est of performance, is the least likely
to be attended by serious complications and is available for the largest
number of cases? Reasons for believing that of the better known
procedures simple iridectomy is the least effective, while those
interventions producing a large, thin, scleral filtration-cicatrix are
the most valuable.

DR. CASEY A. WOOD, Chicago.

Discussion by DR. A. E. BULSON, JR., Fort Wayne

Etiology and Classification of Glaucoma

BY

EDWARD JACKSON, M.D.,

Denver.

It is convenient to start with the conception that glaucoma is increased
tension of the eyeball, plus the causes and effects of such increase;
although a broad survey of the facts may reveal a clinical entity to be
called glaucoma, without increased tension constantly or necessarily
present, and cases of increased intra-ocular tension not to be classed
as glaucoma.

The physiologic tension of the eyeball is essential to ocular
refraction, and closely related to ocular nutrition. Fully to understand
the mechanism for its regulation would carry us far toward an
understanding of the causes of glaucoma. Normal tension is maintained
with a continuous flow of fluid into the eye and a corresponding
outflow. Complete interruption of the nutritional stream would be speedy
death; partial interruption may be held responsible for most of the
visual impairment and pain of glaucoma.

The balance of intra-ocular pressure is not maintained by the slight
distensibility of the sclero-corneal coat. Increased pressure does not
open new channels for the escape of intra-ocular fluid; if, indeed, it
does not tend to close the normal channels.

The affinity of the tissues for water, or, as Fischer explains it, the
affinity of the tissue colloids for water, seems too little related to
the requirements of ocular function to furnish the needed regulation of
tension. The lymph spaces and blood-channels of the eye are large, as
compared with the mass of its tissue colloids. In these spaces and
channels must be sought a means for rapid response to the need for
regulation of intra-ocular tension. Fischer has shown, that when the
enucleated eyeball is placed in a weak solution of hydrochloric acid,
the swelling of the tissue colloids is sufficient in a few hours, to
burst the sclero-corneal coat. But this is an eye in which all
nutritional changes have ceased. He brings together many facts to
support the view that in the living tissues impaired circul