|Year : 1974 | Volume
| Issue : 4 | Page : 1-9
Cryo in ophthalmology
P Siva Reddy
Sarojini Devi Eye Hospital and Institute of Ophthalmology, Hyderabad, India
P Siva Reddy
Sarojini Devi Eye Hospital and Institute of Ophthalmology, Hyderabad (A.P.)
Source of Support: None, Conflict of Interest: None
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Reddy P S. Cryo in ophthalmology. Indian J Ophthalmol 1974;22:1-9
President, fellow members of All India Ophthalmological Society, Ladies and Gentlemen,
I am grateful to the scientific body of the All India Ophthalmological Society for giving me the opportunity to deliver this memorable and great oration. It is a coveted honour for any ophthalmologist of our country. It indicates the love, affection and the regard my collegues have, towards me and the amount of appreciation for my humble contributions to the science and practice of ophthalmology.
I have no words to praise the sincere efforts and purpose which promoted Mr. Cowasji Adenwalla to initiate this award through Dr. B.P. Banai, one of the stalwarts of Indian ophthalmology. The purpose for which the award was donated was both a sad and a memorable occasion. It is my previlage to recall the heroic death of Dinshaw on the beautiful beach of Juhu, where at the blooming age of 21 years Dinshaw met his glorious end, while saving the life of a drowning man. This loss of a young promising son of Cowasji Adenwalla, the founder of this award, was a rude and a treacherous shock. But as a gentle man even in his loss he used his vision in a noble manner, thanks to which we remember them and the social cause for which he dedicated this award. I see the honour of this oration has been now known, but what I shall present, subsequently is the work of not only myself but my staff of Sarojini Devi Eye Hospital and Institute of Ophthalmology Hyderabad, Andhra Pradesh.
CRYO SURGERY IN GENERAL
The word "Cryo" is derived from the Greek word "Kryos" meaning ice cold or frost. The time-worn saying that there is nothing new on the face of the earth is also applicable to medical research. When one contemplates a novel form of experimentation, a careful search of the literature usually discloses that this radical, wonderful concept had already been thought of and in all likelihood had been tried many times before. The therapeutic application of local cold is no exception.
For centuries a method of surgery has been sought which would permit the removal or destruction of diseased tissues without pain and risk of haemorrhage. This hope is closer to realisation with recent developments in cryo surgery. It has attracted the attention of the physicians and patients because it combines destruction of diseased tissue, anaesthesia, haemostasis and localisation. The sharp line of demarcation minimizes the injury to the surrounding structures and permits freezing of the diseased tissue to-180° C. By virtue of the formation of an ice ball between tissue and instrument giving rise to adhesiveness which permits the removal of cataracts more safely than with conventional methods.
The use of cryogenic temperatures has become important in the field of ophthalmology for several reasons. First, the eye is easily accessible for treatment and lends itself easily to investigative efforts. Secondly, within the eye there are many structures, all of which react in different ways to low temperature. Thirdly, recent advances in low temperature physics have facilitated delivery of freezing temperature to small areas with instruments refined enough to be suitable for the ophthalmic surgeon.
During evolution different ophthalmologists have designed different cryo instruments and perfection is still in progress.
Various refrigerants used are solid carbondioxide, carbondioxide snow, liquid nitrogen and nitrous oxide etc.
I. Cryo Extraction of Cataract
Although the cryo extraction of cataract has been introduced only recently, it is becoming more and more popular and the surgeons who have adopted this method of operation are of the opinion that all kinds of cataracts can be removed intra capsularly with great safety.
Cryo surgery of cataract is not a bold or risky method but a procedure dictated by cautiousness on one condition that the established rules are strictly observed. When using cryo extraction, the operator can abide by his favourite technique which need not undergo any essential change.
Cryo extraction has brought about essential progress in cataract surgery, with a distinct improvement in the results and a decrease in the percentage of complications. Compared with other methods cryo extraction gives the best results as far as the visual acuity is concerned. The capsule is always removed as a whole, and the risk of rupturing is considerably reduced.
Ever growing experience has shown that cryo extraction is a method that spares the ocular tissues an unnecessary trauma, by enabling the surgeon to operate more delicately than has so far been possible. It has also been found out that this operation can be simplified to a degree which goes far beyond our early expectations. There is now no need for wide section or counter pressure during the delivery of the lens.
