The Secrets of Specialists/Chapter 28
Among other specialties which physicians have allowed to drift from their possession, is the fitting of glasses. This specialty is a very compensative adjunct to an office practice, and should not be allowed to remain in the hands of the traveling spectacle peddler or local jeweler, who have seemed to monopolize the business, although they are absolutely devoid of any knowledge of the diseases of the eye; other than the manipulation of a trial case.
The cost of equipment for fitting glasses is so small compared with the profits received that every physician should incorporate this specialty with the other routine of office work, and thus place the specialty where it justly belongs, in the hands of the physician.
The case contains pairs, plus and minus spheres, and pairs plus and minus cylinders, also prisms numbered from ¼ to 20 degrees. The spheres are numbered in intervals from 0.12 D. S. up to 3.50 D. S. The interval is 0.25 D. S. from 3.50 D. S. to 8 D. S. the interval is +0.50 D. S., and from 8 D. S. to 20 D. S. the interval is 1.00 D. S.
The cylinders have the same intervals, but only go to 6 or 8 diopters.
The trial case also contains a frame called the trial frame, which is used to place lenses in front of the patient's eyes. The best frames have three cells, two in the front, and one in the back of the frame. The eye pieces of such a frame are numbered on the periphery in degrees of half a circle, so that the axis of the cylinders can easily be seen during refraction. The left of the horizontal line in each eye piece is recognized as the starting place or zero (0) and the degrees are marked from left to right on the lower half, counting around to the horizontal meridian which at the right hand is numbered 180. This horizontal meridian is, therefore, as horizontal zero (0) or 180 degrees. The meridian halfway being zero (0) and 180 degrees is the vertical meridian or 90 degrees. The trial case also contains plano lenses, colored lenses, blinders, stenopaic slit, pin-hole disk, maddox rodete. The frame can easily be adjusted; the pupillary distance measured, bridge properly adjusted, riding bows measured and height of nose piece taken.
Convex sphere lenses in the case are put in nickel rims. These lenses are thick at the center and thin at the edge, and have the power of converging the ray of light.
The convex lens is a magnifier and a 20 D. S. lens is often used in removing foreign bodies from the eye through oblique illumination. Objects viewed through a convex lens as it is moved before the eye appear to move in an opposite direction. If a convex lens is brought toward the eye, objects already enlarged appear smaller and more distant. A concave sphere is thick on the edge and thin in the center and causes the rays of light to diverge. When the lens is moved away from the eye objects appear smaller through a concave lens and larger as the lens is brought nearer the eye.
If a convex cylinder is moved in front of the eye in the direction of its axis, objects seen do not change position, but when moved at right angles to its axis the objects appear to move in the same direction as when a convex sphere is used.
If a concave cylinder is moved in front of the eye in the direction of its axis, objects seen or looked at do not change their position, but when moved at right angles to its axis the objects appear to move in the same direction as when a concave sphere is used.
A cylinder lens has two little diamond scratches on the edge of each lens and these scratches note the axis of the lens and when astigmatism is corrected you can note the axis of the cylinder on the trial frame through these scratches.
A circle viewed through a strong convex cyl. (cylinder, appears as an oval with its long diameter in the opposite direction to the axis of the cyl. The long diameter of the oval will be in the same direction as the axis of the cyl. when the circle is viewed through a concave cyl.
The sides of a prism converge to a thin edge at one extremity of the prism. This is called the apex. At the other extremity they diverge from each other, forming the base. Objects viewed through a prism are displayed toward its apex and that portion of a straight line seen through a prism never coincides with the straight line.
The optician should supply himself with a lens measure, and by the use of the same can in a moment's time find the
curvature on each side of a lens. If a spherical lens, the difference of the sides are subtracted from one another and then you have the strength of the lens.
If a compound lens yon measure the sphero, and cylinder sides and you then have the strength of each side. Now to find the axis of the compound you take a sphero. lens, opposite strength from the one found in the compound lens, also cylinder lens opposite strength from one found on cylinder side of compound lens; place these two lenses before compound lens and looking at distance objects rotate cylinder and when the neutral point is found you have located the axis of the compound lens.
