The angle-closure glaucomas

Angle closure can be caused by one or a combination of the following: (1) abnormalities in the relative sizes or positions of anterior segment structures; (2) abnormalities in the absolute sizes or positions of anterior segment structures; and (3) abnormal forces in the posterior segment which alter the anatomy of the anterior segment. Classification of angle closure by the anatomic level of the cause of the block, defined by the structure producing the ‘forces’ leading to the block, facilitates understanding of the various mechanisms, and appropriate treatment in any particular case becomes an exercise in deductive logic. We have defined four levels of block, from anterior to posterior. Each level of block may have a component of each of the levels preceding it. The appropriate treatment becomes more complex for each level of block, as each level may also require the treatments for lower levels of block.