ORIGINAL COMMUNICATIONS. 11 DETACHMENT OF THE RETINA AND ITS TREATMENT, WITH FOUR ILLUS- TRATIVE CASES. A Ward Lecture in the Philadelphia Hospital. by an effusion of blood in the same sitpation, or by the presence of a solid growth arising from the choroid, or a cystic body lying be- neath the retina. The main causes may be summarized as follows : Advanced (malignant) myopia; traumatisms; effusion of blood, pre- ceded usually by hemorrhages into the vitreous or retina; intraocular tumors; tumorsand ab- scesses in the orbit; diseased conditions of the eye, as retinitis, cyclitis, irido-cyclitis, chronic choroiditis, hyalitis, etc.; and, finally, cases of detachment occur suddenly, in which none of the affections which have been named are present. In old people, warm baths and colds are mentioned as possible exciting causes by Schmidt-Rimpler and Becker. In the collec- tion of cases by Galezowski,§ among 784 de- tachments, there were 532 men and 252 women, both eyes being affected 5 7 times. The causes in his cases of retinal detachment are thus enu- merated: 646, myopia; 194, trauma; 13, after operations; 12, syphilis; 4, sympathetic in- flammations; and 10, tumors. Nordensen's researches (to which I shall have occasion to refer again) agree with the statistics just quoted, that more men than women are affected, and that myopic refraction most frequently is pres- ent, the separation being more apt to occur in an eye in which the visual disturbance has rap- idly developed. Hence one of the complica- tions always to be dreaded in advanced myopia is detachment of the retina. Traumatism, you see, accounts for many cases; for example, the blunt force applied to the globe by the impact of a flying cork from a bottle, a piece of wood, or a raquette-ball. The immediate result of a perforating wound of the sclera, on account of extensive loss of vitreous, may be retinal de- tachment, or this may occur later, as the re- sult of cicatricial contraction when the retina has become adherent to the cicatrix. An or- dinary rupture of the choroid, as has been pointed out by Knapp, may in time be fol- lowed by detachment of the retina. Those retinal separations which result from operation are in one sense properly classed with trau- matisms, the accidept being most often seen some time after cataract extraction, especially when the wound has had a peripheral situation, and has healed with a bulging (cystoid) cica- trix. In irido-cyclitis and irido-choroiditis, the shrinking of organized exudates in the vitreous drags the retina from the choroid, and in many blind and atrophied eyeballs, after removal, a funnel-shaped detachment of the retina is found. This is well illustrated in By G. E. de Schweinitz, M.D., Clinical Professor of Ophthalmology in the.J^.ffeison Medical College ; Ophthalmic Surgeon to the Philadelphia Hospital. DETACHMENT of the retina, by which is understood, in the widest acceptation of the term, a separation of this membrane from its organic connections with the under- lying choroid, is an ocular lesion, destined in many cases to destroy, or, at all events, to vitiate materially the functions of the affected eye. The relative frequency of this affection may be gathered from the statistics published by Galezowski.* This observer analyzed 152,000 cases of ocular disease with reference to this point, and found 784 detachments, or .52 per cent, of the whole number. The serious nature of the disease is evident by a reference to the statistics of the causes of blindness. Thus, in the table of blind- ness, from idiopathic diseases of the eye, given by Magnus, and confined to patients under twenty years of age, we find among 1060 cases 27, or .84 per cent., accredited to subla- tio retina. Again, in 2528 cases of blindness of both eyes, among adults and children, ob- served by Schmidt-Rimpler, Stolte, Uhthoff, Hirschberg, Landesberg, Bremer, Seidelmann, Katz, and Magnus,f 1696 had lost their vision from idiopathic ocular diseases, of which retinal detachment constituted 120, or 4.726 per cent. It is unnecessary, however, to confine ourselves to the European clinics for information on this point. Drs. H. F. Hansell and J. H. Bell J have published an excellent statistical review of the proportion and cause of blindness in 32,000 eyes consecutively treated in the Jeffer- son College Hospital, under the care of Dr. William Thomson; and in examining the spe- cific causes of lost vision, irrespective of age, sex, or other relation, in the order of their fre- quency, have found the percentage of detach- ment of the retina to the whole number of blind eyes to be 2.21. The causes of retinal detachment reside in various morbid conditions of the eye or sur- rounding orbital tissues, so-called idiopathic separation being due to an accumulation of serous fluid between the retina and the choroid, although the affection may also be occasioned * Recueil cP Ophthalmologic, 1888, p. 151. f Quoted by Noyes, " Diseases of the Eye," p. 700. J Archives of Ophthalmology, vol. xxi. p. 51. £oc. cit. 12 THE THERAPEUTIC GAZETTE. this drawing taken from Wedl and Bock's atlas, and also in the specimens which I