Baker report, 1968 congressional hearings

warrant particular scrutiny [3]. When diabetes, for example, is known to be present, the physician will look for specific
related abnormal findings when he checks the eye and does the neurologic and mental status examinations.
Since observations usually begin with the eye and/or some other sensory organ, the next step (once adequate general
medical screening has been done) might naturally be a neuro-ophthalmologic examination. This would concern itself with
the major structures of the visual apparatus and any of their abnormalities which might influence accurate reception of the
visual images [4].
The cornea, the most external structure, accounts for visual distortion through scarring and clouding. These changes are
caused by such insults as trauma to the eye, exposure to toxic fumes, infections, and deficiency or degenerative diseases.
Inspection with an ophthalmoscope and/or slit lamp will positively establish corneal integrity.
The lens of the eye is the main structure for directing light rays from external phenomena to the retina. It has a wide range
of possible variation, on both a genetic basis and, like the cornea, as a result of aging, trauma, deficiency diseases and
infections. The configuration of the lens, as it is suspended in front of the eye by delicate muscles, accounts for the
sharpness (and shape) of the image known as refractive ability.
The aqueous humor which bathes the lens is of particular concern because of the pressure it exerts on the rest of the eye.
Increased pressure changes in this medium, measurable with a goniometer) are responsible for glaucoma which can result
in serious impairment of visual acuity. After a period of time, the increased pressure will also lead to a characteristic
constriction of the visual fields, which can be established by examination (perimetry).
The vitreous humor fills the eyeball and is the other fluid through which the light rays of a visual image must pass before
they reach the retina. This medium is subject to clouding and other signs of early inflammation. "Floaters," which are
abnormal proteinaceous particles in the vitreous humor, are sometimes mistaken by people as moving objects that are in
their outside environment. Again, ophthalmoscopic and slit lamp examination will serve to determine the status of the
vitreous humor.
The retina is the structure on which the visual image is actually received; loosely, it can be likened to camera film. Located
in the posterior eyeball, it is the beginning of the neural perception linkage which eventually reaches the brain and
consciousness. The retina is subject to many and varied abnormalities which can severely disturb both visual sharpness
(acuity) and range (fields), as well as color perception. Retinal pigment accumulation, inflammatory, and other exudates,
vascular problems and other types of pathology can come between an otherwise observable event and the retina, such that
part or all of the event is obliterated or distorted in various ways. Ophthalmoscopic inspection will yield a great deal of
information about the anatomic integrity of the retina, but a complete assessment must also include detailed mapping of
both visual fields by perimetry, with attention to the size and shape of the blind spot. The observer's ability to perceive
color at the retinal level may be challenged with Ischihara charts, which are most popularly used for detecting color
blindness. These charts also will pick up abnormalities in color perception which are due to drugs, other toxic conditions,
and higher, cortical integrative problems.
The head of the optic nerve (disc) can also be easily inspected with the ophthalmoscope, as it sits bare at the back of the
eye. The optic nerve is subject to similar pathologic processes as those mentioned above: i.e., developmental,
inflammatory, metabolic, and toxic. The color, texture and anatomic configuration of the nerve head indicate not only the
integrity of the optic nerve at this vital point but also offer highly suggestive inferential information about the state of the
rest of it, which is not directly visible. In addition, when there is increased intracranial pressure due to any type of brain
abnormality, it can be reflected in the appearance of the optic disc.
The optic nerves from both eyes join in the area of the pituitary gland and then redivide in such a way that fibers from both
eyes are represented in the optic tracts that form. Each tract then travels along either side of the brain (medial aspect of
parietal and temporal lobes) via optic radiations to the occipital cortex. These pathways, although not directly visible, are
accessible through the use of several maneuvers. Composite findings on neurologic examination, including visual field
results, are traditionally used, but opticokinetic studies should also be done because of the abundance of information they
can give about the integrity of the optic radiations. This involves the use of a moving, checkered tape which the patient
watches and to which his eyes should involuntarily respond with rapid, rhythmic movements (nystagmus) [5]. If, on the
basis of these studies, some kind of local pathology or other interfering process is suspected, the physician can then make
use of special x-ray procedures (pneumoencephalography, arteriography) for looking at the areas in question.