Ординатура / Офтальмология / Английские материалы / Visual Fields Examination and Interpretation_Walsh_2011

xx A History of Perimetry

and Wall (see http://www.perimetry.org/PerimetryHistory/index.htm). We are also indebted to Drs. Simpson and Crompton for their exhaustive work on those who have advanced the field of perimetry.2 They searched in many a medical library and resurrected almost-forgotten dusty manuscripts. Among their sources is a library that I have relied on in the past and have been fortunate to have virtually at my doorstep—the Harvey Cushing/John Hay Whitney Medical Library of Yale University’s School of Medicine, which I used extensively in developing this review. This library has a long distinguished history and has played an important role in the history of perimetry. The name of the library honors Dr. Cushing,3 whose lifelong interest in surgery for pituitary disease was as keen as his observation of visual defects. In this, he was helped by Dr. Clifford Walker, who worked in his clinic and conducted perimetric examinations.

Dr. Cushing and Dr. Eisenhardt, in their studies of the optic chiasm in 1926, took exception to Wilbrand’s theory of the location of the inferior nasal optic fibers as the fibers crossed through the chiasm. This issue was elaborated on by Jonathan Horton4 in 1997 and is discussed further in Chapter XX.

Determining who was first to make observations in diagnoses based on perimetry is difficult. The technique of confrontation was probably used much earlier, but late in the 1800s, William Gowers popularized it as a field method.5 In many cases, the phenomenon of a particular defect was observed by one and its anatomic significance was observed by another. Hippocrates was probably the first to describe hemianopia, in the fifth century BC. It was Ptolemy, around 150 BC, who started to quantify the size of the peripheral field.6 Leonardo da Vinci in 1510 also studied this and reported that the temporal field was 90°. This was an important observation, as we will see, with future study changing field testing from a flat screen to an arc perimeter, which, of course, does not diminish the importance of Hippocrates’ observations.

Issac Newton made the observation of a partial decussation of the chiasm in 1602,7,8 which Dr. Johann Spuryheim confirmed in 1820.9 In 1664, Thomas Willis published his work on the functional anatomy of the brain and reaffirmed the crossing of fibers in the chiasm.10 William Wollaston, in 1824, described a case of left homonymous hemianopia11: the patient was himself. The defect cleared, but it was followed by another homonymous hemianopia on the right, which was due to a tumor and which did not clear. He realized each time that the defect concerned only one half of each eye and that the fibers from the eye decussated.

Albrecht von Graefe’s name is prominent in many areas of ophthalmology, including perimetry, ophthalmoscopy, and surgery.12 His friend Hermann von Helmholtz had perfected the first ophthalmoscope but was not impressed with its clinical use. It was von Graefe who introduced this instrument at the German Physical Society. He fell in love with the instrument and used it to make many observations throughout his life. He observed papilledema about 1850 and noted in his first report of that phenomenon that it was seen in cases of increased intracranial pressure from brain tumors and declared that a way of making such a diagnosis should be quantified. Some others, such as Ulmus of Padua in 1602, illustrated a visual field he had observed. In 1856, von Graefe then described a clinical technique to measure this phenomenon. He produced a board with a fixation object and

with peripheral distances marked off (which he called isopters) so that he could reproduce these defects in the future. This was the beginning of the current tangent screen. Although the technique was a major step forward, there were those who could see the potential for perfecting this technique and immediately improved upon it.

