Pneumatic Retinopexy

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Chapter 103 Pneumatic Retinopexy

Daniel A. Brinton, Allen Chiang

Introduction

For more than a half century, the operation most favored for primary retinal detachment had been scleral buckling (SB). Between 75% and 88% of cases attain permanent reattachment with one operation with this procedure.¹^–³ However, it frequently results in tissue trauma, complications,⁴ relatively high expense, and use of a hospital or surgicenter operating room. In recent decades, pars plana vitrectomy has been used with increasing frequency for primary retinal detachments, particularly in pseudophakic eyes. This technique also presents its list of potential complications, and also requires an operating room with similar high expense.

Pneumatic retinopexy (PR) was developed in an attempt to minimize these problems. This outpatient procedure for retinal reattachment consists of an intravitreal gas injection with transconjunctival cryopexy or laser photocoagulation, followed by appropriate head positioning.⁵ No incisions are required. PR is substantially less expensive than scleral buckling or vitrectomy and has become widely accepted as the treatment of choice for selected retinal detachments, with the vast majority of vitreoretinal surgeons employing this procedure.^6,⁷

A multicenter, randomized, controlled clinical trial has demonstrated that the anatomic success rate of PR is comparable to SB, with less morbidity and with significantly better visual results than with SB.⁸ Cataract surgery was required more often following SB than following PR.⁹ PR should be considered in patients who do not have detached inferior breaks, extensive retinal breaks, or significant proliferative vitreoretinopathy.

History

Ohm ¹⁰ performed the first intravitreal air injection for retinal detachment in 1911. In 1938, Rosengren¹¹ reported the use of intravitreal air with drainage of subretinal fluid in a series of 256 retinal detachments. In 1973, Norton¹² reported intravitreal sulfur hexafluoride (SF₆) injection used with SB or vitrectomy for various surgical problems, such as giant breaks, large posterior breaks, and fishmouthing. Blodi and Folk¹³ treated detachments due to a macular hole using intravitreal gas, and retinal detachments treated with “repeated insufflations of expansive gas” were described by Dominguez et al.^14,¹⁵ Hilton and Grizzard⁵ introduced the term “pneumatic retinopexy” at the 1985 meeting of the American Academy of Ophthalmology, a procedure using only transconjunctival cryotherapy and gas injection without conjunctival incision.

Unlike SB or vitrectomy, PR affords no permanent relief of vitreoretinal traction. The fact that detachments can be cured without permanently relieving traction, demonstrated decades before by Ohm ¹⁰ and by Rosengren,¹¹ was reconfirmed in 1979 by Lincoff et al.,¹⁶ who introduced the use of a balloon to achieve temporary scleral buckling. After cryopexy to the tear, they inserted a deflated balloon directly over the tear through a conjunctival and Tenon’s capsule incision, inflated the balloon, and left it in place for a week. The efficacy of this procedure was demonstrated but it never caught on, and the orbital balloon is not commercially available worldwide. However, the principle of repairing a retinal detachment without permanently relieving vitreoretinal traction, well proven by Lincoff’s technique, combined with the demonstrated safety of intravitreal gas, formed the basis for PR.

In 1989, Tornambe and Hilton ⁸ co-directed a multicenter, randomized, controlled clinical trial comparing PR with SB. Tornambe¹⁷ reviewed over 200 studies on PR, including statistical reports on over 1300 cases. The single-operation success rate in these combined series was 80%, increasing to 98% after reoperations¹⁸ – results which have been subsequently replicated.¹⁹ Chan et al.²⁰ reviewed all published reports on PR cases from 1986 to 2007, totalling 4138 eyes. Single-operation success was 74.4%, and success with one or more operations was 96.1%.

Basic principles

Intraocular gases

Sulfur hexafluoride (SF₆) and perfluoropropane (C₃F₈) are the gases most frequently used with PR. Success also has been reported with sterile room air.²¹ In 1993, the United States Food and Drug Administration approved certain SF₆ and C₃F₈ products for use in PR.

The value of the intraocular bubble is based on three features: buoyancy, surface tension, and isolation of retinal tears from intraocular currents.^22,²³ Buoyancy applies upward pressure on the detached retina. The surface tension of the bubble closes the retinal break and prevents the bubble from passing into the subretinal space. With the break closed, the retinal pigment epithelial pump removes the subretinal fluid.

Because of their low solubility in water, SF₆ and C₃F₈ tend to diffuse from the eye very slowly. However, the nitrogen and oxygen that are in solution in the surrounding tissues of the eye are much more soluble and pass relatively quickly into the gas bubble, following the law of partial pressures. The net result is the initial expansion of a bubble of pure SF₆ or C₃F₈ within the vitreous, followed by gradual resorption. Characteristics of gas expansion and resorption for SF₆, C₃F₈, and air are listed in Table 103.1.

Table 103.1 Intravitreal gas duration and expansion

SF₆ and C₃F₈ are chemically inert, colorless, odorless, and nontoxic.²⁴ SF₆ has been studied extensively in experimental animals and has been found to be nontoxic as judged by electrophysiologic testing and electron microscopy.²⁵ One study of rabbits concluded that “eyes only partially filled with C₃F₈ showed no permanent damage, with a total recovery of the cortical matrix, gel, and liquid vitreous.”²⁶ Early concerns²⁷ regarding PVR from intravitreal gas injection have not been substantiated. A 0.22 µm Millipore filter is sufficient to render gas sterile.²⁵

Lincoff et al.²⁸ noted that gas bubble contact with the crystalline lens can produce cataract after several days, but this is avoidable by appropriate positioning. Mougharbel et al.²⁹ have demonstrated with Scheimpflug photography that PR does not cause cataract.

Retina–gas interface

Larger areas of tamponade require disproportionate increases in bubble volume. A 0.3 mL gas bubble in humans covers more than 45° of arc of the retina, but it takes approximately a 1.2 mL bubble to cover 80–90°.⁵ Because surface tension causes the gas to take on a relatively spherical contour, particularly with smaller bubbles, the extent of retina–gas contact is significantly less than that published from studies of model eyes.³⁰ To cover the same arc of the retina, a highly myopic eye requires a larger volume of gas than an emmetropic eye. These factors are considered in deciding how much gas to inject.

