has been reported at a rate of 7-22%. ^{[14, 31, 32, 33]}

New or missed breaks may develop in any quadrant; however, 76% are located in the superior 8 clock hours. The progressive vitreoretinal separation and vitreous traction induce the formation of new breaks and the reaccumulation of subretinal fluid.

New breaks that are located in the superior quadrants and are not widely separated (more than 1 or 2 clock hours apart) may be successfully treated with an additional gas injection followed by cryotherapy and/or laser retinopexy. ^{[4, 30]} Likewise, the formation of a new break in the inferior quadrants is usually an indication for scleral buckling and/or vitrectomy.

Cataract progression

Cataract development and progression is very uncommon after pneumatic retinopexy.

Koch et al (1991) found insignificant loss of lens transparency in eyes subjected to pneumatic retinopexy compared with nonoperated eyes after 2 months of follow-up. ^[34] However, by 6 months, the opacification of the crystalline lens was more evident, particularly the anterior lens cortex. ^[34] This complication can be minimized by careful placement of the paracentesis needle over the iris and avoiding contact between the intraocular gas and the lens. ^{[4, 11]}

Subconjunctival gas

Subconjunctival gas results from either incomplete penetration of the sclera by the needle for gas injection or outward leakage of gas through the needle track of the gas injection. This has not been considered to be clinically significant, and no corrective action is required. To minimize this complication, the surgeon should ensure proper insertion of the needle for gas injection into the vitreous cavity and immediately place a cotton-tipped applicator on the needle track after removal of the needle. ^[4]

Delayed subretinal fluid absorption

Delayed subretinal fluid absorption is uncommon and is characterized by long-term persistence of loculated pockets of low-lying subretinal fluid. When involving the macula, these pockets of fluid cause prolonged postoperative visual symptoms such as decreased visual acuity and metamorphopsia. The presence of subretinal fluid can persist for several months. No specific management is required, but close follow-up is essential. ^{[7, 11, 35]} See the images below.

Subretinal gas

Gas “fish-egg” bubbles may migrate through retinal breaks into the subretinal space, particularly in the presence of large breaks. Hilton and Tornambe (1991) found that any eye retinal breaks larger than 1 clock hour are associated with an increased risk for such bubbles. ^[11] In these cases, the patient’s head should be positioned in such a way that the bubbles migrate away from the tear. It usually takes 24 hours for the bubbles to coalesce.

Placing the patient in a supine position and tilting the head so that the break is at the most superior position followed by gentle scleral depression may release the subretinal gas into the vitreous cavity. If this maneuver fails, vitrectomy is the most direct and effective way of eliminating the trapped subretinal gas. ^{[4, 5, 11]}

Endophthalmitis

The incidence of endophthalmitis as a complication of pneumatic retinopexy is very low. Tornambe and Hilton (1989) ^[14] reported 1 case of staphylococcal endophthalmitis among the 103 eyes that underwent pneumatic retinopexy.

The most effective way to reduce this complication is to be very meticulous with the sterile techniques. In particular, the use of 5% povidone iodine solution prior to any intraocular injection is highly recommended. ^{[4, 11]}

Macular hole and other new posterior breaks

Vitreomacular traction during the perioperative period is thought to play a role in its pathogenesis. The expansion of the intraocular gas produces a vitreomacular detachment, and, as a secondary mechanism, the macula suffers a period of stress by the shifting of a large amount of subretinal fluid under it due to the expanding gas bubble. ^[36] Conventional surgical techniques for repairing idiopathic macular holes such as vitrectomy can be used with good results. ^{[4, 37]}

Cystoid macular edema

Cystoid macular edema is very uncommon after pneumatic retinopexy. Eyes with a history of uveitis, prior cataract extraction, and macular detachment may have a greater tendency for postoperative cystoid macular edema. ^{[4, 38]} Avoidance of excessive retinopexy during pneumatic retinopexy may reduce this complication. Topical steroidal and nonsteroidal anti-inflammatory medications are usually effective for treating this complication. ^[4]

Intraocular hemorrhage

Intraocular hemorrhage is rare. Injections should be performed away from the anterior ciliary vessels along the vertical and horizontal meridians in order to reduce the chance of ocular surface and vitreous hemorrhage. During cryotherapy, the cryoprobe should not be removed from the eye until appropriate thawing of the ice ball on the cryoprobe and the surrounding surface of the globe is evident to avoid fracturing of the frozen blood vessels. ^{[4, 11]}

Epimacular fibrosis and macular pucker

The multicenter pneumatic retinopexy study reported a 4% incidence of asymptomatic epimacular membrane, as depicted in the image below, among the 103 eyes that underwent pneumatic retinopexy. ^[14]

No known method prevents this complication, but the avoidance of excessive cryotherapy and laser treatment may minimize the risk. The management of macular pucker after pneumatic retinopexy is similar to the treatment of this condition associated with other clinical situations, usually with good outcomes. ^{[4, 11, 14]}

Proliferative vitreoretinopathy

The rate of PVR varies depending on the clinical series.

Chen et al (1988) ^[31] reported a 9.8% incidence in a prospective series of 51 eyes that underwent pneumatic retinopexy. Tornambe (1997) ^[29] also noted a 9.6% incidence of PVR with no difference in the incidence of PVR between those eyes that underwent cryotherapy versus laser.

The excessive release of RPE cells into the vitreous cavity after pneumatic retinopexy and the gas bubbles may play a role in the formation of PVR. Eyes with PVR after pneumatic retinopexy can be managed with vitrectomy and membrane stripping. ^{[4, 39]}

Choroidal detachment

Choroidal detachment is uncommon after pneumatic retinopexy. Tornambe and Hilton (1989) ^[14] reported an incidence of choroidal detachment of 3%. Prolonged and severe pain shortly after suprachoroidal gas injection is a typical manifestation of a choroidal detachment. Stretching of the ciliary nerves by the gas may be the cause of the pain. Avoiding hypotony during paracentesis and also reducing excessive cryotherapy could reduce this complication. ^{[4, 11, 40]}

Intraocular pressure rise and glaucoma

Mild to moderate intraocular pressure rise is well tolerated by the average eye with no or minimal corrective measures after pneumatic retinopexy and usually does not lead to any retinal or optic nerve damage. Careful monitoring of the central retinal artery is recommended. In the absence of central retinal arterial reperfusion after 10 minutes, an immediately paracentesis is advised to lower the intraocular pressure. ^[4] A 0.3% incidence of ischemic optic neuropathy was reported by Tornambe (1997). ^[29]

Musculoskeletal complications

Because of the requirement of a consistent head tilt for a prolonged period, pneumatic retinopexy may lead to various musculoskeletal and neurological injuries, especially among elderly patients. Cervical spine, neck muscles, and lower back problems and ulnar nerve injury may occur. These are minor and are typically temporary.

A pillow, cushion, a table or desk with the correct height may provide the required support. If necessary, analgesics, a heating pad, or muscle relaxants may be prescribed to relieve musculoskeletal discomfort associated with pneumatic retinopexy. ^{[4, 11, 41]}

Corneal wound dehiscence

Full-thickness corneal wounds never regain their original tensile strength. ^[42] Immediately following an intravitreal gas injection, the intraocular pressure rises suddenly up to 180 mm Hg, ^[43] which is enough to stress and rupture the corneal scar. Wound dehiscence has been reported to occur during pneumatic retinopexy in pseudophakic eyes that underwent clear corneal incisions and in an eye with a prior penetrating keratoplasty. ^{[44, 45]} In these cases, a slower injection of a smaller volume of gas should be strongly considered.