Contributor: Gordon K. Klintworth
Persistent hyperplastic primary vitreous is a unilateral congenital developmental anomaly of the vitreous. It is characterized by a pink white retrolenticular mass of fibrovascular tissue. This tissue is derived from the embryonic primary vitreous and it is often supplied by a patent hyaloid artery. The retrolental mass, which may form a small plaque or  cover the posterior lens surface, creates traction on the ciliary processes and typically pulls their tips centrally into the pupil.  Microphthalmos is usually present in the affected eye of advanced cases and the lens-iris diaphragm is displaced anteriorly. Leukocoria is common and thus the abnormality may be confused clinically with retinoblastoma. The anterior chamber is usually shallow, a helpful clinical point in differentiating the disorder from retinoblastoma in which the anterior chamber is usually of normal depth until late in the course of the disease, when anterior segment involvement may supervene.
The ciliary processes are elongated and pulled towards the lens where there is usually a break in the posterior capsule with or without cataract or coloboma. This is readily observed clinically after dilation of the pupil and is this feature aids in differentiating persistent hyperplastic primary vitreous from retinoblastoma. If the posterior lens capsule ruptures, a cataract can result. The developmental defect occurs some time between the fourth and sith months of gestation. The anterior chamber is shallow and the posterior part of the tunica vasculosa lentis persists.
Retrolental tissue consisting of undifferentiated neural and fibrous tissue sometimes contains fat, hyaline material, cartilage, and foci of calcification.
A constant feature is the entry of the hyaloid artery into the posterior part of the retrolental mass.
Occasionally a posterior hyperplastic primary vitreous persists. Retinal folds [fold - retina] and vitreoretinal adhesions may develop leading to secondary retinal breaks and detachment. Preretinal nodules growing into the vitreous are foci of glial tissue arising from Müller cells.