Arvo Oksala

MEASUREMENT OF THE VELOCITY OF SOUND IN SOME PARTS OF THE EYE

Mundt and Hughes ( 5 ) found in 1956 and Oksala and Lehtinen (6) in 1957, that an ultrasonic equipment was of benefit in the diagnosis of tumours within the eye. Oksala and Lehtinen (6, 7 , 8) established moreover that ultrasound can be used e.g. in the diagnosing and localisation of foreign bodies within the eye, in detachment of the retina and in rupture of the sclera. The ultrasound apparatus is evidently exceedingly suitable for examinations of the eye, because the eye is a fairly regular ball of fluid, because its numerous parts are separated from each other by clear and regular demarcating surfaces, and because several parts of the eye are normally fairly homogeneous acoustically. The segregation of various parts of the eye from each other is based on the circumstance that they have a sufficiently different velocity of sound. In an earlier paper of ours (6) we carried out determinations of the velocity of sound in various parts of the eye by means of an interferometer. In the present paper we have made these measurements with greater accuracy than before. The knowledge of the velocity of sound in different parts of the eye is of fundamental importance for the diagnostic use of ultrasound in ophthalmology.

Diagnostics of detachment of the retina by means of ultrasound.

It is usually easy to diagnose detachment of the retina by means of ophthalmoscopy. On the other hand, it is at times difficult and even impossible to establish whether the detachment is idiopathic or produced by inflammation, tumour or trauma. From the point of view of therapy it is most important to know whether or not there is any tumour tissue behind the detached retina, which, nevertheless, is frequently most uncertain in spite of the use of the ophthalmoscope, transillumination and radioactive phosphorus. Mundth and Hughes (3) as well as Oksala and Lehtinen (4) have recurred to the use of ultrasound in the diagnostics of tumours within the eye. Oksala and Lehtinen were moreover successful in registering the echo of a detached retina with the aid of an ultrasonic equipment, thus being able to establish whether there was fluid (vitreous or blood) or tumour tissue behind the retina. The investigators just mentioned succeeded, solely by the use of this equipment, in determining the localisation of the detachment of retina with an accuracy of some two millimetres. Since the ultrasound easily penetrates both the transparent and the opaque lens, it is possible to determine, by means of an ultrasonic equipment, the site of the retina even in those cases in which we fail to see the eye ground through the ophthalmoscope for some reason. Simultaneously one can say, with a relatively high degree of certitude, whether there is tumour tissue behind the detached retina or not. Since our search of the literature has failed to reveal any reports on the use of ultrasound in the diagnostics of such cases, we describe below a case of our own.

DIAGNOSIS BY ULTRASOUND IN ACUTE DACRYOCYSTITIS

In some previous studies of mine (5 , 6, 7, 8, 9) part of which were published in collaboration with A. Lehtinen, I have found that an ultrasonic equipment is of great benefit e. g. in diagnosing the following eye diseases: intrabulbar tumours, intra-ocular foreign bodies, detachment of the retina and of the choroid, rupture of the sclera, opacities of the vitreous and luxatio lentis. Finally I have observed that a n ultrasound equipment can be of use also in diagnosing acute dacryocystitis. In fact, the subcutaneous abscess can be very clearly visualised on the echogram. The general principle in the therapy of acute dacryocystitis is that acute inflammations are not treated surgically prior to the formation of the abscess (Arruga, Callahan, Hughes, Meller and Bock, Stallard). In practice it is not always easy to determine when and in what place the pus should be evacuated. Even an experienced eye surgeon may happen to make unnecessary incisions, thus causing needless distress to the patient. On the other hand, an incision made a t the right time will save the patient from severe pain and will promote the improvement of the disease. Since I have not found in the literature that any particular attention has been attached to this possibility of using ultrasonics, I shall report below my method of research and some observations of my own in the light of a typical case.

USE OF THE ECHOGRAM IN THE LOCATION AND DIAGNOSIS OF INTRA-OCULAR FOREIGN BODIES

IT is often difficult to locate an intra-ocular foreign body. Sometimes it may be seen and localized by biomicroscopy, ophthalmoscopy, gonioscopy, or diaphanoscopy. Yet radiological examination is necessary in every case, because the foreign body seen by the foregoing methods is not invariably the only one present in the eye. Although x-ray methods (Comberg, Dixon, Goldmann and Bangerter, Sweet, Vogt) are fairly safe, an error of as much as 2 mm. may occur so that in some cases it may be difficult to determine whether a foreign body in the vicinity of the posterior wall lies within the eye or outside it. Some foreign bodies, such as aluminium slivers, stones, wood chips, and glass splinters, cannot be clearly seen on the x-ray film, and ophthalmoscopy is not always helpful. Those foreign bodies, which it has been difficult or impossible to locate, may now be found by means of the echogram registered by ultrasound equipment. Oksala and Lehtinen (1957) and Baum and Greenwood (1958) found that ultrasonic waves could be used for locating intra-ocular foreign bodies, whether they were visible on the x-ray film or not. Oksala (1958) used both radiological and ultrasonic methods in diagnosis.