ex- hibit. A number of theories have been propounded to explain the mechanism of detachment of the retina, and although its pathology is not defi- nitely settled, it may be stated that all cases of idiopathic separation are preceded by a change in the pressure exerted by the vitreous upon the retina (whereby this membrane is kept in place against the choroid), and it is highly probable that this change consists in detachment and shrinking of the vitreous. It would be interesting to trace the different views which have been held in regard to the pathology of detachment of the retina, but as time Scarcely permits an extended review of this character, I will refer briefly to the resume given by Schoeler. Before the time of Hein- rich Miiller much weight was attached to what is known as the "secretion theory,"-namely, that the phenomena of separation of the retina depended in some way upon an anomalous se- cretion of fluid. In 1856, however, Muller taught that filamentous or membranous opaci- ties in the vitreous, by contracting, might de- tach the vitreous body alone, or being attached to the retina, this might follow the shrinkage, arid thus cause separation of this membrane from the choroid. In 1867 Iwanoff, on the basis of anatomico-pathological investigations, demonstrated that disease of the vitreous body tended to produce detachment of the vitreous, and that the latter condition was a forerunner to retinal detachment. In 1870 De Wecker suggested that the fluid found in the sub- vitrinal space after detachment of the vitreous succeeded in passing behind the retina through a rupture which took place in this membrane. Working upon these lines, Leber, in 1882, and Nordensen, in 1887, have developed the most satisfactory explanation which is given of retinal detachment. The first process is a fibrillar change in the vitreous which leads through shrinking to detachment of the vitreous body, and by extension of the lesion to the equator of the ocular globe, where the retina is most intimately connected with the vitreous, the tension causes a rent in the retina behind which passes the fluid which has gathered be- tween the detached vitreous body and the retina. Now, it is not always possible to find this rent, although Nordensen, whose research goes far to confirm the explanation given by Leber, found the tear in nearly forty per cent, of the cases in which he looked for it. No doubt it was present in many others, but es- caped observation owing to opacities in the media, or because it was far in the periphery of the fundus. The primary cause of the pathological change in the vitreous, which thus shrinks and occasions traction, is believed by Nordensen to be disease of the choroid and ciliary body; hence the greater liability of this accident in eyes affected with advanced and progressive myopia. The -abjective symptoms of detachment of the retina, as furnished with the ophthalmoscope in the direct method of examination, consist in an alteration of refraction at the area of separation, the surface of the elevation thus produced being out of focus as compared with the rest of the eye-ground. The detached retina appears as a gray or bluish-gray membrane, stretching for- ward into the vitreous, and containing folds which give rise to a sheen. The intervening furrows present a greenish-gray reflex, and the whole trembles with the movements of the eye. When the underlying substance is solid, how- ever, neither folds nor tremulousness are present. Not uncommonly it is possible to demonstrate rents in the detached retina, through which the dull color of the choroid is readily visible. The importance of these in regard to the mechanism of the affection has already been pointed out. In extensive detachment of the retina, the membrane may have floated so far forward in the vitreous that it is possible to see it even without the aid of an ophthalmoscope. The retinal vessels present characteristic features. First, they lose the light streak, and finally appear as dark, tortuous cords, often smaller than the normal size, and when they are folded backward, they pass out of focus at the edge of the detachment, which is often sharply marked from the normal fundus. Indeed, there may be a yellowish border and occasionally ac- cumulated pigment. Naturally, the discolora- tion of a detached retina depends upon whether the case is recent or not, and upon the charac- ter of the underlying substance. In the earlier stages the transparency is not lost, and the gray color previously described is not present. The detachment is either partial or complete, and may occupy any portion of the fundus, but most commonly is found below, even when it has begun in the upper part. Detachments in the form of a series of furrows are sometimes found, and also circular circumscribed separa- tions. Occasionally, the subjective symptoms of detachment are present, although the oph- thalmoscope fails to reveal any elevation in the retina. Over this area, however, as Loring has pointed out, there is complete loss of the light reflex from the retinal vessels. Unless the macular region is directly involved, vision is ORIGINAL COMMUNICATIONS. 