The striking of friendships and the meetings of minds have yielded advances in many fields. For example, there is the meeting of Frans Cornelius Donders and Albrecht von Graefe in London in 1851, which joined knowledge of physics and optics to clinical ophthalmology. Another gathering occurred in Hanover, New Hampshire, early in the twentieth century. The founder of the Dartmouth Eye Institute (DEI), Adelbert Ames II (Figs. 1–3), drew leaders in ophthalmology to this rural hamlet and sparked excitement in vision research.
The story of the DEI stands as an example of collaboration among investigators from multiple fields that began as one individual's quest to understand what influences how we see. From 1921 to 1947, Ames brought together, among others, Walter Lancaster, Kenneth Ogle, Arthur Linksz, Paul Boeder, Hermann Burian, and Alfred Bielschowsky. Little evidence marks its erstwhile prominence, but the DEI used a collection of diversely trained researchers committed to furthering the understanding of vision and perception. Many of the topics explored by this fortuitous assemblage of people flourish in modern vision research.
Ames came from a distinguished family. His maternal grandfather, Benjamin Butler, was a general and governor of Massachusetts. General Butler ran unsuccessfully for President in 1884. His father, Adelbert Ames I, had been a general in the Civil War and later a Mississippi governor and United States senator.
As a Harvard undergraduate, Ames took courses from William James and George Santayana. After completing Harvard Law School, he became disillusioned with legal practice and became an artist. Inspired by his sisters, who were painters, he tried “to make exact color reproductions of scenes” (1). With his sister Blanche Ames, he devised a color notation system consisting of more than 3,300 different color variations (1). (By comparison, the influential system created by the artist Albert Henry Munsell, and still used by clinicians and artists, contains only 1200 color variations .) While traveling around New England painting landscapes and sculpting, Ames' analytical mind contemplated the relationship between what one sees and what can be represented in art. How, he wondered, does the visual system reproduce the reality of the environment?
To approach the problem, he sought to understand the basics of image formation in the eye by studying its optical characteristics. In 1914, he accepted a research fellowship with John Wallace Baird, a psychologist at Clark University, and began more formal work in visual perception. In 1919, after a stint in the United States Army, where he gained experience designing instruments, Ames came to Hanover, New Hampshire, to consult with physics professor Charles A. Proctor. Ames, his sister Blanche, and Proctor worked on a “binocular camera” which would simulate the superimposition in the brain of the retinal images seen by each eye.
In 1921, Ames and Proctor published their first paper, “Dioptrics of the Eye,” in the Journal of the Optical Society of America (3). The article attracted so much attention that Ernest Hopkins, the president of Dartmouth College, created the Department of Research in Physiologic Optics. Ames was elected Professor of Research in Physiologic Optics and given a Master of Art Degree by Dartmouth College later that year.
When Ames and Proctor began their collaboration, the geometry of binocular vision was an area of active interest. It was during this time that Gordon H. Gliddon, a lens designer for Eastman Kodak Company, arrived in Hanover to enroll as Ames' graduate student. With Gliddon's help and expertise in lenses, Ames built a camera whose lens could simulate various optical aberrations of the eye. The goal was to produce photographs that could guide artists in portraying a scene as the human visual system allows it to be perceived.
Ames' personal excitement about vision research was drawing other colleagues and graduate students to Dartmouth. In 1930, Kenneth N. Ogle submitted his Ph.D. thesis under Ames with the title “The Resolving Power of the Human Eye.” The combined results of these researchers led to the establishment of the Dartmouth Eye Institute (DEI) as separate from the Department of Physics (Fig. 4). A growing team of investigators shifted from exploring the optical properties of a single eye to the problem of binocular vision and space perception.
The influence of retinal disparity on binocular depth perception had been studied by Panum and others in the early and mid-nineteenth century. In 1858, Panum had described the range of fixation with minimal retinal disparity over which fusion of two images can occur. By 1928, Ames and his colleagues had pursued an understanding of the influence of binocular vision on perception. In particular, Ames recognized that depth perception was not the simple fusion of two images focused on each retina, and that when the two retinal images do not match, distortions of space can result. He believed that prisms could correct horizontal and vertical misalignments of the two eyes, but wanted to better correct what he called “a turning movement of the eye about the visual axis itself” (4). He gained a patent for an instrument he called the Lyman Dingbat, a device mounted on spectacles and designed to correct rotational mismatches between two eyes (Fig. 5).
The DEI's early fame came from the development of instrumentation and techniques for the measurement and correction of anomalies in the size and shape of ocular images. Theorists such as Donders (1864) had appreciated that large differences in image size from anisometropia make binocular vision difficult or impossible. The DEI group fastened on this problem and used mathematical models to determine some of its causes, including unequal optics between the two eyes. Meticulous clinical experiments were performed to verify the anomalies. The technology developed was used to evaluate patients and correct the phenomena. The term “aniseikonia,” combining the three Greek words meaning “not equal image,” was coined in 1932, based on input from Harvard professors Charles Gulick, professor of classics, and Walter Lancaster, MD, a leading ophthalmologist who would later join the Dartmouth group. DEI researchers reported evidence that image size differences as small as 0.5% to 2% might cause problems with fusion and that patients perceiving this image size difference might experience distortions of space and depth (5). Ames, Ogle and Gliddon believed that people with aniseikonia might not recognize the distortions but would have “asthenopic symptoms.”
