Mechanics of pupil block.

New considerations on pupillary block mechanim

“…In this study, the LPI increased the ILCD and reduced the ILA (neutralizing the action the iris dilator muscle) (4) . According to Mapstone (23,(25)(26) , the forces described in the mathematic model (23) would be the same, owing to the fact that the angle among them does not modify after the pupillary block resolution. In consequence, these forces have no importance in the genesis of pupillary block.…”

In Vivo Analysis of Vectors Involved in Pupil Constriction in Chinese Subjects with Angle Closure

“…2 In 1968, using vector force analysis, Mapstone theorized that pupillary block results from the iris sphincter pulling the iris toward the lens, overcoming resistance of the dilator, and creating a ''pupil blocking force.'' 1 Huang and Barocas concurred, having used steady-state computer simulations to model the mechanical interaction between the aqueous humor and the iris. 3 However, in vivo measurement of iris muscle vector magnitude and direction is difficult, if not impossible, to obtain with traditional methods.…”

“…T he major mechanism implicated in primary angle closure glaucoma (PACG) is pupil block, which is characterized by increased resistance to aqueous flow from the posterior to the anterior chamber at the level of the lens-iris interface. 1 The etiology of pupil block is poorly understood. Lowe first suggested that pupil block is the consequence of excessive contact between the iris and the anterior lens surface.…”

“…2). As changes in the pupil diameter time series are nonlinear, standard second-order polynomials (or quadratic functions) can be fitted to the data (see equation [1])…”

Gonioscopy During Surgery for Aphakic Eyes with Pupillary Block

“…The most characteristic signs of pupillary block are an over-all shal- [4][5][6][7][8][9][10][11][12][13][14][15] In the early stages it may be possible to relieve the block by mydriasis alone, but the condition is prone to recur and operation is usually advisable. '6 When pupillary block is unrelieved by mydriasis one usually finds the angle entirely closed.…”