In a recent paper it was reported by Burian, Braley, and Allen1 that the trabecular zone is externally visible by slit-lamp biomicroscopy in all normal eyes and that a thickening and prominence at the edge of this trabecular zone on the chamber side, constituting the so-called embryotoxon corneae posterius, is a relatively frequent occurrence. In no patient seen up to the time of publication of that paper could the region of the canal of Schlemm be identified in external examination. Ascher2 had previously described a patient in whom the canal of Schlemm was visible owing to a coloboma of the corneoscleral limbus, but this case had remained unique. In the present paper we wish to report on two patients in whom we were able to observe the region of the canal of Schlemm by external slit-lamp examination and in whom we could verify this finding by gonioscopy. The
BURIAN HM, RICE MH, ALLEN L. External Visibility of the Region of Schlemm's Canal: Report on a Family with Developmental Anomalies of Cornea, Iris, and Chamber Angle. AMA Arch Ophthalmol. 1957;57(5):651–658. doi:10.1001/archopht.1957.00930050663003
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