The vitreous humor is the jelly-like liquid that fills the central cavity of the eye. Normally, it is of a very consistent thickness, or viscosity, and is crystal clear. Several eye conditions that occur that effect our vision have their root in changes to the vitreous (see Info on Retinal and Vitreous Problems and the Flashes and Floaters page by Retina Vitreous Associates (source of the eye drawing below).
Floaters are caused by inconsistencies in the viscosity of the vitreous or accumulations of debris (similar to cataracts in the lens) that distort or block the vision. Very often these floaters are not much more than a nuisance and also have a tendency to come and go. They can, however, become very disturbing and don't go away.
These inconsistencies in the vitreous can also cause stress on the retina. The retina is attached to the vitreous like a label on a jar. If this junction is not perfectly consistent, stresses on the retina result. At first, a slight tugging excites the nerves of vision and the brain thinks it is seeing something; This is a "flash". More stress can cause damage to the retina (see below).
The very high concentrations of vitamin C in the vitreous, lens and retina are there for a reason. The vitamin C protects these components of the eye and maintains the consistency and clarity of the lens and vitreous. Vitamin C may be the single most important nutrient for long-term eye health.
A visitor to Cforyourself shared this from Prevention magazine, Dec. 1974, p. 171: "For about 4 yrs I had considerable trouble with spots (floaters) behind my eyes. After seeing an optometrist I was told that they would probably always bother me so I more or less resigned myself to this annoying problem. Then about 4 months ago I decided to treat myself for a sinus headache with vitamin C. I took 2 grams every hour for about 16 hours. The headache disappeared overnight and I realized at the same time that the spots in my eyes had disappeared as well. I haven't had a sign of them since."
Obviously, anyone that has "floaters" or "flashes" should try taking mega-dose vitamin C (see How Much to Take).
Retinal Tears and Detachments
Most of the mechanical damage to the retina, the dense nerve-endings (rods and cones) that receive the light on the back surface of the eyeball, are due to changes in the vitreous that create stress on the retina. As we age (there's that clue to nutrition), the vitreous becomes less a consistent mass and loses some of its viscosity. Small lines of more liquid vitreous form strands and can become "floaters". They can also put stress on the retina (remember the retina is like a label on a jar, so if the jar is not perfect, the label will take the stress), pulling away from the retina either tearing it or pulling it away with it, a detachment.
Tears and detachments are serious stuff. Laser surgery to fix these problems has amazing results, but once again, if the vitreous is maintained in its proper state, most of this damage won't happen in the first place. Vitamin C is required to maintain the vitreous. Just like cataracts of the lens, these vitreous problems can be generally avoided by proper C supplementation.