ABSTRACT
The lens is a biconvex clear structure located behind the iris in the patellar fossa of the anterior vitreous. The lens is also unique in its transparency, high protein content, high carbonic anhydrase levels, high glutathione levels, and lack of vascularity and innervation. Lens coloboma may be associated with iris coloboma or, if isolated, may be occult due to its peripheral location, or it may be observed incidentally when the pupil is dilated. Aphakia is a congenital absence of the lens. Primary aphakia is a developmental lack of lens tissue and is associated with severe ocular malformations. Secondary aphakia refers to degeneration and resorption or expulsion of the lens from the eye and may not be accompanied by severe ocular anomalies. Primary lens displacement without intraocular disease is seen sporadically in a variety of other breeds, including the Border collie, Australian blue heeler, German shepherd dog, and Shar Pei.