Case selection

The multicenter clinical trial excluded cases with the following characteristics:⁸

1. Breaks larger than 1 clock-hour or multiple breaks extending over more than 1 clock-hour of the retina.

2. Breaks in the inferior 4 clock-hours of the retina.

3. Presence of PVR grade C or D (Retina Society Terminology Committee, 1983).³¹

4. Physical disability or mental incompetence precluding maintenance of the required positioning.

5. Severe or uncontrolled glaucoma.

6. Cloudy media precluding full assessment of the retina.

A review of 1000 consecutive detachments ⁵ revealed that 41% met these limited criteria. Subsequent experience has demonstrated that selected cases that do not strictly meet these criteria can also be successfully treated with PR.^32,³³ In our hands, about half of all primary retinal detachments are treated with PR.

Extent of breaks

Breaks spanning more than 1 clock-hour can be treated with PR. Single or multiple tears spanning up to 3 clock-hours pose no particular problem. Detached tears 6 clock-hours apart are difficult to fix with PR, although alternating positioning has been used successfully. Even detachments with giant retinal tears have been cured with PR.³⁴ However, scleral buckling or vitrectomy is usually preferred for detachments with widely separated or giant tears.

In the decision of whether a case is amenable to PR, the difference between attached and detached breaks needs to be considered. For cases in which an attached break is present on the opposite side of the eye from the detached break(s), alternate positioning would not be needed. The attached break may be treated with laser before the gas injection. Care should then be taken, such as by using the steamroller technique (see below), to prevent the bubble from pushing the subretinal fluid into the attached break and causing it to detach. By following these two steps, multiple attached breaks may be ignored in the calculation of bubble size and in positioning.

Inferior breaks

Most cases involving breaks in the inferior 4 clock-hours of the eye have been difficult to treat with PR, despite various attempts.³³ Even for flexible patients, it can be difficult to tilt the head below the horizontal plane for extended periods. Friberg and Eller³⁵ first reported success with inferior breaks in eight of eight patients using dependent positioning. In 2003, Chang et al.³⁶ reported single operation success in 9 of 11 patients with inferior breaks using PR with inverted positioning for only eight hours. Hilton et al.³⁷ treated retinal detachment with inferior breaks by augmenting pneumatic retinopexy with in-office partial vitrectomy, allowing injection of a large enough gas bubble to close the breaks with side positioning. In 2011, Hwang et al.³⁸ reported 10 out of 13 single-operation success with a 10–30 cm downward head tilt.

However, we believe a detached break in the inferior 4 clock-hours represents a relative contraindication to PR in most cases. Attached inferior breaks do not necessarily contraindicate PR if treated as described above, taking care to avoid iatrogenic detachment of an attached break caused by the gas bubble.

Proliferative vitreoretinopathy

Because PR does not relieve traction like SB or vitrectomy, significant preoperative tangential traction on a retinal tear (as in periretinal proliferation) is a relative contraindication to the pneumatic procedure. When a tear is adjacent to a star fold, PR is not generally the procedure of choice. Mild to moderate proliferative vitreoretinopathy (PVR) (such as a star fold) that is distant from any retinal break generally does not contraindicate PR. More severe PVR requires SB or vitrectomy, or both.

Inability to maintain positioning

Failure to maintain the appropriate position faithfully is probably an important cause of failure of PR. It is important to ask patients about back or neck problems and to assess mental competence before deciding on PR. Some positions are quite easy to maintain, whereas others are more difficult. Positioning is easiest with tears between 11 and 1 o’clock. Positioning is probably easier for horizontally oriented tears (between 2 and 4 or between 8 and 10 o’clock) than it is for obliquely oriented tears (between 1 and 2 or between 10 and 11 o’clock).

Glaucoma

The majority of patients with primary open-angle glaucoma can be treated with PR without a problem. Performing paracentesis prior to gas injection may be prudent. Patients with severe glaucoma (e.g., splitting of the macular field as a result of glaucoma) might suffer noticeable damage even from brief elevations in intraocular pressure, and PR with expansile gases might be contraindicated. In glaucomatous eyes which have had trabeculectomy or may need it in the future, PR is advantageous in that it minimizes scarring of the conjunctiva. Except in cases of severely impaired trabecular outflow facility, serial measurements of intraocular pressure after gas injection are not necessary.

Cloudy media

For PR to be successful, all detached retinal breaks must be identified and treated. Opacities that preclude an adequate view of the peripheral retina, such as peripheral vitreous hemorrhage or pseudophakic lens capsular opacification, represent relative contraindications to PR. Because PR does not seem to jeopardize an eye for future SB if needed, it may be reasonable to use the pneumatic procedure even when opacities obscure part of the attached retina, but this represents a calculated risk.

Lattice degeneration

In several studies, the presence of lattice degeneration did not adversely affect single operation success with PR,^17,³⁹ but in other studies, extensive lattice degeneration tended to decrease the chance of success with PR. It does not appear that mild to moderate lattice should be considered a contraindication.

Aphakia and pseudophakia

Retinal detachments in aphakic/pseudophakic eyes have a poorer prognosis than phakic eyes, no matter what surgery is performed.⁹ In some series, aphakic eyes did poorly with PR,⁴⁰ especially if the posterior capsule was open,⁴¹ but in other reports this was not the case.^8,⁹ Aphakic and pseudophakic eyes are prone to multiple, tiny, far-peripheral breaks and require an especially careful preoperative examination. In pseudophakic eyes, the view of the peripheral retina can be quite limited if much peripheral capsular opacity is present. PR should probably not be performed in these cases unless retinal detachment is rather limited. In our opinion, if the peripheral retina can be adequately examined, aphakia or pseudophakia is not a contraindication to PR.

