Abstract: Secondary cataract is the most common postoperative complication, which causes repeated significant reduced visual acuity, even after a successful operation on the lens. Due to significant clinical heterogeneity of secondary cataract of a man a comparative morphological and functional study in the formation of its fibrous and proliferative forms is especially important for identification of pathogenesis foundations of this disease. The used morphological, histochemical and clinical techniques in the conducted study have provided some evidence of the important role of trophic nervous influences on the type formation of secondary cataract in humans. It is important to note that the revealed similarities in changes of bioamine status, immunoreactivity of the epithelium and fibers of the human crystalline lens in different types of age-related cataract (cortical and nuclear) and its postoperative complications (proliferative and fibrous types of secondary cataract, respectively) can serve as an important proof of their common pathogenesis and, consequently, the type of age-related cataract can be offered as an accessible marker for predicting the risk of postoperative secondary cataract of certain type and its early prevention. The results allow for the first time to put forward a new concept of the secondary cataract pathogenesis. The presented in this chapter concept emphasizes the importance of the fundamental problems of medicine – maintaining the stability of tissue differentiation of a living organism in a variety of physiological and pathological conditions, under the influence of neurotrophic factors.Abstract: Secondary cataract is the most common postoperative complication, which causes repeated significant reduced visual acuity, even after a successful operation on the lens. Due to significant clinical heterogeneity of secondary cataract of a man a comparative morphological and functional study in the formation of its fibrous and proliferative forms is...Show More