Seat your patient twenty feet from the charts used; these charts should be well lighted and "Snellen's" type of chart is considered the best. The trial frame is then adjusted. Be
sure that it fits the patient comfortably. The pupillary distance properly placed and see that the eye lashes do not touch the lenses when inserted in the frame. Now you proceed to test your patient's eyes. First place a blank before the left if this helps the vision. If it does add +0.25 D. S. lens and see if this helps the vision. I fit does add +0.25 D. S. more and keep on adding a +0.25 until you have given the best vision possible. Now you have the Hyperopia corrected.
Next is to determine if there is any astigmatism present. Have the patient look at the clock dial placed beside the test type, and see if all lines appear the same shade of black, and if some of them are lighter than others, the patient has astigmatism and these lines are to be made uniform by the aid of a cylinder lens. The correction of astigmatism will always give
the patient better vision. If the patient is far sighted and has astigmatism the 9 to 3 line on the clock dial will appear darker. Plus cylinder placed at 90 degrees is used to make the proper correction. In finding the axis of the astigmatism the cylinder is rotated to where the best vision is found, and can be proven by rotating the axis a small distance from this point each way, where the vision will blur. If the patient should be myopic minus lenses are used, instead of plus lenses, and the same course as heretofore described is followed with minus spheres instead of plus and after the myopia is corrected have your patient look at the clock dial, and if astigmatism is present a minus cylinder is used and rotated from zero to 180 degrees, until the lines are all uniform, combining the spherical and cylinder lenses after the myopia and astigmatism is corrected you have a compound lens and the proper correction for the eye. The same course here described is used in examining the left eye with the blank placed over the right eye.
After your examination is completed and all errors of refraction corrected the next thing to note is the kind of glasses the patient wishes to wear. If spectacles are wanted note on your prescription blank whether they are to be rimless or with rims, quality of frame wanted; whether with cable temples or plain wire temples, the cable temples are best as they do not irritate behind the ears, and should always be recommended. Next note the length of temple required, then the pupillary distance is taken, and the size of lenses that will give proper pupillary distance. Next thing to note is the base of the bridge on the nose, also the height of the bridge, whether the bridge is inward or outward, so as to bring the lenses a proper distance from the eyelashes. If nose glasses are preferred note whether the patient wants rimless or with rims, style of nose glasses, also distance between guards, at top and bottom, pupillary distance measured, size of lens required to bring about pupilliary required and see that the eyelashes do not touch glass at any point; if they do use an offset guard or stud in eyeglasses so as to avoid lashes touching lenses. If the lashes be long toric lenses should be recommended, as they give a wide field of vision, and with their inside curve of six diopters the glass can be placed very near the eye and still avoid the eye lashes.
If bifocal lenses are required, or both distance and reading lenses together, you note the style of bifocal, whether cement or invisible, and this is checked off on prescription blank.
In prescribing bifocals the size and shape of segment should be noted and the segment should never come above the center of the distance lens, and the lenses should be tilted a little downward, as this will give better vision. Your nearest optical house will furnish you with prescription blanks, gratis, which you will find very handy for putting down frame measurements.
If a physician will secure a test case and practice the heretofore rules laid before him he will be able to correct ninety per cent. of patients coming to him with defective vision.
A Maddox rod is found in every trial case, and can be used as a most reliable test for the muscles of the eye. In making the examination of the muscles of the eye you place your patient six metres from a small flame, place the rod horizontally before one eye, a red colored glass before the other; if the line formed from the Maddox rod passes through the flame, there is orthophoric, as far as the horizontal movements of the eye are concerned. Should the line be to either side of the flame, as in most people it will, there is either latent convergence or latent divergence, the former if the line is the same side as the rod, the latter if to the other side.
In order to test the vertical deviation the rod is placed vertically before the eye, a horizontal line of light appears and the patient is asked if the line passes directly through the flame, or if it appears above or below the flame. If the flame is lowest there is a tendency to upward deviation of the naked eye; if the line is lowest of the eye before which the rod is placed.
The measurements of the extent of the deviation may be made in the ordinary way, by finding that prism placed before the naked eye, for the eye covered with a red glass, which brings the line and flame together.
