|Year : 1959 | Volume
| Issue : 2 | Page : 43-51
Photocoagulation in ophthalmology
Ophthalmological Clinic of the University of Ghent, Belgium
|Date of Web Publication||7-May-2008|
Ophthalmological Clinic of the University of Ghent
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Francois J. Photocoagulation in ophthalmology. Indian J Ophthalmol 1959;7:43-51
Photocoagulation,as developed by MEYER-SCHWICKERATH (1949, 1954, 1957), has proved to be of paramount importance in ophthalmological treatment.
Today it can be effected with the aid of the apparatus developed by the firm of Carl ZEISS under the guidance of Dr. LITTMANN. [Figure - 1] presents a diagram of the special arc lamp, showing the source and the path of light. An image of the arc lamp crater is formed by the lens system (L 1 ) in the diaphragm(B) ; from this aerial image at (B), a second image is formed on the patient's fundus by the eye-piece (L 2 ) and the mirror (Sp). The crater image on the fundus is observed through a hole in the mirror. This hole has a diameter of only 0.75 mm. so as not to blind the observer. The size of the diaphragm (B) can be varied in order to produce coagulations of different sizes. The largest possible coagulation covers an area of half a disc diameter. Errors of refraction in the patient's eye which exceed 5 dioptres are corrected by a contact lens. The fundus observations are made in subdued light.
The apparatus is used as an ophthalmoscope which provides a light so vivid as to produce coagulation at the point observed and lighted [Figure - 2].
This is the principle of photocoagulation. Owing to the transparency of the refringent media it is possible to apply a radiating energy to the eye without any considerable loss. This transparency, however, only applies to part of the electromagnetic spectrum, i.e. to visible light and to part of the short infra-red waves, viz. radiations between 300 and 1000mµ.
Outside this range, radiations are not only useless but even dangerous, as ultra-violet rays may produce corneal lesions, while infra-red rays may cause lenticular injuries.
Using visible radiation, there is no affection of the transparent media when the radiations only traverse them, are dispersed or even reflected. The electromagnetic wave only acts on the point of absorption, i.e. there is photocoagulation only at the site at which the light is absorbed.
In the normal eye, this absorption prevails at the level of the pigmented epithelium and the choroid, i.e. in tissues of relatively dark coloration. The adjacent retina is in such close contact with the tissues which have absorbed the light that it is simultaneously coagulated by the heat released.
When the retina is subject to detachment it absorbs so few of the light waves that photocoagulation is a rule impossible.
On the other hand, the efficacy of photocoagulation is limited due to the fact that the heat liberated is rapidly transported via the blood vessels.
The quantity of light which is transformed into heat during absorption must be of great importance in attaining the temperature of coagulation at a certain point. Also, coagulation can only be effected with light waves of a very high density of radiation.
1. Maximal dilation of the pupil with the aid of atropine and phenylephrine.
2. Immobilization of the eye by injection of procaine into the four muscles.
3. Constant wetting of the cornea with physiological saline throughout the intervention.
4. If the retinal periphery is to be coagulated, then the sclera must be depressed with the aid of a strabismus hook.
5.The duration of coagulation is only 1/5 second for the macular region, and 1/2 second for the periphery.
Photocoagulation is indicated in the case of macular perforation, peripheral retinal tears, cystic degeneration of the retina, retinal periphlebitis, melanosarcoma of the choroid, carcinomatous metastases in the ocular fundus, choroid angioma, retinoblastoma, phacoma of the ocular fundus, COATS' retinopathy, choroiditis, etc.
| 1. Macular Perforations|| |
Macular perforations, whether traumatic or spontaneous, constitute one of the best indications for photocoagulation. The difficulty of obturation of a macular perforation by diathermy is well-known. Even if the intervention succeeds, moreover, central vision is as a rule abolished.
