To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree.
- Charles Darwin
The eye. That marvel of evolution that so intrigued Charles Darwin has similarly fascinated poets, playwrights, philosophers, and even comedians through the ages. So why should we neurologists be any less in awe of an organ that tells us somuch about the nervous system? Indeed, long ago Cicero acknowledged the importance of the eyes:"The eyes, like sentinels, hold the highest place in the body."
For this exciting issue CONTINUUM of, Drs Wayne Cornblath and Eric Eggenberger have joined forces to chair a faculty that brings you up to speed on our current understanding of neuroophthalmology. In so doing, they have elicited the help of many knowledgeable colleagues, too numerous to list in this brief preface. I encourage you to look at the faculty listing at the beginning of the issue that will put a face to the name of each contributor.
Nervous system structures and functions subserving the eyes exist to optimize binocular vision. This goal can only be achieved through the combination of an intact visual system and a properly operating system of coordinated eye movements. Indeed, the primary purpose of such eye movements is to maintain the visual image on the fovea, the area of keenest vision in the retina. Reflecting on these two aspects, Drs Cornblath and Eggenberger have chosen to divide this issue into the broad categories of the afferent visual system, the efferent system, and the pupil.
An old Yiddish proverb says, "The eyes are the mirror of the soul.'While that may, indeed, be so, for neurologists it is more often true that the eyes are the windows to the brain. Chapters relating to the afferent visual system include discussions of visual loss, both transient and permanent, as well as the important subject of functional visual impairment. An additional chapter on visual hallucinations supports Mark Twain's observation, "You can't depend on your eyes when your imagination is out of focus.' In approaching a patient with neuro-ophthalmologic abnormalities, the neurologist should bear in mind the observation of comedian Bill Cosby that, "Every closed eye is not sleeping, and every open eye is not seeing.' Discussions of efferent abnormalities focus on diplopia, supranuclear and internuclear abnormalities, neuropathic and neuromuscular disorders, as well as disturbances of pupillary function. Ptosis is also included among the disorders covered. Misogynistically inclined, Benjamin Franklin apparently considered marriage to be a cause of this affliction, for he admonished, "Keep your eyes wide open before marriage, and half-shut afterwards.' You will, however, learn of other etiologies of ptosis.
After digesting the rich main courses of this issue, don't forget to work through the patient management problem, crafted by Dr Cornblath, and the multiple-choice questions developed for this issue by Drs Ronnie Bergen and Douglas Gelb. In addition, this issue features one of the two annual versions of Quintessentials, which gives you the opportunity to apply your knowledge in a case-based format that will provide you instant feedback. The module, prepared by Dr Robyn Wolintz, will then give you the chance to ascertain what you have learned by repeating the exercise with a new set of cases a month or so after you have submitted your responses.
This issue of CONTINUUM is, indeed, an eye-opening experience. Cap off your education by feasting your eyes on the CD-ROM that Drs Eggenberger and Cornblath have organized to better illustrate the points the contributors have made in the text. As you approach future patients with neuroophthalmic problems, I know you will share my appreciation of the efforts of Drs Cornblath, Eggenberger, and colleagues who have brought us to the state described by French philosopher Henri Bergson who noted, "The eye sees only what the mind is prepared to comprehend.'
- Aaron E. Miller, MD