Posterior vitreous detachment

Phakic eyes with complete posterior vitreous detachment tend to have a higher success rate with PR than those with partial vitreous detachment.⁴²

Cases where pneumatic retinopexy presents a particular advantage

Compared with SB, PR is especially advantageous in the management of the following six situations:

1. Macular breaks and other posterior retinal breaks. Posterior retinal breaks are difficult to treat with SB, so PR is the procedure of choice in many of these cases, especially in phakic eyes. It also has been reported as an effective option in the treatment of optic pits with macular detachment.^43,⁴⁴

2. Redetachment or persistent detachment after scleral buckling. When subretinal fluid accumulates or persists because of a superior break after SB, PR may be much easier to perform than buckle revision.⁴⁵ This is especially effective if the break is located on or anterior to the buckle.⁴⁶

3. Isolated tears under the superior rectus. Placing a segmental buckle under a vertically acting muscle runs the risk of iatrogenic diplopia; this is eliminated with PR.

4. Filtering blebs. If a functioning filtering bleb is present, or if a filtering procedure may be necessary in the future, PR should be considered.

5. Impending macular detachment. Because PR can be performed promptly in the office without the delays required to prepare a patient for the operating room, and because the gas bubble can be used proactively to move the fluid away from the macula, a macula at imminent risk of detachment may be best served by PR.

6. Bullous detachment. When retinal detachment is highly bullous, retinal tears can be difficult to localize and treat with SB, a problem which is avoided by two-session PR.

Surgical technique

The details of the procedure should be explained to the patient and the potential risks and complications reviewed, including the possibility that a SB or vitrectomy may be required if the eye does not respond to PR. The restriction on air travel while the gas is in the eye is explained.

Anesthesia

Topical anesthesia, usually with subconjunctival anesthesia or application of lidocaine-soaked pledgets may be adequate, but in sensitive patients or if extensive cryopexy is planned, retrobulbar anesthesia is often helpful.

If subsequent general anesthesia is used in a patient who has an intraocular gas bubble, nitrous oxide should not be used. When gas is to be introduced into an eye during surgery, nitrous oxide should be turned off at least 15 minutes before gas injection.

One-session versus two-session procedure

See Box 103.1 for indications for the one-session and two-session procedures.

Box 103.1

Indications for one-session versus two-session procedure

Indications for a one-session procedure with cryopexy

• Issues of convenience or logistics

• Small or hard-to-find breaks

• Media opacities preventing laser

• Pigment atrophy preventing adequate laser burns

• Appropriate laser not available

Indications for a two-session procedure with laser

• Use of the “steamroller” procedure

• Large or extensive breaks (to minimize retinal pigment epithelial dispersion)

• Bullous detachment precluding accurate cryopexy

• Tear overlying a scleral buckle

• Recently operated eye (incision not healed)

• Very posterior breaks

Indications for a two-session procedure with cryopexy

• Initially bullous detachment but cryopexy preferred

• Media opacities preventing intended laser treatment

• Persistent subretinal fluid precluding adequate laser burns

PR can be done in one session, with cryopexy applied to the retinal breaks just before gas injection, or as a two-session procedure, with initial gas injection followed by laser photocoagulation 1 or 2 days later, when the retina is reattached. One-session procedures always involve cryopexy, since the laser cannot be applied to detached retina. Two-session procedures are usually, but not always, done with the laser.

The chance of dispersing retinal pigment epithelial (RPE) cells into the vitreous may be minimized by a two-session procedure, flattening the retina with gas before later applying retinopexy, particularly if large retinal breaks are present or if the “steamroller” technique is used. Also, if a tear is so bullously detached that a cryopexy iceball will not reach the retina, it may be difficult to place the cryopexy spots with sufficient accuracy, so a two-session procedure may be preferable.

Issues of convenience or logistics frequently dictate that a one-session procedure be performed. In addition, small or hard-to-find breaks may become impossible to locate once the retina is reattached, so cryopexy treatment before gas injection in a one-session procedure maximizes the chance of all tears being treated. For this reason, whenever a two-session procedure is selected, it is important to make a careful preoperative drawing of the location of the breaks relative to vascular and other landmarks.

Cryopexy versus laser

Cryopexy may be necessary if vitreous hemorrhage or other media opacities make laser treatment difficult. Laser application may be ineffective for tears that develop in areas of pigmentary atrophy. Cryopexy may be easier to apply than laser in some patients who have difficulty keeping their eyes still. In some cases, even after a few days of positioning, enough subretinal fluid remains that laser cannot be applied, and cryopexy may be necessary.

If a laser indirect ophthalmoscope (LIO) is not available, tears in the far periphery may not be treatable with laser delivered by slit lamp, necessitating cryopexy. The LIO is ideal for PR because it allows treatment of the far periphery and facilitates maneuvering of the gas bubble out of the way.³⁵ Although most tears can be treated with laser through a slit-lamp delivery system by tilting the patient’s head as necessary to move the bubble away from the tear, this is difficult with tears from 11 to 1 o’clock. It is often possible to apply laser treatment through a large gas bubble, but it can be difficult with the smaller bubbles utilized with PR because of optical factors. Application of laser through gas causes concentration of heat due to the insulating effect of gas, and excessively hot burns may result.

Certain circumstances might indicate use of laser instead of cryopexy. Laser is required if a tear develops overlying a previously placed scleral buckle, since cryopexy cannot penetrate the silicone. In eyes with a recent surgical incision (within the past 4–6 weeks), laser may be safer than cryopexy because the scleral depression of the cryoprobe elevates the intraocular pressure. Very posterior breaks are easier to treat with laser than with cryopexy, although a small conjunctival incision in the cul-de-sac allows passing of the cryoprobe posteriorly.

Chorioretinal adhesion may be quicker and firmer using laser rather than cryopexy.^47,⁴⁸ In addition, some authors believe that cryopexy may be associated with a higher incidence of proliferative vitreoretinopathy and other complications,^49,⁵⁰ although others could find no such association.⁵¹ Laser also has the advantage of less morbidity compared with cryopexy, especially if multiple or large breaks are present.

Although laser generally cannot be applied to detached retina, if the detachment is very shallow, it may be possible to apply laser using firm scleral depression to flatten the retina combined with increased laser power. However, this technique may cause retinal breaks as a result of excessive laser intensity, and it must be used with caution.

Transscleral diode laser photocoagulation offers some potential advantages over both cryopexy and transpupillary laser for retinopexy treatment.⁵² Like transpupillary laser photocoagulation, one can see exactly where the treatment has been and will be applied. As with cryopexy, it allows treatment in detached retina. Treatment can even be applied through a pre-existing buckle.

