THE ELECTRO-MAGNET 
IN 
OPHTHALMOLOGY, 
WITH A DESCRIPTION OF A NEW MAGNET. 
BY 
HENRY W. BRADFORD, M. D., 
ASSISTANT AT THE MASSACHUSETTS CHARITABLE EYE AND EAR INFIRMARY. 
[Reprinted from the Boston Medical and Surgical Journal of 
March SI, 1881.] 
CAMBRIDGE: 
jprinteb at tfje ftitocr^ibe 
1881. ELECTRO-MAGNET 
(Full size cut). 
Suspensive force, twenty ounces THE ELECTRO-MAGNET IN OPHTHAL- 
MOLOGY, WITH A DESCRIPTION OF A 
NEW MAGNET. 
BY HENRY W. BRADFORD, M. D-, 
Assistant at the Massachusetts Charitable Eye and Ear Infirmary■ 
The rapidly extending use of the electro-magnet for 
the purpose of removing fragments of iron and steel 
from the interior of the eye, the slight attention pre- 
viously bestowed on this method of procedure, and the 
imperfect knowledge of the subject displayed in many 
of the published articles, have induced me to bring 
forward the following views. They are the result of 
several years’ practical study. And their main object 
is to demonstrate that in the application of a properly 
constructed magnet we possess an efficient means of 
treating cases for which enucleation has hitherto been 
practically considered the sole resort. 
Magnetism may be applied to the eye from either a 
permanent or an intermittent source, that is, either 
from a so-called permanent magnet, which, once ex- 
cited, retains its magnetic power indefinitely, or from a 
magnet which becomes such only when excited by the 
electric current. And the superiority of the latter is 
incoutestible. It exceeds its rival by many times in 
power, when of less weight and smaller size. The 
permanent magnet is, moreover, open to the objection 
of being liable to a constant dissipation of its energy 
upon receiving any sudden shock or blow, upon mov- 
ing across the magnetic meridian of the earth, and 
even when at rest, unless guarded by an armature 
whose weight nearly equals its suspensive power. 
The electro-magnet must then be the one employed 
for the purposes of ophthalmic surgery. And in mod- 2 
The Electro-Magnet in Ophthalmology. 
eling such an instrument for use about the eye, it is 
evident that we must combine the minimum of size 
with the maximum of power. To this may be added, 
for the sake of convenience, with the smallest and most 
compact battery that proves itself available. 
It is in precisely this three requisites that previous 
electro-magnets have been deficient. When small their 
power has been insufficient. When large they have 
been clumsy, have supplied little power in proportion 
to their size, and have required a large number of 
cells to develop their full force. 
Having, in the course of the experimental study of 
this subject, constructed some fifty magnets, of every 
variety of shape and size, I would advance the follow- 
ing magnet, as giving the best results accomplished: — 
The core is composed of soft Norway iron, one 
third of an inch in diameter, and two and one half 
inches in length ; to one end of this solid cylinder is 
riveted a flat circular disc of the same material, one 
inch in diameter, and one sixteenth inch thick. 
The surrounding helitf is composed of insulated cop- 
per wires, weighing twenty-nine grains to the foot, 
making eight convolutions of one and three quarters 
inch in length. 
The polar extensions are respectively five, four, and 
three thirty-seconds of an inch in diameter, and one 
half inch in length; their suspensive power equals 
twenty, sixteen, and eleven ounces each, when an ar- 
mature of soft iron, one inch by one tenth in diameter 
is used, which is within two ounces of the saturation 
point. 
The battery used is a single bichromate of potash 
cell, having eight square inches of negative surface. 
The magnet weighs about five ounces, and the inten- 
sity of its field by the addition of another cell is made 
as great as that of a magnet capable of lifting a ton. 
The use of large magnets capable of lifting enor- 
mous weights offers no advantage over the one above 
described, as their field is no more intense, and, unless The Electro-Magnet in Ophthalmology. 
3 
the foreign body is of many pounds weight, does not 
exert any greater force. It may be laid down as a 
law that the size of the magnet should be in proportion 
to the size of the body acted upon: if a large body of 
iron is to be suspended, then a large battery power 
and correspondingly large magnet must be used; but 
should the foreign body be of small size, such as would 
be met with in the eye, a small single cell magnet 
magnetized to saturation will give the same amount 
of suspensive force, as the magnetic field of each will 
be the same in intensity, differing only in size. 
