Flashes and floaters

Brief flickers of light in the corner of your vision.  Floaters are irregularly shaped objects, variously described as resembling smoke rings tadpoles, strands of hair or spiders.  They are usually more obvious when looking at a bright, white background.

These symptoms can be caused by a “posterior vitreous detachment”.  This is NOT the same as a retinal detachment.  The vitreous is a jelly-like transparent substance made of collagen fibrils that fills the eye between the lens and the retina.  Ageing changes in the collagen result both in an irregular loss of transparency and in a contraction and shrinkage of the vitreous. Usually vitreous is only loosely attached to the retinal surface, but in some areas vitreous attachment to the retina may be firmer.  Once such area, where the vitreous is attached to the optic nerve, is known as the Weiss ring.

Floaters – causes
1 When the gel contracts, the Weiss ring moves away from the optic nerve into the middle of the vitreous cavity, where it can cast shadows onto the retina.
2 Occasionally, the gel is more firmly attached to retinal blood vessels.  Contraction  of vitreous pulls on the blood vessels resulting in mild bleeding.  A shower of small red or black dots may represent bleeding in the vitreous cavity.
3 Irregular loss of transparency in the gel structure.

Flashing lights
These are caused by contracting vitreous tugging on the retina as it “detaches” from the retina.

Retinal tears
Gel contraction results in vitreous pulling and tearing the retina..  If a tear is diagnosed early, before a retinal detachment occurs, laser can be used to ‘weld’ the retina to the underlying choroids.  Only about 5 – 10% of patients with flashing lights and floaters have a retinal tear.

Retinal detachment
Fluid can seep through the tear and spread under the retina separating the retina from the underlying tissue known as the choroid.  Initially, only a small area of retain is detached , but this can spread over a few hours or days, resulting in loss of vision in the areas affected by the detached retina, the most important part of which is the macula.  Provided surgery is performed before the macula is detached, vision can be preserved.

Patients with flashes and floaters need to be examined by an ophthalmologist to check for a retinal tear.  Most tears occur in the hidden part of the retina behind the iris, so your pupils will need to be dilated. This may blur your vision for between 3 and 12 hours.  Ideally, you should arrange for someone to come with you so that you can drive home afterwards.

Treatment for posterior vitreous detachments
Flashing lights may persist for up to 6 weeks and subside when the vitreous is fully detached.  Theoretically, a retinal tear can still occur until the vitreous is completed separated from the retina posteriorly (it remains attached at the vitreous base over the anterior retina).  Retinal tears are most likely to occur, however, at the start of the vitreous contraction phase.

Floaters may persist forever.  However, as the vitreous condensations move forward, the shadows they cause become more diffuse and less noticeable.  Furthermore, the brain learns to adapt to their presence.  In practice, this means that floaters are usually noticed by patients for only two years or so.  Very, very rarely, the symptoms they cause persist, particularly in patients with only one eye.  Exceptionally, such patients may be offered a vitrectomy operation to surgically remove the offending vitreous.

Warning symptoms of a retinal detachment
1 a curtain-like shadow or bubble in the corner of your vision, which over hours increases in size.
2 a marked increase in floaters, particularly small red or black dots (indicating a retinal bleed)

Patients should present themselves to the eye casualty department at EEMU or get in touch with us here at kenteyesurgery without delay.