The flat screen was adequate for the central field but not for the peripheral field, which has been described as reaching 90° by da Vinci and again by Thomas Young in 1801 and Johannes Purkinje in 1825. In 1817, Joseph Bier in Vienna was studying the central field concept and identified defects such as central scotoma, paracentral scotoma, and central contraction. Richard Foster in 1860 constructed an arc-type perimeter to cover the peripheral field, but it was of no use for diagnosing a central scotoma. Schweiger then produced a patient hand-held arc-type perimeter, but it was not better and it was very cumbersome. In 1889, Jannick Bjerrum became very interested in the tangent type of technique and constructed a revised one on his office door. He standardized it so that a defect could be reproduced. Later, others added different-sized test objects to make the more subtle defects identifiable. Behrens thought that the flat test objects were inaccurate because the test object could move from the center of the visual field, so he devised a set of test objects in the form of balls. The test objects would then cast the same size image on the retina regardless of where they were projected in the field. However, these were always visible and could not be “turned off” from the patient’s perception.

Perimetry was developing a following, and in 1874, a book on perimetry was written by William Schon.13 Published 1874Schon worked with Dr. Horner of Zurich, renowned for his study of the pupil. Hermann Munk in 1887 performed experiments on dogs, first ablating one half of the occipital lobe and demonstrating hemianopia in each eye. Then he performed a similar experiment in another dog, on the other side of the lobe, demonstrating reverse hemianopia. This location of different types of defectc brings us to interest in decussation of the chiasm. Dr. Edward Schafer performed the same experiment as Horner’s in monkeys and achieved the same result. However, he added another observation to our fund of knowledge. He saw that there was a difference between an occipital hemianopia and one in the tract. Optic tract A tract hemianopia would have a hemianopic pupillary abnormality, which had been observed previously by Wernicke. There would not be a pupillary response in the blind field of a tract hemianopia. Although this is an established fact, the defect is a difficult clinical sign to elicit. By the end of the 1800s, interest in perimetry was well established. Dr. Salomon Eberhard Henschen identified the location of the visual fibers on the medial surface of the occipital lobe and that occipital cortical location was the same for the retinal field location.

Adolph Meyer reported in 1907 the course of the visual fibers from the lateral geniculate body. He reported that the lower visual fibers did not return directly through the temporal lobe.14 They went anteriorly into the temporal lobe and fanned out before they turned posteriorly along the course of the lateral ventricle. He also noted that they did not reach into the most anterior part of the temporal lobe. This information had neurosurgical as well as perimetric implications. In the 1950s, Falconer and Wendland were performing temporal lobectomy on patients

xxii A History of Perimetry

with epilepsy.15,16 As part of that operation, meticulous measurements were made from the tip of the temporal lobe to the area resected, and a correlation was made as to how much of a field defect was created. Up to 5 cm from the temporal tip could be resected before any field defect was created. Because of their work, surgery for epilepsy is done differently today, resultng in fewer field defects and better therapeutic results in most patients. That their results were truly anatomic rather than only perimetric confirmed the statement made earlier by Traquair in 1933 that hemianopias in that area are congruous. Some authors disagree with that proposition, so recently Kedar and colleagues17 raised the question again. This is discussed in the chapter on The radiations radiation. That is what it is called and that author is Thomas Hedges It is title of tracts from the temporal, parietal and occitpital lobes.

Many physicians have looked at field defects in the radiations and have noted other findings seen with different deficits. Purkinje noted one of these phenomena while watching a parade in Vienna.18 He noted that the people across from him all had horizontal nystagmus as the lines of soldiers moved past. Then, later in his clinic, he noted abnormalities in one direction and not in the other in persons with hemianopia. He thought that this might be a new way to diagnose hemianopia in nonverbal patients, but this was not found to be valid in all patients with hemianopia. Ohms corrected this theory and localized the hemianopia to the deep parietal lobe.

