The jelly-like substance filling the space between the crystalline lens and the retina is called “vitreous humour”. The vitreous humour degenerates and liquefies when we get older, at which time we start to see floaters. Floaters can be moving opacities of various shapes and sizes (dots, circles, lines or spider webs). Physiological floaters usually occur when we are looking at a bright homogenous background such as a white wall or the blue sky. The floating opacities are few in number and remain unchanged over time. They represent normal physiological changes of the vitreous humour. As we age, the vitreous humour undergoes the processes of synchysis (liquefying) and syneresis (dehydrating and shrinking). These are normal agerelated degenerations.
Pathological floaters appear suddenly and may occur in great numbers. They may suggest bleeding within the vitreous humour, inflammation of the uvea or separation of the posterior vitreous humour from the retina. If the floaters are accompanied by flashes or visual field defects, it may indicate retinal tear or retinal detachment. When the vitreous humour contracts and detaches from the retina, it is called acute posterior vitreous detachment (acute PVD), at which time sudden onset of floaters and flashes occur. Floaters can be caused by vitreous opacities or haemorrhages, whereas flashes are caused by the vitreous humour pulling on the retina. An urgent dilated eye examination is essential to check for retinal tears, which should be repaired with laser as soon as possible, to prevent it from evolving into retinal detachment within a few hours.