The accommodation diminishes gradually from early life onward, and the near point recedes farther from the eye with each succeeding year. As long as it remains within 20 or 30 C. M. no appreciable inconvenience in reading is noticed, but when the near point has fallen off to a greater distance than this, it is not possible to read fine type without the aid of convex glasses unless the visual acuity is much above the average. This condition is termed presbyopia and is a normal result of growing old,
The cause of presbyopia consists of hardening of the crystalline lens, which is thus prevented from assuming the increased convexity which constitutes the essential factor of accommodation. The increase of convexity necessary for seeing near objects must be supplied to the eye by a spectacle lens. In early stages of presbyopia weak convex lenses are used and as the patient grows older and the power of accommodation diminishes, stronger convex lenses will have to be prescribed.
Retinoscopy is a system of examination of the refractive errors and measuring the eyes for glasses, and it was discovered by Cuignet and later by Sir William Pagent Bowman in the sixties. Since that time many writers have produced works covering this subject, but in every instance it is quite apparent they have had a greater desire to show their profound knowledge rather than to make plain this intricate yet fascinating method for diagnosing difficult cases.
This system is the objective method for estimating the refraction of the eye by the character of reflected images thrown from a plane or concave mirror, observing the movements which the retinal illumination makes by rotating the mirror. It gives the advantage of a quick diagnosis of the case without asking a question. Positive information is obtained as to whether the case is hyperopic or myopic, except in low degrees of either defect; when spasms of the ciliary muscle or accommodation exists, then the true condition of the eye is uncertain; this may be obviated to a certain extent by having the eye turned slightly inward, thus preventing the light from falling directly on the macula lutea, and by so doing the test is made much easier by removing at least part of the spasm.
There are four methods in retinoscopy, named as follows: First, the McFatrich; second, the static; third, the dynamic, fourth, the fogging. In the following explanations let it be understood that only the plane mirror is used.
The McFatrich method is to seat the optician fifty-three inches from the patient, and with the retinoscope reflect the light into the eye, directing the patient to look slightly inward: this illuminates the retina; then rotate the mirror in such a manner as to cause the light to move directly across the face from left to right. If the shadow moves with the mirror the case is hyperopic, caused by the eye being too short, thus making the focus come back of the retina of the eye, and a plus lens is required. Place a +0.50 D. lens in the trial frame before the eye, and if the shadow still moves with the mirror keep adding plus lenses until you find the weakest lens that just reverses in that meridian. Then if it is a simple case of hyperopia you will find that if you rotate the mirror in the vertical meridian, the shadow will just reverse in that one also.
We will take, for example, a case where we find in the right eye in the horizontal meridian that the shadow moves with the mirror and it takes +5.50 D. to just reverse it, so after making a +0.75 D. deduction, (an allowance made for bringing the far point of the eye to a point in front of him), we have a +4.75 D. lens for the correction of the horizontal meridian. We next examine the vertical meridian and find that the shadow still moves with the mirror, and that it takes a +3.25 D. lens to just reverse it, and after making the +0.75 D. deduction we have a +2.50 D for the result. Now, if it takes a +2.50 D. to correct the vertical and a +4.75 D. to correct the horizontal meridian, we have a difference of a +2.25 D. between the two meridians, so we can use a +2.25 cyl. axis 90 over the +2.50 D. sphere, thus making a compound, and the correction for the right eye would be as follows: O. D. + 2.50 D. () +2.25 cyl. axis 90.
We next examine the left eye and find that the shadow moves with the mirror in the horizontal meridian, and find that it takes a +4.50 D. to just reverse it; after making the +0.75 D. deduction, we have for the result a +3.75 D. We now rotate the mirror in the vertical meridian and find that it takes a −1.75 D. lens to just reverse the shadow, so we add a −0.50 D. (an allowance made in myopia, as the far point has been carried back of the operator, so that a −0.50 D. must be added to the concave lens that just reverses the shadow), making a −1.75 D. in the vertical meridian. Now the difference of the two meridians would be the sum of 3.75 D. and 1.75 D., which is 5.50 D., so that the retinoscopic corrections for the eye is as follows: 0. S.-1.75 D. + 5.50 cyl. Axis 90.
