Many surgeons prefer also to use retrobulbar or peribulbar anesthesia when general anesthesia is to be used. There is added safety in case of retching during recovery from general anesthesia. It also aids in controlling post operative pain.
Induction of anesthesia and intubation usually can be accomplished while the balloon is in position. Thus ocular compression can be maintained until shortly before the surgery is begun.

Excess finger pressure resulted in dislocation of some lenses into the vitreous. Insufficient pressure did not achieve desired results. The amount of digital pressure could not he regulated or standardized.

Instrumentation was developed, allowing pneumatic pressure with a bellows device inflated with a sphygmomanometer bulb air pump and monitored by an aneroid manometer. It allowed more precise application of pressure. External compression could then be applied at a predetermined level.

Other less precise devices used were rubber balls strapped to the eye and gravity-dependent bags of lead shot or mercury laid on the eye.

Clinical observations have suggested that intraocular pressure is lower after continuous extraocular compression. After compression at 3Omm Hg for 30 to 60 minutes, intraocular pressure has been recorded at 12 to 20 scale reading units with a Schiotz Tonometer with a 5.5g weight.

One of the hazards of intracapsular cataract extraction was expulsion of vitreous. Preoperative ocular compression resulted in soft, safe surgical eyes. After extraction of the lens in its capsule with capsule forceps, erysophake or by Smith expression technique, the vitreous would fall posteriorly and the cornea would exhibit a concave configuration or dimple.

When anterior chamber and iris plane intraocular lenses were introduced, it was important to avoid touching the cornea. Polymethylmethacrylate plastic has a destructive effect on the corneal endothelium. Preoperative ocular compression produced soft eyes with absence of pressure from the vitreous to force the intraocular lens against the corneal endothelium.

Prior to the availability of viscoelastic substances, ocular compression helped to protect the corneal endothelium.

Phacoemulsification instruments have a positive pressure control to prevent the forward protrusion of vitreous and lens-iris diaphragm. Viscoelastic substances can be used to protect the corneal endothelium for surgical maneuvers and lens insertion. Preoperative ocular compression can add an additional safety factor by decreasing the tendency of the posterior capsule to bulge forward during phacoemulsification.

Extraocular compression, following injection of retrobulbar or peribulbar anesthesia, can aid the diffusion of the anesthetic solution. Akenesia is enhanced, thus obviating the need for a separate lid block.

How much pressure and how long should preoperative ocular compression be used? A pressure lower than diastolic pressure should allow adequate perfusion. Continuous pneumatic pressure of 30mm Hg has been applied 30 to 60 minutes by many surgeons for several years. The resulting intraocular pressure at the time of surgery has been a Schiotz scale reading with 5.5g weight of 8 to 20 scale units. One surgeon reported that he has used 5Omm Hg pressure for several years with good results and no untoward incidents.

My practice is to use 3Omm Hg preoperative ocular compression for 20 minutes for the first case in the morning. The second ease is blocked before the first surgery is done and the balloon is applied at a pressure of 15mm Hg for 30 to 60 minutes until it is removed when the surgical prep is done. The Schiotz pressure reading, with a 5.5g weight, is usually 5 to 10 scale units. The eyes are surgically soft and safe.

When general anesthesia is used, the pressure apparatus can remain in place during intubation and removed just prior to
the surgical prep. In the 1970's, we used general anesthesia for many cataract surgeries.
Extraocular pressure was applied at 20 to -3OmmHg for up to an hour. Patients did not complain of discomfort.

When only topical anesthesia is used, we have applied extraocular compression at 3Omm Hg for the first case for 20 minutes. On the second and succeeding cases, 15mm Hg is used for 30 to 60 minutes.

How long does the pressure lowering effect last after compression is released? Practically, the duration of action is sufficient to do the surgery safely. Occasionally, a surgery is delayed for some reason and the patient may be on the operating table prepped and ready for surgery for perhaps 30 to 45 minutes. In those cases, there may be a tendency for the lens-iris diaphragm to bulge forward during surgery.