Applying retinopexy

Transconjunctival cryopexy consists of multiple contiguous applications that entirely surround the retinal tear and is monitored with binocular indirect ophthalmoscopy. Cryopexy to bare RPE in the middle of the hole should be avoided if possible. The RPE is pushed into apposition with the overlying retina, if possible, causing a visible white reaction. In very bullous detachments when the RPE cannot be brought into contact with the detached retina, the endpoint for cryopexy is the appearance of a dull, orange glow at the level of the pigment epithelium.

Laser application begins at a low intensity and is gradually increased until a dull, gray-white burn is achieved. If a red or infrared wavelength is used, an even less-intense burn is desired. Multiple rows of almost contiguous burns are applied to surround all tears completely, with generous treatment along the anterior aspect of a horseshoe-shaped tear where it is most likely to extend.

Amount and type of gas to inject

PR usually requires a gas bubble large enough to cover all detached breaks simultaneously for about 5 days. The size of the gas bubble should reflect the extent of the break(s). Generally, the injected gas bubble before expansion must be moderately larger than the largest retinal break to prevent subretinal gas. In most cases, our goal is to have a bubble volume of approximately 1.0 mL, which requires an injection of 0.5 mL of pure SF₆.

If filtered room air is injected, we recommend at least 0.8 mL. If it is desired to inject more than 0.6 mL, multiple paracenteses (one before and one or more after the gas injection) or multiple gas injections likely will be needed.

We believe that it is optimal for the gas bubble to cover the break(s) for 5 days and then disappear as soon as possible. However, successful reattachment has been reported after as little as 6–8 hours of tamponade, as with inverted positioning for inferior tears.³⁶ The longevity of an air bubble is probably sufficient for most cases, but occasionally the chorioretinal adhesion may not be sufficiently mature when the air has resorbed. The use of air also forfeits the advantage of postinjection bubble expansion within the eye, necessitating injection of a larger volume, but it offers the advantages of decreased expense and universal availability.

In most cases the prolonged longevity of a perfluoropropane (C₃F₈) bubble is a disadvantage. Air travel is contraindicated for a much longer period of time with C₃F₈, and patients are instructed not to sleep on their back until the bubble disappears to prevent prolonged contact between the gas bubble and the lens. However, the use of C₃F₈ may eliminate the need to reinject gas if a new break develops, and C₃F₈ allows the injection of a smaller amount of gas initially, thereby reducing the need for paracentesis. We recommend C₃F₈ only when an unusually large gas bubble is needed.

Our usual procedure is to perform a preinjection paracentesis, followed by injection of 0.4–0.6 mL of pure SF₆. The amount of fluid removed by paracentesis helps determine how much gas to inject. One can usually inject that amount of gas plus 0.2 mL without needing a second paracentesis, particularly if the eye was initially softened by cryopexy.

Sterilization of the ocular surface

Meticulous attention to sterile technique is mandatory. Sterilization of the ocular surface requires topical antiseptics; antibiotics are inadequate. We recommend povidone–iodine solution,⁵³ and we do not recommend other preparations that contain detergent or alcohol.

A sterile lid speculum is utilized. Several drops of povidone–iodine solution are instilled directly onto the conjunctiva and left in contact with the eye while the gas is prepared. The injection site is then dried with a sterile cotton-tipped applicator, and the eye is ready for paracentesis and injection of gas. With these precautions, the occurrence of endophthalmitis after PR is extremely uncommon, with very few reported cases in the literature.^54,⁵⁵

Preparation of the gas

A pressure-reducing system is attached to the gas cylinder to allow drawing of the gas from a low-pressure system. High pressure can blow out the Millipore filter and render it useless in sterilizing the gas.⁵⁶ A condom catheter can be attached to the cylinder, as shown in Figure 103.1, or a step-down valve system can be used. Alternatively, the gas can be drawn into a large syringe and then transferred to a small syringe.

Fig. 103.1 The gas is transferred from the high-pressure tank into a low-pressure balloon made from an external urinary catheter. Gas is then easily withdrawn through a Millipore filter into the syringe.

(Reprinted from Hilton GF, Grizzard WS. Pneumatic retinopexy. A two-step outpatient operation without conjunctival incision. Ophthalmology 1986;93:626–41. ©1986, with permission from the American Academy of Ophthalmology.)

The selected gas passes through a Millipore filter into a 3 mL syringe in sterile fashion. The tube connecting the gas cylinder with the syringe, including the filter, is flushed through with gas to ensure no dilution with room air. The syringe is filled with a few milliliters of gas and the gas is discarded. The syringe is then refilled. Passive filling of the syringe ensures that room air is not drawn in. A disposable 30-gauge, -inch (12 mm) needle is then placed tightly on the syringe, and excess gas is expelled to leave the exact amount intended for injection. The gas should not be stored in the syringe for more than a few minutes before injection because room air infiltrates the syringe and dilutes the gas sample.⁵⁷

Performing a paracentesis

Although gas can be injected before paracentesis, we generally recommend a paracentesis first. Paracentesis performed after gas injection can result in gas in the anterior chamber. Preinjection paracentesis helps determine how much gas to inject and avoids marked intraocular pressure elevations. Dehiscence of a recent clear corneal cataract incision has been reported following PR when preinjection paracentesis was not performed.⁵⁸

These recommendations are contrary to the practice of most retina surgeons, 62% of whom perform the paracentesis following injection, with the same percentage preferring C₃F₈ over SF₆.⁵⁹

For a paracentesis, we use a -inch, 30-gauge needle mounted on a 1 mL syringe without a plunger. After sterilization of the ocular surface, the needle is passed obliquely through the limbus into the anterior chamber, with the needle tip kept over the peripheral iris to avoid touching the lens. This maneuver may be facilitated by forcing aqueous toward the angle by applying gentle pressure on the center of the cornea with a cotton-tipped applicator (Fig. 103.2). However, care must be taken to avoid contact between the cornea and the lens. Instead we prefer applying pressure with the cotton-tipped applicator at the equator of the eye, facilitating maximum aqueous removal.

