An experimantal study of cryoapplication on ocular tissues

Kim, Hee ChuI

Abstract

Cryosurgery has been used with a measure of success recently in several fields of medicine. In ophthalmology, cryosurgery has been employed during the past year in the treatment of corneal neovascularizations, retinal detachments, cataracts, and glaucoma. It is the purpose of this paper to demonstrate the importance and potentialities of cryogenics in the treatment of ocular diseases. The instrument used is a modification of the one used by Veil in 1928. Dry ice is cut to size with a hammer and chisel and the chamber of the cryocautery is filled two thirds with ice chips. Approximately 5.00cc of acetone are then added and the top is tightly closed. This instrument was used experimentally upon five anesthetized rabbits to observe the effects of cryoapplication on the cornea, ciliary body, choroid and retina. The cryoinstrument was applied to the center of the cornea, and the exposed surface of the sclera corresponding to the sites of the ciliary body and the choroid. The cryoapplication lasted one minute to the right eye and five minutes to the left eye in each rabbit. The ocular tissues were observed with a loupe, ophthalmoscope, and slitlamp. At varing intervals of time, that is, 12 hours, 60 hours, and 21 days respectively after cryoapplications, eyes were enucleated for sectioning and microscopic study. The results of this experiments will be described as follows: The application of the supercooled silver tip to the epithelial surface of the cornea produced an immediate whitish opaque area of congealment. This grossly visible effect immedately disappeared upon the removal of the applicator from the epithelial surface, leaving merely an area that was fenuded of epithelium. The corneal epithelium was completely regenerated and the cornea possessed normal clarity within three weeks. Microscopic pictures of the ciliary body, showed a moderate degree of edema and congestion of the ciliary processes as initial findings. But later, histologically the ciliary body in the treated area showed signs of endarteritis obliterans. A congealed area was observed on the sclera and retina correspoding to the place of contact. In the sclera this was denoted by an increased opaqueness of the tissue. In the fundus, the normal retinal markings, including the retinal vessels were temporarily obliterated. But a microscopic picture of the choroid and retina showed a change that it consist of a marked adhesive chorioretinitis leaving chorioretinal scar. In all instances, in comparison with the duration of the cryoapplication for one minute to the right eye and five minutes to the left eye showed less severe destructive changes in the former than in the latter. In general, the histological studies demonstrate a considerable destruction of the smaller blood vessels and capiHaries, while the larger vessels are less involved. It can be naturally deduced that the results of my experiment and the views of other authors will give a suggestion, if we can set on the desirable condition in the degree and the time of cryoapplication, that this method is a valuable to be applied in the retinal detachment and glaucoma surgery with safety and accuracy. Minimizing of corneal neovascularizations prior to keratoplasty would improve the chances of success. In retinal detachment surgery the cryoapplication produces an exudative reaction similar to that seen with diathermy. It appears to have the advantage of being more selective and producing less cell damage than diathermy. In cataract surgery. cryocautery has been used to freeze the lens in situ, thus facilitating the extraction of a hard, frozen lensrather than a soft, fragile lens as is the case in the more orthodox fashion. In the field of the glaucoma therapy, it suggest that the application of subfreezing temperatures to the ciliary body results in a decreased rate of aqueous flow resembling the changes observed when cyclodiathermy was used. The use of cold is more selective in nature and less destructive than cyclodiathermy and therefore seems to have less complications and fewer disadvantages. Although, the author has some information concerning the effect of cold on a few isolated eye tissues, the author still do not know what cryocautery will do to all of the ocular tissues that we encounter. It is hoped that this report will stimulate others to explore the use of cryogenics in opthalmology.

An experimantal study of cryoapplication on ocular tissues

Abstract

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