Flashes and Floaters

//Flashes and Floaters
Flashes and Floaters 2016-09-02T11:18:46+00:00

Flashes and floaters is probably the most common symptom that we encounter in practice with the vast majority occurring due to fairly normal changes. These symptoms, however, are some of the most concerning that we, as Optometrists, can come across. This is due to the possibility of a retinal detachment.

A retinal detachment happens when the light sensitive layer of the eye, the retina, separates from the globe of the eyeball, peeling away much like wallpaper falling off a wall, ultimately causing severe sight loss. If a detachment is treated rapidly then the sight can be restored almost back to normal, but if the detachment is left for more than a day or two then the patient can be left with a devastating sight loss. The symptoms of flashes and floaters can be caused by a number of benign scenarios, however, It is vital that any symptoms are investigated thoroughly to rule out the possibility of a retinal detachment.

When presenting with these symptoms at the practice you may be asked not to drive as we would usually dilate the pupils to get a detailed look at the peripheral retina inside the eye. The drops cause blurring of vision and photophobia (pain or discomfort in light) meaning it would be dangerous to drive a car while dilated. The affects of the drops last for between four and six hours.

Vitreous Floaters

A brief eye anatomy lesson for you… The vitreous humor is the viscous jelly-like fluid which forms the main eye chamber between the retina and the intra-ocular lens. It is optically clear and it’s primary function is to form the globe shape of the eye much like the inner-tube of a football does. It also exerts a pressure onto the retina keeping it affixed to the globe of the eyeball. Unlike most other bodily fluids it is not replenished and is in fact stagnant from birth. This means that any cells, tissue or debris from the retina that gets caught up in the gel will be present continually.

Small vitreous floaters seen on this scan hovering above the retina

This debris within the vitreous is what we call “Vitreous Floaters”. They are ever-present although will float in and out of view so that you will not always notice them. They are particularly noticeable when viewing a light coloured or white scene such as at the beach or in a clinical white room.

Floaters are completely normal and benign and will gradually increase over time. However, a sudden onset of many floaters, possibly described as “a shower” particularly when associated with flashes of light are a cause for concern and we would suggest an emergency appointment to investigate.

Posterior Vitreous & Retinal Detachment

Posterior Vitreous detachment (PVD) is probably the most common source of flashes and floaters symptoms. It happens in most adults over the age of 40 but can occur at a younger age; once it has occurred your chances of a retinal detachment are significantly lower.

Although the vitreous gel is not replenished, it does change consistency with age and can contract, thus peeling away from the retinal surface. Usually the gel is not strongly attached to the retina, aside from at the optic disc, but where it has formed a strong adhesion it can tug on the retina pinching it up like you would when picking fluff of a jumper. This tugging action causes the retinal tissue to be stimulated resulting in the appearance of flashes of light in the field of view. Once the vitreous eventually detaches, the retina sits back down and no more flashes are seen, the PVD has been and gone. If the vitreous gel tugs a little too hard, however, the retina can be torn which is the precursor to a retinal detachment. When a patient presents with the flashes and floater symptoms, retinal tears and holes are what we are looking for to prevent or diagnose a retinal detachment. We dilate the pupils in order to get the best view possible so that we can pick up these tiny lesions.

If the vitreous does pull the retina off the eye globe then the retina will quickly deteriorate and die having been denied it’s nutritional source. The patient will see this as shadows forming in the peripheral vision, such as an inability to see to the left out of the corner of the eye. If caught quickly the retina can be replaced and recovers well but the symptoms need to be identified quickly and treated rapidly.

A scan of a PVD in action which has produced a small floater (seen here as a small green blob above the scan)
A scan after a PVD where the posterior vitreous face has completely detached from the retinal surface thus significantly lowering the chance of a retinal detachment.
The appearance of "lightening Strikes" in the peripheral vision of one eye is strong sign that the retina is in distress
Floaters are quite normal for everybody, however, a sudden shower of lots of spots over the visual field is very unusual and likely to be related to a retinal tear or break
Shadows in the peripheral visual field can mean that the retina has detached and needs URGENT attention
This is a scan image of a PVD in action. The thin upper layer is the posterior surface of the vitreous gel and as you can see it has peeled away from the retina for the most part. Where it is more strongly adhered at the optic nerve it has "tented up" the tissue as peels away. Once detached the tissue should sit back down into a more normal flatter position.

Once a PVD has occurred the risk of a retinal detachment is far less (although NOT completely eradicated). The risk is lowered as the primary source of traction to the retina, the vitreous pulling on the retina, is no longer present.


Another common cause for flashes and floaters symptoms is a migraine aura. This is another subject entirely, however, migraine does not just encompass a headache. If you see coloured patterns like zig-zags or kaleidoscope affects this can be due to a migraine visual aura. There does not always have to be a headache involved. The acid test is to check whether or not the symptoms occur in both eyes or just one. If in both eyes simultaneously it is very unlikely to be a retinal detachment issue. and much more likely to be a migraine aura. However, if you are not at all sure of this then we advise you to contact the practice for an emergency appointment as we can quickly rule out any concerns. It is not worth “leaving til the morning”.

If you are at all concerned please contact the practice so that one of our Optometrists can advise you of the best course of action. See the section on Emergency Eyecare for more information on how we can help.