Fig. 103.2 Paracentesis of the anterior chamber with a -inch, 30-gauge disposable needle on a 1 mL syringe without a plunger. The lumen is open toward the cornea and positioned over the peripheral iris. Gentle pressure on the cornea with a cotton-tipped applicator forces aqueous into the periphery of the anterior chamber near the needle tip, thereby facilitating more complete drainage.

(Reproduced with permission from Hilton GF, Tornambe PE, and the Retinal Detachment Study Group. Pneumatic retinopexy: an analysis of intraoperative and postoperative complications. Retina 1991;11:285–94.)

Paracentesis through the limbus may be done in phakic eyes and in pseudophakic eyes if the posterior capsule is intact or if a small capsulotomy is firmly closed against the intraocular lens (IOL); otherwise, paracentesis should be performed through the pars plana to prevent vitreous strands from incarcerating in the limbus. When performing paracentesis through the pars plana, the plunger is left in the syringe to prevent occlusion of the needle with vitreous. The needle is directed anteriorly into the anterior chamber, either through the pupil adjacent to the IOL or through the iris. Paracentesis of the anterior chamber is contraindicated in the presence of an iris-supported IOL because of the possibility of the implant touching the endothelium.

Injection of gas

With the ocular surface still sterile and the patient supine, the head and the eye are turned a total of approximately 45° to one side to place the pars plana injection site uppermost. The gas usually is injected temporally unless the pars plana epithelium is detached or large retinal breaks are present in that area, in which case another site is selected. The injection is made 3–4 mm posterior to the limbus with a -inch (12 mm), 30-gauge needle. The needle is directed toward the center of the vitreous and inserted to a depth of 7 or 8 mm to ensure penetration of the pars plana epithelium and the anterior hyaloid face. It is then partially withdrawn so that approximately 9 mm of the needle shaft is seen outside the eye, leaving only 3 mm of the needle tip inside the globe. With the injection site uppermost and the needle vertical, the gas is injected moderately briskly. This technique creates one single bubble at the needle tip (Fig. 103.3C) rather than multiple small bubbles, often referred to as “fish eggs” (see below).

Fig. 103.3 Summary of pneumatic retinopexy procedure. (A) The volume of the subretinal fluid is determined by the inflow of fluid vitreous (green arrow) and the outflow through the retinal pigment epithelial pump into the choroid (red arrow). (B) The area of the retinal break is treated with multiple contiguous applications of transconjunctival cryotherapy. (C) With the pars plana injection site uppermost, the needle vertical, and the needle tip placed shallowly within the vitreous, the gas is injected moderately briskly through a 30-gauge needle. For purposes of illustration, the artist has drawn the injection in the same meridian as the retinal break, but usually this meridian is avoided. (D) The head is positioned so that the intravitreal gas bubble closes the retinal break. (E) With the break closed, the retina usually is reattached by the first postoperative day. (F) The gas bubble is spontaneously absorbed.

(Reprinted from Hilton GF, Kelly NE, Salzano TC, et al. Pneumatic retinopexy. A collaborative report of the first 100 cases. Ophthalmology 1987;94:307–14. ©1987, with permission from the American Academy of Ophthalmology.)

It is not necessary to visualize the needle tip within the vitreous with the ophthalmoscope. As the needle is withdrawn from the eye, the needle tract is immediately covered with a sterile cotton-tipped applicator by rolling it onto the needle shaft simultaneously as the needle is withdrawn to prevent the loss of gas. The head is then rotated to the opposite side, moving the gas bubble away from the injection site, and the cotton-tipped applicator is then removed. Alternatively, the head can be rotated prior to removing the needle. Within seconds the needle tract swells closed, preventing further leakage.

Assessing intraocular pressure

Despite preinjection paracentesis, the central retinal artery sometimes closes after gas injection. Several studies suggest that the retina can tolerate 60 minutes without blood flow as a result of elevated pressure.^26,⁶¹^–⁶⁵ If the artery does not reopen within about 10 minutes, intraocular pressure should be lowered by repeat paracentesis.

While waiting for the central retinal artery to reopen, intermittent ocular compression can hasten the return to normal intraocular pressure. A scleral depressor is pressed against the lateral aspect of the eye so that the eye is compressed against the medial orbital wall. This raises the intraocular pressure, augmenting fluid egress and stretching the scleral wall.⁶⁶ This is not recommended in eyes which have had recent surgery or penetrating trauma.

The patency of the central retinal artery is evaluated with ophthalmoscopy. If it is difficult to tell whether the artery is patent, the eye is compressed with gradually increasing force while monitoring with an indirect ophthalmoscope. If pulsation of the central retinal artery cannot be induced in this manner, it is probably closed. In addition to ensuring patency of the central retinal artery, the ophthalmoscope is used to rule out the possible complications of anterior gas entrapment or fish egg bubbles.

Once patency of the central retinal artery has been re-established, the outflow of aqueous is more than adequate to compensate for the expansion of the gas bubble in nonglaucomatous eyes. Accordingly, we no longer check postoperative pressures unless severe glaucoma is present.

When checking intraocular pressure in a gas-filled eye, it is important to remember that indentation tonometry (e.g., Schiøtz) can give falsely low pressure readings, necessitating an appropriate correction factor.⁶⁷ With a 1 mL gas bubble volume, the error of Schiøtz tonometry is approximately 8 mmHg for intraocular pressures in the range of 10–20 mmHg and approximately 15 mmHg for intraocular pressures in the range of 30–40 mmHg. Applanation tonometry is preferred.

Instructing the patient

The eye is irrigated, an antibiotic-steroid ointment is instilled, and the eye is patched. Most patients require no pain medication. The axis of the retinal break is marked with an arrow on the bandage, and the head is tilted so that the arrow points toward the ceiling. Alternatively, a commercially produced “pneumo-level” disc can be attached to the forehead to indicate the head tilt. Using a mirror to demonstrate, the patient is carefully instructed to position his head so that the break is uppermost. The patient is instructed not to lie on his back facing upward because prolonged gas contact with the lens may cause a cataract or, in the case of an aphakic eye, pupillary block with angle-closure glaucoma. The appropriate position, with the retinal break uppermost, should be maintained at least during waking hours for 5 days. If possible, maintaining the position during sleep may be helpful, especially until the retina is reattached.

