The following very well written and accurately descriptive two part article is reproduced on this site with permission of the author.  It was posted on the Racing Pigeon Discussion Centre.   I have tried to interpret Mike van der Jagt's thoughts with animations.  Also, I have linked his descriptions to some of Nick Brent's photo's.  

The animations are from original photos of my birds; however, they have been digitally enhanced to reflect what I think the author is describing.        

By Mike van der Jagt (209.212.50.112 - 209.212.50.112) on Thursday, January 18, 2001 - 07:02 pm:

Hi All.  As promised, here are my personal thoughts on eye sign.  Most of my ideas were taught to me by Roy Butson back in the 70’s.  I have added to my ideas through reading, discussion and constant observation and testing over the past 30 years. It is 100% my opinion.  I like working with it, it has increased my enjoyment of the hobby immeasurably and I believe has helped me develop a better team of racers and breeders.  But it is not science, I cannot prove any of it through the scientific method, I have conducted no controlled experiments. It is my OPINION.  If this will offend anyone’s delicate sensitivities I suggest they exit now, quick.

As an overview of the eye, I read above where someone talked about the 5 circles. There is black circle that encircles the eyeball right at the point where it meets the eye socket.  I have heard this called the heart muscle, why I have no idea.  I first heard about this circle about 5 years ago and have watched for it since then but have not paid a great deal of attention to it.  It is clearly visible on some birds, broken and incomplete on others and entirely absent on some.  According to what I have heard, the wider and blacker this ring is the better.  I must admit that on the truly outstanding breeders I have handled, there does seem to be some correlation there.

Next comes the iris.  This will be either a yellow base or a white (pearl) base.  I like this to be very rich in colour.  Not bright, like neon, what some might call a wild eye, but rich and deep like polished mahogany.  The best way to read the eye is under direct sunlight with a 10 power lens.  A stronger lens shows too much detail and loses perspective.  A lower power will work, but I get the effect I like with a 10 power.  Under a ten power in direct sunlight the iris has to have a real 3D look, with mountains and valleys and lots of structure.  Things have to have very distinct shapes. Not blended into a landscape but clear beginnings and ends.  Good clear definition.

Next comes the circle of correlation.  Again it must be a rich colour with excellent definition.  It should be instantly clear where the iris stops and the correlation starts.  The iris edge of the circle of correlation can be irregular and starred and running out into the iris, but the boundary between the two must always remain quite distinct.  To me the wider the circle of correlation the better.  Serration and stars around the outer edge are desirable.  This is what is called the pop bottle cap.  This is highly desirable especially in a hen with black eye sign.

 

Between the Circle of correlation and the pupil in another circle.  It is not visible on all birds but is very important to me.  This is called the sphincter muscle.  I believe it controls the opening and contracting of the pupil as the light changes, but I stand to be corrected on that one.  It looks like a knotted rope and can be brown or black.  The thicker and blacker this ring is, the better I like it.  If it is not visible, I rate the bird a poor breeder.

The final or fifth circle is the pupil.  I look for a very small pupil in direct sunlight.  Some refer to a pupil the size of a pin head, but I have never seen this and would consider that abnormal.  A small pupil to me is about as big around as the end of a BIC pen refill.  What is even more important than the size of the pupil is how responsive it is to light.  Dave Rodgers had a bird at the Friday night gathering whose pupil would instantly enlarge as soon as it passed into a light shadow after being held under the light.  As I held the bird under the light I could pass my hand back and forth over top of the bird in a waving motion and watch the pupil expand and contract instantly as I blocked and unblocked the direct light.  This is perfect. An outstanding quality.  Dan agrees with me here.

Next comes colour of correlation.  Unlike some I believe that colour is very important.  To me the ultimate racing eye is a wide bright highly defined yellow circle of correlation in a cock bird.  This is the bird I want flying into a head wind on the 500.  The ultimate breeding eye to me is the wide dark black bottle cap circle in the hen.  Here is where I have problems picking between racing and breeding eyes. If the race is very hard, or very long and particularly if it is a two day race I want my money on the black eyed hen, not the yellow eye cock.  Other variations in colour include green, gold, gray, brown and purple.  It is very important to me that the colour is distinct. If it is green it is green not sort of yellowy, grayish green, but green.  Same for the other colours.  One exception is the composite sign where there is a clear black smudge on top of a good clear yellow sign.  This can be deadly.

The violet eye is unique.  What I call recessive violet is a pearl eye sign.  The other rules remain.  It must be wide, sharp, clearly defined etc.  The dominate violet is not really a colour but a hue.  Like the iridescence on the neck feathers.  I see it in the sphincter muscle after staring in the eye in full sunlight for 15 or 20 seconds.  It falls over the sign almost like a shadow, but it is clearly violet.  I have only seen this twice in my life time.  Both birds were cocks and both birds were the foundation sires to famous lofts.

I am sure that you have heard enough from me for now. Let me know if you want any more.  As I said.  I love talking about eye sign.

Part II

By Mike van der Jagt (142.106.180.133 - 142.106.180.133) on Friday, January 19, 2001 - 07:42 am:

Hi Wye Loft.  I have seen the pictures of Probor eyes and I know what you mean.  I would call those pearl or violet recessive.  What is a dominate violet to me is more in the inner circle and is not actually the colour of the circle of correlation but more like a film or mist floating above it.  It is very rare.  It is just what I call Violet Dominate.  I have never had it explained to me so I am using my own interpretation of what the term dominate violet means.  For sure there are other meanings and interpretations.  I also agree with your observations that the 3D effect and sharpness of contrasts are more important than the width of the circle of correlation, but I still rate a wide circle superior to a narrower circle when other factors are equal.  Tony and Thumper.  In a sense you are both correct.  I too have seen the eye sign (circle of correlation) continue to get better as the bird gets older, for sure.  Once the bird starts to suffer the ravages of old age the other characteristics of the eye all start to deteriorate along with everything else about the bird except the circle of correlation.  It is like wine and keeps improving with age.  As a point of interest John Lehman won the eye sign show at Humber Valley this year with a very old hen.  I think she was 12.  I suspect the Judge, Louis Forget, was limiting his evaluation to the circle of correlation only.  If you are talking to him Peter, that might be an interesting point to verify.  At the Friday night gathering Burt Goncalves had a 2000 bred youngster with one of the best eyes in the place.  I hope that bird is around in a couple of years.  I would love to have a look at it then.