d above the usual normal limit.

For nine years I have watched the progress of such a glaucoma in a man
now aged 87, with slow development of glaucomatous cupping of the optic
disc, now more than 3 D. deep. The tension has never been noted at more
than Plus T (?), and when taken with the tonometer varied from 9 to 32
mm. for the worse eye, and 13 to 24 mm. for the other. Similar cases in
which the tension lay within the commonly accepted normal limits have
been reported recently by Bietti and Stock.

In the eye there is probably a normal equilibrium between blood
pressure, tissue activity, and intra-ocular tension. This may be
destroyed either by increasing the intra-ocular tension, or lowering the
tissue activity, or the blood pressure. Lowered blood pressure has been
suggested by Paton as an explanation of symptoms usually ascribed to
vascular obstruction. Rising blood pressure may be required in old age
to compensate for diminished tissue activity; and it is conceivable,
under normal intra-ocular tension, that diminished nutritional activity
may result in the same symptoms as are produced in other eyes by
increased tension. Glaucoma is probably not so much an increase of
tension as a loss of balance between intra-ocular tension and
nutritional activity.

In contrast with the above are the cases marked by sudden elevations of
ocular tension recurring repeatedly over long periods without permanent
visual impairment. Laqueur's case continued of this character for six
years, under the use of miotics, and then was cured by iridectomy, the
cure remaining permanent with normal vision until his death after 30
years. Millikin has reported the case of a patient who in five years had
"many hundreds" of attacks, in which vision was impaired, haloes
appeared about the light, the pupil dilated, the cornea became steamy,
and tension rose to plus T. 1 or plus T. 2. After iridectomy the attacks
ceased, leaving no pathological cupping of the disc, full vision, and a
good field. I have seen cases of this type in women under middle age,
and of marked nervous instability.

A third type which will come to be more generally recognized, as the
tonometer comes to be more widely used, includes cases in which there is
little beside the increase of intra-ocular tension to justify their
mention in a discussion on glaucoma. A patient, then aged 21, suffered
three years ago from a scotoma almost central; and was first seen six
months after tha