Special procedures

Fish eggs

Multiple small intravitreal gas bubbles, or “fish eggs”¹⁸ (Fig. 103.4), can result in gas getting under the retina, particularly in the presence of large retinal breaks. This occurrence is generally preventable by performing the following steps, in order of importance (Fig. 103.5):

1. Make sure that the needle tip is placed shallowly within the vitreous at the time of injection.

2. Make sure that the injection site is uppermost.

3. Inject moderately briskly, not too briskly, nor too slowly.

4. Inject with the needle vertical.

Fig. 103.4 Fish eggs – multiple, small intravitreal gas bubbles, generally caused by faulty injection technique – can result in gas getting under the retina.

Fig. 103.5 How not to inject gas in the presence of detached retinal breaks.

If fish eggs do occur, the patient is strictly positioned to keep the bubbles away from retinal breaks. If all retinal breaks are small, this may not be necessary, but keep in mind that breaks can stretch a little. The bubbles usually coalesce spontaneously within 24 hours, and then the patient can adopt a position with the retinal break(s) uppermost.

Alternatively, the bubbles usually can be caused to coalesce by flicking the eye with a cotton-tipped applicator or gloved finger. The eye is turned so that sclera without underlying retinal breaks is uppermost, and then this site is flicked moderately firmly. This maneuver should be attempted particularly if significantly large breaks are present in the superior several clock-hours, since it may not be possible to keep the fish eggs away from such breaks. Impending macular detachment might also indicate this procedure or indicate a face-down position until the bubbles coalesce.

Gas entrapment at the injection site

After gas injection, the head is turned to the opposite side and mobility of the gas is confirmed ophthalmoscopically. If the gas bubble remains trapped at the injection site, it is probably trapped in the canal of Petit (between the anterior hyaloid, the lens and zonules, and the pars plana epithelium). Typically, the gas is visible peripherally behind the lens, forming a partial ring, variously described as the “bagel,” “donut,” or “sausage” sign (Fig. 103.6).

Fig. 103.6 Gas entrapment at the injection site. (A) Gas trapped in the canal of Petit (between the anterior hyaloid, the lens and zonules, and the pars plana epithelium). (B) Gas is visible peripherally behind the lens, forming a partial ring (the “sausage sign”).

If only a small amount of gas is trapped, no treatment is necessary. If most of the gas is trapped, the patient is advised to follow face-down positioning for 1 day. As the gas subsequently expands, it will generally break through and float up to the macula. Thereafter, the patient assumes the desired position with the retinal break uppermost.

Waiting for trapped gas to break free may jeopardize an attached macula imminently threatened by detachment. A trapped bubble can be removed by passing a 27-gauge needle back through the injection site. This needle is mounted on a syringe without the plunger, containing a small amount of sterile saline solution. The injection site is positioned uppermost and the needle passed vertically into the bubble. Sometimes it takes a little manipulation to break the surface tension of the bubble and get it to escape. Most of the gas will escape, bubbling up through the fluid in the syringe. At another site, the gas is reinjected deeper into the vitreous, with 4–5 mm of the needle in the globe. This procedure also may be indicated if trapped gas does not become mobile after face-down positioning, which may constitute the rare and potentially painful occurrence of gas trapped beneath the pars plana epithelium or in the choroid.^68,⁶⁹

Steamroller

If bullous subretinal fluid extends almost to an attached macula, placement of a bubble against the bullous detachment may push fluid into the macula and cause it to detach.⁷⁰ This complication, as well as the impending threat of spontaneous macular detachment, usually can be avoided by the “steamroller” technique (Fig. 103.7).⁶⁰

Fig. 103.7 “Steamroller” maneuver: prevention of iatrogenic macular detachment. (A) Bullous retinal detachment near an attached macula (M), indicating the “steamroller” maneuver. (B) What to avoid – the gas bubble may force subretinal fluid posteriorly (arrow), causing iatrogenic detachment of the macula. (C) Steamroller step 1 – iatrogenic macular detachment is prevented by placing the patient in a face-down position immediately following gas injection, making sure that the gas bubble traverses attached retina on its way to the macula. This frequently causes some subretinal fluid to pass through the break into the vitreous (arrow). (D) Steamroller step 2: over 1–10 minutes, the patient’s head position is very gradually moved along the meridian between the macula and the retinal break (arrow) until the retinal break is uppermost. This causes the bubble to roll toward the retinal break, pushing the subretinal fluid away from the macula and back into the vitreous and flattening the retina. Cryopexy should generally not be performed before a steamroller maneuver.

After injection of the gas bubble, the patient’s head is placed face-down by turning the patient in a direction planned to ensure that the bubble traverses only attached retina en route to the macula. Over 1–10 minutes, the patient’s head position is gradually changed until the retinal break is uppermost, causing the bubble to roll toward the retinal break, pushing the subretinal fluid away from the macula and back into the vitreous, and flattening the retina.

Subretinal fluid will be expressed through the retinal break into the vitreous cavity at a rate dependent on the size of the break. Because cryopexy causes liberation of pigment epithelial cells, which may cause PVR if they enter the vitreous cavity, cryopexy should generally not be performed before steamrolling.

Whether steamrolling is necessary to prevent macular detachment depends on several factors: (1) how close the detachment is to the macula (only detachments well within the arcades usually need steamrolling); (2) how bullous the detachment is; and (3) how large the gas bubble is.

Possible indications for steamrolling include the following:

1. Prevention of iatrogenic macular detachment

2. Prevention of iatrogenic detachment of an attached retinal break

3. Reduction of a bullous detachment overhanging the optic nerve, preventing visualization of the central retinal artery during the procedure

4. Reduction of subretinal fluid to encourage more rapid resolution of retinal detachment. This might be of use in cases where all retinal breaks cannot be covered at one time by the gas bubble

5. Avoidance of posterior gaping of the tear and subretinal gas in the presence of large retinal breaks. The extreme example of this is a somersault maneuver performed to unroll the inverted flap of a giant retinal tear.

The movement of subretinal fluid into the vitreous has raised theoretical concerns about the production of PVR. However, there were no cases of PVR in the 19 eyes that were managed by the steamroller technique in a multicenter clinical trial.⁷¹ Yanyali et al.⁷² similarly, did not observe a higher rate of PVR with steamrolled cases versus basic PR technique.