It is not necessary to have extra assistance than is required for the traditional methods of cataract extraction. Thanks to this modified technique almost the whole burden of the operation can now be placed on the surgeon. The assistant can be freed from the very responsible function of pulling the iris upwards with the retractor. We do not now feel any need for the use of such instruments.
The indications for cryo extraction comprise now all types of cataract, including complicated cataracts. Virtually no contraindications are known, which means that in all cases in which the intra capsular technique of cataract extraction was formerly used cryo surgery will always give better results.
The essential danger of cryo extraction might lie as was intially feared, in the transmission of low temperature to other parts of eye causing damage to the surrounding tissues. The temperature of the tissues which surround the lens, during experimental cryo extraction, has proved to be virturally the same as when the traditional methods of cataract extraction are used.
Accidental touching of the adjacent tissues, especially of the iris, with the cold cryo extractor is an infrequent and rather harmless complication, as the adhesion can be instantaneously abolished by washing the point of contact with the stream of physiological saline or by activating the defrosting system. Such incidental freezing of the iris or cornea is usually of no importance for the visual acuity.
All instances of progress in cataract surgery are important, and that represented by cryo extraction is especially so because every year thousands of patients can be operated upon without the fear of capsular complications and with increasingly good results.
Out of these 400 cases were studied and followed up from 1st October, 1972 to 30th September, 1973. The cases were followed weekly in the begining up to six weeks and later on i.e. after prescription of glasses they were examined fortnightly.
Clinical Experience: At Our Institute so far we have done 11,737 cryo extraction of cataracts during the period from 14th May, 1969 to 29th November, 1973. These extractions include some immature and intumescent cataracts which means that with cryo we can operate upon patients who earlier would have to wait until their cataracts have matured. The average per cent of intracapsular cryo extraction as can be seen from our clinical material is 96.9% whereas in the world literature it is a 98%. The incidence of capsular rupture occured in 3.1% of the cases and vitreous loss in 2.5% of the cases. [Table - 1],[Table - 2],[Table - 3],[Table - 4],[Table - 5].
As we found that the cryo extraction of lens was quite safe, we carried the equipment to the districts and taluqs also. This helped us to perform extraction of lens safely and at a faster rate. During the year 1972-73 we have done 3536 cataract extractions in eye camps.
II. Cryo Retinopexy
The experience of several ophthalmologists lead to the conclusion that the cryo retinopexy is indicated for prophylaxis and the management of the rhegmatogenous retinal detachment in general and particularly the following conditions.
1. Prophylaxis: When a large area of lattice degeneration is to be treated or when retinal breaks are numerous and also when the breaks are large in size, cryo is useful. Since extensive treatment is required in such cases, it is particularly desirable to avoid methods associated with generation of heat.
2. Curative: It is indicated in the following conditions
(a) When there is haziness of the ocular media; the visibility is poor, and the laser can not be used, (b) when there is massive preretinal organisation or starfold formation. In such cases one may welcome a form of treatment not involving heat which is likely to aggravate the existing condition. (c) when the pathology of sclera is discovered. If staphyloma or necrosis of sclera is encountered the use of cryo therapy avoids further damage to the sclera already in poor condition.
3. Cryo surgery is very useful in the management of following: (a) anteriorly located tears. (b) tears at the region of vortex veins and at the large ciliary vessels.
(i) Difficulty has been encountered in the visualisation of minimal lesions of cryo in the early post operative stage. (2) There is a greater degree of retinal and choroidal atrophy following the production of lesions greater than minimal. (3) There is increased incidence of choroidal haemorrhage. (4) Continuous cryo application may result in considerable destruction of the normal structures of the choroid and the retina. (5) The size of the standard cryo probe which is being used is always larger and more voluminous which gives larger area of cryo reaction which may be dangerous. (6) Cryo application results in less stronger chorioretinal adhesions than diathermy.
At our institute 58 cases of cryo retinopexy alongwith other operations like encircling or scleral plumbing were done and 30 cases of cryo retinopexy were followed for a period of 3 years. [Table - 6]
From the [Table - 7] it is observed that improvement of vision beyond 6/24 could not be achieved in 43% of the cases due to the retinal detachment of long duration.
Cryo surgery has definite advantages for certain specific cases, namely (1) as the prophylactic treatment of retinal breaks or retinal degenerations when they are located in the anterior portion of the fundus i.e. anterior to the equator because in that case you do cryo surgery transconjunctivally without opening the conjunctiva, (2) when sclera is very thin or when there is a weak sclera or when the sclera has been considerably damaged by previous surgery or by further thinning (scleral undermining) of the weak sclera one may run into complications such as hemorrhage or rupture of the globe. In my opinion, these are the two main indications for cryo surgery in retinal work.
