Retinal ganglion cells (RGC) play a crucial role in the visual pathway. As their axons form the optic nerve, apoptosis of these cells causes neurodegenerative vision loss. RGC death could be triggered by increased intraocular pressure, advanced glycation end products, or mitochondrial dysfunction. In this review, we summarize the role of some neuroprotective factors in RGC injury: ciliary neurotrophic factor (CNTF), nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), pigment epithelium-derived factor (PEDF), glial cell line-derived neurotrophic factor (GDNF), and Norrin. Each, in their own unique way, prevents RGC damage caused by glaucoma, ocular hypertension, ischemic neuropathy, and even oxygen-induced retinopathy. These factors are produced mainly by neurons, leukocytes, glial cells, and epithelial cells. Neuroprotective factors act via various signaling pathways, including JAK/STAT, MAPK, TrkA, and TrkB, which promotes RGC survival. Many attempts have been made to develop therapeutic strategies using these factors. There are ongoing clinical trials with CNTF and NGF, but they have not yet been accepted for clinical use.

The tear film is a thin fluid layer covering the ocular surface. It is responsible for ocular surface comfort, mechanical, environmental and immune protection, epithelial health and it forms smooth refractive surface for vision. The traditional description of the tear film divides it into three layers: lipid, aqueous and mucin. The role of each layer depends on the composition of it. Tear production, evaporation, absorption and drainage concur to dynamic balance of the tear film and leads to its integrity and stability. Nonetheless, this stability can be disturb in tear film layers deficiencies, defective spreading of the tear film, in some general diseases and during application of some general and/or topical medications. Dry eye disease is the result of it. In this review not only physiology of the tear film is presented. Moreover, we would like to discuss the influence of various diseases and conditions on the tear film and contrarily, spotlight tear film disorders as a manifestation of those diseases.

No abstract