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I believe that eserin irritation is most successfully avoided, not by preparations of the myotics in combination with the antiseptics, for example, tricresol, which has been so much advocated, but by ordering very small quantities of the solution, insisting that it shall be frequently renewed and sterilized at each preparation, and that a half an hour after its instillation, during the day time at least, the eye shall be thoroughly flushed with some mild antiseptic solution, for example, boric acid and sodium chlorid.
Personally, it has always seemed to me that the salicylate of eserin is preferable to the sulphate, but I have not persuaded myself that the nitrate of pilocarpin possesses material advantages over the hydrochlorid, although some authors prefer it.
Experiments, however, for example, by E. E. Henderson, have shown that the rate of filtration in an eye with artificially raised pressure is considerably larger when it is under the influence of eserin than it is when under the influence of atropin; that is by the contraction of the pupil the iris-surface filtration is increased and consequently the pressure is reduced.
Whether the action of the eserin on the choroidal circulation, which is maintained by Wahlfours, aids in this favorable action of the myotics remains to be proved. It has been maintained by this author and by others who have followed him.
The substance isophysostigmin, found with eserin in Calabar bean, according to Ogiu, exceeds in its myotic activity the sulphate of eserin, i. e., 1/80 of a grain of the drug is equal to 1/60 of a grain of the sulphate of eserin, but it is certainly not less irritating than physostigmin, and according to Stephenson's researches, is more so, and in this sense has no superiority over the usual alkaloid.
It has always been easy to attribute the myotic action of these drugs, or at least, of eserin, to their stimulant action on the peripheral ends of the oculo-motor, thus causing sphincter contraction, and to a depressing action on the sympathetic fibers, thus causing removal of the action of the dilatator of the iris.
It is my own belief, and that of many who have studied this subject, that if, without eserin irritation, a myosis can be maintained, and if the treatment can be begun early enough, the chances of preserving vision and the field of vision are good.
It is hard successfully to maintain in a patient with chronic glaucoma what I may call an eserin life, just as it is hard to maintain in a person with an enlarged prostate a catheter life and escape infection, resulting, if it occurs, in the one instance in a difficult and stubborn conjunctivitis, and in the other in a cystitis.
In acute glaucoma, and every one knows that in this disease their action is often prompt and sometimes curative, eserin in a strength of one to four grains to the ounce may be instilled with sufficient frequency to establish myosis, and its action in this respect is enhanced if the congestion of the eye is lowered by measures to which I shall refer later.
In general terms, it may be said that the time has not arrived to make a preachment "on the passing of eserin and pilocarpin." Physiologic Action. Concerning the ocular, physiologic action of the two chief alkaloids respectively of Calabar Bean and of Jaborandi, there still exists difference of opinion.
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