Apoptosis is a Greek word describing leaves dropping from trees. (Ptosis, drooping of the upper eyelid, comes from the same root.) Apoptosis is the process of programmed cell death that occurs in multicellular organisms, in contrast to necrosis, a form of traumatic cell death that results from acute cellular injury. Biochemical events in apoptosis result in characteristic cell changes and cell death. Morphological changes include cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation. Several key events in apoptosis focus on the mitochondria, including the release of caspase activators, changes in electron transport, loss of mitochondrial transmembrane potential, altered cellular reduction-oxidation (redox) reactions, and activation of pro- and anti-apoptotic Bcl-2 family proteins.
Apoptosis is crucial in the developing human embryo; scaffolding cells such as those involved in eyelid opening are removed by epidermal apoptosis. In later life, excessive apoptosis causes atrophy, such as occurs in RP or glaucoma, whereas insufficient apoptosis results in uncontrolled cell proliferation, such as occurs in cancers, including retinoblastoma.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.