Hi David,
Can you post a picture please?
If more than one shubunkin has this I would guess either it to be bacterial infection or a parasite of some kind.
I would start treating for a bacterial infection first with either amoxicillin or gentamycin.  Look for a oral medication.
You fish store probably will have it or you can maybe get it online.  If your fish isn't better then You could start treating with a parasite medication. Such as Paracide or one with Metronidazole -or- Quinine Sulfate -or- Nitrofuracin Green in it.
Good luck.

Does he swim odd or in circles?
Could be brain flukes, apparently no treatment available. Do you have snails in your pond?

Hard to tell without photos, and the different sites I look up, some say no treatment, others bacterial treatment. Now I am really confused too.. 

As promised I have got some photos to assist in the diagnosis.

The fish are home breed (by accident) and are now about 7 months old. One close inspection none have both eyes affected and only 3 or 4  (of 9)have the "halo" which may be normal??

Thanks in advance for your help.

David

Sorry only 1 downloaded, 3 more here

Could you pick your fish up and have someone take a picture real quick of the infected eye?  I know this sounds crazy but for a few seconds of picture taking it won't hurt the fish.
What I see from these last pictures posted is that maybe the eye in question is protruding a bit?
But I'm not even sure if that is for sure what I am seeing!
If the eye is protruding a bit which would cause the skin around the eye to show which would be white tissue, then here is what I would do:

1) Check your water chemistry.  If nitrates are really high it can cause the eyes to protrude.  You will need to do a major water change on your pond.
2) Start feeding a medicated oral antibiotic fish food.  I use a product by jungle.  It's small pellets.  Feed just that for at least a week.
Keep us updated!

David,
I have a few questions for you.  How big is your pond?  Your fish look quite big and high nitrates could be from over crowding and waste build up.  Also, do you have any plants in your pond?  Plants are really good for helping to absorb some of the nitrates.  It's hard to tell from the pictures if there are plants growing in the pond.
Well anyway I hope you will give us an update when you can.

That's a gorgeous picture.
ok so your pond is about 581 us gallons.
I'm thinking baterial infection possibly from water quality.
Is there any fountain or water running to or in the pond?  Any filtration system?
water circulation?  The oral medication would be the best thing I feel.  It would treat all the fish at the same time.
I would feed twice a day only what they will eat in about 5 minutes each time.  I use this medication and treat new fish with it as a preventative.  See if you can get any Jungle products.  You might get it at a pond supplier store instead of a regular pet store.
If your water quality checks out to be off kilter then you will still have to do a major water change.

Yes your water test seems fine except for the nitrites,  I would keep an eye on a spike and re-test every week or more.  Have you recently re-filled the pond?  If a pond is cycled then ammonia and nitrites should be at zero. I didn't see what the ammonia levels were. Did you test for ammonia too? Some fish are sensitive to nitrite even in the smallest amount.
 I still think then that it is a bacterial infection and should be treated orally like we discussed in an earlier post.  Snakes, frogs, bird droppings could have caused this.  It is not normal for the eyes to protrude like that.
Glad to help and glad you tested your water anyway.  It's a good thing to do.
Well please keep us posted on how things go.
You have a lovely pond and very lovely fish!