Which one of the following statements, concerning persistent hyperplastic primary vitreous (PHPV) is not true ?a) It is generally unilateralb) Visual prognosis is usually goodc) It may calcifyd) It is most easily differentiated from retinoblastoma by the presence of exophthalmos or cataract

PHPV is almost always (90%) unilateral. Visual prognosis is bad as neither conservative treatment nor surgery can improve visual acuity. There is no calcification, which is a differentiating feature from retinoblastoma. PHPV can be differentiated from retinoblastoma by presence of cataract in PHPV but not by exophthalmos.