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Owing to the use of wide-angle observation systems 1,2 the lens can be preserved during the vast majority of pars plana vitrectomies. When such lenses later develop cataracts, they frequently exhibit nuclear sclerosis of such a degree that phacoemulsification would no longer be a safe procedure, even for experienced anterior-segment surgeons who are more and more comfortable emulsifying denser and denser lenses. The vitreous cavity of these eyes is filled with aqueous or silicone oil. This fact renders standard extracapsular cataract extraction with expression of the lens nucleus potentially hazardous because pressure on the globe may lead to collapse of the posterior segment in eyes filled with aqueous or to a localized rupture of the zonule and subsequent formation of a persistent pathway through which silicone oil can pass from the vitreous cavity into the anterior chamber. To avoid such complications, extracapsular cryoextraction, followed by an irrigation-aspiration procedure, has proven

Routine use of cryosurgery in a series of 200 cataract extractions resulted in a marked increase in the incidence of irreversible corneal edema when compared with a series of 900 deliveries by conventional methods (increase from 0.66% to 4¼%). This is presumably due to inadvertent freezing and lysis of a critical number of endothelial cells. These clinical observations are consistent with laboratory findings of other workers who induced irreversible corneal edema in rabbits by surface freezing techniques. Further research appears indicated before cryosurgery can be routinely adopted as a safe method of cataract extraction. Until such time caution is urged.

Severe complications associated with the extraction of the dislocated lens have made many surgeons hesitant to operate in such cases. However, with cryoextraction of the lens, using a controllable probe inserted into the eye at ambient (room) temperature, the operative risk is greatly reduced. Previous work in cryoextraction of the dislocated lens 1 described the use of a double-pronged needle, which was inserted with the patient in a prone position, to trap and support the lens prior to cryoextraction. Frequently, the probe had to be applied a few times before good contact with the lens was obtained. This was due to refraction of light rays by the vitreous anterior to the lens, disturbing the operator's judgment of depth. The technique was not entirely satisfactory mainly because of the damage inflicted to the pars plana by insertion of the double-pronged needle. It was impossible to remove a lens fixed to the

TWO papers in this issue of theArchives(pp 3-9) report on cataract cryoextraction and the complications encountered. Both agree that the incidence of capsular rupture is reduced by cryoextraction. On the other hand, one paper reports an alarmingly high incidence of irreversible corneal edema following cataract cryosurgery while the other paper scarcely mentions any problem concerned with the cornea. In view of the increasing popularity of this technique, this apparent discrepancy deserves further explanation. Taylor and Dalburg report an incidence of 4.5% of postoperative corneal edema, often progressing to severe bullous keratopathy, in a series of 200 cases employing one of three types of cryoextractors. In a larger control series, the authors report an incidence of corneal edema of only 0.66%. Their speculation based on certain animal experimentation in the literature, is that freezing or excessive chilling of the corneal endothelium was the factor responsible for the greater incidence

Because cryoextraction is a technique of cataract surgery that is still on trial, it is important that those who are testing the method should put their experiences on record. For that reason, we are publishing the account of 100 consecutive extractions performed by this technique, by the residents in ophthalmology on the ophthalmologic service of Louisiana State University School of Medicine at Charity Hospital of Louisiana at New Orleans, with an instrument devised by one of us (D.L.) for this purpose. A new epoch in cataract extraction—for so we believe it to be—began in 1961, when Krwawicz1described the simple, functional instrument he had devised for cryoextraction of cataracts. His extractor was a pencilshaped, nickel-plated copper instrument, which was cooled in a mixture of solidified carbon dioxide (Dry Ice) and methyl alcohol at -79 C. With it, he had been able to perform intracapsular extraction of 48 of 50

THE RAPID increase in use of electromedical apparatus in clinical medicine and medical research has, for the most part, resulted in significant benefits for the patient and, in general, improved medical care. However, the introduction of these instruments into the hospital environment has created new patient hazards which must be recognized by both the clinical user and the electronic designer-manufacturer. There are two distinct types of electrical hazards in the hospital environment: "macroshock" and "microshock." Macroshock is the familiar hazard of superficial contact shocks that we face every day. Microshock, however, is a new hazard, peculiar to the hospital environment. This type of shock cannot be felt by the operator and may occur without warning. Your patient is increasingly surrounded by and connected to many instruments carrying electric currents. If these instruments are not well grounded, small currents, called leakage currents, can result in undesirable side effects. They will be