THE ECHOGRAM IN RETINOBLASTOMA

The use of the echogram registered by an ultrasonic apparatus in diagnosis of intrabulbar tumours has only been known for about 3 years. Moreover, the high price of the research equipment has hitherto restricted its use to a limited number of eye hospitals. Mundt and Hughes (1956) noted a markedly pathological echogram in eyes which were affected with retinoblastoma or melanoma of the choroid, but on the other hand, they were unable to register with any certainty echoes given off by a detached retina. Oksala and Lehtinen (1957) and Baum and Greenwood (1958) found that melanoma with a diameter of 2 mm and 1 mm, respectively, could already be visualised in an echogram, and that the melanoma echogram was usually easy to differentiate from echograms produced e. g. by detachment of the retina, vitreous opacities or a foreign body. According to Oksala ( 5 ) the echogram is, at the present state of our knowledge, the most reliable method of examination in the clinical diagnosis of melanoma. According to all the above-mentioned workers, the size and localisation of an intrabulbar tumour can be fairly accurately assessed solely on the basis of the echogram. Since the ultrasonic wave successfully penetrates eye parts with even completely opacity, the tumour can be diagnosed also in those cases in which ophthalmoscopy and diaphanoscopy are not possible. Up to the present I have had no opportunity of examining retinoblastoma with an ultrasonic equipment. Therefore, and since the echograms obtained by me greatly differ in shape from those of the authorities mentioned above, on account of dissimilar research equipment and methods of research, I have deemed it advisable to report the following two cases of retinoblastoma. The research equipment I used and my technique have already been described in some papers of mine (3,4), to which I refer in this connection. The maximum

ABSORPTION OF ULTRASOUND IN THE AQUEOUS HUMOUR, LENS AND VITREOUS BODY

In some earlier studies of ours (5, 6, 7) we were able to demonstrate that ultrasonic equipment is a new and valuable means of investigation in the diagnostics of eye diseases. By means of ultrasound we also succeeded to make observations on the structure of the vitreous body (8) and to measure the internal parts of the eye (5). The serviceability of the ultrasonic equipment in ophthalmology is based on the facts that the eye is a ball of fairly regular structure filled with fluid, that several parts of it are largely homogeneous acoustically and segregated from each other by clearly delimited border surfaces, and that several eye parts have a sufficiently dissimilar acoustic density. We have also previously investigated the velocity of sound in various parts of the eye (9). In the present paper we have extended our researches on ultrasound and have measured its absorption in certain parts of the eye, i. e. the aqueous humour, the lens and the vitreous body, by means of an ultrasonic equipment. Since we could not find any corresponding studies in the literature, and considering that our studies open up new and interesting vistas, we describe in the following our researches and report their results.

About selective echography in some eye diseases.

In the course of the last six years several investigators ( 1 , 2-4, 5, 6-9, 10-12) have noted that ultrasonic examination of the eye has proved to be a very serviceable diagnostic method of research in numerous eye diseases. Such diseases are e. g. intraocular foreign bodies and tumours, detachment of the retina and vitreous opacities. Although differentiation between these diseases is usually easy on the basis of echograms, there are none the less cases in which the interpretation of echograms is very difficult. In addition, there are other eye diseases which present difficulties in the interpretation of echograms. During the last two years I have mainly concentrated on the clinical side of ultrasonic examinations of the eye, and by way of one of the results of this investigation I shall describe the following method which, in my experience, facilitates the analysis of echograms. By selective echography I mean a study in which some eye diseases are differentiated from each other on the basis of the amplitudes of the echograms obtained. In order to enhance the accuracy of determinations I have decreased the amplitudes up to the disappearance of the echoes from the screen, in such a way that the power of both the issuing and the returning impulse was reduced. The clinical study reported below shows that the echoes reflected in some pathological conditions can usually be clearly distinguished from each other on the basis of the amplitudes. A prerequisite of selective echography is that we have a sufficiently sensitive crystal at our disposal. The frequency of the crystal may not be so high

