Tuesday, December 11, 2007

4.8 The "flying mosquito" syndrome

Floaters, known as the "flying mosquito syndrome" in Chinese, are little specks, threads, or tiny cobwebs that you see against a blank wall or while looking at the sky. And they move with your eyes. There are many different kinds of floaters, all of which deserve close scrutiny.

First, a quick review of the structure of the vitreous. The vitreous occupies the bulk (80%) of the eyeball. It is 99% water and has a lattice of collagen fibers with coils of hyaluronic acid distributing within the structure. Essentially, the vitreous is an optically clear gel. In the aging eye, parts of the vitreous become liquefied, and the collagen fibrils condense to form the floaters.

An example of this type of floaters is shown below:
Notice the tadpole-shaped shadow in the 2 o'clock position. Cataracts also cast small shadows which are more centrally located, i.e., in the macular area. Floaters are more noticeable if they are situated close to the retina. However, not all intra-vitreous opacities are perceived by the patients. A good example is the tiny soap-like particles known as the asteroid hyalosis:
These particles usually appear in only one eye. Sometimes it is an indication of (often undiagnosed) diabetes, so a blood glucose test is recommended.

Sudden onset of floaters can be a sign of trouble. A good example is tractional retina detachment (RD) during which, a blood vessel is ripped open. The blood cells appear as a sudden shower of floaters when they enter the vitreous. Retinal detachment requires surgical repair, that in itself is an entire branch of ophthalmology. An image of RD is shown below:
(This one image courtesy of Optos)
And the encircling scleral buckle that helps the retina to re-attach itself is seen as a black circular band in this post-op RD:

Again, the image may look like a total mess, the central vision is actually preserved.

Then we have vitreous hemorrhage from a leaking artery:
Notice the origin of the hemorrhage (the dark red spot) is next to the optic disc in the 5 o'clock position. This hemorrhage actually extends into the vitreous seen by the patient as a large floater. A stated before, extensive vitreous hemorrhage requires vitrectomy in order to regain vision.

Finally, a very common condition known as posterior vitreous detachment (PVD). PVD affects 50% of people over 50. Typically the patient sees a sudden appearance of flashes together with a long curvilinear or a circular floater. Sometimes PVD is accompanied by hemorrhage and/or RD, but mostly quite benign except for the annoying floater. One such is shown below:
This circular floater (which appears oval, a sideway view) is initially part of the vitreous attachment to the optic disc, in other words, a rim, which is pulled off during the vitreous separation from the retina. Luckily, no blood vessels are disrupted this time. Once the traction is relieved, the flashes are no longer seen.

So sudden onset of floaters must be treated as an emergency and the etiology identified.

14 comments:

Anonymous said...

I have experienced this effect since a very young age. Is it really a condition that only occurs in the elderly?

EyeDoc said...

Floaters can be an indication of pathological changes in the retina and/or the vitreous. Indeed seen more in older eyes. In the young eyes, sometimes you see a "remnant of the hyaloid artery" which remains attached to the back of the crystalline lens. It can be a big, noticeable, yet harmless floater.

Anonymous said...

anyway to heal this syndrome??need to have operation??

EyeDoc said...

Floaters are almost never removed with surgery as they MAY disappear (sink) as the vitreous gradually liquefies with aging.

In cases where floaters interfere with vision, vitrectomy by a very skilled retinal surgeon can be done.

Green said...

I'm sorry but I couldn't read your wall of text, but to get to the chase, what harm can it cause? I currently have it and it's disrupting my sight of the sky.

EyeDoc said...

Floaters are the results of changes in the eye, i.e., a warning sign. They can be annoying but do not cause any harm per se.

winnietan said...

may i know what causes these floaters/mosquitoes ?

EyeDoc said...

Causes vary, already described in the post. The most common one is condensation of the collagen fibers in the vitreous - part of aging of the eye.

winnietan said...

thanks. some told me it is because of pressure and too much tension....what can i do at the meantime before i go to see a doctor?

EyeDoc said...

Floaters are unrelated to pressure/tension. If your floaters are of a sudden onset, then it suggests a retinal issue that must be seen by an eye doc ASAP. It is also possible that you maybe seeing aura, a prodrome to ocular migraine or migraine headaches. Then you'll need to see an internist first.

Deo Narayan Singh said...

Thanks for the valuable info. My mother is experiencing the floaters in both the eyes. in one eye its like a mosquito flying in front of the eye and in the other eye its like a web of threads. My mom's age is 65+, the doctor has said that its due to aging. So, do I really not to worry.

EyeDoc said...

As stated in the post, other than vitreous liquefaction which is relatively benign, there are potential problems that need to be checked out by a retina specialist. It pays to be careful.

Dirgni said...

Yikes! Noticed floater in my right eye about a month ago. Now I get a semicircular arc of light in my peripheral vision. I'll make an appt. with the dr., but I have to take a plane trip first. Is there a problem flying with undiagnosed retinal detachment?

EyeDoc said...

Sounds like posterior vitreous detachment rather than retinal detachment. Should see an eye doctor first to confirm either way, though.