In 1932, Ames, Gliddon, and Ogle published “Size and Shape of Ocular Images, Part 1” in the Archives of Ophthalmology (6), describing the theory and methods used in their new ocular measuring instrument, the eikonometer, to determine differences in the size and shape of images perceived by the two eyes (Fig. 6). The instrument design grew out of the theory of Hering's longitudinal horopter apparatus and Tschernak's binocular devise developed in 1930. The authors made an argument for the impact of this size and shape difference on binocular depth perception and the impact of a disturbance in binocularity on “mental causes of discomfort” (6). The second part of this article, published a month later by DEI researchers Elmer H. Carlton, MD and Leo F. Madigan, OD, reported case studies proving that innumerable symptoms could be relieved by correcting refractive errors and interocular image size differences (7). Carlton, who had graduated from Dartmouth Medical School in 1897, served as a clinical instructor in otolaryngology and ophthalmology until he lost his right arm to an infection developed while he was operating. With his left arm, he became an expert refractionist and remained at the DEI from 1928 until it closed. Madigan had been a former student under Gliddon at the Rochester School of Optometry. These collaborators alleged that aniseikonia causes mysterious and incurable headaches, nervousness, bodily fatigue, stomach disorders, dizzy spells, carsickness, and unaccountable drowsiness. They reported that correction of image size differences brought complete relief of symptoms to 20% of patients, partial relief to 60%, and no relief to 20% (7).
According to Ames and his colleagues, retinal image asymmetry could be produced by retinal anatomic differences or by the lens system of the two eyes. The accommodation of one eye might differ from that of the other eye, or one eye alone may have astigmatism. When correction of the differences required lenses with powers greater than 0.50 diopter, there was a difference in the exterior focal distance that would blur one image. Ames and Gliddon developed aniseikonic lenses, submitting in 1929 a patent based on a telescopic combination of plates to allow the enlargement of an image on the retina along one axis to equalize dimensions without alteration in the vergence of light. Spectacles could be individualized for each patient based on measurements that would equalize the nodal points in the two eyes. Eyeglasses were made with multiple and superimposed lens elements to correct changes in vergence and retinal dimensional inequality (Fig. 7).
Laid out in more than a hundred subsequent publications in such journals as the American Journal of Ophthalmology and the American Journal of Optometry, the DEI's work became the premise for the instruction in aniseikonia in optometry and ophthalmology clinics and academic departments across the United States. In 1933, Ames and Gliddon were awarded a bronze medal by the American Medical Association for their work on aniseikonia (Fig. 8). Advertisements and publicity for the DEI group emphasized that traditional methods of refractive measurement did not uncover all the abnormal physiology that might cause symptoms. Thousands of patients from all over the world were drawn to little Hanover, New Hampshire in the hope that detection and correction of aniseikonia would obliterate their symptoms. DEI exponents practiced in Boston, New York, Baltimore, Washington DC, Atlanta, and San Francisco (8).
Perhaps the most famous ophthalmologist to work at the DEI was Dr. Alfred Bielschowsky (Figures 9–11). A well-known European ophthalmologist, Bielschowsky had studied under Drs. Ewald Hering and Carl Sattler in Leipzig, Germany. Early in his career, he became the director of the Eye Clinic at the University of Breslau and published the first sensory description of monocular diplopia and later many articles on ocular motility disorders. In 1934, the “pope of strabismus” accepted an invitation to visit the United States from Arnold Knapp MD, an ophthalmologist and the editor of the Archives of Ophthalmology.
On his tour of the United States, Bielschowsky met Ames, who invited him to visit Hanover and the DEI. Bielschowsky was offered the position of clinical director of the DEI. At first he decided to return to Breslau, but as a Jew, he became a target of anti-Semitic demonstrations outside his office and in his lectures. He later accepted the DEI offer and returned to Hanover.
The presence of Bielschowsky augmented the scientific reputation of the DEI. “Herr Doktor” spent a productive 5 years examining patients, performing surgery, and publishing his comprehensive “Lectures on Motor Anomalies,” including “The Etiology of Squint” and “Functional Disturbances of the Eyes” (9,10), Although he enthusiastically supported the development of “evidence of a causal connection between aniseikonia and the deficiency of fusion” as a cause of strabismus, Bielschowsky's own involvement in aniseikonia was limited (11). Early in his time at the DEI, he brought his former student Dr. Werner Herzau to Hanover. Herzau had trained in Prague and later worked under Bielschowsky in Breslau. When Herzau decided to return to Germany in 1935, Bielschowsky invited another European trained ophthalmologist, Dr. Hermann Burian from Prague, to join the group (Fig. 12). Burian stayed at the DEI for 10 years before leaving for a private practice in Boston, and, in 1951, for the University of Iowa, where he continued to contribute greatly to the field of ophthalmology. Bielschowsky died suddenly after attempted pneumoencephalography in New York as part of the diagnostic investigation of a brain tumor. His grave lies in the cemetery in the center of the Dartmouth College campus.
