SKIASCOPY; WITH A DESCRIPTION OF AN AP- 
PARATUS FOR ITS READY EMPLOYMENT. 
SWAN M. BURNETT, M.D., 
OPHTHALMIC AND AURAL SURGEON TO PROVIDENCE HOSPITAL ; DIRECTOR OF THE EYE AND EAR 
CLINIC, CENTRAL DISPENSARY ; PRESIDENT OF THE MEDICAL SOCIETY OF THE 
DISTRICT OF COLUMBIA, WASHINGTON, D. C. 
(With a wood engraving.) 
SKIASCOPY has now a recognized place among the 
scientific methods of testing the refraction of the eye, 
and its employment, while perhaps not general, is increasing 
in extent. The principles on which it is based are now ex- 
plained (though not in every case fully or accurately) in 
several recent text-books on the eye, and in most of the 
manuals on refraction,1 so that it is not necessary to consider 
here the theoretical part of the subject. 
While deeming it one of our most valuable means of 
determining refraction, I still do not hold it superior to all 
others for all sorts of cases. It has its limits as well as its 
advantages. Thus, I think that the accommodation of the 
patient comes in to vitiate the result to a much greater 
extent than in the direct ophthalmoscopic method. But for 
children and high degrees of ametropia it is the easiest of 
any of the methods at present in use, and is as scientifically 
accurate as any. And, as I have elsewhere2 remarked, we 
cannot have at our hands too many means of verifying our 
diagnosis in refraction. 
But while there are few who doubt the scientific ac- 
1 See paper, by the author, on “ Skiascopy,” in Medical News, Sept. 15,1888. 
a Theoretical and Practical Treatise on Astigmatism. Chambers, St. Louis, 
1887. 
Reprinted from the Archives of Ophthalmology, Vol. xix, No, 2, 1890. Skiascopy. 
Tig.l. Swan M. Burnett. 
262 
curacy of the method, a large number are no doubt debarred 
from its use by the lack of an easy method of employing it. 
In using it in the manner most generally employed, it is 
necessary to fit a trial frame before the eye, and place lenses 
therein in succession until one is found which gives em- 
metropic movements to the shadow. This, however, is so 
consumptive of time and patience that the surgeon in the 
hurry of practice is likely to select some other and shorter 
method. It was for the purpose of facilitating this examina- 
tion that I devised the simple apparatus described below, 
and which I exhibited first at the meeting of the American 
Ophthalmological Society, at Washington, in 1888. I have 
been using it since that time in my daily practice to my 
own complete satisfaction, and I have no hesitation in 
recommending it to the profession for the purposes intended. 
It consists of a hard-rubber disk, A, Fig. 1 (Fig. 2 being a back 
view), containing 23 lenses on its periphery—lo convex and 
13 concave. This disk is movable on the brass-rod B, which 
is attached at either end to two other bass rods, D D, which 
turn on the pivots E E fastened to the wooden board C, 
which is attached to the wall of the ophthalmoscopic room. 
This enables the disk to be placed, by means of the screw 
H, Fig. 2, at any height, and to be turned and retained in 
any desired position, and the whole apparatus can be turned 
back against the wall when not in use. 
The patient is placed in a proper position near the oph- 
thalmoscopic lamp, and the disk is brought before the eye to 
be examined. By turning the disk on its axis all the lenses 
can be brought in rapid succession in front of the eye, and 
the one giving emmetropic movements to the shadow soon 
found. The revolving of the disk can be done by the patient 
or by the surgeon himself, who can easily reach it by a step 
from his examination distance of one to one and a half-metres. 
Of course the disk can be made large enough to contain any 
number of lenses. But those I have used are, according to 
my experience, ample for all ordinary cases, and keep the 
size of the disk to easily manageable dimensions. When 
other and stronger lenses are required, a lens from the trial- 
case of a number higher than the highest in the disk can be 263 
Skiascopy. 
placed in the clip /, Fig. 2, which can be turned on the rod 
B to either side as desired, and the disk rotated as before, 
beginning at 0.25. The lens in the disk thus found is, of 
course, to be added to that in the clip, in order to have the 
full strength of the lens demanded. Not the least impor- 
tant use of the clip, however, is for holding the cylinder 
which has been selected for the correction of any existing 
astigmatism. This is very important, in many instances, for 
verifying the findings by other methods. 
The graduated tape-measure Fattached to the disk enables 
the observer to measure his exact distance from the eye 
under examination, which is necessary in the method as 
used by Jackson and others. 
This apparatus, I claim, has the advantage over a some- 
what similar disk devised by Doyne of Oxford, and exhibited 
at the International Medical Congress in Washington in 
1887, in so far as it is less cumbersome, more easily manip- 
ulated, and is much less expensive. The disk can also be 
mounted on a stand, like a photographer’s head-rest, which 
would allow of its being moved from place to place. Under 
certain circumstances this is the preferable form—for in- 
stance, where a special dark-room is not available. The 
instrument is made under both forms by Queen & Co., 
Philadelphia.