SkiNLaB, I also have these crescents around the edge of my iris. In iridology, they are considered a sign of liver/kidney congestion, although they alone do not indicate damage to the liver. From my limited understanding of the subject, I believe they are considered to be an early warning sign.
With the type of crescents I have, conventional science/ medicine(optometry/ ophthamology) see these
cholesterol and calcium deposits as being harmless to the sight in young people (even the not so young like me apparently). From speaking with my optometrist, they are generally ignored unless the patient is aged 60+, when it is considered that these lipoproteins can affect sight. If you look at the physiology of the eye, noting the role of the "Canal of Schlemn" (sinus) which circulates the "Limbus" (the outer darker boarder of the iris) you should get picture of how such deposits can occur. Crescents <10mm diameter are often associated with nearsightedness (myopia) but can also be connected with other eye disorders.
As to how permanent these marks are; even if you manage to control your levels of LDL (low density lipoproteins) these crescents will be unlikely to change over time. From first noting one in my left eye in 1987, mine have actually advanced to where they almost form circles.
Interestingly, last year I had an ultrasound to check abdominal integrity. The radiographer thought she saw a fatty liver, but upon closer inspection said no. But there was contrast between my liver and right kidney which can indicate the condition, normally seen with those suffering liver disease. Triacylglyceride levels came back fine and my concerns were dismissed by my doctor. But I can't help wondering if there could be connection between all this, perhaps signalling a warning for the future. I know my intake of fatty foods and drugs is decreasing as I get older, and such reminders will undoubtedly serve to hasten the process.
If you are concerned by these deposits then get an eye examination and a routine physical. Some pigmentations can represent degeneration due to other diseases or genetic factors, so it's certainly worth finding out what condition you have.
If occult science is within your sphere of credibility; many schools of magic associate these marks with special qualities of the magician. Depending upon the appearance, some teachings also depict some such marks to be elementaries -man created entities- which attach themselves to a persons mental sphere of consciousness. Some are considered benign, others are purposeful and usually destructive.
To properly rid oneself of these, one must locate the source -creator- of the elementary and ask him/her to destroy the entity (not to be confused with elementals - mentally created spirits from a single element, limited in purpose and with no ability to act on their own). It is often found that it was not the desire of the magician to have his elementary inflict trouble, but if an elementary is not destroyed following completion of it's purpose, they are known to roam, attach themselves to unwary hosts and cause all manner of mischief and ill ease.
So put your mind at ease and go see a magician, an optometrist or a doctor, or all three
talcum powder: on the dance floor maybe? I didn't think that was done much these days, but break dancing could definitely benefit from it I guess.