Intralenticular foreign bodies are neither unequivocal antecedents of cataract nor indications for immediate lens extraction. Minute foreign bodies either chemically active or nonmagnetic are preferably left in the lens. Small to medium size magnetic foreign bodies should be extracted with minimal magnetic gauss carefully along the entrance pathway. Capsular tears under 2 mm tend to seal, whereas those of 3 mm or larger may lead to opacity. Major foreign bodies causing extensive cataract should be removed by cryoextraction of the lens, unless multiple capsular tears or perforations are present. Under these conditions, the lens may be allowed to absorb unless glaucoma or uveitis require removal. Foreign bodies should be placed in culture broth after extraction rather than taped to the chart.

A small cryoextractor has been used in 1,000 cataract extractions, and the results have been compared to results in a control series of 1,000 extractions by other techniques. Regardless of the previous experience of the surgeon or the maturity of the lens, the incidence of rupture of the capsule was reduced when cryoextraction was used. The incidence of rupture was reduced by 8% in immature, 40% in mature, and 43% in hypermature cataracts. The incidence of loss of vitreous was the same in the cryoextraction and control series. The cryoextractor adhered to the iris in 7% of cases, to a suture in 2%, to the cornea in 1.5%, and to vitreous in 0.3%. This unwanted sticking to iris, suture, and cornea did not appear to represent a significant hazard to the eye. In the majority of the cases, the surgeon concluded, after employing cryoextraction, that this was the best of the techniques from which he might have chosen.

IRIS retraction in round pupil cataract cryooextraction by a surgeon, operating without the aid of another surgeon, can present problems such as iris adhesions to the cryoextractor. The delivery can be facilitated by the use of a 6-0 black silk suture threaded through a peripheral iridectomy at the 12 o'clock position and used for retraction. Iris retraction with a suture has been described before, 1 but apparently has not been popularized. This method is particularly useful during cryoextraction. The corneal flap is lifted by the nurse assistant with a preplaced or postplaced suture. The surgeon grasps the iris adjacent to the peripheral iridectomy with iris forceps, and the needle and silk are threaded through the iridectomy entering at the posterior border of the iris and exiting from the anterior border (Fig 1). Traction on the suture is applied by the surgeon with one hand (Fig 2) while the cryoextractor is

A new technique of cryoextraction employs an instrument with the freezing confined to the undersurface of the probe tip. The probe lip can be used to retract the iris and apply the freezing to the equator of the lens without the use of an iris retractor. Spread of surface ice is prevented and the warm sides of the probe will not damage the corneal endothelium if it is inadvertantly touched. No assistant is required to retract the cornea which is performed with the surgeons free hand. This hand can also be used to break the zonules or vitreous adhesions under direct vision. Corneal folding is minimized as its cut edge can lie on the probe sides. Extraction is more easily controlled. The new method obviates the few disadvantages of cryoextraction.

A cryoprobe working on the Joule Thomson principle using the expansion of carbon-dioxide gas is described. It is the first cryoprobe that can be applied to the lens at ambient temperature (room temperature) having almost instantaneous freezing and rewarming characteristics. Iris adhesion and laceration are virtually impossible. Automatic foot switch control as well as reserve freezing power, for difficult cases, are incorporated. The probe is light, small, and well-balanced and the tip is constantly visible. There is no gaseous carbon-dioxide discharge near the operative site. The probe has facilitated the technique of cryoextraction using a superior polar grip and iris retraction as first described by the author. The instrument is especially valuable in the extraction of dislocated, subluxated, and complicated cataracts.

WITH the increasing popularity of cryoextraction of cataracts, various methods have been described to deal with the iris in such a way that, when the tip of the cryoextractor is applied to the lens, there will be plenty of room so that the iris is not also frozen to the extractor. A sector iridectomy simplifies iris retraction but the problem remains that for a round pupil extraction some method of retraction of the lens, an absorbable sponge cut retractors have been devised for this purpose. This brief presentation reports a simplified method which has some advantages for lens extraction with either a round pupil or a sector iridectomy. When the surgeon is ready to begin extraction of the lens, an absorbable sponge cut in a triangular shape on the end of a small hemostat is inserted into the anterior chamber, and the excess fluid and aqueous is rapidly absorbed. A