Photocoagulation causes only a very small scar, which often makes it possible to preserve central vision in a more or less considerable degree. It is more effective, moreover, as demonstrated by the 90% success rate obtained by MEYER-SCHWICKERATH.
Photocoagulation of the macular perforation should meet the following requirements [Figure - 3] :
1. The retina should not be too far from the layer of tissue which absorbs the light, i.e. the choroid and pigmented epithelium ; the intervening distance should not exceed 1 - 2 dioptres (1 mm.at the maximum).
2.Coagulation shuld be brief, so as to exert no destructive influence ; 1/10 to 1/4 second is sufficient.
3.The focus of coagulation should be slightly larger than the perforation.
Among other things, it is of importance to coagulate the choroid through the perforation, using a diaphragm smaller than the latter ; this ensures a more favourable cicatricial reaction.
| Peripheral Retinal Tears|| |
Peripheral retinal tears are amenable to photocoagulation if not associated with detachment of the retina.
It is not uncommon to find such tears, particularly in the eye contralateral to the one that shows detachment of the retina ; in fact, such detachment becomes bilateral in 20% of cases.
Case 1. V., Leontine, aged 53, showed myopic choroiditis of the right eye. Vision was 0.8 (6/7.5) after correction (-9 d.).
Vision on the left had been disturbed for a few days. Ophthalmoscopic examination showed a retinal tear, surrounded by hxmorrhages in the superotemporal peripheral region (near one o'clock). The torn flap of retina was seen opposite the tear, inside the vitreous. There was no detachment. Vision was 6/6o after correction (-7 d.).
The retina was photocoagulated around the tear, and the choroid through the laceration. It was considerably more distinctly outlined after coagulation [Figure - 4]
Pigmentation of the region in question was seen after a week, and cicatrization was virtually completed 8 days later [Figure - 5] Vision was restored to 0.7 (6/9)
In certain patients predisposed to retinal detachment, degenerative changes (and more particularly microcystic degenerations) are seen in the retinal periphery. Photocoagulation constitutes the preventive measure of choice.It is not sufficient to destroy the lesions proper ; instead, a real barrier should be created all around the lesions.
If lesions affect the larger part of the retinal circumference, no attempt must be made to coagulate them all in one session. To begin with, about to I- of the circumference should be destroyed; another I may be treated two days later, and so forth until destruction is completed.
Photocoagulation is also indicated in the case of true detachment, which can be restored by bed rest and immobilization of the eyes effected by a binocular bandage rather than by means of a pair of stenopaeic spectacles; 20% of retinal detachments of not more than two months standing can be completely restored. It should not be overlooked, however, that photocoagulation is not only ineffective but even dangerous when the retina is more than 2 dioptres away from the choroids, in which case it may cause new defects.
Simple puncture of the pouch formed by detachment leads to reattachment of the retina only in exceptional cases.
It may also be that, after an operation for retinal detachment, after simple diathermocoagulation or coagulation with scleral resection, the tear proves to have been only partly touched and incompletely filled. Closure can then be finished with the aid of photocoagulation, which may be carried out immediately at the end of the operation, or a few days later.
| Retinal Periphlebitis|| |
No known effective medical treatment exists for retinal periphlebitis, the cause of which is still obscure. The condition involves a serious affection, as a rule, of both eyes and often involving loss of vision due to proliferative retinitis or recurrent haemorrhage into the vitreous.
On the other hand, it is known that diathermocoagulation of the lesions in question can lead to a lasting cure ( FRANCESCHETTI, 1954 ). It is not surprising, therefore, that even better results can be obtained by photocoagulation, which can be carried out in a simpler fashion, more precisely directed and directly affecting the internal membranes of the eyeball.
We have used this technique in 6 cases of periphlebitis, and obtained perfect cicatrization in all cases. Obviously, the prognosis is more favourable in the initial stages, before proliferative retinitis occurs, although this, too, is susceptible to improvement when treated by photocoagulation.
This can be applied even in cases in which the lesi9ns involve the posterior pole. A cure may be obtained, and'central vision can be preserved.