In the autumn of 1940, Lancaster (Fig. 13) agreed to replace Bielschowsky as the clinical director of the DEI. While many others had been skeptical of the work at the DEI, Lancaster had been involved with the group for many years while in practice in Boston. His wife Emma Winter was a descendant of Eleazer Wheelock, the founder of Dartmouth College. Lancaster found that he had little influence on the direction of DEI research or policy and resigned after just 2 years to return to his practice in Boston.
Over the course of almost 20 years, members of the DEI (Fig. 14) collaborated under Ames' direction to overcome technical and theoretical challenges involved in understanding the physics, physiology, and psychology of vision. In their research synopsis for the staff bulletin in 1941, they wrote collectively:
“As civilization advances, life increasingly depends on the efficiency of our space-perception capacity. Piloting airplanes and driving motor cars are examples of modern activity placing increasing dependence upon this function of vision. The most important contribution made by the Dartmouth Eye Institute has been its advance in the basic knowledge of space perception. Dartmouth's discoveries of such basic scientific laws and its application of these laws to the relief of human suffering and in the individual's occupational capacity, have in turn led to the Institute's collaboration with instrument and lens makers to make this new knowledge widely available. ”(8)
Despite the enthusiasm and efforts of the researchers, financial support for the DEI was always a problem. The Rockefeller Foundation contributed funding in the early years. But the combination of Ames' shift in interest away from the clinical work of the DEI, postwar changes, and hierarchical interplay between Dartmouth College, the Medical School, and the Hitchcock Clinic made for an uncertain fiscal environment. Lack of independent support and politics within the university eventually led to the DEI's closure in 1947. David C. Bisno, MD has written an extensive description of the DEI, attributing its closure to Dartmouth College president Hopkin's greater loyalty to the undergraduate college than to the graduate schools (12).
In the DEI's final years, Ames and some of his colleagues shifted their interests toward psychology. While this shift reflects Ames' broad interest in perception, it may also be the result of the inability of his optical systems and iseikonic lenses to correct or explain visual experience. Ames' later writings discuss an “assumptive world” based on an internalized perceptual system, a reminder of his original quest to understand the interplay between perception of reality and art. From the middle of the 1930s until his death, he studied visual illusions, collectively published under the title “Ames' Demonstrations in Perception” (13). He moved freely between historically unrelated fields, a skill that might have served him well today with the current emphasis on multidisciplinary scholarship. In an example of his interest in the philosophical and social implications of vision, he wrote that “the insights gained in the study of visual sensation can serve as indispensable leads to better understanding and more effective handling of the complexities of social relationships” (14). In his later years, Ames was trying to elucidate the interdependencies between perception, action, and purpose. For example, he developed “demonstrations” of trompe l'oeil for the psychology laboratory that challenged perceptual interpretation by creating illusions. With the creation of “the leaf room,” he hoped to achieve an environment with a minimum of monocular depth cues. In a cube of wire mesh mounted on a wire frame, oak leaves were used to cover all but one open side (Fig. 15). Ames then used eikonic lenses to enlarge the image on the retina along one axis without altering the optical properties of the two retinal images. With this protocol, he studied binocular space perception with altered binocular disparities without affecting other distance clues (13). His work had a strong influence on the evolution of psychology, particularly through his relationship with Hadley Cantril, PhD, professor of psychology at Princeton University.
Ames died in Hanover in 1955, after receiving a Doctor of Laws degree from Dartmouth College in 1954 for his significant influence as a “lifelong student of human perception.”
Reminders of Ames and the DEI linger in Hanover. There is the patient who brings an odd set of spectacles to the clinic. A past employee of the DEI fondly recalls the enjoyment several researchers would get from sending a newly hired nurse on an urgent errand to the hospital storage rooms in search of one hundred feet of Fallopian tube. But the DEI's work on aniseikonia has not endured within the scientific or clinical arenas of ophthalmology. Claims of curing so many nonspecific symptoms with eikonic lenses seem over zealous today. A small amount of aniseikonia is now considered common and of no clinical consequence. The mathematics involved in understanding or correcting large differences in the size of optical images of the two eyes has disappeared from ophthalmology training, perhaps because advances in contact lenses and refractive surgery have eliminated large interocular image size disparities.
The legacy of the DEI lies rather in the productive effort of a cohort of researchers devoted to understanding vision. Ames propelled the careers and research efforts of many others who spread out from Hanover to make substantial contributions in the fields of optics, visual perception, and psychology.
A special thanks to Sarah Hartwell at the Rauner Special Collections Library, to Patrick Saine, CRA, M.Ed. and Kimberly Strain, COA, CRA, for their assistance with archived photographs and manuscript preparation and to David Bisno, MD and Arthur Jampolsky, MD for their help and expertise with the manuscript and subject matter.