13 not obliterated, although there is always more or less interference with sight. This may sud- denly, or, like the detachment itself, may arise slowly. The field of vision if? lost in an area cor- responding to the detached retina, the com- pletely darkened portion often being bordered by a zone of imperfect vision, which cor- responds to an area of the retina not yet sep- arated, but elevated above the normal plane. If the retina is detached below, the upper por- tion of the field is obliterated; if above, the lower; and so on. Occasionally disturb- ances in the visual field are not present in the early stages of retinal detachment, because the recently-detached retina retains its function; hence the restriction of the field may escape observation, unless, as Berry suggests, the ex- aminations be made with subdued light. The objective symptoms of this affection con- sist in a distortion of objects, floating spots before the eye due to frequent vitreous opacities, an appearance like a cloud due to the scotoma produced by the separated area, and sometimes phosphenes. There is very little difficulty in making a diagnosis of extensive detachment of the retina by attending to the symptoms which have al- ready been described, and if the media are suf- ficiently clear, the ophthalmoscope is usually an all-sufficient method of investigation. When the vitreous is full of opacities, however, or when the detachment of the retina has oc- curred in connection with irido-cyclitis, and the inflammatory products have blocked the pupil and rendered ophthalmoscopic examina- tion impossible, the field of vision gives the retina and sarcoma of the choroid, or, indeed, any intraocular growth. The points upon which a differential diagnosis are based are the following: In choroidal sarcoma the defect in the field of vision is more sharply circum- scribed, the central vision less decidedly affected, and the overlying retina exhibits no tremulousness. Moreover, the tension is apt to be diminished in detachment of the retina and raised in intraocular growth. None the less, errors in this respect have not infre- quently been made, and more than one acute diagnostician has hesitated for a long time be- tween the diagnosis of idiopathic retinal de- tachment and choroidal sarcoma. To illustrate the subject which we are dis- cussing, I present for your consideration four cases of detachment of the retina. Case I.-Mary S., a woman, aged thirty- eight, about two years ago suddenly experi- enced a cloud before the left eye, and on test- ing in a rough way her own vision, found that it was materially reduced or practically absent in this eye. Presumably the detachment of the retina, which you can see with the ophthalmo- scope, happened at this time. About a year and a half ago she was under treatment in the Fig. 2. Fig. i. Field of vision of Case I., left eye. Philadelphia Polyclinic, but without material benefit. The right eye is not far from normal, being slightly hypermetropic in refraction. In the left eye, also hypermetropic, there is a huge detachment of the retina, the whole lower half of this membrane being separated, floating for- ward in the vitreous as a grayish-green mem- brane at an elevation of 7 or 8 D. This dia- gram illustrates the field of vision, the outer continuous line marking the boundary of the normal visual field, the shaded area where vision was lost, and the inner white area that portion of the field which is still preserved, representing the extent of retina which is still functionally active and in placd. Case II.-Franz G., a young man, aged twenty-two, born in Germany, states that as Field of vision of a case of chronic irido-cyclitis, with detachment of the retina. best information. This is well illustrated in the diagram which I present to you taken from a case of chronic irido-cyclitis and probable letachment of the retina. It is not always easy, however, to make a dif- erential diagnosis between detachment of the 14 THE THERAPEUTIC GAZETTE. long as he can remember he has never seen well. There is no history of blindness in his family. He has suffered from rachitis, and now has well-marked phthisis of the left apex. In 1890 he consulted Duke Carl Theodore, of thirteenth year he had good eyes. Then he experienced an attack of chorea, after which the vision was poor, and he attended Wills i hfospital under the care of Dr. Harlan, being an in-patient for about six weeks, and after-. Fig. 3. Fig. 4. Field of vision of the left eye of Case II. Field of vision of the right eye of Case II. Bavaria, and Berlin, of Stuttgart, and underwent two operations, probably scleral punctures, to the method of performing which I shall pres- ently refer. The vision of each eye is ex- tremely poor, fingers being counted with diffi- culty in the lower field. In the right eye the cornea is clear, the disk is oval, gray, and at its outer margin there is a slight crescent of choroiditis. There is a huge detachment of the retina not far from complete in the right wards an attendant at the dispensary service for a number of months. Improvement occurred, because he was able to go to work, but