The retina is a light-sensitive tissue at the back of the eye and is crucial for vision. As RP progresses, the field of vision narrows, a condition known as tunnel vision until only central vision (the ability to see straight ahead) remains. Many people with Usher syndrome also have severe balance problems.
Calves can be ready for weaning by 3 to 4 weeks of age; however, in Penn State studies calves weaned at 3 weeks required extra attention. The increased time and labor required to get these calves eating starter suggest that waiting until 4 weeks of age would be prudent.
Re: 6 month old angus bull calf. My guess would be more feed. When weaning they should eat 1-1.5% of their body weight working up to 2%. My thought was that the calf was maybe on too much feed. 12 lbs of feed and Sure champ plus 2 scoopfuls of cottonseed hulls is a pretty big load for post 3 weeks weaning.