Summary of procedure

The following constitutes the sequence of a typical pneumatic retinopexy procedure (Fig. 103.3):

1. Anesthetic: topical/subconjunctival or retrobulbar

2. Cryopexy: if one-session procedure, in lieu of laser

3. Sterilization of ocular surface: povidone–iodine solution

4. Paracentesis: limbal, or via pars plana if capsule is open

5. Intravitreal gas injection: 0.4–0.6 mL of SF₆

6. Second paracentesis and/or ocular compression: as needed to open artery

7. Special procedures: e.g., steamroller if needed (cryopexy should not be performed before steamroller)

8. Antibiotic and patch: draw arrow

9. Laser: next day or when retina is reattached (in lieu of cryopexy as two-session procedure) with 360° laser if desired.

Most frequently, the authors do a one-session procedure using cryopexy instead of laser. Judging by published surveys, our recommended procedure differs from the technique used by the majority of retina surgeons in the following three ways:

1. We perform paracentesis prior to, rather than following, gas injection.

2. We usually inject SF₆ instead of C₃F₈.

3. We inject a larger gas bubble, 0.5–0.6 mL in most cases.

Postoperative management

The patient is usually examined in the office on the 1st or 2nd postoperative day, at which time the retina is usually reattached (Fig. 103.3E), although an occasional case may take an extra day or two. If the fluid is not resorbing, there may be a new or missed break, traction may be keeping the break open, the bubble may be too small, or the patient may not have maintained proper positioning. The importance of proper positioning should be re-emphasized.

Inferior subretinal fluid or loculated pockets of subretinal fluid on rare occasion will persist for weeks or months. As long as the fluid is not increasing, there are no detached retinal breaks, and the macula is attached, reoperation is not necessary.

As a general guideline, the patient is examined on about the 1st or 2nd, 5th, and 14th postoperative days and periodically thereafter, looking especially for new retinal breaks. If close follow-up results in early detection and treatment, these breaks do not jeopardize the final outcome.⁸ At least half of these can be cured with an office procedure without resorting to SB.

The gas bubble will resorb spontaneously (Fig. 103.3F). Until it does, the patient is advised not to fly because the lower atmospheric pressure that exists in flight can cause expansion of the gas bubble with a marked increase in intraocular pressure. We recommend that patients be allowed to return to work in 1–2 weeks.

Results

In 1991, a compilation of 26 statistical series from seven countries including 1274 eyes treated with PR, showed a single-operation success rate of 80%, with 98% cured with one or more operations.¹⁸ More recently, Chan et al.²⁰ reviewed 81 published PR series from 1986 to 2007, totalling 4138 eyes. Single-operation success was 74.4%, and success with one or more operations was 96.1%. New retinal breaks occurred in 11.7% of eyes, and PVR occurred in 5.2% (Table 103.2).

Table 103.2 Summary of 81 published statistical reports on pneumatic retinopexy, 1986–2007: anatomic results and two postoperative complications

Tornambe ¹⁷ reviewed the causes of failure and concluded that pseudophakia/aphakia, detachment >50% of the retina, and multiple retinal breaks adversely influence single-operation success.

The multicenter clinical trial ⁹ confirmed the conclusion of Ambler et al.⁷³ that initial failure with PR, subsequently requiring SB, does not adversely affect the final visual outcome compared with SB alone.

Comparison of pneumatic retinopexy with scleral buckle

The multicenter randomized controlled clinical trial compared PR and SB in 198 eyes, establishing two statistically similar groups with similar preoperative visual acuity. The conclusions of the study include the following:⁸

1. Postoperative morbidity was less and had a shorter duration in the PR group.

2. Postoperative visual acuity was significantly better with PR than with SB for eyes in which the macula was detached for up to 2 weeks (P = 0.05). In this group, 80% of the PR patients regained 20/50 or better vision, compared with only 56% of SB patients.

3. With one operation and with occasional postoperative cryotherapy or laser supplementation, retinal reattachment was 84% in the SB group and 81% in the PR group. This difference was not statistically significant. However, subsequent studies have confirmed a modestly higher single operation success rate with SB.⁷⁴

4. With reoperations, the final reattachment rate was 98% in the SB group and 99% in the PR group, also not statistically significant. Subsequent studies have confirmed comparable final reattachment rates.⁷⁴

5. Complications were similar, based on a score system that weighted heavily the need for postoperative laser or cryotherapy.

6. Cataract surgery was required four times more often after SB than after PR.

7. New and missed retinal breaks occurred more frequently after PR but did not usually produce an unfavorable outcome. New and missed retinal breaks after SB had the worst prognosis, requiring more extensive reoperation with decreased visual results.

8. An open or absent posterior capsule was associated with an equally lower single-operation success rate in both groups.

9. Postoperative proliferative vitreoretinopathy occurred in 5% in the SB group and 3% in the PR group (not statistically significant).

Comparison of pneumatic retinopexy with vitrectomy

Unfortunately, similar prospective data for a direct comparison of PR to primary vitrectomy are unavailable. As SB has declined in favor among retinal surgeons, vitrectomy for primary rhegmatogenous retinal detachment has gained tremendous popularity in recent years,^75,⁷⁶ driven by continual advances in vitreoretinal instrumentation, microincisional techniques, endoillumination, and wide-field viewing systems. Similar to PR, vitrectomy avoids some of the morbidity more frequently associated with SB, such as induced myopia. Unlike PR, it tends to induce cataract and demands the time and expense associated with an operating room procedure.

Vitrectomy presents advantages in some circumstances where PR is inadequate. It is the procedure of choice in dealing with significant PVR and vitreoretinal traction, and it may be ideal when vitreous or capsular opacity causes poor visualization. By facilitating placement of a large gas bubble, vitrectomy shares with SB the ability to treat inferior and widely spread breaks.

Because vitrectomy tends to induce cataract, it is used most commonly in pseudophakic eyes. Tiny breaks, common in pseudophakic eyes, may be most readily identified by internal search during vitrectomy. In a multicenter clinical trial of SB versus primary vitrectomy for rhegmatogenous retinal detachment,⁷⁷ vitrectomy yielded significantly better single-operation success rates than SB in pseudophakic eyes, but no difference in final vision. In phakic eyes, vitrectomy yielded poorer visual results than SB with no benefit in single-operation success.

