3. Those that cause obstruction of the filtration angle by advancement of the iris and lens, as occurs when the volume of the contents of the vitreous chamber is increased, as from retinal or chorioidal hemorrhage or neoplasm.
The various changes are so numerous that they need not be described further here. The ultimate changes due to high tension resemble those already described.
Dr. John E. Weeks' Paper on Pathology of Glaucoma
Discussion,
E. V. L. Brown, M.D.,
Chicago.
I would like to emphasize one of the newer features of the pathologic anatomy of glaucoma, one which has received too little attention in this country: the lacunar or cavernous atrophy of the optic nerve.
The name accurately describes the condition. Tiny clear spaces form in the lamina cribrosa and in front and behind it in the nerve tissue. Their exact nature is unknown. Usually they are entirely empty, often they are traversed by fine glial fibers. They seem to be in no relation to the blood vessels. Adjoining lacunae are supposed to fuse to form larger cavernae and these finally merge and constitute the final glaucoma cup. The lamina may then bridge across the space like a cord, or lie back against the end of the nerve trunk.
Schnabel considered all glaucoma cups to be formed in this way, independent of tension. His views were strongly supported by Elschnig, but as vigorously opposed by others. Axenfeld cites the fact that the glaucoma cup may disappear after operation. (I myself have seen a cup of 7 D. reduced to 1 D. in the course of a year after the tension had been lowered from 62 to 12.) Stock found the same lacunae in eight cases of myopia. The last extended study of the subject was made by E. v. Hippel, who found lacunae in 20 of 33 cases (60 per cent); enough certainly to make one look for them carefully in every case. He publishes a large number of excellent photo-micrographs, but none more typical than one I have in my possession.
I have been especially interested in this subject because I have met with a complete and total glaucoma cup, with the typical (ampulliform) undermining of the scleral ring, in a pair of eyes without increased tension. The (Schiotz) tonometer was used daily for 70 consecutive days and never registered more than 12-14 mm. Hg. The man had been blinded by wood alcohol. At the time I could find no other report in the literature, but overlooked a publication by Lewin and Guillery. Friedenberg has since reported cases of the same nature.