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| ARTICLE |
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| Year : 1967 | Volume
: 15
| Issue : 6 | Page : 213-221 |
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Rapid eye surgical techniques
RI Pritikin
Rockford, Illinois, USA
| Date of Web Publication | 22-Jan-2008 |
Correspondence Address:
R I Pritikin
Rockford, Illinois
USA
 Source of Support: None, Conflict of Interest: None  | Check |
How to cite this article:
Pritikin R I. Rapid eye surgical techniques. Indian J Ophthalmol 1967;15:213-21 |
Several new ideas have been developed in the past few years in the never ending battle against blindness. These include rapid eye surgical techniques, electronic pencils for the blind, ultra-sound, cryosurgery, lasers, intravenous fluorescein in fundus photography of the eye, regular vs. applanation tonometry, and radioisotopes.
Diagnostic and surgical instruments have been developed to assist the work of rapid eye surgical techniques, so that eye surgeons can take care of many patients following a disaster resulting in mass casualties, particularly with the destruction of facilities. Instruments that have been developed include iris scissors, scleral punches [Figure - 1],a and corneal splints [Figure - 2] to facilitate rapidity of operations, as well as mulptiple-tip diathermy needles to be used in retinopexy. [Figure - 3].
The use of alpha-chymotrypsin has been further developed to make lens removal in cataract extraction much easier. Whereas in an ordinary forceps extraction 10% pull with the forceps and 90% push with the lens hook is exerted, the process is reversed when alpha-chymotrypsin solution is injected over the lens in a cataract extraction.
Some record advances which facilitate corneal surgery include:
(a) An improved automatic corneal trephine
(b) Refinements in the use of the operation telescope and microscope.
(c) A simplified method for preserving donor eyes for use in lamellar corneal transplantation.
(d) A sterile kit for the long term preservation of donor eyes.
There are currently four techniques for the preservation of donor corneas:
(1) Freezling, (2) dessication, (3) dehydration, (4) use of polyvinylpyrrolidone combined with freezing. A small Mass is now available into which has been fitted expanded styrene containing 1.5 gm. of molecular sieve and 11 cc. of anhydrous glycerine. The cornea with a rim of sclera is immersed and hermetically sealed in this vial, which has been sterilized by dry heat. Donor material may then be preserved for an indefinite period of time at room temperature. When the cornea is ready to be used for lamellar grafting it is removed from the glass container and placed in an antibiotic solution for reconstitution or rehydration.
Most artificial cornea studies prior to fifteen years ago were concentrated on full thickness implants that had the appearance of collar buttons. These implants were eventually extruded like any other foreign body. It was found that to keep implants in the cornea indefinitely they must lie as deeply as possible in an intra-lamellar stromal pocket, and have wide skirt-like appendages. This is a more hopeful type.
A non-magnetic foreign body deep in the eye presents great difficulties, especially if it cannot be seen because of hemorrhages in the eyeball or a cataractous lens which blocks vision on attempting to look into the eye. When surgical removal of a foreign body is indicated in an eye, precise information on the location of that foreign body is of importance. Usual localization is performed first with X-ray. Ultrasound as used in foreign body localization and other diagnostic techniques is fundamentally similar to sonar. Short bursts of high frequency sound are transmitted by a crystal loud-speaker. When the outgoing bundle of sound strikes an object in its path, a small amount is reflected as an echo and returns to the same crystal which also acts as a receiver. Echoes are obtained from nearly any material. Foreign bodies that are radiolucent are detected as readily as those that are radiopaque. The information is presented to the examiner visually on a television-like cathode ray tube screen. This may be photographed [Figure - 4],[Figure - 5].
