the retinal pigment epithelial pump can reabsorb the subretinal fluid (Figure 8–1D).

2.Buoyancy of the gas provides the force which pushes the uppermost retina back against the wall of the eye. Apposition of the retina against the retinal pigment epithelium is necessary in order that an adhesion can occur, just as two surfaces to which glue has been applied must be clamped together while the glue dries (Figure 8–1E). When the gas is gone, a permanent seal remains, preventing reopening of the tear (Figure 8–1F).

PREOPERATIVE EVALUATION

Good preoperative evaluation is vital to the success of pneumatic retinopexy. PR is not a good procedure for surgeons lacking in excellent retinal examination skills, for three reasons:

1.Scleral buckling with encirclement may achieve retinal reattachment even if a retinal break is missed. It can be a very “forgiving” procedure in this sense. With pneumatic retinopexy, any missed retinal break might open into a detachment. The presence of a gas bubble within the vitreous cavity causes shifting of the subretinal fluid or vitreous which can open previously attached breaks.

2.When scleral buckling or vitrectomy are performed, the surgeon gets a second look in the operating room with the patient sedated, with full control of the globe, and with open conjunctiva for deep scleral depression. With pneumatic retinopexy, this is not available.

3.Scleral buckling, especially encirclement, supports the peripheral retina, reducing the traction which the vitreous will be able to exert on the retina in the future. Lacking this with pneumatic retinopexy, careful follow-up examinations are required to find any retinal breaks which develop postoperatively.

In addition to a thorough examination of the retina, the preoperative evaluation for possible pneumatic retinopexy should include assessment of the following:

1.Is the patient mentally capable of following positioning directions?

2.Is the patient physically capable of maintaining positioning as needed, especially with regard to neck and back problems?

3.Will it be feasible from the standpoint of the patient’s home situation for the patient to maintain the appropriate position postoperatively?

4.Will the patient be able to return to the surgeon’s office for frequent follow-up as required?

5.Does the patient have plans to travel in the near future, especially by air, which might pose a hazard with an intraocular gas bubble?

6.Does the patient have evidence of severe glaucoma?

7.Has the patient had recent surgery on this eye which would require care to avoid dehiscence of the healing incision?

8.Does the presence of a fi ltering bleb or a corneal transplant require special handling?

186II: Practice

9.Would the induction of increased myopia that generally occurs following an encircling buckle be an advantage or disadvantage given the patient’s refractive status?

Because postoperative patient cooperation is essential, the nature of the procedure and what will be expected of him should be discussed thoroughly with the patient before surgery.

INDICATIONS AND CONTRAINDICATIONS

In the multicenter clinical trial which compared pneumatic retinopexy with scleral buckling, cases with the following characteristics were excluded:

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

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

3.Presence of proliferative vitreoretinopathy grade C or D.

4.Cloudy media precluding full assessment of the retina.

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

6.Severe or uncontrolled glaucoma.

Subsequent experience has demonstrated that selected cases that do not strictly meet these criteria can be successfully treated with pneumatic retinopexy, subject to certain limits.

LIMITS TO INDICATIONS

Extent of breaks

Clearly, breaks spanning more than one clock-hour can be treated with pneumatic retinopexy. Single or multiple tears or dialyses spanning three clock-hours pose no particular problem. Detached tears six clock-hours apart are difficult to fix with pneumatic retinopexy, although alternating positioning has been used successfully. Even detachments with giant retinal tears have been cured with pneumatic retinopexy, but it is rarely the procedure of choice. The size of the gas bubble should generally reflect the size of the problem, although it is not always necessary to cover all breaks simultaneously with a single bubble.

When deciding whether a case is amenable to pneumatic retinopexy, recognize that there is a difference between attached and detached breaks. In cases where an attached break is present on the opposite side of the eye from the detached breaks, alternate positioning would not be needed. The attached break should probably be treated with laser prior to the gas injection. Care should then be taken, such as by using the steamroller technique (described below) if necessary, to prevent the bubble from pushing the subretinal fluid into the attached break and causing it to

detach. By following these two steps, multiple flat breaks may be ignored in positioning and in determining bubble size.