III. Study of Cyclocryotherapy in advanced Glaucoma
The cases of this study were selected from the patients attending the glaucoma clinic in Sarojini Devi Eye Hospital and Institute of Ophthalmology, Hyderabad. These patients were selected at random and were found to be between the ages of 40-89 years. A detailed examination was carried out in each case.
Cyclocryo therapy was done in 35 eyes suffering from various type of glaucoma [Table - 8]
Medical therapy was stopped in advance in all these cases. Keeler's Amoil surgical unit using nitrous oxide as a coolant was employed in the study and the temperature was kept at -80° C. The 3 mm. tip of the probe was placed on the conjunctival surface of the the eyes, the edge of the probe being about 3 mm. from the limbus. Only one half of the globe i.e. lower half was treated with six applications.
The other half was kept aside for a second sitting if necessary.
In two patients the procedure was repeated twice and in an other patient this procedure had to be repeated thrice to bring down the intra ocular pressure. The cases were followed upto the period of 13 months. In the postoperative period the cases were kept on local antibiotic drops. The study of the reaction of the eye to the operative insult, estimation of visual acuity, fundus and slit lamp examination and measurement of intra ocular pressure were attempted in all the cases in the post operative period.
From [Table - 9],[Table - 10] it can be inferred that the eyes which had raised tension previously have shown a definite fall in the post operative period. Normalisation of intra ocular pressure was seen in only 18 eyes (51.4%).
IV. Experimental study
Experimental study of the effect of cyclocryotherapy on aqueous dynamics in normal and artifically induced glaucomatous rabbit's eyes was conducted.
The purpose of this investigation was to obtain tonographic information concerning the changes in aqueous production and outflow facility in normal and artificially induced glaucomatous rabbit's eyes following local freezing of the ciliary body and to study the histological changes that occur as a result of this procedure. Accordingly the experiments are made in two phases. The first phase involving the production of experimental glaucoma and a second phase wherein the effects of cyclocryotherapy on glaucomatous rabbits eyes are studied.
Tonometry :-Animal was anaesthetised with intra-venous sodium pentathol (30 mg per Kg. body weight) and instillation of a few drops of anethane. Two recordings were made one with 5.5 gms. and other with 7.5 gms. weight. Four minute tonography was performed to record the "C" value.
The I.O.P. was recorded in each eye of every rabbit on at least three occasions before the first subconjunctival injection was given and at weekly intervals thereafter until the experiment were terminated. The intraocular pressures are followed graphically.
Subconjunctival injection : Rabbits after being anaesthetised as before, the sclerosing agent (5% phenol in almond oil) is injected into the episcleral tissue through the conjunctiva. The injections are made in each quadrant with one c.c. of fluid. They are repeated at two weeks interval if necessary. The injections are given in only one eye of each rabbit leaving the other as control. After the experimental glaucoma had set in two of the rabbits were killed and their eyes were sent for histological study. The remaining rabbits were taken for the second phase of the experiment.
Normal I.O.P. in 40 eyes of 20 pigmented rabbits showed an average value of 19 mm Hg. Average "C" value obtained from 4 minute tonography was 0.26 on the average.
The average "C" value obtained from recordings on 20 injected eyes was 0.08 as against the average "C" Value of 0.26 in 20 control eyes.
Histologic picture : Histology of angle of anterior chamber and ciliary body of injected eyes was studied by enucleating them after a steady rise in intra ocular pressure was obtained. The angle was found to remain open with no evidence of any iridocyclitis.
The applications were done with a cryoprobe of 3 mm in diameter lasting for 20 seconds resulting in a temperature of -80°C. These were applied 1 mm away from limbus on the conjunctiva. 4 groups of animals were given applications over varying extent of the circumference of the limbus.
I.O.P. was measured once in two days and tonography performed once in a week for the first 14 days. Thereafter tonometry was done twice a week and tonography once a week.
Thus cyclocryotherapy was done in each rabbit on the normal as well as on the glaucomatous eye. The extent of application was same in both eyes of each rabbit.
Group I : Cyclocryotherapy given over half the circumference of the limbus (7 applications)
This procedure reduced the I.O.P. in the control eye by 8 mm. Hg. and of the glaucomatous eye by 20 mm Hg.