after ceasing his attendance at the hospital, he did nothing for his eyes except to visit an irregu- lar practitioner, who promised to cure him by furnishing him with glasses. Gradually the disease progressed, and finally his eye-sight became so deficient that in January of last year he entered the hospital. His condition Fig. 5. Fig. 6. Field of vision of the left eye of Case III., taken with two candles. Field of vision of the right eye of Case III. eye, and nearly complete in the left. The greatest height of the detachment is -|- 7 D, and the undetached patch of retina in the right eye shows evidences of slight choroiditis. In the left eye the disk is oval, the veins very large, and there is a similar but not quite so extensive detachment of the retina, the greatest height of which is 5 D. There are no demon- strable vitreous opacities. The accompanying diagrams, constructed on the plan previously described, show what a very small portion of the field remains and how very near the macula the lesion has progressed. Case III.-Charles A., a man, aged twenty- five, American by birth, states that up to the then was very much as it is now, and did not improve under the medicinal treatment, which I shall presently describe. He declined opera- tive interference, and, indeed, it does not ap- pear to be a case in which much hope could be extended from this source. In the right eye he can barely count fingers in the lower and outer quadrant of the field, and in the left eye he has light perception in the lower portion of the field. There is extensive detachment of the retina, so that in the right eye, as you see from the diagram, there remains only a very small portion of vision in the lower and outer quadrant of the field. In the left eye it is pos- sible to determine the field of vision with can- ORIGINAL COMMUNICATIONS. 15 dies, one being used for fixation and the other for the test-object, and you see that light per- ception is present only in part of the lower half of the field. In both eyes the detachment involves the macular region. With the oph- thalmoscope an extensive detachment of the retina is evident, which floats up in the vitre- ous, spots of choroiditis being evident in the portion not yet detached, while the vitreous is full of floating opacities. This is an extensive state of disorganization, offering very little hope so far as remedial agents, either operative or otherwise, are concerned. Case IV.-Hugh M., a man, aged fifty, pre- sents an interesting state of affairs. The right eye was injured by a blast twenty-four years ago, and was considered by the patient to be valueless until his left eye was affected. Now it is the more useful organ of the two. There is an irregularly oval pupil, with adherence of the iris to a small scar in the cornea, and a separation of the iris at the outer ciliary mar- gin. Over the cornea are scattered several cic- atrices. The remains of the capsule of the lens is seen to border the pupillary margin. It is not possible to obtain a view of the fundus, but from the diagram of the field of vision, which I present to you, you observe that probably there is detachment of the whole lower half of the retina, with concentric restric- detachment until it became total, and scleral puncture was made upon the left eye December 1, 1891. There was no reaction whatever from the operation, except slight oedema of the con- junctiva, which lasted three days. Material improvement in vision was noted from the second day following the operation. The patient remained in bed three weeks, and left the hospital January 15, 1892, with the retina in its normal position and vision The patient states that, contrary to Dr. Sut- phen's orders, he went to hard work, and very speedily his sight became as bad as ever. He declares that he was ashamed to go back to consult Dr. Sutphen, and well he may have been, because, owing to his own foolishness and disobedience, the benefit of Dr. Sutphen's excellent treatment was lest, and there has Fig. 8. Fig. 7. Field of vision of the left eye of Case IV. Test-object a candle-flame. been a return of the disease, so that there is now an extensive detachment of the retina, which has involved the fixing-point. The disk, which is visible, is oval, and contains a small, central excavation, with a dot of pigment upon its margin. The detached retina floats up as a gray veil in the vitreous, which, in its turn, is filled with opacities, the lens is hazy, and there are considerable cortical opacities in the crystalline lens downward and inward. The accompanying diagram exhibits the field of vision, and was obtained by causing the patient to fix upon a candle placed at the centre of the perimeter, while a large, white test-object was utilized to map out the field. These cases serve to illustrate the affection which we have been discussing this afternoon, and also to introduce the concluding remarks in regard to the treatment, which naturally divides itself into non-operative or medical treatment, and operative interference. In former times many of the patients were subjected to the severe, so-called antiphlogistic regimen which was so