Aetiology of the anatomical basis for primary angle-closure glaucoma. Biometrical comparisons between normal eyes and eyes with primary angle-closure glaucoma.

Shallowness of the anterior chamber received special attention after the demonstration by von Graefe (1857) that iridectomy could cure acute glaucoma. Bowman (I862) referred to the care required in performing iridectomies on eyes with shallow anterior chambers. Over many years, and by careful dissections of cadaver and enucleated eyes, Priestley Smith (I89I) concluded that the shallow anterior chamber occurred already before the disease (glaucoma), was an expression of disproportion between the size of the eyeball and the lens, and was an important aetiological consideration for glaucoma. Using Lindstedt's apparatus, accurate anterior chamber depth measurements were performed on large numbers of living eyes by Rosengren (193I, I950), who showed that shallow anterior chambers predisposed to acute congestive glaucoma and that the shallowness existed before the increase of pressure and was not a consequence of it. In the same person, measurements of the affected and fellow eyes were practically identical. Barkan (1954) was able to describe fully the mechanics of primary angle-closure glaucoma and the dependence of the relative pupil block upon a forward position of the anterior lens surface. However, explanations of the shallow anterior chamber remained unsatisfactory. Many patients with shallow anterior chamber glaucoma were found to be hypermetropic, and as anterior chambers tend to be more shallow in hypermetropia than in emmetropia, and especially different from myopia where anterior chambers are usually deep, many authors referred to angle-closure glaucoma as occurring in "small hypermetropic eyes" (these papers are reviewed by Tornquist, 1953). Correlations between anterior chamber depths and refractive errors have been demonstrated by many investigators (Stenstr6m, I946). Weekers and Grieten (I96I) confirmed the correlation between anterior chamber depth and refractive error provided cases of "complicated myopia" were excluded, but for myopia greater than 5 dioptres no correlation was found between refractive error and anterior chamber depth. Grieten and Weekers (I962) showed further that the mean measurements for eyes with angle-closure glaucoma gave anterior chambers o073 mm. more shallow, corneal curvatures 020 mm. less, and corneal diameters o048 mm. smaller than for eyes of the same age with the same degree of hypermetropia.