The great advantage of photocoagulation is that it can be repeated as often as necessary. The least relapse or the slightest spread of lesions can be immediately controlled. Transcleral diathermocoagulation - a veritable operation-cannot be so readily and so frequently repeated.
| Melanosarcoma of the Choroid|| |
For 25 years WEWE (1952) has treated certain cases of melanosarcoma of the choroid by diathermocoagulation ; his pupil MELCHERS reported on 20 cures obtained by this method, with not a single death due to metastases.
In these cases, too, it is not surprising that photocoagulation may also give satisfactory results, particularly since the pigmented tumours are -unusually favourable in this respect, as they are highly light-absorbing.
MEYER-SCHWICKERATH obtained several cures by his method, the oldest dating back to 1952 ; vision was perfectly preserved, and no relapse has so far occurred.
We have treated 5 cases of melanosarcoma of the choroid. Two patients were apparently cured ( one with inferotemporal peripheral sarcoma and the other with parapapillary sarcoma; follow-up periods, however, are still insufficiently prolonged to warrant confirmation of a definite cure.
In one case, photocoagulation failed to cause disappearance of the tumour, which had already become rather voluminous ; this patient had to be submitted to enucleation of the eye. The remaining two cases are still under treatment ; developments have so far seemed favourable.
Coagulation should be commenced by forming a ring around the entire outline of the tumour, in the unaffected retina, so that all choroid vessels are coagulated. Only after this can the tumour itself be coagulated.
The first series of coagulations can only be expected to have limited results, as the retina almost instantly becomes white, reflecting the light applied. This white coloration disappears at the end of about two weeks.
One month after the first, a second series of coagulations is applied. The light absorption is then so intensive sometimes as to cause a real eruption of tissue fluids, recognizable by the appearance of bullae.
Photocoagulation is thus repeated every month, five or six times if necessary, until the desired effect has been obtained.
If photocoagulation is to be used with success, the tumour should not affect more than one quadrant of the fundus, and its thickness should not exceed 12-15 dioptres.
The following are two personal observations on sarcomata of the choroid cured by photocoagulation.
Case I. Mrs. D. R., aged 42 ½ , showed a prominent new growth on the inferior periphery of the right retina ( 6-8 o'clock ) ; the growth was grey in colour, with an irregular surface and showing a number of haemorrhages. Since scleral diaphanoscopy was negative, a sarcoma of the choroid was diagnosed [Figure - 6].
Two photocoagulations at a two-month interval sufficed to cause a complete cure [Figure - 7],[Figure - 8].
Case II. Mrs. F. H., aged 48, showed an incipient choroid sarcoma localized below the blind spot [Figure - 9] and giving rise to a large paracentral scotoma ; central vision remaining amounted to Io/Io.
Five series of photocoagulations applied at intervals of 4-6 weeks led to complete recovery [Figure - 10],[Figure - 11]. The field of vision showed a fascicular defect, but vision was still 10/10.
| 5. Carcinomatous Metastases of the Choroid|| |
When confronted with a cancerous metastasis of the choroid, regardless of whether the primary tumour is a cancer of the breast or of another organ, the choice can only be between enucleation of the eye, which is useless from a vital point of view, and its complete destruction. Photocoagulation of such tumours of metastatic origin is the more clearly indicated the more other metastases of the primary tumour are radiosensitive or can be surgically extirpated. In any case this is a form of conservative treatment which cannot be in any way detrimental.
| Angiomata of the Choroid|| |
Angiomata of the choroid, which in the initial stages are often confused with melanosarcomata of the choroid, and which result in loss of vision due to retinal detachment or to glaucoma, are susceptible to treatment by photocoagulation.
| Von Hippel-Lindau's Angiomatosis|| |
The haematic cysts seen in VON HIPPEL'S disease may be destroyed by repeated photocoagulation, even when there are multiple tumours.