As terrible as war is in terms of human sacrifice and suffering, it sometimes results in new methods of treatment by caring and bright physicians. During the early twentieth century, Dr. Tatsusi Inouye examined soldiers with head wounds and eye complaints during the Russo-Japanese war.19 He used an arc perimeter for his observations and recorded the tract of the wounds and the type of field defect that would suggest the cortical location of those wounds. During World War I, Gordon Holmes, together with Chief British Army Ophthalmologist Lister, used a hand-held perimeter to confirm previous work showing that the upper calcarine cortex corresponded to the upper part of the retina and that similar correspondences held for other parts of the calcarine cortex. He also supplied evidence that acuity is spared even if an entire occipital lobe is removed. However, he did not support the theory that the macula is duplicated in both occipital lobes. Then, in World War II, the neurologist John Spalding studied 180 cases of missile wounds with defects limited to the posterior radiations and occipital cortex and confirmed the work of Holmes.20 Holmes created a map of the defects occurring in the occipital cortex. He allowed about 25% of the striate surface to represent central vision. Jonathan Horton and William Hoyt enlarged the field map, showing a much larger area for the macula.21 They also proposed that a 30–2 field would cover 89% of the field and would be adequate except for cases of central and peripheral defects that did not involve the monocular temporal crescent.

The arc perimeter had its supporters, and when I started performing perimetry, the Aimark perimeter was very popular. However, another perimeter was to take its place. In 1945, Dr. Hans Goldmann of Bern had devised a projection perimeter that took the shape of a bowl and that provided a way to change the stimulus. This again changed the way perimetry is performed. However, it was inadequate

for static perimetry. The value of static perimetry was pointed out in 1933 by Dr. Louise Sloan, but it did not gain ready acceptance. The next development was the Tübingen perimeter in 1959, and then in 1971 Stephen Drance and Mansour Armaly introduced suprathreshold testing.22

Dr. William Hart, Jr. developed the first perimeter to measure color contrast. Then Lars Frisén developed a technique of high-pass resolution, leading to the Octopus and Humphrey perimeters that are so familiar today and that are now equipped with software programs that make the test even more user-friendly. In 1951, Max Chamlin pointed out the significance of a step defect at the vertical meridian, suggesting an early sign of a field defect such as a bitemporal defect that might otherwise not have been seriously considered. This advance was achieved with just a tangent screen, but it can be performed with a Goldmann perimeter as well. Harrington then published his text on perimetry, which represented the state of the art at that time. Wilber Rucker in 194623 also began to publish his studies on perimetry under the auspices of the American Academy of Ophthalmology (AAO). We are continuing that tradition today with this book in the Ophthalmology Monographs series published by Oxford University Press in cooperation with the AAO. Rucker also provided an in-depth review of the history of the semidecussation of the optic nerves. Rucker,C W The concept of a semidecussation at the chiasm. Arch. Ophthalmol 1958:59: 159–171. Here we sought to give the reader an idea of how many people it takes to make an idea evolve. This is true in all branches of medicine. New testing techniques will continue to be developed in the future, and those physicians who succeed us will look back at us just as we are looking back at those practitioners who were using A confrontation technique. Although we look to computerized perimetry as the technique of choice, a good perimetrist must learn other techniques, such as confrontation and the tangent screen, because they are still very useful when computer-based techniques are not appropriate. If a patient cannot be examined adequately with the use of a computer program, a well-executed tangent screen test may be the answer.

The reader can see from this short historical glimpse that this is a very dynamic area and that advances are still occurring. The perimetrists mentioned in this review put us on our current path as we await the next developments in the field.

REFERENCES

1.Imaging and Perimetry Society. 2010. webeye.ophth.uiowa.edu; http://www.perimetry. org/.

2.Simpson DA, Crompton JL. The visual field: An interdisciplinary history, 1. The evolution of knowledge. J Clin Neurosci. 2008;Feb:579–609.

3.Cushing H. Selected Papers in Neurosurgery. New Haven, Conn: Yale University Press; 1969.

4.Horton JC. Wilbrand’s knee of the primate optic chiasm is an artefact of monocular enucleation. Trans Am Ophthalmol Soc. 1997:579–609.

5.Gower WR. A Manual and Atlas of Medical Ophthalmoscopy. 2nd ed. London, England: Churchill; 1882:57–61.

6.Heitz R. The history of contact lenses. 2003;1:50.