What is the mode of action of preoperative ocular compression? It has been proposed that the lowering of intraocular pressure is due to decreased vitreous volume. It is also theorized that the entire orbital contents are compressed with decrease in orbital volume. Thus, the retrobulbar contents are compressed, so that they do not exert their normal pressure on the globe.

Other benefits of ocular -compression: There are benefits of preoperative ocular compression other than prevention of bulging or expulsion of intraocular contents during surgery. Retrobulbar or peribulbar hemorrhage secondary to injection of anesthetic agents seem to be inhibited by application of compression after injection.

One theory of the cause of subchoroidal hemorrhages during surgery is that fragile vessels are stressed at the time of sudden pressure decrease at the time of incision. Older arterioscleratic vessels may be more fragile. Lowering the intraocular pressure by preoperative ocular compression decreases the pressure differential at the time of a keratome incision. There may be less stress on the vessels with the lowered pressure differential.

Retrobulbar or peribulbar hemorrhages and subchoroidal hemorrhages, during or following surgery, are very rare. Fortunately, I have not experienced either complication in several thousand surgeries using preoperative ocular compression since the early 1970's.

Our results were not satisfactory when we first tried peribulbar anesthesia in 1984. The use of shorter needles increased our success. One and one half inch retrobulbar needles were used at first. One and one fourth inch and later one inch needles resulted in improved anesthesia. Greater improvement occurred with a change to 3/4 inch needles.
The need of re-injection is unusual. There are reports of successful peribulbar anesthesia with 5/8 inch needles.

Using the following present technique the anesthetic is very satisfactory. Patients experience no pain or discomfort during administration of the anesthesia, during surgery and usually through the post operative period.

The peribulbar injections are made under very short acting intravenous Brevital anesthesia (usually 50 to 70 mg) administered by the anesthesiologist. Flatgrind (duck-bill) 3/4 inch needles by B.D. are our needles of choice at present. Four cubic centimeters of anesthetic agent are injected in the superior nasal area and the same amount also in the inferior temporal area. The needles are inserted peripheral to and angled slightly away from the globe. The Honan Intraocular Pressure Reducer is applied after tape is used to assure closure of the lids.

Duranest 1.5% with 1:2000,000 epinephrine and hyaluronidase 150 TRU added is the current anesthetic of choice.
Duranest is a long lasting anesthetic. It usually provides comfort and prevents pain through the entire immediate post operative period. Sometimes ptosis and numbness persist until the day after surgery. In our experience the anesthesia lasts longer than the Xylocaine-Marcaine mixture. Extraocular compression following injection of the anesthesia serves two purposes. It facilitates spreading of the anesthetic agent in addition to creating a soft eye for safe intraocular surgery. A separate lid block is not needed.

Pneumatic extraocular pressure can be used at a pressure of 15 to 30mm Hg. It is usually used at 30mm Hg for approximately 20 minutes on the first case of the morning. Prior to the first surgery the second case can be injected and the pressure applied at 15mm Hg for 30 to 60 minutes or until time for surgery. To insure a soft eye during surgery it is important to leave the pressure device in place until just prior to the surgical prep. The surgery should be started shortly thereafter.

Rarely anesthesia is not complete and there is some extraocular muscle movement or sensation. Two approaches are available. Three more milliliters of the anesthetic can be injected in the inferior temporal peribulbar area plus two milliliters in the superior nasal region. The Honan Intraocular Pressure Reducer should be reap-piled for at least five additional minutes to diffuse the anesthetic solution. A second and very satisfactory added anesthetic effect can be achieved by subconjunctival injection near the active intraocular muscle. We usually add the
extra peribulbar injections.

Peribulbar anesthesia can be adequately administered by an anesthesiologist. Administration of the anesthesia by an anesthesiologist greatly facilitates smooth patient flow in the surgery suite.