That such profound epithelial changes occur might indicate the need to dwell less on protein changes in the formation of other kinds of cataract and more on epithelial alterations resulting in abnormal or absent lens fibre production. Complicated retinal detachment and particularly that due to giant retinal tear causes profound epithelial changes in the lens. These take the form of migration of equatorial and possible anterior cells posteriorly, metaplasia of these cells and of the anterior epithelium, cytoplasmic vaccuolation of anterior and migrated cells, swelling and destruction of migrated cells to form balloon cells and finally, cessation of normal lens fibre production. Many of these changes are related to those occurring in non-retinogenic cataract but are on a massive scale which in a predictable time leads to complete loss of metabolic control in the lens with the formation of acute cataract.