THE MADDOX ROD OR THE PHOROMETER; WHICH?
In the last issue of the Journal there appeared an abstract with the above title, and believing the subject to be of much interest at the present time, our readers have been invited to send us their opinions on the matter, as based on the experience obtained in practice. The communications below have been received and are presented in the order of their reception. We shall be glad to hear from any physicians who are interested [Ed.].
Dear Dr. Deady: In reply to your favor requesting my opinion regarding the respective merits of the Maddox rod and the diplopia test, I wish to say that my experience leads me to rely more and more upon the obscuration test, and while I have not followed out the comparison to any great extent, such as is shown by your tables, results obtained by relying upon the rod test in the detection of heterophoria, as well as in determining when the weak muscles have been sufficiently developed, have been such as to warrant my continuance of its use.
E. D. Brooks.
I have with interest watched the discussions of late, as to the relative value of the Maddox or Stevens tests for heterophoria, as I have for years used them both.
My muscle tests have been made for the last five years at least, with a Risley phorometer, which combines both tests upon one arm and has proven for me a most satisfactory instrument.
I am sorry to say that I have not kept any comparative statistics of my examinations; at the same time they have all left an impression upon my mind, which is this: that I feel more confidence in the results obtained from the use of the Maddox test in the routine tests that I always make of refractive cases. If this test shows any marked degree of heterophoria it has been my habit to retest the patient by the Stevens method, which is usually the same, provided the patient has a sufficient amount of intelligence to give correct answers to the questions put to him. During this test the patient is allowed to sit for some time in front of the prisms, and the eye muscles allowed to relax from that first impulse at muscular effort that follows the placing of the prisms in front of the eyes.
To my mind both tests are good and fairly accurate in the hands of one who is thoroughly familiar with their use and shortcomings, provided your patient is able to answer correctly.
Many times, on re-examining a patient, I have discovered what appeared to be a great change in the muscular conditions, but after repeated examinations I have usually found it was the patient, and not the muscles, that was erratic.
When Dr. Hubbell speaks of ¼° of difference between the Maddox and Stevens tests, he has more confidence than I have in the average judgment of patients that come under our care.
Sayer Hasbrouck.
Dear Doctor: Your note asking my opinion of the comparative usefulness of the Maddox rod and the phorometer is at hand.
In the detection of heterophoria I regard the rod as the most convenient and trustworthy instrument used.
The distance at which the test is made and the dissimilarity of the images seen usually eliminate all actual effort to hold the eyes in any particular position other than that in which they stand the most easily. Accordingly the deviation is quickly noted and readily measured.
So satisfactory has this modest little instrument been in my examinations that I now rarely resort to other methods. The amount of deviation sometimes shown between this and other instruments is so slight as to make little or no difference in the measures employed for correction.
It is to be noted that cases not unfrequently occur in which a hyper-sensitive, or, on the contrary, an enervated condition exists, which is not fully indicated by any instrument. An educated judgment will here have to supply conclusions not to be drawn by any hard-and-fast rules.
After the rod and the phorometer came into use and an opportunity was presented to compare the results obtained by each, I made a careful test of eighty pronounced cases of errors of refraction accompanied by heterophoria. Of this number only nine showed a persistent difference of deviation and in none of them a difference greater than 1½°. But this was not always on the one side or the other, as six out of the nine showed a higher degree of deviation by the rod than by the phorometer. Eighty cases may not be enough upon which to base an orthodox conclusion; but my experience with the rod has been so satisfactory that I now seldom use the phorometer at all. It appears quite possible practically to estimate the degree of heterophoria as accurately with the one instrument as with the other; and while it is true that a correction of the error of refraction will commonly correct the deviation, still all cases of optical defect should be tested with the rod or phorometer before the lenses are prescribed.
Wm. A. Phillips.
My Dear Dr. Deady: Dr. Hubbell limits the discussion “to the comparative value of the diplopia test, by Stevens’ phorometer” and the Maddox rod test.
It would be interesting to follow out the idea with other phorometers,—and with the Wilson phorometer my records do not show quite such a marked difference in results,—but I have not taken pains to get comparative results in any considerable number of cases.
Dr. Hubbell says: “In the diplopia test, the dissociation is effected by changing the visual axis of one eye by means of a prism. The displacement of one image cannot be done without associating with it, more or less, an impulse to some form of ocular effort.... In the obscuration test (Maddox rod) no such effort is invited, no change of innervation takes place.” But in the rod test the light seems nearer to the patient than in the prism test. This may account for much of the difference in results and amount to “an extraneous impulse to muscular contraction.”
Dr. Hubbell is entirely justified in his conclusion as made upon experiments with the Maddox rod and the Stevens phorometer. I shall watch cases along similar lines with the Wilson phorometer and report later.
In the mean time the rod and the prism tests may well be taken in each case and let judgment decide as to treatment.
Thos. M. Stewart.
I agree with the writer that the rod test is the more scientific test for heterophoria, and of late years have virtually discarded the prism test, except in special cases. The tables are interesting, but their value would be materially increased if the author would supplement them with tables showing the refraction, and inflammation or its results.
Was it an accident that Stevens’ phorometer showed the same amount of right hyperphoria in one-ninth of the cases, and in thirteen of thirty-three cases of left hyperphoria? In which of these cases was there anisometropia and of what kind was it?
What was the refraction of the two cases of exophoria, two of left and one of right hyperphoria by the phorometer; and was the refraction the same in the six cases which were orthophoric by both rod and prism?
Such studies are necessary to a clear understanding of the relative value of these tests.
John L. Moffat.
Dear Dr. Deady: Your letter and inclosed article on “The Maddox Rod or Phorometer; Which?” has been received and examined with interest.
I have examined a good many cases in my office by both methods and find variable results, but where there is a radical difference I have found the Maddox rod the more accurate, and from experience I have learned to rely upon it instead of the phorometer, as in prescribing prisms in hyperphoria in connection with glasses for constant use I rely wholly upon the rod test.
J. M. Fawcett.
Dear Doctor: Concerning the discussion of Maddox Rod vs. Phorometer about which you wrote me—can say that I believe that the Maddox rod is the more reliable test. My reasons on theoretical grounds for so believing are briefly these.
Given a case for examination; the test which least disturbs the muscular co-ordination under investigation must give the best result. Now I think that when we throw the images into non-corresponding retinal points that we almost certainly cause some tension of certain muscles, because it is putting the eyes in an unnatural relation with one another; and this is done by the phorometer. The Maddox rod is theoretically free from this objection.
Practically the deviations are more certainly measured, because a patient knows when the streak cuts the light; and you cannot trust their eye alone to tell when the lights are exactly in a line. Have used both tests in every case I have examined in my private practice, and I find the Maddox the more reliable test. It is more to be depended upon.
Edw. Hill Baldwin.