In the more simple cases appropriate for PR, especially in phakic patients, PR may be preferable to vitrectomy or SB.

Complications

Fish eggs, gas entrapment, and iatrogenic macular detachment are discussed under “Special procedures”, above. Other intraoperative complications of PR are minimal. A number of postoperative complications have been noted in the literature, but most of these occur with an incidence of less than 2% (Table 103.3). The two major concerns are PVR and new or missed retinal breaks. The management of subretinal gas also warrants discussion.

Table 103.3 Complications * in 565 eyes in 10 series^†

	Eyes
	n	(%)
Operative
Incarceration of vitreous	8	1.4
Subconjunctival gas	6	1.1
Postoperative
New or missed breaks	75	13.3
PVR	26	4.6
Redetachment	17	3.0
Mild macular pucker	10	1.8
Persistent subretinal fluid	12	2.1
Minimal epiretinal membrane	8	1.4
Reopening of original break	6	1.1
Vitreous haze, 3–8 days	6	1.1

*Complications of 0.3–1.0% omitted: choroidal detachment, anterior gas entrapment, vitreous hemorrhage, subretinal gas, shift of subretinal fluid, and macular hole. Complications, one case each (0.2%): peripheral subretinal hemorrhage, hyphema, pars plana detachment, cataract, malignant glaucoma, and endophthalmitis. ^†See references.^5,^8,^33,^35,^40,^41,^60,⁷⁸^–⁸⁰

Proliferative vitreoretinopathy

PVR is the major complication for all types of retinal reattachment surgery. A review of the PR literature revealed an incidence of 4% (Table 103.2). PVR developed in 3% of eyes managed with PR compared with 5% in the SB control group in the multicenter clinical trial.⁸ Evidence does not support the concern that intravitreal gas might stimulate PVR.

New or missed retinal breaks

The incidence of new and missed retinal breaks in a compilation of 81 series including 4138 eyes was 11.7% (Table 103.2). This is remarkably less than the 14% figure reported in a study of 171 eyes with retinal breaks, treated with laser photocoagulation or cryopexy but without gas injection.⁸¹ This, along with other evidence suggests that intravitreal gas may play little role in causing new retinal breaks and underscores the natural history of the disease, which includes the rather frequent development of additional breaks. The most common cause of detachment requiring reoperation following pneumatic retinopexy appears to be development of a new retinal break with new rather than persistent retinal detachment.⁸²

In long-term follow-up, the need for reoperation is evident within the first 3 months in 89% of cases.¹⁹ With or without gas, the majority of new breaks appear within the first postoperative month, suggesting that incomplete posterior vitreous detachment may be responsible for some postoperative breaks.^8,⁸¹ In phakic eyes with complete rather than partial posterior vitreous detachment, as determined by B-scan ultrasonography, Rezende et al.⁴² reported a higher rate of single-operation retinal reattachment, particularly in eyes treated with PR.

Since PR failures are sometimes caused by new retinal breaks in untreated areas of the retina, Tornambe has recommended that 360° laser retinopexy be applied between the insertion of the vitreous base and the ora serrata.¹⁷ He reported a significant improvement in single-operation success with this approach, but only about 1 in 12 PR surgeons employs this technique.⁵⁹

New retinal breaks following pneumatic retinopexy do not portend a poor outcome. Some 96% of such eyes were successfully treated in the multicenter trial. New retinal detachments following pneumatic retinopexy do not necessarily require vitrectomy or scleral buckling and can often be treated by a repeat pneumatic procedure alone.

Subretinal gas

Subretinal gas is usually a preventable complication, as described above (see under “Fish eggs”). However, if gas does get under the retina, the bubble can generally be teased back through the break if the break is larger than the gas bubble or if the diagnosis is made promptly before gas expansion. Under indirect ophthalmoscopic visualization, scleral depression is used to maneuver the bubble to the break and force it through.

If this fails but the amount of subretinal gas is small relative to the intravitreal gas, it may not be necessary to remove the subretinal gas. In this instance, strict prolonged positioning may still resolve the detachment, since the intravitreal gas will outlast the subretinal gas. Larger amounts of subretinal gas can be removed with a needle passed through the sclera and into the subretinal space, similar to the technique described above in the section “Gas entrapment at the injection site”. Rarely, vitrectomy may be necessary to remove the gas.

Acceptance of Pneumatic Retinopexy

The popularity of PR increased markedly in the 1990s, following the multicenter clinical trial.⁷ In a 2002 survey of the American Society of Retinal Specialists (then called the “Vitreous Society”), 72% of respondents selected PR for a phakic macula-on detachment with a 12 : 00 tear, and PR was also the most commonly selected option if the eye was pseudophakic (45% for PR versus 13% for primary vitrectomy).⁵⁹ However, acceptance of PR in Europe has lagged far behind that in the USA.^83,⁸⁴

Recent gains in popularity of vitrectomy have been mostly at the expense of scleral buckling. A 2010 analysis of Medicare claims showed that vitrectomies for primary retinal detachment increased 72% from 1997 to 2007, while SB decreased 69% and PR remained relatively unchanged.⁷⁵ Microincisional vitrectomy may present a new alternative to PR in selected cases.

Algorithm for choosing Pneumatic Retinopexy versus other procedures for retinal detachment

In Retinal Detachment: Principles and Practice, Brinton and Wilkinson ¹ presented an algorithm (Fig. 103.8) intended to organize the decision of type of surgery to use for a given retinal detachment case. It does not reflect all factors which may influence a decision, and the individual circumstances of each specific patient, as well as the experience of the surgeon and the availability of equipment, should also be taken into account. This algorithm provides only guidelines reflecting the opinion of the authors and does not establish the standard of care for a given case.

Fig. 103.8 Algorithm demonstrating an approach to selection of an appropriate retinal reattachment procedure. RD, retinal detachment; PVR, proliferative vitreoretinopathy.

(Reprinted from Brinton DA, Wilkinson CP. Retinal detachment: principles and practice. 3rd ed. New York: Oxford University Press/American Academy of Ophthalmology ©2009, with permission from Oxford University Press.)