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Updated: May 11, 2025
Myosis produced by means of solutions of various drugs, a myosis followed by reduction of intra-ocular tension. Reduction of tension by means of various mechanical measures, notably massage, vibration massage and suction massage, and by means of electricity and diathermy. Indirect reduction of intra-ocular tension, accomplished by lowering general vascular pressure.
It is possible that as the positive pole is a sedative, if there were any influence, the influence of sedation would be present, but certainly it has over and over again been experimentally proved that irritation of the cervical sympathetic quite rapidly produces elevation of intra-ocular tension of 2 to 4 mm.
This may be in the lymph drainage system of the eye; but it may also be in the ocular veins themselves. Experimentally the eyeball can be made to burst by tying all the venous outlets from it. I have seen very high intra-ocular tension develop in a few hours after general thrombosis of the orbital veins. The absence of the canal of Schlemm is noted in congenital buphthalmos.
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.
But true as this is, we are not yet in a position to discard non-surgical procedures because operation is not always possible, because operation is not always permitted, and because in certain circumstances operation is not advisable. Hence a glance at the non-surgical methods of reducing increased intra-ocular tension is not out of place, and for convenience they may be catalogued as follows: 1.
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 application of these perfectly obvious principles to the eyeball makes the intra-ocular pressure the same as that within the elastic venous walls, which is the lowest circulating pressure within the bulb.
Now, although the negative pole is a stimulant and therefore not generally indicated in inflammation, as Coleman points out, the object in view is to diminish the density of the ocular capsule and its tension, hence the negative rather than the positive pole should be used, inasmuch as the former, according to him, while it is a sedative, hardens tissue and would tend to increase intra-ocular tension by diminishing excretion.
I have never been able to persuade myself that, except as an adjuvant to operative work, there was any real therapeutic value in the instillation of adrenalin. A word in regard to the effect of general narcosis on intra-ocular tension. Thus, Neuschuler has observed that narcosis causes an elevation of the intra-ocular tension of from 2 to 6 degrees as measured with Fick's tonometer.
The question of the source of the normal intra-ocular pressure must first be solved before any discussion of a pathological increase can be engaged in. This question primarily hinges on whether the corneo-sclera is to be regarded as an unelastic capsule with a fixed volume, or as a yielding envelope with an ever changing capacity.
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