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  Discussion on Research Summary: Incidence and Cause of Night Blindness in Apps
Author Message
Moderator:
DrO

Posted on Sunday, Nov 4, 2007 - 11:45 am:

This is a ground breaking study of a Canadian population of appaloosas that found night blindness associated with the gene that codes for a leopard or "spotting" skin pattern. All horses that had clinical symptoms of night blindness carried two "active" leopard alleles: LpLp. At least one active (Lp) allele was present in one third of all the horses in the study.

In that same study it was found that homzygous active leopard allele (LpLp) and heterozygous leopard allele (Lplp) groups had significantly smaller vertical and horizontal corneal diameters than the lplp group had. This would appear as the "appaloosa eye" where large amounts of white, the sclera, show around the cornea. However it remains uncertain what the predictive value of the presence of one or two inactive leopard genes (Lplp or lplp allele) or the presence of "appy eye" is for the condition in other populations of Appys and will require further study. For more on this disease see " Night Blindness in Horses" which you can directly access from the navigation bar at the top of this page.
DrO
PS, If we have members who have horses with a strong Appy eye I would be interested in knowing if they have symptoms of night blindness.

Vet Ophthalmol. 2007 Nov-Dec;10(6):368-75. Clinical and electroretinographic characteristics of congenital stationary night blindness in the Appaloosa and the association with the leopard complex.

Sandmeyer LS, Breaux CB, Archer S, Grahn BH.
Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 584.

Objective: To determine the prevalence of congenital stationary night blindness (CSNB) in Appaloosa horses in western Canada, investigate the association with the leopard complex of white spotting patterns, and further characterize the clinical and electroretinographic aspects of CSNB in the Appaloosa.
Animals studied: Three groups of 10 Appaloosas were studied based on coat patterns suggestive of LpLp, Lplp, and lplp genotype.
Procedures: Neurophthalmic examination, slit-lamp biomicroscopy, indirect ophthalmoscopy, measurement of corneal diameter, streak retinoscopy, scotopic and photopic full-field and flicker ERGs and oscillatory potentials (OPs) were completed bilaterally.
Results: All horses in the LpLp group were affected by CSNB, while none in the Lplp or lplp groups was affected. The LpLp and Lplp groups had significantly smaller vertical and horizontal corneal diameters than the lplp group had. Median refractive error was zero for all groups. Scotopic ERGs in the LpLp (CSNB-affected) group were consistent with previous descriptions. The CSNB-affected horses had significantly longer photopic a-wave implicit times, greater a-wave amplitudes, and lower b-wave amplitudes than the Lplp and lplp (normal) groups did. No differences were present in photopic flicker amplitude or implicit times. Scotopic flickers in the CSNB-affected horses were markedly reduced in amplitude and abnormal in appearance. No differences were noted in OP implicit times; however, amplitudes of some OPs were reduced in CSNB-affected horses. There were no differences in scotopic and photopic or flicker ERGs or OPs between the normal groups.
Conclusions: CSNB was present in one-third of horses studied and there was a significant association between CSNB and the inheritance of two Lp alleles. ERG abnormalities support the hypothesis that CSNB is caused by a defect in neural transmission through the rod pathway involving the inner nuclear layer.
Member:
dakotab

Posted on Friday, Feb 29, 2008 - 6:52 pm:

Dr O
My flea bitten TNW has motted eyes. and I have had problems with his left eye swelling and watering . It is hot to the touch, I have been treating him about 2 times a year with steroids. They thought is was and allergy because of the time of year he always seemed to get it. Well he got it again in the middle of our snowy season.
I asked about ERU one of the Vets said it was the same thing as moon blindness. So I asked if I could get a blood test to find out if it was. They are coming March 4th to take that blood test.
Is this the information you are questioning.
Hilma
Moderator:
DrO

Posted on Friday, Feb 29, 2008 - 7:45 pm:

Appaloosa night blindness does not cause inflammation as your horse demonstrates Hilma. You should note there are no blood tests for ERU, it requires a careful examination and consideration of history as explained in the Recurrent Uveitis article.
DrO
Member:
dakotab

Posted on Saturday, Mar 1, 2008 - 5:35 pm:

Dr O
The test they are going to do is called Leptosporosis Titer.
My Vet said it was for moonblindness. The article in Equss magazine said that ERU and moonblindness were the same. So I guess I am confused. I'll research it more. Thank You.
I will have to talk to the Vet on Tue.
I noticed a white spot in the eye this morning
Which has me a little concerned.
You have quite a lot of information on your website, I read a lot of it, but still have a lot more to read.
Thank You Again
Hilma
Moderator:
DrO

Posted on Sunday, Mar 2, 2008 - 10:30 am:

Moonblindnees and ERU are the same but not the same as Appaloosa night blindness. I know the terms sound similar: "night blindness" and "moon blindness" but they are NOT the same.

Leptospirosis has been associated with ERU in some studies but not others. A positive titer to lepto would not be diagnostic for ERU however. It might be suggestive that treatment for lepto would be helpful but it will be a long shot. You will find more on this in the article I referenced above.
DrO
Member:
dres

Posted on Sunday, Mar 2, 2008 - 1:36 pm:

Hilma , not that this might help you but i know i put fly masks on my horses all the time.. the appy's have very sensitive eyes.. the masks help with the wind and the UV rays.. I read on a Appy board one time that it does help the sensitive ones.. So just to be safe that is what i do.. daily when the sun is out bright..
good luck..

On the first day God created horses, on the second day he painted them with spots.
Member:
dakotab

Posted on Monday, Mar 3, 2008 - 9:34 pm:

Thank You Ann
I put one on the other day when I let him out. The eye seemed to be doing well. But the next day it was closed swollen and running. The vet is coming tomorrow and I will see what is up with it.
I hope Dr O is right and it isn't ERU.
Moderator:
DrO

Posted on Tuesday, Mar 4, 2008 - 7:45 am:

I am sorry Hilma but I am not implying that I do not think it is ERU. ERU will require an exam and history to rule in or out. But it does not sound like Appaloosa night blindness.
DrO
Member:
dakotab

Posted on Wednesday, Mar 5, 2008 - 6:53 pm:

Dr O
The first thing the Vet said to me yesterday was this horse is and Appaloosa. I told her no, he is TNW. fleabitten .
Anyway the vet took his blood for a Lepto titer
test. Said she would look for the antibody level. I took a copy of your chart to her and she explained it to me. Still sounded like greek. But I ask her about so many horses showed positive. She said they would take another blood test in two weeks to see if the levels had changed. I was real grossed out about taking a eye fluid test which you said was a more positive test for Lepto.
I really appreciate the information you have on ERU. Most of it was above my understanding but I read it more that once to get more knowledge about it.
Thank You, thank you
Hilma
Member:
dakotab

Posted on Wednesday, Mar 5, 2008 - 6:59 pm:

Dr O
I mean't to respond about nightblindness.
I will look that up also.
I do understand that you said there is a difference in the two. It will be intresting to research that.
Thanks Again
Hilma
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