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7.Brester D. Memories of the Life, Writing and Discoveries of Sir Isaac Newton. Vol 2. Edinburgh, UK: 1855.

8.Newton I. Opticks: Or a Treatise of the Reflextions, Refraction and Colours of Light.

New York: McGraw-Hill; 1931.

9.Spuryheim G. The Anatomy of the Brain, With a General View of the Nervous System.

TR Willis, London, England: Highly, 1826.

10.Willis T. The anatomy of the brain and nerves. In: Feindel W, ed. Classics of Neurology and Neurosurgery. Trans. by Pordage S. Facsimile 1st English ed. 1681. Birmingham: 1983:63.

11.Wollaston WH. On semi-decussation of the optic nerves. Phil Trans R Soc Lond. 1824;114:222–231.

12.von Graefe A. Ueber die unterschung des Gesechtsfeldes bei amblyopischen affectionen.

Graefes Arch Ophthalmol. 1856;2:255–298.

13.Ferrier D. Munk on localization of function of the brain. Rev Brain. 1878;1:229–231.

14.Meyer A. The connections of the occipital lobes and the present status of the cerebral visual affections. Trans Assoc Am Phys. 1907;22:7–15.

15.Falconer MA. Visual field changes following anterior temporal lobectomy. Brain. 1958;81:1–14.

16.Windland JP. Visual field studies after temporal lobectomy for epilepsy. Arch Ophthalmol. 1960;64:195–200.

17.Kedar S, Zhang X, et al. Congruity in homonymous hemianopia. Am J Ophthalmol. 2007;143:856–858.

18.Smith JL. Optokinetic Nystagmus. Springfield, Ill: Charles C Thomas; 1963:3–4.

19.Inouye T. Visual disturbances following gunshot wounds of the cortical visual area based on observations of the wounded in the recent Japanese war. Brain. 2000;spec suppl:123.

20.Spalding J. Wounds of the visual pathway, 1. The striate cortex. J Neurol Neurosurg Psychiatr. 1952;15:169–183.

21.Horton J, Hoyt W. The representation of the visual field in human striate cortex. Arch Ophthalmol. 1991;109:816–824.

22.Armaly M. Selective perimetry for glaucomatosis defects in ocular hypertension. Arch Ophthalmol. 1972;87:518–524.

23.Rucker W. The concept of a semidecussation of the optic nerves. Arch Ophthalmol. 1958;59:159–171.

Visual Fields

Visual Fields

4Visual Fields

Interpreting the blind spot remains a standard part of any field examination. Interpreting the blind spot size requires experience. The blind spot may be enlarged because the patient is a slow responder or because a large myopic crescent is present. An important use of measuring the blind spot is to show the patient what a scotoma is and to test his validity of fixation by putting the target in the blind spot from time to time.

A cataract causes contraction of the peripheral field. Miosis due to the use of miotics and a small cataract can cause different defects that suggest a worsening of the patient’s glaucoma, which may be fallacious. In kinetic testing, if the examiner moves the test object too quickly, the sensitivity is altered and a defect is missed. If the kinetic test object is moved too slowly, the patient becomes distracted and loses fixation. (These problems are somewhat obviated by the use of computerized testing machines.) There are many different programs from which to select depending on the defect being sought and the patient’s field testing history and defects. The selection of the most ideal program to produce a good review of both central and peripheral fields was reviewed by Horton and Hoyt1 on an anatomic basis. They believe that a 30-2 program meets the requirements for central and peripheral field evaluation, except for monocular temporal crescent syndrome.

Another variable in testing may be which eye to test first. If this is a patient’s first time with field testing, then the eye with better vision eye should be tested first to give the patient experience. If the patient has performed the test previously, then perhaps the worse eye should be tested first while the patient is fresh. All of these considerations are part of the performance and evaluation of field testing.