For non-magnetic foreign bodies ultrasound offers an ideal method of guiding forceps to the object in the vitreous body of the eye, particularly when it is obscured by blood [Figure - 7]. When ultrasonic radiation penetrates into the eye, discontinuities in the tissue will affect them. If a tumor is located behind the retina, it gives an echo clearly distinguishable from that of the sclera. The speed of sound is relatively constant in soft tissue. Thus by knowing the time required for sound to reach the object and return, it is possible to determine the distance from the crystal to the object responsible for the sound. Since the bursts of inaudible sound are emitted 200 , times a second, even variable distances to a moving object can be measured accurately with ultrasound. When the depth of the field of search is limited, as for example in an eye where only three to four centimeters of tissue are examined, the beam of sound is not dispersed significantly, and it is essentially the diameter of the transmitting crystal. This directional characteristic of ultrasound is basic to its use in the localization of foreign bodies. Only when an object is in line with the axis of the beam that transmitted sound will an echo be detected. Thus, an object is localized in two planes by obtaining an echo when the search probe is held in alignment with it, and localization in terms of depth of the third plane is obtained simultaneously by measuring the time of travel of the reflected sound. Echo reflection depends solely upon the acoustic properties of substances in the path of the sound beam. Echoes are obtained from nearly any material, including glass, grass, stone, and even paper. Foreign bodies that are radiolucent in composition are for that reason detected as readily as those that are radiopaque. The use of ultrasound is completely painless. At the energy level employed for diagnostic purposes ultrasound is safe, even when repeated lengthy examinations are performed. When the machine is used with its television-like cathode ray tube screen, the echoes that are received by the crystal are converted into electrical energy, then amplified and displayed as deflections along a linear trace. In this time amplitude displayed, the distance of any echo deflection from the zero point is proportional to the travel time of the sound to the echo source and back to the crystal. The display may be photographed to obtain a permanant record known as an echogram. A polaroid camera is usually used for this purpose.
The technique for localizing extraocular foreign bodies is as follows: The one eighth inch external probe is held against the skin, using water or methylcellulose as a coupling medium. Liquid coupling is essential because sound of this frequency range travels poorly through air. Since fascial planes, muscles nerves, blood vessels and bones all present acoustic interfaces, echoes result from all of these, and a good cross-sectional knowledge of the anatomy of the area being searched is necessary to distinguish foreign body echoes from all others. Usually, however, a foreign body, especially if it has been recently introduced into the tissue, will produce a stronger echo than other structures and thus be readily recognized. The crystal requires a certain amount of time to recover following the "main bang". Consequently, an object very close to the surface cannot be detected because its echo is submerged in the "main bang" echo. However, it is usually possible to angle the probe obliquely, localizing the shallow foreign bodies by triangulation. Ultrasound should not be used to the exclusion of X-ray, the Berman locator, the Goldmann rings, or any other method. It is actually a supplement to existing methods [Figure - 4],[Figure - 5],[Figure - 6].
The purpose of the external localization is to select the best site for insertion of the extractor forceps. Two factors should be taken into consideration in making this selection. Since much more sound is reflected from a flat surface than from a pointed corner, and the echoes are therefore correspondingly stronger, it is well to determine the direction from which the strongest foreign body echo is obtained. The probe is placed at several potential points of entry, the foreign body is localized, and the amplitude of the foreign body echo as obtained from each direction is compared to find the most favourable route of approach. The condition of the eye also affects the available sites for insertion of the forceps. If the wound of entry has passed through the lens and a cataract is threatened, a standard cataract incision is made, and the lens material is expressed.
The extractor probe [Figure - 6],[Figure - 7] is then introduced at the point in the lens area from which the strongest foreign body echo is obtained. If the lens is clear, however, the extractor is introduced through the pars plana, after suitable application of diathermy again at the point where echo reception is maximal. When the extractor has been inserted into the vitreous, the jaws are opened enough to allow the free passage of sound from the crystal, and the instrument is angled toward the previously determined site of the foreign body, until the foreign body echo appears. Since the diameter of the beam of sound is approximately the diameter of the crystal, forceps must be pointing directly at the foreign body for an echo to appear. While the surgeon observes either the one inch or the five inch cathode ray tube, the extractor is slowly moved toward the object. If the echo grows smaller, forward movement should cease and the extractor should again be angled until a strong echo from the foreign body appears. Once the object is seen to be 5 mm. from the crystal, the forceps arc slowly closed, since the foreign body must now lie in the jaws of the forceps. The forceps, with the object, is then removed from the eye.
Cryosurgery depends on the precise use of extreme cold. Cryopexy is the name applied to the use of an application which causes sub-zero temperatures to penetrate through the retina to the choroid layer when applied to sclera, without damaging the scleral wall. This method was developed as a result of searching for a method to accomplish the objectives of diathermy without scleral or retinal damage and side effects. The intense cold of the crysosurgical probe can be applied through the whole thickness of the scleral wall without destroying its integrity. The need for scleral resection is reduced by this method. Cryopexy can be used in the treatment of impending retinal tears where coagulation is contraindicated because of lens changes or vitreous hemorrahage.
