Influence of various miotics on cataract formation.

The literature suggests that the use of miotics locally causes an increase in the size of the vascular bed of the iris and ciliary body through increased congestion (Seidel, 1920; Goldmann, I95I; Scholz, I946; Leopold and Comroe, I946; Hodgson, I955). Hyperaemia is a known effect of all miotics. All anticholinesterase agents produce vasodilatation of the ciliary body and conjunctiva. Metabolic changes in the lens due to the use of miotics have also been reported (Miller, Kleifeld, Hockwin, and Dardenne, I956). As the miosis is produced, a ciliary muscle spasm is accompanied by an increase in the blood supply and in the protein content of the aqueous humour. Iris cysts (seen in the pupillary area) have been reported after the use of most miotics, such as pilocarpine, phospholine, fluoropryl, and eserine (Vogt, I923; Abraham, 1954). The prolonged use of miotics tends to produce a low-grade uveitis. In acute glaucoma there is a marked increase in the vascular bed. The existence of this basic hyperaemia is emphasized by the reactions which follow glaucoma surgery in such cases and the decreased reactions which follow the omission of miotics for an interval before such surgery (Abraham, I959). Miotics may, at times, produce an increase in the intraocular pressure (Posner, 1955)even an acute glaucoma (Butler, I952). Iritis and detachment of the retina have been reported by Leopold (I966) and Lemcke and Pischel (I966). A small series of 45 cases of chronic open-angle glaucoma followed by one of us (S.V.A.) showed this tendency to increased intraocular pressure. In these 45 cases the glaucoma could not be controlled by strong miotic therapy alone or in combination with I or 2 per cent. epinephrine three or four times daily. The miotics used were either pilocarpine 6 per cent., phospholine *, i, or i per cent., or Humorsol 0 25 or 0 I25 per cent. The tension fell to normal in 28 of the 45 cases, and was reduced in another eleven cases, when the local therapy was discontinued. The pupils remained miotic as before in ten out of the 45 cases for the 2 months of observation, and the tension was under control during the observation period. In the remainder the pupil was noted to be increasing in size 2 to 8 weeks after discontinuing the local therapy; at the same time the tension rose, but 2 per cent. pilocarpine controlled this rise, where the stronger miotic had failed to do so earlier. The pupils were never observed to be over 3 mm. in diameter when the miotics were discontinued. These observations tend to support the idea that miotics have a dual action-on the one hand therapeutically beneficial in glaucoma and on the other hand counteracting this benefit by their effect on the vascular bed and on the permeability of the vessels involved. Amid the general enthusiasm for the benefits of miotics, their opposite effects have not been fully considered.