Interpretation of the fields of vision forms a key part of ophthalmic and neurologic examinations. If the visual field is not intact, something is wrong in the retina or in the visual pathway—a bundle of nerve fibers that extends from the eyes, across the entire lower portion of the brain, to the visual centers of the occipital lobes. Not only will a field defect reveal almost any disease process occurring in the region, it can also help locate the site of the lesion. When lesions interrupt various parts of the visual pathway, they cause specific types of field defects; the nature of the defect frequently helps pinpoint the location of the lesion.

The function of perimetry is to indicate the site and the extent of involvement of the visual pathway. For purposes of clinical perimetry, the field of vision is usually regarded as the inner surface of part of a hemisphere. On this hemisphere, the level of vision is determined from the point of fixation of gaze by the use of targets of various sizes and colors. A line, or an isopter, is drawn on the chart of the visual field to represent the limit of the area within which a specific target can be recognized. The chart of the visual field usually contains several concentric isopters, one for each target. This is best demonstrated in the Goldman perimeter. Now with computerized printouts, grayscale and numeric readouts in decibels are used to demonstrate the location and density of the defect.

The Snellen acuity charts evaluate the foveal part of the visual field. The remainder of the field cannot be evaluated as easily as the central vision is evaluated with the Snellen chart. However, a 20/20 Snellen report does not rule out a paracentral scotoma, which may be the cause of the patient’s complaint about their reading.

We do not have a Snellen system as such for the rest of the field, nor does every part of the field have the same sensitivity as other parts. The ability to just see a certain test object is called the threshold for that area of the field. Field testing is unlike Snellen testing, which is the same from person to person. However, the lightsensitivity threshold for given degrees away from fixation has been established in all four quadrants until the outside limits of the island of vision have been reached. More details on this subject are explored in Chapter 3.

Moving a test object of the same size and brightness from a nonseeing to a seeing area is called kinetic perimetry. If instead a stationary test object that increases in brightness until the patient sees it is used, this method is called static perimetry. Static suprathreshold testing uses a single test object that is above the expected threshold for that part of the field. The threshold for a kinetic test object is lower than that of a static test object. This finding is consistent with the work of Riddoch,2 who found that moving objects are seen sooner than are stationary areas in a patient recovering from an occipital lobe lesion.

There are many ways to evaluate the visual system. The tangent screen is the traditional way of examining the central fields. The recording of distant and near acuities, color vision, and fusion testing, as well as the dazzle test and pupillary responses, all primarily evaluate the macular area. It is equally important to evaluate the peripheral field, which can be regarded as an extension of macular vision. Too often, physicians make the mistake of assuming that a good central acuity obviates the need for doing a central field. Patients with glaucoma defects, however, expose that error.

Good perimetrists learn many techniques, both gross and sophisticated, for examining each area of field. They choose the type of test for the specific areas where a defect is most likely to occur, based on the patient’s history, state of alertness, and ability to communicate. The mark of good perimetrists is not that they can conduct one type of field test superbly but rather that they can evaluate the individual patient well and select the appropriate field technique for that patient. Most of this monograph will deal with computerized perimetry, which is used in the overwhelming number of patients. I believe it is important in this introduction to point out the usefulness of these techniques when the occasion presents itself. Examples of these techniques are shown for comparison in different sections of this monograph.

1-1-1 Peripheral Fields. The peripheral portions of the field are explored on a perimeter with the aid of an arc that can be turned in any desired meridian and that is marked from 0° to 90°. One technique requires that a white test object 3 mm in diameter outside an area of seeing be carried from the point of fixation along the arc until it disappears from view and then is returned to the seeing field. The point at which the test object reappears is recorded as the edge of the field for a test object of that size. Larger targets are used if the patient is not able to see well enough to permit use of the 3-mm test object or if there is a dense defect in the field. At least 12 radii of each field should be investigated. It is not sufficient to determine merely the peripheral limits of the field; the interior part of the field should also be