A Newer Conception of the Aqueous Humor of the Eye

In the time of Galen (13I-20I) the vacant spaces between the cornea and the lens were assumed to be filled with a viscid fluid resembling the white of an egg. It was believed that this tissue-the lens, iris, and cornea-forming the boundary of these spaces was kept from desiccating by this fluid medium. This assumption prevailed for nearly I 300 years until Andreas Vesalius (5 I4-I564) revealed, by his dissection of ocular tissue, that the teaching of the older masters was fallacious. He demonstrated that the anterior humor of the eye did not resemble the white of an egg, but was watery in nature. Not until I703 was the truth concerning the intraocular fluid presented by Jacob Hovius. His dissertation created a considerable stir among ophthalmologists, as well it might, for therein was described the influx and efflux of the ocular humors, and a method for measuring these fluxions. At about the same time Frangois-Pourfour du Petit reported his results of measurements of the intraocular fluids. This work was elaborated upon by St. Ives (I722), who injected foreign fluids into the anterior chamber of the eye as a therapeutic measure. With the advent of the microscope a better understanding of the structure of the ocular tissue was introduced. Several investigators studied the histology of the ciliary body and its processes, disclosing the fact that the intraocular fluid originates in these processes and is apparently a secretory product. This early work has been splendidly compiled by Parson (1904) in "The Pathology of the Eye", but a study of the methods employed and an analysis of the interpretations derived, show that the one was as crude as the other was illogical. Even at the present time, our knowledge of the intraocular fluid is still indefinite for there is considerable disagreement concerning the nature and origin of the fluid. Several theories have been advanced to explaiin its origin, the more important of them dealing with processes of secretion, filtration, and dialyzation.