much in vogue,-namely, Field of vision of the right eye of Case IV. tion of the field of vision furnished by the unseparated area. Fortunately, however, the macular region is not involved, and with a cataract-glass the patient's visual acuity is The sight of the left eye was good until July, 1891, and then, while he was working, sudden blindness occurred. There has never been pain nor inflammation. He consulted Dr. Sutphen, of Newark, N. J., who has very kindly fur- nished me with an account of what he did for the patient at this time. He was ordered to bed and treated by injections of pilocarpine, and later iodide of potassium was administered internally. There was steady increase in the 16 THE THERAPEUTIC GAZETTE. free bloodletting from the temple, either with leeches or wet-cups, sinapisms, drastic purges, active foot-baths, and even setons. Pursuing the same line even at the present time, derivative medication has been largely em- ployed, and many cases of detachment of the retina, in addition to this, have received full doses of iodide of potassium and mer- cury, either by the mouth or by means of in- unction, with the hope of absorbing the sub- retinal fluid, very much on the same principle as it was hoped to influence an effusion into the pleural sac. Less depressing, but requiring a great amount of patience on the part of the sufferer, is what the field of vision. Central vision, however, did not improve. A third form of treatment may be character- ized as the diaphoretic method. In this the pa- tient is confined to bed, either with or without a pressure bandage, and, according to his power of endurance, freely sweated with hypodermic injections of pilocarpine, alternating sometimes with the administration of salicylate of sodium. This treatment has much to commend it, and there are numbers of cases on record in which de- cided improvement has occurred. It should be remembered, however, that not every patient is able to withstand the depressing influence of exhausting sweats, and very often, in the hope Fig. 9. Fig. io. Fig. 11. Field of vision in a case of retinal de- tachment before the use of eserine. Field of vision after one month of eserine-instillations. Field of vision after five weeks of eserine-instillations. may be called the rest-cure for detachment of the retina. This consists in placing the pa- tient on his back, giving him an almost en- tirely liquid diet, chiefly composed of milk, and keeping both eyes closed with a pressure bandage. In a few instances this method has been followed by good results, and there has been reattachment of the separated membrane; but, like all other procedures connected with the treatment of detachment of the retina, it has a long list of failures to its credit. In some instances, especially on the recom- mendation of Guaita, there has been ameliora- tion of the symptoms of retinal detachment and increase in the field of vision under the influ- ence of eserine instillations, although there was resumption of the symptoms upon ceasing the use of the drug. In several cases under my own care I tried very faithfully this use of eserine, adding to it at times a pressure band- age, but not confining the patient to bed. In one instance small doses of iodide of potassium were also taken, but only for a short period of time, and probably not in sufficient dose to in- fluence the progress of the disease. The ac- companying diagrams illustrate what effect was produced by this method in one case, and you observe there was slight increase in the size of of reattaching a separated retina, undue depres- sion of nutrition has been produced by the vig- orous measures employed. It is, however, a method which should be thought of first of all, and in suitable cases should always be em- ployed, as we have the experience of many ob- servers for encouragement; for example, Roosa reports that in the Manhattan Eye and. Ear Hospital, in quite a large proportion of cases, good results have been obtained from the rest-, bandage-, and pilocarpine-treatment. A number of operative procedures have been devised; for example, sclerotomy (Wolfe, Abadie), iridectomy (Dransart, Brettremieux), methods which, although they have a few cures to their credit, are generally dondemned. Naturally, most of the attempts have been to- wards the evacuation of the subretinal fluid by puncturing the sclerotic, as was originally sug- gested by Sichel in 1859. At one time after the puncture De Wecker suggested drainage of the subretinal fluid by the introduction of a gold or catgut thread. Aspiration without drainage has been practised by Galezowski, and Graefe, in some instances, entered the globe with a broad cataract-needle at the side opposite the detachment, cut into the retina from the vitreous, and allowed the subretinal ORIGINAL COMMUNICATIONS. 