Sir,

Congratulations on the important article by He, Foster, Johnson and Khaw in the January 2006 issue of Eye. It is clear that the chronology of steps leading to angle-closure are not fully understand. One reason for this, I believe, is the continuing practice of describing the configuration of the anterior chamber angle almost exclusively in terms of the angle created by a tangent to the posterior surface of the cornea and the anterior surface of the iris. There still does not appear to be recognition that accurate description of the anterior chamber angle configuration demands considering at least three separate characteristics: the locus of the attachment of the iris to the inner wall of the eye (the ciliary body, the angle recess, or the cornea), the curvature of the peripheral iris, and the space between the iris and the cornea as measured with diametry, or anterior chamber depth or estimate of angularity as in the Shaffer system. No one has yet figured out a way to put these three variables together in a meaningful way. Even more seriously misleading, however, is the practice of ignoring one or more of the variables. Consequently, the results of various studies are literally comparing ‘apples’ and ‘oranges’ so it is not surprising that there is so much disagreement amongst these. For example, UBM is a beautiful way to evaluate two aspects of configuration, specifically the curvature of the iris, and the ‘angularity’. However, because the site of the posterior trabecular meshwork is not well defined in UBM and because the relationship of the posterior trabecular meshwork with the insertion of the iris varies markedly, UBM is not a good method of characterizing the entire nature of the anterior chamber angle, or explaining why patients are likely to develop angle closure. He and colleagues' article points out some of these shortcomings and moves the field ahead. However, what is still missing is a unifying description that recognizes that configuration requires incorporating various variables.