Re: Can 'floaters,' debris in intraocular fluids, vary in shape among people?

Hi Lou,
 I have had a lot of fun researching your great question about what 
you very intuitively called "floaters". They are indeed known to 
ophthalmologists and vision scientists as "vitreous floaters" as they 
are found in the vitreous, this clear, avascular, gelatinous body that 
comprises two-thirds of the volume and weight of the eye.  Good call 
on that one!
 It was Purkinge (1823) who first identified the floaters as being the 
cause of the "shadows" in the eyes that have been familiar to 
humanity at least since the ancient Greeks and Romans (Plange, 
1990). Purkinge originally called the floaters muscae volitantes, 
which is Latin for "flies that flutter back and forth"!
 You were also right in linking them to cell debris or proteins. They 
are indeed believed to be dead cells (including red and white blood 
cells) and fine aggregates (lumps) of vitreous protein that are opaque 
enough to throw a shadow on the retina (Scheie and Albert, 1977; 
Vaughan and Asbury, 1986). These retinal shadows are projected by 
the brain as a corresponding dark form in the appropriate area of the 
visual field 
 Vaughan and Asbury (1986) state that floaters are most readily seen 
against bright lights or, as you found out, against a uniform light 
background. They add that the shapes of the floaters are known to 
vary from one individual to the next and reports that they have been 
described to him as "spots", "soot", "particles", "cobwebs", "threads", 
"a ring", "dark streaks", "worms" and "spiders"! They are most mobile, 
as demonstrated by the fact that they continue to migrate (drift) after 
the eye ceases to move. They are very common in people with 
myopia or syneresis (separation of the gel and the liquid in the 
vitreous). They tend to be more numerous in older adults, and are 
believed to have a genetic component.
 Now on to the most important part of your query, namely do they 
adversely affect our visions and do they say anything about our vision 
or general health. Vaughan and Asbury (1986) and Hart (1992) say 
that floaters in the periphery may easily be overlooked, but that 
relatively immobile, centrally located floaters are visually annoying 
and may even be disabling. In themselves, it seems that floaters are 
relatively inoffensive but they may be an indication of a more severe 
condition.
 Scheie and Albert (1977) state that the condition is "usually 
innocuous" but Vaughan and Asbury (1986), 10 years later, state that 
"vitreous floaters should never be dismissed as harmless". They link 
the presence of floaters to various disorders of the vitreous, 
expatiating that floaters can be caused by small haemorrhages into 
the vitreous due to retinal tears or diseases such as diabetic 
retinopathy, hypertension, leukaemia, old retinal branch vein 
occlusion, Eales’ disease, Coats’ disease and subacute bacterial 
endocarditis. Even more recently, Hart (1992) claim that "most 
vitreous opacities are harmless", then differentiates between "slowly 
developing" and "abruptly appearing" floaters. He argues that the 
second type is more likely to be an indication of haemorrhage into the 
vitreous body and retinal break.  
 When are floaters a problem, then? Diamond (1992) studied 170 
patients with floaters and detected a more severe disorder in 41 
(24.1%) of them. The most frequent problem observed was retinal 
break. He adds that patients with a single floater were much less at 
risk than patients with numerous floaters, and that the latter should 
seek the opinion of an ophthalmologist. Byer (1994) studied 163 
patients with one or two floaters and reported that 12 (7.3%) 
developed a retinal tear. He states that adults over 45 years of age 
experiencing vitreous floaters should seek ophthalmological 
consultation without delay. He concludes that "a national public 
educational effort should be pursued to publicize the importance of 
these symptoms", no less!
 That’s the story on floaters. Cheers!
    Benoit     

References:
Byer (1994) Ophthalmology, 101, 1503-1513.
Diamond (1992) Eye, 6, 102-104.
Hart (1992) in Adler’s Physiology of the Eye (Hart WM, ed) London:  
     Mosby YearBook. 
Plange (1990) Gesnerus 47, pt 1, 31-43.
Purkinge (1823) Beobachtungen und Versuche zur Physiologie der  
     Sinne, Prague. (Cited by Duke-Elder (1962) Systems of 
     Ophthalmology, London: Kimpton).
Scheie and Albert (1977) Textbook of Ophthalmology. London: 
     Saunders.
Vaughan and Ashbury (1986) General Ophthalmology (11th ed). Los 
     Altos: Lange.