Healthy chicken gone blind

[TheOddOneOut]

But can ocular Mareks show up spontaneously in a 17 month old hen that was vaccinated and shows no other signs of Mareks (paralysis, lethargy, etc....)? From my understanding, that would be rare because it is primarily a virus that affects young chicks up to 20 weeks of age.

It can show up in any age of bird. Ocular Mareks presents different than the other forms.