Although a cryosurgical probe had been developed some years ago, and it could be cooled to a temperature of -79°C, it could not be readily disengaged from the tissues until a temperature control could be developed that would raise the temperature swiftly.
For cryoextraction of cataract, solid carbon dioxide (-69° F) yields larger ice crystals with marked adhesive properties. However, an instrument was finally developed, based on the original work, in which a probe was placed in a mixture of CO 2 and alcohol. The new supercooled cryoextractor stays cooler longer and can be defrosted more rapidly. The usual operative cataract procedure is carried out, substituting the cryoextractor for the forceps. The tip is applied to the surface of the lens and adheres to it in a few seconds. The intact lens at the end of the instrument is then removed.
In glaucoma, cryocyclotherapy is used instead of cyclodiathermy. The application of a cooling agent to the ciliary body reduces the aqueous output by congelation instead of coagulation. In diathermy the needle penetrates partially into the sclera; in cryocyclotherapy the effect is milder and partially reversible.
Methods are being developed to use freezing techniques for burns of the cornea and the obliteration of blood vessels in eye diseases characterized by proliferation of blood vessels.
In searching the history to find out who first used cryosurgical techniques in ophthalmology, we note that in 1934 Bietti used the solid carbon dioxide in treating retinal detachment, but never followed up his early findings. In 1950 Bietti went a step further by applying solid carbon dioxide to the scleral region of the ciliary body for the treatment of glaucoma. The operative procedures used today are a refinement on the method reported in 1961 by Krwawicz who dipped a probe in a mixture of solid carbon dioxide and alcohol. The present-day cryoextractors, however, maintain their supercool temperature for much longer periods than the Krwawicz probe. An elaborate cryogenic device has been employed by Kelman and Cooper, consisting of a large monitoring and storage unit, and a long cannula with an applicator. The cryoextractor using carbon dioxide used by Dr. John Bellows is simpler. The Alcon Laboratories are perfecting a cryophake. This instrument is a small hand-held instrument that has a can of cryogen in it. At first the cans of cryogen were replaceable, and then an instrument was developed that would be used for just one cryoextraction and then discarded. This instrument does not use replaceable cans of cryogen, but is a single-use sterile disposable instrument. [Figure - 9].
| Summary | |  |
Diagnostic and surgical instruments have been developed to assist the work of rapid eye surgical techniques, so that eye surgeons can take care of many patients following a disaster resulting in mass casualties, particularly with the destruction of facilities. Instruments that have been developed include iris scissors scleral punches and corneal splints to facilitate rapidity of operations as well as multiple-tip diathermy needles to be used in retinopexy. Some recent advances which facilitate corneal surgery include:
(a) An improved automatic corneal trephine.
(b) Refinements in the use of the operation telescope and microscope.
(c) A simplified method for preserving donor eyes for use in lamellar corneal transplantation.
(d) A sterile kit for the long term preservation of donor eyes.
Ultrasound as used in foreign body localization and other diagnostic techniques is fundamentally similar to sonar. For non-magnetic foreign bodies ultrasound offers an ideal method of guiding forceps to the object in the vitreous body of the eye, particularly when it is obscured by blood. Cryosurgery depends on the precise use of extreme cold. Cryopexy is the name applied to the use of an application which causes sub-zero temperatures to penetrate through the retina to the choroid layer when applied to sclera, without damaging the scleral wall. For cryoextraction of cataract, solid carbon dioxide (- 69° F) yields larger ice crystals with marked adhesive properties. In glaucoma, cryocyclotherapy is used instead of cyclodiathermy. Methods are being developed to use freezing techniques for burns of the cornea and the obliteration of blood vessels in eye diseases characterized by proliferation of blood vessels.[4]
| References | | |
| 1. | BRONSON. N. R., Techniques of Ultrasonic Localization and Extraction. American Journal of Ophthalmology, October, 1965.  |
| 2. | PRITIKIN, R. I„ Multiple Retinal Detachment Electrodes, EENT Monthly. September, 1958. |
| 3. | PRITIKIN, R. I., Zonulysin and Instrumentation in Mass Eye Surgery, Military Medicine. June, 1961. |
| 4. | PRITIKIN, R. I., Injuries of the Lids: Management EENT Monthly, April, 1965; 44: 54-60. |
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9]
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