Figure 1. Iridocorneal and keratolenticular adhesions. Peters anomaly (PA) classically describes a congenital corneal opacity resulting from an iridocorneal (A, B) or keratolenticular adhesion (C, D). The opacity may be central (C, D) and may take up a small part or the whole of the cornea, or may be eccentric (A, B). It is unreliable to ascribe this term judging only from the clinical picture without making use of ultrasonography, notably ultrasound biomicroscopy (UBM; B, D), which helps visualize the structures of the anterior segment and prove or disprove the presence of adhesions (B, D). The use of UBM in A and B shows contact between the cornea and iris (iridocorneal adhesion) and in C and D contact between the cornea and the anterior lenticular surface (keratolenticular adhesions), resulting in disorganization and loss of clarity in the central cornea, confirming the diagnosis of PA. NB. These opacities are avascular (see Figure 3) and in these cases the lens is of a normal size.