An attempt must be made to coagulate the tumour itself, while leaving the vascular terminations intact ; too rapid or too energetic destruction should be avoided lest retinal detachment be provoked (although this is generally transient) or disturbances in the retinal circulation take place.
The following is a personal observation : H. S., aged 30, showed two haematic VON HIPPEL tumours in the right eye (one at 9 and the other at 11.30 o'clock), at the level of the retinal periphery. On January 27th, 1957, transscleral diathermocoagulation was carried out, which completely destroyed the tumour at 9 o'clock but only incompletely that localized at 11.30 o'clock.
On July 16th, 1958, the latter tumour was photocoagulated ; this led to a complete cure. It should be pointed out that, on the day after the intervention, there was a suffusion of blood from the haematic cyst into the vitreous.
| Retinoblastoma|| |
It might be thought, at first sight, that destruction of such a tumour by photocoagulation would be impossible due to the white colour of the retinal glioma, which causes a considerable degree of light reflection. It must be borne in mind, however, that recent gliomata are relatively transparent-a fact which makes it possible to coagulate the subjacent choroid through the gliomata. Among other things, it is possible to coagulate the retinal vessels which terminate here, and also the vessels of the tumour itself.
It is also possible, in 2-3 sessions, to transform the small flat tumour nodules into a pigmented scar, in the centre of which a few calcified whitish nodules often persist.
Such tumours as may appear in other localizations should be immediately attacked. Their multiplication need not finally prevent a definite recovery.
It must be pointed out that photocoagulation cannot be effective if the tumour thickness exceeds 5 dioptres or its size 5 disc diameters (71 mm.) ; also, it should be circumscribed at the extreme veriphery, at least after depression of the sclera.
Photocoagulation of a retinoblastoma, like that of sarcoma of the choroid, should be started by forming a barrier around the tumour. The number of photocoagulations which are applied at intervals of 2-4 weeks should be at least 4-5.
The following is a personal observation : D.H., aged 13 months, was seen 8 months after submitting to enucleation of the left eye for retinal glioma. In the right eye, two tumours were found, one at the extreme periphery at 9 o'clock, and the other above and on the nasal side of the disc. Three photocoagulations, made at one-month intervals, effected a ewe of these tumours. Examination 4 weeks later, however, revealed a new nodule, very fresh, localized below and on the temporal side of the disc. This nodule was immediately coagulated. Recovery has since seemed complete.
| Choroiditis|| |
Foci of the choroid, isolated or localized, particularly if they do not involve the macular region, also constitute an indication for photocoagulation, particularly since the etiology of the affection, and therefore its correct treatment, is unknown in at least two-thirds of cases.
Photocoagulation can likewise be used for the iris, for example in the case of seclusion of the pupil in aphakia, and in the case of iridal tumours.
In conclusion it can be stated that,although the indications for photocoagulation are generally the same as those for diathermocoagulation, the former has a great many advantages, viz. :
1.It can be rapidly performed, without difficulty.
2.It is more exact as it can be more exactly localized.
3.It can be repeated as frequently as required.
4.It does not interfere with such surgical treatment as may be necessary.
5.It causes only a minimal ocular injury and gives rise to fewer complications than do other methods.
| References|| |
FRANCESCHETTI A. et FORNI S. (1954) Ophthalmologica, 127, 339.
MEYER-SCHWICKERATH G. (1949) Dtsche Ophth. Gas. Heidelberg, 55, 256.
MEYER-SCHWICKERATH G. (1954) Graefe's Arch. Ophth., 156, 2.
MEYER-SCHWICKERATH G. (1952) Armee therapeutique et clinique an Ophtalmologie,' 3, 345.
MEYER-SCHWICKERATH G. (1957) Trans. Ophth. Soc. U.K., 77, 421,
WEVE H. ( 1952 )-Annee therapeutique en Ophtalmologie, 3, 345.
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9], [Figure - 10], [Figure - 11]