Inferior breaks

Most cases with breaks in the inferior four clock-hours of the eye have been difficult to treat with pneumatic retinopexy. Even for limber patients, it is very difficult to tilt the head below the horizontal for very long. As a rule, a detached break in the inferior four clock-hours represents a contraindication to pneumatic retinopexy.

Proliferative vitreoretinopathy

Since pneumatic retinopexy does not relieve traction like scleral buckling or vitrectomy can, significant preoperative traction on a retinal tear is a relative contraindication to the pneumatic procedure. When a tear is adjacent to a star fold, pneumatic retinopexy is usually not the procedure of choice. Mild to moderate proliferative vitreoretinopathy which is distant from any retinal breaks does not necessarily contraindicate pneumatic retinopexy. More severe PVR usually calls for vitrectomy and scleral buckling.

Cloudy media

It is important to the success of pneumatic retinopexy that all retinal breaks be identified and treated. Opacities such as peripheral vitreous hemorrhage represent relative contraindications to pneumatic retinopexy. Since pneumatic retinopexy does not seem to jeopardize an eye for future scleral buckling if needed, it may not be unreasonable to use the pneumatic procedure even when opacities obscure part of the attached retina, but this represents a calculated risk.

Inability to maintain positioning

Failure to faithfully maintain the appropriate position is probably an important cause of failure of pneumatic retinopexy. It is important to inquire regarding back or neck problems and to assess mental competence before deciding on pneumatic retinopexy. Recognize that some positions are quite easy to maintain, while others require excellent cooperation. Positioning is easiest with tears between 11:00 and 1:00.

Glaucoma

Glaucoma has proven to be relatively unimportant as a contraindication to pneumatic retinopexy. The large majority of glaucoma patients can be treated with pneumatic retinopexy without problem. Patients with quite severe glaucoma, such as with splitting of the macular field due to glaucoma, might suffer noticeable damage (even from brief elevations in intraocular pressure), but pneumatic retinopexy can be performed in a manner to avoid elevations in pressure. Except in cases of severely impaired trabecular outflow facility, serial measurements of intraocular pressure following gas injection are not necessary.

Isolated tears under the superior rectus

Placing a segmental buckle under a vertically acting muscle runs the risk of iatrogenic diplopia; this potential complication is eliminated with pneumatic retinopexy.

Contraindications to general anesthesia

If performing scleral buckling or vitrectomy under local anesthetic is not an option, medical contraindications to general anesthesia may indicate pneumatic retinopexy as an optimal alternative.

Optic pit with macular detachment

Pneumatic retinopexy may be an effective option in the treatment of optic pits with serous macular detachment.

Extensively scarred conjunctiva

Conjunctival scarring may make dissection for a scleral buckle difficult, and may make it difficult to get the conjunctiva to cover adequately at the end of the case. These problems are avoided with pneumatic retinopexy.

Very thin sclera

With scleral buckling, thin sclera poses a risk of needle penetration or inadequate anchoring of sutures to secure the buckle, problems that are avoided with pneumatic retinopexy or vitrectomy. When ultra-thin sclera is discovered in the operating room, a pneumatic procedure combined with drainage of subretinal fluid can provide a means of repairing relatively extensive detachments, since a very large gas bubble can be obtained.

Need to retain emmetropia or to prevent anisometropia

Patients with excellent preoperative vision, particularly if they are uncorrected or have a history of refractive surgery, may consider the loss of emmetropia to be a substantial disadvantage of scleral buckling.

Cosmetic concerns

Scleral buckling is associated with a higher risk of ptosis, enophthalmos, and strabismus than that seen after pneumatic retinopexy.

Operating room not available

In some settings or at some times, an adequately equipped and staffed operating room may not be available or may require an unacceptable delay. In these instances, an office-based procedure may be a good alternative.

Limited financial resources

Pneumatic retinopexy is much less expensive than scleral buckling or vitrectomy because all operating room expenses, ancillary hospital or surgicenter charges, and anesthesia fees are avoided. Preoperative medical and laboratory evaluation is also generally not necessary.