We will suppose another case; that in the horizontal meridian that the shadow moves against the mirror, and we find the weakest minus lens required to just reverse the shadow is a −0.25 D.; then we add the −0.50 D. and that makes a −0.75 D. for the horizontal meridian to just reverse it, so after deducting the +0.75 D. from it we find the eye emmetropic in that meridian. Our retinoscopic finding for this eye is a cylinder written as follows: O. D. −0.75 cyl. ax, 180.
We next examine the left eye in the horizontal meridian and find that the shadow moves against the mirror and the weakest minus lens required to just reverse it is a −1.50 D., and after adding the −0.50 D., we have the result, a −2.00 D. for the above mentioned meridian. We then examine the vertical meridian and find that the shadow with the mirror and it takes a +3.75 D. to just reverse it, so after deducting the +0.75 D. we have a +3.00 D. for this meridian. Now if it takes a +3.00 D. to correct the vertical and a −2.00 D. the horizontal, we take the sum of these two for our cylinder, which is a −5.00 eyl. ax. 180, so that our retinoscopic finding for the left eye is as follows: O. S. +3.00 D. () −5.00 cyl. ax. 180.
Then again we have the numerous cases where the shadow does not run with or against the mirror in either the horizontal or vertical meridians, but runs obliquely instead; then we rotate the mirror in the oblique at right angles to each other, and proceed using the same rules as heretofore described.
The static method is to place a +1.00 D. lens in the trial frame in front of each eye; then rotate the mirror at a distance of 40 inches from the eye, requesting the patient to look at the test card 20 feet away, and if the shadow remains still in the meridians, then the case is emmetropic, as the +1.00 D. lens just neutralizes the distance between the optometrist and the patient. If the shadow moves with the mirror, the case is hyperopic, and if it moves against it is myopic, and from all retinoscopic findings in this method, a +1.00 D. should be deducted.
The dynamic method is just the reverse of the static, and a system of shadow testing where the accommodation is active. In this method the patient is directed to read a small card of different size letters, placed on the forehead of the optometrist 40 inches away; now to do this he has to use 1.00 D. of his accommodation. Now let the deep thinking optometrist follow this explanation closely, then he can judge as to the real value of this method, as it is the writer's intention to give facts and prove that this method, which seems so nice in theory, does not meet with accurate results then in practical use.
Here are a few examples, as follows: First case: If the eye is emmetropic the rays of light will emerge parallel and the 1.00 D. of accommodation will converge these rays and cause them to focus at a distance of 40 inches and no motion will be observed in either meridian, as the 1.00 D. of accommodation used takes the place of the +1.00 D. lens that is used in the static method.
Second case: If the patient has 1.00 D. of hyperopia he will be obliged to use 1.00 D. of his accommodation to see the test card clearly at a distance of twenty feet and 1.00 D. to read the brow card at a distance of 40 inches, thus making a total of 2.00 D. of accommodation used.
Third case: Suppose a patient has 1.00 D. of myopia; his far points for distance vision is 40 inches and the emergent rays will focus at this point, and the patient will not use any accommodation to read the brow card.
Now, it is claimed by the exponents of the dynamic method that it is impossible to separate accommodation and convergence by placing the plus lenses in front of the eyes, except for hyperopia, they may have. In the first case we find the eye emmetropic using 1.00 D. of accommodation. They place plus lenses in front of the eye and find the strongest that will be accepted without reversing the shadow. In an emmetropic eye they state that a +0.25 D. will cause a reversal even though the eye is accommodating 1.00 D.
In the second case we find the eye using 2.00 D. of accommodation. They claim that this eye will relax 1.00 D. for it is that much hyperopic, but it cannot relax any of the other 1.00 D. as the convergence checks it so it will not relax.
In the third case, the eye being myopic 1,00 D., no accommodation is in use. They place an over correction of minus spheres, rendering the refraction of this case hyperopic. Then they gradually reduce with minus spheres until they find a point of reversal.
