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What causes Flashes and Floaters?


Floaters look like small specks, dots, circles, lines or cobwebs that floats in your vision.  These floaters are tiny clumps of gel or cells inside the vitreous that fills your eye.  The vitreous is like a jelly-like substance that usually fills the back cavity of the eye behind the lens.  What you see are the shadows these clumps cast on your retina.  Flashes generally can look like flashing lights or lightning lines in your field of vision usually in the periphery. Some people compare them to seeing “stars” after being hit on the head. Flashes could come on suddenly at the same time as floaters.  You might see flashes on and off for weeks, or even months. Flashes happen when the vitreous rubs or pulls on your retina. 

The most common cause of floaters and flashes is Posterior Vitreous Detachment, which is a common aging effect in the eye’s jelly.  However it is important for patients with floaters and/or flashes to have careful eye examination as the same symptoms can be caused by a tear in the retina or retinal detachment.

Posterior vitreous detachment

Posterior vitreous detachment (PVD) happens as a normal part of aging usually happen between 40 to 50 year old. The vitreous gel shrinks and the gel separates from the retina. PVD normally happens over a period of time, and it's something that you won't feel.  It is painless.  The common symptoms are floaters and occasional flashes. 

Posterior vitreous detachment is diagnosed by your eye specialist by careful examination of the eye to exclude the possibility of a tear in the retina or retinal detachment.

What happens after you are diagnosed with posterior vitreous detachment:

  • There is no specific treatment.  The symptoms of floater and flashing lights from posterior vitreous detachment should gradually improve over the duration of 1-2 months.  Sometimes occasional floaters may still be noticeable for longer periods of time.

  • Your doctor would generally give advice to you to avoid contact sports or strenuous physical activities for a period of time to help the symptoms improve and prevent risk of retinal tears

  • Your doctor will arrange a follow up examination in 4 to 6 weeks to ensure there is no development of retinal tear.

  • If you experience any worsening of your symptoms, such as sudden decrease in vision, increase in floaters, increase in flashes or noticing a shadow in your vision then you should arrange an urgent appointment with your eye doctor for urgent repeat examination.

Retinal tear and detachment

If the vitreous gel is strongly attached to the retina, the gel can pull so hard on the retina-a process called traction-that it tears the retina. The tear then allows fluid to collect under the retina and may lead to a retinal detachment.  Retinal detachment is an emergency that can lead to vision loss.

People with the following conditions have an increased risk for retinal tear and detachment:

  • Nearsightedness;

  • Previous cataract, glaucoma or other eye surgery;

  • Glaucoma medications that make the pupil small (like pilocarpine)

  • Severe eye injury;

  • Previous retinal detachment in the other eye;

  • Family history of retinal detachment;

  • Weak areas in the retina that can be seen by an eye doctor during an eye exam.

If a retinal tear is discovered early it can be treated with laser treatment.  The laser spots on the retina causes the localized spot of retina to become more adherent to the back of the eye.  By treating the retina around the tear, there will be a high chance of prevent fluid from collecting under the retina causing detachment. 

If retinal detachment is found to have occurred, then urgent surgery is required to reattached the retina to prevent vision loss.  Your eye doctor will refer you to a retinal surgeon for surgical repair of the retinal detachment.

Flashes and Floaters: Feature
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