In regard to the quality of material nothing but the 
most soft and pure iron should be used ; the use of im- 
pure commercial iron is open to the objection that its 
saturation point is much lower than that of the brand 
known as Norway iron, and as it retains its magnetism, 
upon making attachment to the battery a second time 
this may have to be overcome, thereby raising the tem- 
perature and lowering the magnetism ; this takes place, 
if the poles of the magnet are reversed, by connecting 
the battery in a different manner than at the first. 
Having finished the construction of the electro-mag- 
net we will pass over to its application and use in oph- 
thalmology. 
Foreign bodies that enter the eye may lodge in 
any one of the following structures, and, commencing 
with the most superficial, the cornea, they might pass 
through the anterior chamber, the iris, lens, vitreous, 
and choroid. Of the metallic substances which enter 
the eye none are removable with the magnet except 
pieces of iron and steel. Those that enter and lodge 
in the cornea may be divided into two classes: first, 
those minute fragments which enter its surface and are 
removed by means of the needle, and over which a 
magnet has no practical effect because of their small 
size ; and, second, those which have an appreciable size. 
These latter may be extracted in the following man- 
ner : The point of the above-constructed magnet is 
brought in direct contact with the foreign body, and 4 
The Electro-Magnet in Ophthalmology. 
then moved away to the distance of a fourth of an 
inch; this manoeuvre is repeated several times, and if 
the case is seen before the corneal wound has had a 
chance to heal, the foreign body will finally be found 
adhering to the point of the instrument. If, however, 
the wound has healed a change in the procedure is 
necessary. While keeping the magnet in close prox- 
imity to the foreign body, an incision through the 
wound is to be made for the purpose of allowing a free 
exit, the manoeuvre of touching and withdrawing the 
instrument must be gone through with again and again, 
and ultimately the foreign body will be easily removed. 
These two methods are entirely sufficient for the ex- 
traction of all fragments in this tissue, as long as any 
part of them is in the cornea, even though the greater 
portion of their bulk projects into the anterior cham- 
ber. 
The anterior chamber may be the resting-place of a 
fragment, and if so, it should be drawn to the margin 
of the cornea, and extracted through an incision in 
that region either by the forceps or magnet, at the 
option of the operator, who should bear in mind the 
importance of keeping the magnet in close proximity 
to the metal to be extracted if forceps are used, in 
order that the fragments may not be lost by means of 
the forceps slipping. 
Fragments situated in the iris may be extracted by 
two different methods by the use of the attractive or 
suspensive force ; in the first method the magnet does 
not enter the eye at all, but exerts its influence from 
the outside in the following manner : The eye is seized 
with a pair of fixation forceps, an assistant keeps the 
point of the magnet directly over the fragment im- 
bedded in the iris, the operator, with a stop needle, 
enters at the margin of the cornea nearest the frag- 
ment, in a horizontal plane, and with the extremity of 
the needle loosens the fragment from its point of at- 
tachment, the magnet then seizes and withdraws it to 
the edge of the cornea, where an incision is made for The Electro-Magnet in Ophthalmology. 
5 
its removal. The second method, which is by far the 
simplest, is to make an incision nearly at the edge of 
the cornea, and pass the point of the magnet directly 
inwards until contact is made, and upon withdrawal 
the fragment will be found attached to the polar ex- 
tension ; the certainty of this fact is assured, as this 
magnet is able to draw through normal iris tissue a 
fragment of iron the size of a pin head. 
Fragments imbedded in the lens may, if a traumatic 
cataract has formed, be removed by either of the above 
stated methods. If, however, a foreign body is found 
resting against the anterior capsule and external to it, 
the magnet alone must of course be used to effect its 
removal, an incision through the margin of the cornea 
being practiced for that purpose. 
Fragments in the vitreous may be classified under 
two heads: those that are fixed in position, and those 
that are free; in the former case no attempt at re- 
moval by means of the attractive force of the magnet 
will be successful, except by bringing the point of the 
instrument in the closest proximity to the foreign body 
when we no longer use this power, but its associate, 
the suspensive force. In other words, contact with 
the body should be made with the magnet in order to 
overcome any adhesions that may exist. This, how- 
ever, does not apply when the fragment exists in the 
vitreous, unattached to any surrounding tissue, for then 
the attractive force of the magnet will draw the body 
to the choroid at the nearest point, from which position 
it can be removed through an incision ; this action, 
however, is not an instantaneous one, for the time 
needed in the manoeuvre will vary according to the 
consistency of the vitreous and size of the foreign 
body; should the fragment be fixed in the substance 
of the choroid and sclera the eye should be rotated in 
the necessary direction until the site of impactmeut is 
brought into view, and in order to accomplish this 
some division of muscle may be necessary in order that 
sufficient rotation may be accomplished. An incision 6 
The Electro-Magnet in Ophthalmology. 
is then made as close as possible to the imbedded body, 
and the magnet, which, during this time, is held in 
position to keep the fragment from being dislocated, 
should be passed straight into the eye, avoiding all 
lateral movements; upon withdrawal the fragment 
should be found adhering. 
