Posterior Vitreous Detachment
(Light Flashes and Floaters)
The vitreous is a jelly like material that fills the central cavity of the eye between the crystalline lens and the retina. The vitreous is 98% water with the remaining portion being fibrous proteins and collagen that give it a stiff consistency similar to an egg white. In newborns, the vitreous is firmly attached to the retina. With age, the vitreous begins to thin and there is a separation of the watery elements from the fibrous components. As the vitreous liquefies it also begins to shrink. As a result, part of the vitreous actually becomes detached or peeled away from the back of the eye. This is called a posterior vitreous detachment (PVD), which is common and usually harmless.
Traction or a residual connection to the retina is responsible for the characteristic "flashes" or streaks of light which often accompany PVDs. The "floaters" frequently reported are from the condensation of vitreous collagen or possibly from some fragments of retina which may have been dragged into the vitreous cavity by this separation. “Floaters” can be seen in the absence of a vitreous detachment and are simply caused from cells or bits of coalesced vitreous casting shadows on the retina.
There are, however, other more serious causes of flashes and floaters. Retinal tears, retinal detachment, infection, inflammation, hemorrhage, or a head injury may also cause floaters and flashes. Occasionally, flashes of light are caused by neurological problems such as a migraine headache and can cause certain type of flashes of light. When related to a migraine headache, the flashes of light are seen in both eyes and usually occur 20-30 minutes before the headache starts.
Signs and Symptoms of Posterior Vitreous Detachment
- Black spots or “spider webs” that seem to float in the vision in a cluster or alone
- Spots that move or remain suspended in one place
- Flickering or flashing lights that are most prominent when looking at a bright background like a clear, blue sky
Symptoms that may indicate a more serious problem
- Sudden decrease of vision along with flashes and vitreous floaters
- Veil or curtain that obstructs part or all of the vision
- Sudden increase in the number of floaters
Treatment and Prognosis of Posterior Vitreous Detachment
Because the risks outweigh the benefits, surgery is rarely indicated for PVD except when the floaters obscure the vision significantly. In these cases, surgical removal of the vitreous (vitrectomy) may be considered; although, treatment is seldom needed since floaters typically become less bothersome over a period of weeks to months as they settle below the line of sight. Nevertheless, it is important that all eyes with recent onset of flashes and floaters be immediately examined carefully by an optometrist or ophthalmologist. Changes can occur rapidly and time can be of the essence if a retinal detachment is present. If the retina is normal and intact it is still monitored for several weeks with eye dilation to watch for complications, until the PVD is complete. It is important to maintain the directed follow-up schedule with your doctor until instructed otherwise. The second eye also should also be carefully examined and the retina treated if necessary.
Complications of Posterior Vitreous Detachment
In the majority of cases nothing unusual is found, although up to 20% of eyes with a vitreous detachment may develop a tear or hole in the retina. Retinal tears or holes can continue to worsen without treatment, resulting in severe and permanent vision loss due to a retinal detachment. A retinal detachment is a very serious sight threatening condition requiring a major surgical procedure to repair. Even with the best surgical care, vision loss from the detachment cannot be restored and results can be unpredictable.
If the retina only has a tear and had not detached, treatment is simple and very effective. Repair is done by either laser light or with a freezing probe (cryopexy). Both accomplish the same purpose with good results and low complication rates. The procedure is done as an outpatient under a local anesthetic.