17 fluid to pass into the vitreous body. Galvano- puncture was at one time proposed by Abadie, the puncture being made backward from the ciliary region. In fresh cases, but not in old ones, some good results were reported. This method has quite recently been advocated again by some French surgeons. In a number of instances, in addition to scleral puncture, irritating fluids-for example, Condy's fluid and tincture of iodine-have been injected with the hope of producing adhesive inflammation. The cure of retinal detachment by the injection of iodine into the subretinal space received a great impetus after the pub- lications of Schoeler, in Berlin, who reported a number of successful cases. Soon, however, other operators who tried the method recorded exam- ples in which destructive inflammation followed the method, with complete loss of the eye; and in a valuable series of cases reported by Dr. Bull, of New York,-valuable because they seem • to show very conclusively the danger of the method,-Schoeler's injections of iodine were oved to be of no value. Perhaps experience with this measure. is not sufficiently great to condemn it entirely, but it is not enough to recommend it as a therapeutic measure free from danger. Scleral puncture may be recommended as the method least likely to do harm, and perhaps most likely to do good, but only after a thorough ra- tional medicinal treatment has been employed. The precise position of the retinal detachment must be ascertained, the eyeball is rotated in a suitable direction, a narrow Von Graefe cata- ract-knife is thrust directly through the sclera and choroid, turned slightly upon its axis, and the subretinal fluid allowed to drain away be- neath the conjunctiva. Very little reaction follows, and, as in the case quoted from Dr. Sutphen, good results will sometimes follow. Great care should be taken to perform a per- fectly antiseptic operation, and, as Dr. Sutphen suggests, the rotation of the eyeball back to its normal position when released by the fixa- tion forceps, virtually converts the scleral wound into a subconjunctival one, and this appears to be advantageous in preventing in- fection. Hugh M., the case to which I have already called your attention, has implored me to re- peat the operation which more than a year ago, when performed by Dr. Sutphen, was produc- tive of good results. It does not seem to me to hold forth much hope now, but, as experi- ence shows it can do no harm, I will perform for you the operation of scleral puncture. I seize the eyeball with fixation forceps, rotate it inward, and thrust a Graefe cataract-knife through the sclera between insertion of the ex- ternal and inferior rectus at about the equator. I now turn the knife slightly upon its axis, the wound gapes, and you see the escape of serous fluid, which forms a good-sized bleb beneath the conjunctiva. A double figure-of-eight bandage is applied, and the patient put to bed. A very interesting resume of the methods of treatment of detachment of the retina has been published by Emil Grosz.* After gath- ering together his statistics from the reported cases of the various procedures, he finds that in sixty-five per cent, of the cases puncture of the retina, in forty-four per cent, puncture of the sclera, in sixty-six per cent, iridec- tomy, and in fifty-nine per cent, pilocarpine injections remained fruitless. He holds, how- ever, that these results are not trustworthy, be- cause most of the authors were satisfied with an indefinite expression of improvement without careful investigation of the visual acuity and the duration of the improvement. In contrast to these statistics, he gathers together those from the Ophthalmic Clinic of Professor Schu- lek, in Buda-Pesth. In the last fifteen years 6971 cases were treated, and 67 of these were affected with retinal detachment. The various methods and the results are thus summarized : 1. Puncture of the sclera in 21 cases, with negative result 14 times, improvement 4 times, and deterioration three times. 2. Iridectomy in 18 cases, with negative re- sult 7 times, improvement 6 times, and deteri- oration 5 times. 3. Puncture of the retina in 2 cases, with negative results in 2. 4. Pilocarpine injection in 16 cases, with negative results in 10, and improvement in 6. 5. Combined puncture of the sclera and pilo- carpine injection in 9 cases, with negative re- sults in 6, and improvement in 3. 6. Iodine injections, after the method of Schoeler, in 2 cases, with negative results in 2. Improvement, therefore, was obtained with pilocarpine injections in thirty-three per cent., iridectomy in thirty-three per cent., puncture of the sclera in twenty per cent., combined pilocar- pine injection and puncture of the sclera in thirty- three per cent. He naturally concludes from these statistics that pilocarpine injections should be considered first of all, then iridectomy, and afterwards puncture of the sclera. Iridectomy should be first performed because, after an * Abstract in Nagel's " Jahresbericht fur Opbthal mologie," vol. xxi. p. 95. 18 THE THERAPEUTIC GAZETTE. improvement in the circulation of the globe, there is more probability of absorption or drainage of the subretinal fluid. No doubt all of us agree that pilocarpine injection should receive the first place in our methods of treat- ing this disease, but most of us do not accord the second place to iridectomy, but, as I have already stated, prefer puncture of the sclera in the manner just performed.