causes of floaters

Last edited 09/2021

• floaters are the result of small pieces of debris that float in the vitreous humour of the eye
  
  
• floaters occur as part of the natural ageing process
  • some people may also have posterior vitreous detachment (PVD), which may cause a sudden increase in the number of floaters they have
    
    
• floaters and increasing age
  • risk of developing floaters increases with age
  • floaters tend to occur in people who are over 40 years of age and are most common in those who are in their 60s and 70s
  • with age, the vitreous humour can become less firm and strands of collagen may become visible within it
    
    • collagen strands may appear as swirls that move with change of gaze
      
      
• posterior vitreous detachment (PVD)
  • floaters can be a symptom of posterior vitreous detachment (PVD)
  • a common condition that occurs in about three-quarters of people over 65 years of age
  • PVD can occur as the result of changes to the vitreous humour as the eye gets older
  • with age, the central part of the vitreous humour becomes more liquid and the outer cortex (which contains more collagen), starts to shrink away from the retina
  • floaters develop as a result of the collagen thickening and aggregation
  • as well as floaters, flashing lights can be another symptom of PVD
    • flashing lights may occur when the outer part of the vitreous humour pulls on the light-sensitive tissue of the retina
      • the retina interprets the pulling as a light signal and hence creates the sensation of flashing lights
        
        
• retinal tears
  • in approximately half of all people, the vitreous humour has separated from the retina by the time they are 50 years of age
    • usually this is non problematic
  • in a few cases of PVD, when the vitreous humour pulls on the retina it can cause the multiple small haemorrhages of retinal vessels into the vitreous humour
    • the haemorrhages may appear as tiny black dots or look like smoke. However, as the blood is absorbed back into the retina, these floaters tend to disappear over the course of a few months
  • in some cases, the vitreous humour remains attached to parts of the retina and it tears the retina as it pulls away
    • if the retina tears, the haemorrhage that escapes into the vitreous humour can cause a shower of lots of floaters at once.
    • a patient may see flashes of bright, white light that look a little like lightning streaks
      
      
• retinal detachment
  • if a patient has a retinal tear, then this needs to be treated as soon as possible because tears can lead to retinal detachment
  • retinal detachment is rare, affecting one person in every 10,000 every year
  • other causes of floaters:
    • following eye surgery
      • there is an increased likelihood of a patient to experience floaters, PVD and, more rarely, retinal tears and retinal detachment
    • other causes of floaters may also be caused by:
      • infection
      • inflammation (uveitis)
      • eye injury
        
        
• floaters are also more common in
• myopia
• diabetes

Notes:

• floaters may also been occur in other conditions for example
  • migraine with aura
• vitreous humour is a clear, jelly-like substance
  • mostly made up of water (99%)
  • other 1% is made up of substances that help to maintain the shape of the vitreous
    

Reference:

• 1) NHS choices - floaters (accessed 31/1/12)