Group II : Cyclocryotherapy done over 3/4 of the circumference of the limbus (10 applications). This procedure caused a reduction of 15 mm. Hg. in I.O.P. of control eye and reduction of 26 mm. Hg. in the glaucomatous eye.
Group III : Cyclocryotherapy done over the whole of the circumference of the limbus (12 applications). This procedure resulted in phthisis of all the four control eyes whereas the glaucomatous eye reached a level of I.O.P. which is 28 mm Hg. below the pre-operative tension.
Group IV : An initial treatment of cyclocryotherapy was given over half of the circumference of the limbus followed after six weeks by a second series of application over the other half of the circumference. This two stages application of cryo resulted in an I.O.P. 13 mm below the pre-operative level in the glaucomatous eye. This steady level was obtained 9 weeks after the initial and 3 weeks after the final cryo application. [Table - 11]
The first specimen was taken four hours after the applications of cryo. The sections revealed much swelling of the ciliary processes due to oedema. Here and there were few haemorrhages in the stroma of the ciliary processes. The pigmented and non-pigmented epithelium showed areas of destruction. Iris blood vessels showed congestion with exudation in and around the iris tissue.
Second specimen taken one week after applications showed considerable re-epithelialisation of the ciliary processes. Few inflamatory cells are seen scattered under the basal layer in the stroma.
Third specimen taken 18 days after applications showed complete regeneration of the epithelium. There were areas of hyperplasia of pigmented epithelium. The histological changes occuring after cryo were same in normal as well as glaucomatous eyes.
Discussion and results : Glacuoma resulted in all the 20 eyes of rabbits injected with sclerosing agent. An I.O.P. of 54 mm Hg on the average could be obtained and was sustained for a period of 12 weeks after injection.
The average C value obtained after establishment of glaucoma (0.08) was far below the initial C. value (0.26) indicating effective obliteration of out flow channels. The I.O.P. in the control eyes were remained normal. The injected eyes did not show any gross ocular damage which rules out any possibility of glaucoma being secondary in nature.
The results of the second phase of the experiment revealed that a state of permanent hypotension can be produced in glaucomatous rabbits eyes by cyclocryotherapy just as it was in normal rabbit eyes. [Table - 11]
The effect of cyclocryotherapy done over half the circumference was not satisfactory in a glaucomoatous eye even though it was able to cause hypotension in a normal eye. This is because the fall in I.O.P. obtained by this procedure in a glaucomatous eye leaves the eye with a tension far above the normal permissible level of I. O. P.
Comments : As said at the the outset the main idea of these experiments is to bridge the gap between the eye of experimental animal and diseased human eye. By producing an open angle glaucoma in rabbits eye and then succeeding in causing a lasting hypotensive state in them by means of cyclocryotherapy, should raise hopes of confident clinical trial in early human chronic simple glaucoma apart from the very late cases of glaucoma to which cyclocryotherapy is applied hitherto.
V. Cryo therapy of corneal ulcers
Our experience in cryo therapy is limited to 40 eases. As the number of the patients is very small, it needs further study of new cases and follow up of old cases. However, it can be said that cryo therapy in corneal ulcers is of some help. It helps in the following ways:
1. Ulcer is made more accessable to the antibiotic used. 2. It removes collagenase which destroys the stroma. 3. Necrotic slough is removed which helps in healing of the ulcer. 4. It exposes any corneal abscess if present. 5. The fact that freezing and thawing changes the constitution of the virus in the lesion and temporarily halts the function of D. N. A. and R. N. A. of the virus and the epithelial cells.
VI. Indications for cryo therapy in miscellaneous ophthalmic conditions
1. Spring catarrah 2. Pterygium 3. Corneal vascularisation 4. Post cataract blebs 5. In performing Iridectomies 6. Iris prolapse 7. Tumour biopsy 8. Treatment of tumours by freezing 9. Solidification of lid tumour during excision 10. Enucleation 11. Cryo preservation of corneal tissue 12. Peripheral uveoretinitis.
Conclusions : The more-we know, the more we realise how little do we know. I dedicate this oration to our young ophthalmologists in the hope that they will unreveal many more facts of cryo in ophthalmology which we are ignorant about at present.
Friends and guests before I conclude I would like to gratefully acknowledge the great help afforded by our well knit band of young ophthalmologists working with me in all special clinics of our institution.
[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5], [Table - 6], [Table - 7], [Table - 8], [Table - 9], [Table - 10], [Table - 11]