Technique

Pneumatic retinopexy is either performed in one or two steps, depending on whether cryopexy or laser is utilized to form the chorioretinal adhesion (Tables 4.3,4.4).Anesthesia may be applied

Table 4.3. Required materials

Anesthetic of choice Povidone-iodine 5% solution Eyelid speculum and caliper Several sterile cotton-tip applicators

1-ml syringe/30-gauge needle - plunger removed (if paracentesis) Gas cylinder/tubing Millipore filter

1-ml or 3-ml syringe/30-gauge needle Cryotherapy unit or laser Antibiotic/steroid combination ointment Patch materials

Table 4.4. Pneumatic retinopexy technique steps

Apply anesthetic of choice

Prepare eye - povidone-iodine 5% - 5 min x2

Prepare chosen gas

Place eyelid speculum

Perform cryopexy (one-step procedure)

Paracentecis (surgeon's choice)

Position patient, head

Caliper measurement - 4 mm

Inject gas bubble/location

Inspect gas location, central retinal artery perfusion Check intraocular pressure until normalizes Patch with arrow drawn Laser (next day, if two-step procedure)

by topical, subconjunctival, peribulbar, or retrobulbar routes. A retrobulbar or parabulbar injection is given when cryopexy is planned, while topical or subconjunctival administration is sufficient for gas injection alone. The globe, eyelids, and periocular skin are prepared with a 5% povidone-iodine solution applied twice at 5-min intervals. Some surgeons choose to add a topical antibiotic solution; however,these need to be started 24-48 h prior to the procedure with frequent use to substantially affect the ocular flora, limiting their usefulness as a true prophylactic method in this setting. A wire-lid speculum is used to open the lids, avert the lashes from the field, and protect the lid margin from cryopexy damage. If the patient is to undergo a one-step procedure, then cryopexy is performed prior to gas injection, as small breaks may be difficult to visualize following gas injection. Cryopexy is the preferred method in cases where media opacities limit the view, when the break(s) are located in the far periphery, or when there is underlying pigment epithelial atrophy. Laser, via a two-step method, is preferred with bullous superior detachments with large retinal breaks, when breaks occur over a previously placed buckle element, and with posteriorly located tears. Some surgeons feel that there is a lower incidence of PVR with laser retinopexy compared with cryopexy. Laser can be difficult to perform through or around the gas bubble and will not provide adequate adhesion if there is still a small amount of fluid present near the tear site. Small breaks may be difficult to find with the laser once the retina is reattached. Laser might form a chorioretinal adhesion faster than cryopexy, which decreases the critical duration of required post-operation positioning. Multiple rows of confluent laser are placed around each tear with careful attention to carry the treatment anterior to the ora serrata. It should be noted that the two methods are not mutually exclusive, and many instances are best managed by a combination of both modalities.

Preparation of the chosen gas is performed by withdrawing gas from a cylinder via a valve system through a Millipore filter into a 1-ml or 3-ml syringe. The valve, tubing, filter, and syringe are flushed with gas once, and the process is repeated to eliminate room air from the system. High pressures may damage Millipore filters, so care must be taken to maintain lower pressures during gas filtration. The filter is replaced with a 30-gauge needle, and excess gas is pushed out of the syringe until the desired amount for injection remains behind.

Paracentesis of the anterior chamber is a controversial step in the procedure. Some surgeons routinely soften all eyes prior to injection, while some perform the step only rarely. Others perform paracentesis after the gas injection as required by the IOP. Paracentesis is less important with one-step procedures where the scleral depression associated with cryopexy softens the globe and in cases where smaller volumes of expansile gas are utilized. Paracentesis is most often required in two-step (laser) cases and when injecting large gas volumes. The step is performed by entering the anterior chamber with a 30-gauge needle affixed to a 1-ml syringe without the plunger. Aqueous humor is allowed to passively egress until the anterior chamber shallows. A sterile cotton tip applicator is rolled onto the needle track as the needle is withdrawn to avoid additional fluid egress. Care is given to avoid needle tip-lens touch. Paracentesis is contraindicated in aphakic and pseudophakic patients with vitreous prolapse into the anterior chamber.

Gas injection is the most important component step of PR, and many postoperative complications can be avoided with proper technique. The surgeon utilizes the indirect ophthalmoscope for lighting, visualization of needle tip, and later to assess gas location and patency of the central retinal artery. The patient is placed in a recumbent position with the head tilted 45° away from the operative eye. This places the temporal pars plana as the highest point on the globe. The injection is given 4 mm posterior to the limbus, usually in the temporal quadrant, unless the retina is bullously detached in the area. The needle tip is advanced into the mid-vitreous cavity, under direct visualization with the indirect ophthalmoscope to penetrate the anterior hyaloid face. Then the needle is withdrawn until just the tip is visible, 2-3 mm through the pars plana epithelium. Gas is injected in a brisk but controlled manner. Following gas injection, the head is carefully rotated to a neutral position in order to move gas away from the injection site and avoid egress of gas out the needle track. A sterile cotton tip applicator is rolled over the track as the needle is removed to minimize gas reflux. Following gas injection, the bubble size and position are assessed, and central retinal artery perfusion is assured with indirect ophthalmoscopy.

IOP rises abruptly in most patients who receive greater than 0.2 ml gas. The IOP is checked immediately following gas placement. Frequently, pressure measurements fall in the 50-70 mmHg range. If the patient has a normal aqueous outflow mechanism, he or she can be monitored with serial tonometry every 10-15 min, which frequently demonstrates a return to more normal pressures over 15-30 min. Paracentesis, as noted above, may be performed before or after gas injection (or both) to normalize IOP. The pressure should be near normal and the central retinal artery perfused prior to the patient's departure.

Postoperatively, an antibiotic/steroid combination ointment is placed in the eye, and a patch is applied. An arrow is drawn on the patch, such that the arrow points straight at the ceiling when the patient is properly positioned (break in uppermost position of the globe). The patient and caregiver are reminded of the required position with special emphasis on the need for compliance, especially at night while asleep. The patient returns for follow-up on the first postoperative day. The SRF is usually substantially improved or entirely resolved. The gas bubble size and location are assessed, and the IOP is measured. Laser may be performed as part of a staged procedure (see above). For patients with extensive cryopexy, antibiotic and steroid drops may be prescribed for a few days. The importance of proper position is stressed yet again. In cases where there is little or no change in the SRF, patient compliance is reassessed, and an exhaustive exam for new or missed breaks is undertaken. In the typical scenario where the fluid is substantially better, the patient is re-examined on the third to fifth postoperative day.

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