DIAGNOSTICS OF RUPTURE OF THE SCLERA BY MEANS OF ULTRASOUND

Rupture of the sclera following a contusion or perforation lesion of the eye is a very common accident to that organ. Usually the diagnosis is easy, since such rupture occurs as a rule in the anterior part of the eye, and is then visible either to the naked eye or through a biomicroscope. If subconjunctival hematoma prevents direct observation, the true state of things may be established by opening the conjunctiva and evacuating the hematoma. On the other hand, it is often difficult to diagnose rupture of the sclera on the equator or the posterior part of the eye, since ophthalmoscopic exploration of the eye grounds is prevented by hemorrhages usually resulting from contusion or perforation lesions, as well as by opacity of the lens. If we do not see the eye grounds, a poor projection of light and prolonged hypotonia of the eye give rise to a suspicion of ruptured sclera. Rupture of the sclera in the anterior part of the eye is usually subjected to surgical treatment. On the other hand, ophthalmologists have adopted very dissimilar attitudes towards treatment of rupture of the sclera on the equator and the posterior part of the eye. Slight ruptures are usually treated conservatively. But conservative treatment applied to severe ruptures has frequently led to proliferation or detachment of the retina, severe astigmatism and even to phthisis bulbi. If the rupture is large and its position can be accurately determined, part of these eyes can be saved by surgical treatment. Since, in our Ophthalmological Department, we have successfully recurred for over a year to the use of ultrasound in the diagnostics of rupture of the sclera in the posterior half of the eye, and since our search of the literature has failed to reveal any previous reports on this matter, we present below a patient of ours as well as some experimental observations.

EXPERIMENTAL RESEARCHES ON VITREOUS HAEMORRHAGES AND ON THE ECHOGRAM EMITTED BY THEM

The echogram registered by an ultrasonic equipment has proved very useful in diagnosing e. g. the following diseases of the eye: intrabulbar tumours (1, 2, 3, 10) in which, according to our opinion, it is the most reliable method of research among those known hitherto, detachment of retina, determination and localization of foreign bodies within the eye, opacities of the vitreous (1, 3, 4, 8), rupture of the sclera (5 ) , choroid detachment and luxation of the lens (8, 9). By means of the echogram it is possible to measure the diameter of the living eye with an accuracy of about 0,2 mm and also to carry out measurements of several other intra-ocular parts (3). Examination with the ultrasonic apparatus does not entail the slightest danger to the eye (1, 2, 3, 8). The method applied by us is quick and simple, and does not cause greater distress to the patient than for instance in tonometry. The research equipment and method of Baum and Greenwood (1) are both more complicated and more expensive. When examining patients at our Ophthalmic Department we observed that recent vitreous haemorrhages often produce on the screen of the Braun tube slight but clear echoes. Whereas no echoes are as a rule reflected from older vitreous haemorrhages. Baum and Greenwood were also able to visualise reflections from vitreous haemorrhages. Since these observations are obviously of great clinical significance, we have conducted experimental researches, now reported in this paper, on vitreous haemorrhages and the echograms traced by them, and have also attempted to clarify the anatomic and physical background of these echograms.

ON THE OCCURRENCE OF SOME TRACE METALS IN THE EVE

In addition to organic matter, the organism also contains to a lesser degree some inorganic substances which, in spite of their sinall amounts, are highly significant as structural and motive power material of the organism. Among these inorganic substances the so-called trace elements form a group of their own. Our knowledge about the occurrence of trace metals in and significance for the living organism is very deficient. We do not even know about several substances whether they are essential to life or whether, when found e.g. in organs, they have chanced to drift there by way of nutrition. Different species of animals may be in need of different trace substances. and this need can even be affected by age. I t has been proved e. g. that the mang,anese content of the liver greatly increases with advancing age, whereas the iron content increases until the age of virility and begins to fall thereafter. Instead, the copper and zinc content of the liver slightly decrease with advancing age. Approximately 40 elements belonging to the trace substances have been found in the organism. However, only a few of them have been proved essential for humans and animals. These are iron (Fe) , copper (Cu), manganese (Mn), zinc (Zn) , cobalt (Co) , iodine ( I ) and fluorine (F) . The essentiality of a h ininium (Al), boron ( B ) , bromine (Br) , silicon (Si) , molybdenum (Mo) etc. ist still a matter of controversy.