New England College of Optometry - Scope Yearbook (Boston, MA)

Page 20 text:

THE SCOPE When the contractions of the fields are uniform or concentric, one may look for FUNCTIONAL rather than ORGANIC causes. As a rule, the depressions are not uniform. In charting scotomata, the defect is absolute when no light perception exists. For this reason a strong light should be used on all scotomata as it will be found that absolute defects are not as common as lesser tests might lead us to believe. fTliis is of importance to the Optometrist specializing in the development of vision in amblyopic conditionsj Vision for colors may be seriously affected while the field for white remains practically unchanged and vice versa. Any enlargement of the blind spot, relative or indistinct, is indicative of a path- ological change. An enlargement of two degrees is considered as pathological. The di- rection of the enlargement is of vital importance. An enlargement from above and be- low indicates glaucoma. In toxic amblyopia and myopia of a high degree, the enlarge- ment is toward the fovea. In glaucoma, perimetric readings have shown us that changes take place in the peripheral fields especially on the superior nasal side leaving the central area more or less unaffected. In its incipient stages glaucoma yields to medical and surgical treatment, in the latter stages, due to atrophy and hemorrhages, if it yields at all it is with a variable amount of success. Inasmuch as early treatment is necessary for success in glaucoma, early recognition of the condition cannot be too greatly stressed. In choroidal disturbances the fields of red and green are usually contracted with a fairly normal blue and form field. Disturbances of the rod and cone layer of the retina have the reverse affect, there being a shrinkage of the blue fields while there is little change in the fields for red and green. Much can be said in regard to various perimetric signs in various conditions but I believe it would be unwise to delve further into the subject at this time. However, a few simple marks which optometrists might follow to a certain degree would not be amiss. GREEN Involvements of the green fields are indicative in IHOSI cases of focal infections. This in turn may ffrom the toxemiaj cause some form of retinal disease. Clioroidal in- volvements may be due to some direct source of infection. In green constriction, look for abscessed teeth, sinus infections, diseased tonsils or foci of infection of any kind. Acute poisons of various types can be the cause. RED. A constricted red field when not secondary to green constriction primarily in- dicates a systemic toxic condition. When both fields are constricted the toxemia is be- coming general. A high leucocyte count will substantiate this diagnosis. The general systemic depression may be caused by faulty diet, intestinal stasis, or anything causing a general systemic poisoning. BLUE. The involvement of the blue field is often indicative of an organic disorder. A specific heart involvement will contract the blue field prior to any disturbance of the red or green. On the other hand an ulcerated tooth could cause heart trouble. In this case there would first be a constriction of green, the red involvement being secondary. In general systemic toxemia the blue field is seldom constricted alone. There is usually a contraction and overlapping of red and green fields. TOXIC AMBLYOPIA. Toxic Amblyopia may be caused by two general types of poisoning, exogenetic or endogenous. Exogenetic poisons are usually selfradministered such as coffee, tea, tobacco, alcohol, etc. U61

Page 19 text:

THE SCOPE Form and Color' lffiiellcils B-y la'OS'l'hQR H. NAlXfllAS, '52 The field of vision, as we know, is the whole of space visible when we are fixing upon any object. Witli the changing of our point of fixation the fields naturally change their areas, however, remaining practically the same. The image of the point of fixation falls upon the fovea. It is here that we read, and for this reason, many refractionists pronounce a patients vision as normal, when the case may be far otherwise. More important to the patient is a normal para-central and peripheral field. My choice would most emphatically be in favor of the latter. It is often the case that one may be able to distinguish a minute object at a great distance yet be unaware of the presence of a speeding automobile almost directly within one's path outside the central field. Nature has given us central vision by which we may read or closely study an ob- ject. More important, she has given us peripheral vision that we may protect ourselves from whatever dangers may approach us. W-'ith this in mind, we can understand the im- portance of a wide field. The visual apparatus has oftimes been compared to a telephone system, with its receiver, wire and station. Trouble various kinds. The perimetrist is position and nature of the trouble. Fields may be charted either cially adapted for peripheral study central area up to 50 degrees. is apt to occur at any point along the line and be of the trouble shooter whose duty it is to locate the on the perimeter or campimeter, the former is espe- while the latter is adapted for the central and para- When vision is poor due to a central scotoma so that the patient is unable to fix with that eye, a red glass may be used over the patients good eye with a fixation object of the complementary color fgreenj. For all practical purposes, however, a large fixa- tion object may be used. The examiner must keep in mind that perimetry is not an exact science but a sub- jective test. Therefore, while all refinements in either the perimeter or campimeter are of value, their necessity must be estimated with a sense of proportion. As facial characteristics will affect the sizes of the fields, the positions of the eyes, brows, nose, and cheeks should be taken into consideration in analyzing the finished graph. The patient should be made acquainted with the test objects-demonstrating the nature of the technique, that he may co-operate more intelligently. It is well to demon- strate the blind spot. This will impress upon him the necessity of steady fixation even though the test object disappears. Conserve the patients energy by concentrating attention on the defective areas bringing out the features of most diagnostic value. Most technicians chart the blind spot first, then the form and color fields, then look for scotomata. In charting the color fields record the position of the spot where the patient rec- ognizes the color with the same degree of saturation as it appears to him with central fixation. The various colors go through various changes before reaching their full satur- ation, therefore the patient is to be carefully instructed in this phase. It is well to remember: first, that the shape of the field fwithin limitsj is more important than the sizeg second, that rapidity of examination and comfort of the patient are of prime importance, and third, that the scope of perimetry is limited on the one hand by the nature of the tests involved, on the other by the ability of the patient to respond to them. U51

Page 21 text:

THE SCOPE Endogenic poisons are usually generated within the body, i. e., diabetic poisona ings, glandular, kidney, etc. A distortion and contraction of the form field combined with intei-lacing of the fields for color is indicative of infections due to exogenic poisons. ln tobacco amblyopia there is first a constriction and interlacing of the red field, the form field becomes distorted. There is usually an enlargement of the blind spot and the red field will be most contracted especially in the upper and outer quadrant. It may be unilateral or bilateral. Endogenic poisonings usually leave the field contracted while distortion is less marked. The form and color fields are affected alike. Certain drugs, such as quinine and aspirin affect the field as endogenic poisons. In the early stages there will be a marked enlargement of the color field with probable contractions in either the lower or upper areas possibly towards the nasal side. The color field becomes greatly constricted in the advance stages. This is also true of the form and white field. Under treatment the return to normal is slow being more marked laterally than vertically. Perimetry thus offers us a means of diagnosing impending pathology long before the exploration of the fundus with the ophthalmoscope can ofier assistance, Wfith this means at the disposal of the Optometrist skilled in color field analysis, he may be able to enter new iields of useful professional endeavor. As Brombach states, This method of optometric interpretation of color fields may well take the place that X-Ray analysis occupies in dentistry. REFERENCES! An Introduction to Clinical Perimetry by H. M. Traquaire. The Principals and Practice of Perimetry' by Peters. Practical Guide for Charting and Interpreting the Visual Fields by Win. A. Mendelsohn, Dr. Svendlsengs Selliiooll Clliiniie Students aiippireeiiaite Anatomy teaelhetgs interest The senior class wish to extend humble and profound gratitude to Dr. Wil- helmina Svendson, who through unstinted and unselfish effort, established a wonderful clinic at the school. The students had complete charge of their patient under the super- vision of Dr. Svendson, and each student who took an interest received an immeasurable amount of good out of this method of conducting a clinic. All were loud in their praise of Dr. Svendson, and each feels that she has given him something that it would have been impossible to obtain without her timely assistance. l17l