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Lens capsule thickness was measured in 105 cataractous lenses with and without exfoliation syndrome. The lenses were removed by intracapsular cryoextraction. Forty lenses (38%) showed exfoliation, while 65 (62%) were exfoliation negative. Thickness values were measured by light microscopy from the central anterior capsule, central posterior capsule and from the equator. The mean thickness values were for the central anterior capsule 8.2 ± 3.2 μ, for the central posterior capsule 3.2 ± 1.4 and for the equator 3.9 ± 1.3. There was no statistical difference between the exfoliation-positive and exfoliation-negative lenses. The capsule thickness varied greatly throughout the present material. The highest value, 22.4 μ, was measured from an exfoliation-negative central anterior lens capsule of a male patient aged 33 years. The lowest value, 0.6 μ, was measured from an exfoliation-positive central posterior capsule of a male patient aged 64 years. The central posterior capsule is the thinnest area of the lens capsule. The findings call for great caution in polishing the posterior capsule during extracapsular cataract surgery. The higher complication rate in eyes with exfoliation syndrome cannot be explained by thinner lens capsules but rather on the more friable zonules.

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

SUMMARY We developed the new iris retractor for the cryolens extraction under the microscope.

To the Editor: It is amazing that Dr. Andrew de Roetth, whose work and opinion is so much respected, should so lightly dismiss recent progress in adapting cryosurgical techniques in ophthalmology with apparently little knowledge of the procedures and principles involved in cryoextraction (Arch Ophthal 72 :590-91, 1964). Much of the blame for this must certainly rest with those of us who have worked in this field, for remarkably little has appeared in the literature, to date, on this subject. Perhaps we are always skeptical of those who too forcefully endorse a surgical technique and have hesitated to "push" our own work into this category. Perhaps, too, we have been too cautious in claiming for cryoextraction the excellent results that can (and have) been demonstrated. Finally, instrumentation has only recently been refined to the point at which it may be used by any competent ophthalmic surgeon. My experience with cryosurgical

To the Editor: I have received several inquiries about the sterility of the cryogens used in the cryoextractors described in "Indications and Technique of Cryoextraction" (Arch Ophthal, April 1965). When the cryogens employed with my instruments (solid carbon dioxide and liquid nitrogen) are used in the manner described, there is an excellent assurance of asepsis because: Repeated commercial and hospital bacteriological tests of the cryogens have been consistently negative for bacteria, fungi, molds, and spores. I have performed more than 200 operations using solid CO 2 and liquid N 2 without a single incidence of infection. The number of these instruments that have been sold is now well over 200, and there has not been any report of infections following their use. Admittedly, extreme cold does not kill all infectious agents, for some bacteria, molds, and spores resist even extremely low temperatures. However, in the process of manufacture, the cryogens are purified

From the seemingly infinite variety of techniques employed in cataract surgery, Dr. Havener has chosen to present in this book those techniques he finds most useful. A combined descriptive and pictorial format is used to show each step of the surgery. Discussions are very complete and meticulously precise. The illustrations by Sallie Gloeckner are superb, combining half-tone realistic drawings of the surgeon's view of the eye with graphic cross-sectional drawings of the same procedures. Every basic aspect of cataract surgery is covered beginning with premedication, cleaning and draping the eye, and local anesthesia. Readers will seldom find such a detailed description of these important, but often underplayed, preliminary steps. The operative procedures described include conjunctival flaps, corneoscleral incisions by several methods, details of suture placement, iridectomy, and use of alpha-chymotrypsin. Lens extraction is presented by methods of cryoextraction, erisophake, and forceps delivery. Although several alternative procedures are mentioned, Dr. Havener

To the Editor. —Wirtschafter and Sohmer have documented the electrical hazards of cryoextraction in theArchives(87:117, 1972). A potential mechanical hazard also exists with the same instrument. On July 25, 1972, cataract extraction with the patient under local anesthesia was attempted using the Amoils curved cataract probe. Following the usual testing of ice-ball formation by activating the instrument against a drop of saline, the probe was placed on the lens while warm. Immediately upon activation of the foot switch, a marked air explosion occurred at the probe tip. The explosion, caused by fracture of the probe tip, propelled the 1-cm segment of broken probe tip, the lens, and a large amount of compressed carbon dioxide gas into the vitreous cavity, with displacement of the vitreous body out over the scleral wound lip. After the cornea was again elevated, the CO 2 gas escaped from the eye, most of

To the Editor. —John M. McLean, MD, is to be complimented on his editorial "Cryosurgery in Ophthalmology" in the June 1967 issue of theArchives( 77 :715). The interest in cryosurgery is evidenced by the numerous reports and discussions at clinical meetings. In contrast to some writers who have magnified the dangers and difficulties of cryoextraction, Dr. McLean finds only minor objections. Two of the procedural modifications termed "drawbacks" in the editorial actually may be advantageous to the surgeon: Thus grasping the lens superiorly in cryoextraction allows this procedure to be performed under direct vision. Retracting the cornea more than usual causes less trauma than tucking the cornea against the cataract and instrument as required in the tumbling procedure. Striate keratitis rarely occurs after cryoextraction. Admittedly the iris presents a problem particularly in round pupil cyroextractions. Iris freezing can be avoided by (1) adequate iris retraction, (2) careful placement of

The final status of cryoextraction of the lens and the application of cryotechniques to other forms of ophthalmic surgery is not yet clear. Therefore we welcome comments from those who have had experience. Dr. Kelman, one of the pioneers in this country, has provided an excellent atlas of his own techniques. It should be studied by all attempting cryoextraction for the first time and is worth review even by those who have had considerable experience. Reference is almost entirely to the author's own instrument which many operators find clumsy to use. A comparative analysis of the good and bad features of currently available instruments would have been helpful. Whether or not the use of cryoextraction significantly reduces the number of complications in cataract surgery can not be stated. Dr. Kelman discusses complications which may occur at the operating table but I know of no longterm comparative studies between this and

The symposium on cataracts, held by the New Orleans Academy of Ophthalmology in 1964, must have been as interesting a meeting as that held in 1957. Enzymatic zonulolysis and the use of high magnification for intraocular surgery are thoroughly analyzed, but little mention is made of cryoextraction. The older problems of congenital cataracts, surgical technique, wound healing, and the complications of cataract extraction are reevaluated. Both the individual presentations and the lively round table discussions contain much useful information. McDonald reports on congenital cataracts, McCaslin discusses complicated cataracts and their surgery, and McLean gives, in detail, his surgical technique for cataract extraction. Zonulolysis and high magnification for cataract extraction are described by Troutman, who, with Willard, reports on the management of the aphakic patient. The complications of cataract extraction, their prevention, and their management are discussed by Boyd, Christensen, and Irvine, Jr. In this volume there is a wealth of