The special advantage claimed by the exponents of this system is: In case of a spasm of accommodation sometimes found in a case of hyperopia the eyes will test myopic at 40 inches because the spasm holds the focus in front of the retina. The spasm covers the 1.00 D. of hyperopia and renders the eye myopic 1.00 D. and at 40 inches requesting the patient to read the brow card; this calls for 4.00 D. of accommodation, and as the patient has a spasm of 2.00 D. covering his 1.00 D. of hyperopia, thus bringing the focus 1.00 D, in front of the retina, so it will only be necessary for him to use 3.00 D. of hyperopia; but right here the dynamic exponents claim that he will accept just 1.00 D. as this is the amount of his hyperopia and that his convergence checks relaxation at this point, but does it?
This whole system hinges upon their theory that accommodation and convergence are so closely related that by placing plus lenses in front of the eyes this relation cannot be disturbed. If we allow the exponents their premise in an argument, we generally have to admit it, as their reasoning will be logical all the way through. If right here we take pains to experiment so we can determine the truthfulness of their first proposition, and then we will discover why this method proves up inaccurate in nearly 90 per cent. of all its cases. The writer states fearlessly that convergence is not a check upon accommodation and will prove it by the following experiments:
If the exponents are right in the relation of these two functions in their shadow test, it surely ought to be demonstrated with lenses subjectively. Take a person with emmetropic eyes, and if we place −2.50 D. sphere in front of their eyes, and in order that they can read the 20-20 line, on the test card 20 feet away, they will have to use 2.00 D. of their accommodation. The 20-20 line on the test card 20 feet away is perfectly plain, bearing in mind that their accommodation is fixed for 16 inches. This ought to prove most conclusively to any optometrist that under the above-named conditions the accommodation can be exercised 2.50 D. while the convergence remains fixed for 20 feet. If we were to increase the strength of the minus spheres, it would produce diplopia, thus showing that 2.50 D. is the limit of their power of separation between these two functions.
In another experiment we find that they can read the 20-20 line perfectly with 25 degree prisms (half of the amount over each eye) base out. This shows that they can send a nerve force to the internal muscles without affecting the ciliary muscles in the least. It seems to the writer as if these two last experiments, which can be made on yourself or anyone else, ought to convince any deep-thinking optometrist of the inaccuracy of the theory of the dynamic method.
In all cases of hyperopia, except the "squints," we find these two functions working entirely out of harmony with each other, showing the wonderful power of adjustment in nature. In all cases of myopia we have the same conditions reversed, for while the convergence is fixed for 20 feet, the accommodation is nearer to the eye according to the myopia.
The fogging method of retinoscopy is one that relaxes all accommodation, as it is an active accommodation that is responsible for many errors in refraction. The test is made by placing a plus 4.00 D. lens before the eyes, and have the patient look off into space. This renders the eyes myopic and puts them in a condition of rest. If the eyes are emmetropic, the emergent rays will be parallel and a +4.00 D. sphere will bring these parallel rays to a focus at 10 inches in front of the lens. As you observe the motion of the shadow from 40 inches, you will find the eye decidedly myopic. Move closer and closer until you reach the point of no motion. Measure from the lens to the mirror, and if the eyes are emmetropic you will find the neutral point or conjugate foci to be 10 inches. If your case happens to be hyperopic of 1.00 D. the rays of light will emerge 1.00 D. divergent; as it requires 1.00 D. of your +4.00 D. to make these rays parallel, they will be brought to a focus 13 inches from the eye. The motion will reverse at this point. In all cases of myopia the emergent rays are convergent and the +4.00 D. will make them still more convergent. If there is 1.00 D. of myopia, the convergent rays would focus at 40 inches without any lens. Placing a 4.00 D. sphere in front of the eye causes the rays to focus at 8 inches in front of the lens.
If we wish to be exact in our measurements in this or other methods we can attach a tape measure to our trial frame and hold the same in one hand, while we rotate the mirror with the other, at the required distance. In the fogging method this will give you the exact distance between the lens and the mirror and you will find your conjugate foci. The rule to follow is: place a +4.00 D. sphere in front of both eyes. Reflect the light with a plane mirror into the eye and find the point where there is no motion. If it is the focal point of the lens 10 inches, the eye is emmetropic.