Having stated the method of treatment for frag- 
ments which may lodge in any of the different tissues 
of the eye, a few remarks in regard to the general 
facts of the employment and use of the magnet may 
be introduced. The amount of suspensive power of 
any magnet, when saturated, as every magnet used in 
ophthalmic surgery should be, depends upon the size 
of the foreign body. Hence, the larger the fragment 
the more probable its removal, and, conversely, the 
smaller the fragment the more difficult its extraction. 
Finally, a point may be reached where the resistance 
to be overcome exceeds the amount of polarity capable 
of being induced. This is illustrated in the case of 
minute foreign bodies in the cornea, where the magnet 
is of no avail. All incisions for removal of foreign 
bodies anterior to the plane of the lens should be mar- 
ginal incisions of the cornea, those that concern the 
vitreous should be scleral, and made posterior to the 
ciliary border; in both cases, by so doing, the ciliary 
body is avoided, and in the latter case the surrounding 
tissues form the best support for the wound. 
One important point in regard to all incisions made 
for the entrance of the magnet, and the removal of a 
foreign body from the eye, is that the cut should he not 
one with parallel edges, but T-shaped, as in the former 
case, when the extraction of the foreign body takes 
place, it is invariably stripped off the end of the mag- 
net, and is retained at the site of the wound, or drops 
into the interior of the eye. This is a foregone con- 
clusion unless the lips of the wound be held apart, and 
no amount of skill or carefulness upon the part of the 
operator can guard against it, unless the incision is of 
the above-mentioned shape. The Electro-Magnet in Ophthalmology. 
7 
Every magnet having a north and south pole, the 
supposition would be that they would have the same 
amount of suspensive force; this, however, is not so, 
and the explanation of this fact must be sought for in 
the laws of tension of the electrical current. Should 
we wish to gain the maximum of attractive force the 
magnet must be constructed with a diameter propor- 
tioned to its length as one to twenty-four or more, this, 
of course, requiring more battery power. 
The following cases of removal of fragments of iron 
and steel from the eye have occurred in the clinic at 
the Massachusetts Eye and Ear Infirmary. This elec- 
tro-magnet or modifications of it have been used, and 
the gradual decrease in size and the increase in suspen- 
sive force of the instrument are worthy of notice. 
Case I. November 18, 1879. F. S., machinist, 
aged twenty-four, received a blow upon the eye while 
at work chipping steel; piece penetrated cornea, and 
lodged in the substances of and posterior to the iris, 
with an exposure of only a point of one of its extrem- 
ities upon it. The lens was opaque. Iridectomy was 
attempted, but unsuccessfully, haemorrhage ensuing, the 
fragment disappeared, and could neither be seen or felt; 
the point of the electro-magnet was then passed into 
the eye at the place where the foreign body had been 
situated, and after the second trial it was seen engaged 
in the wound and removed with forceps. The magnet 
used weighed seventeen ounces, and had a suspensive 
force equal to eight ounces. Dr. F. P. Sprague, in 
whose clinic the case occurred, soon after removed the 
cataract, and when last seen, August 16, 1880, the 
patient had vision of six eighteenths. 
Details of the second and third cases occurring in 
the services of Dr. B. Joy Jeffries, and Dr. C. II. 
Williams, may he found in the December 30, 1880, 
number of the Boston Medical and Surgical Journal. 
The magnet in each of these cases weighed eight 
ounces, and the ratio of suspensive force had increased 
to sixteen. 8 
The Electro-Magnet in Ophthalmology. 
In the fourth case, that of J. S., stone cutter, aged 
twenty seven, who came to Dr. Henry L. Shaw, the 
foreign body, a thin scale of steel, had passed through 
the cornea, and projected nearly two thirds its diam- 
eter into the anterior chamber. As the corneal wound 
had partially healed over the fragment, all attempts 
towards its removal were unsuccessful until the wound 
was reopened with the knife, when the fragment was 
immediately grasped by the magnet and withdrawn. 
The weight of the instrument, whose construction was 
the same as previously described, was five ounces, and 
its suspensive ratio had increased to over twenty. 
The point of the magnet, shown in the engraving, 
can be removed, and smaller ones attached. Several 
of these accompany the instrument, which may be ob- 
tained of the manufacturer, Thomas Hall, 19 Bromfield 
Street, Boston. Boston Medical and Surgical Journal. 
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