Why are some blue eyed cats cross-eyed and some not

I have a siamese red flame kitten/cat 9 mos old, has very light blue crossed eyes. When I go outside to get him, he always has his eyes shut I think maybe is sensative to bright light.anyone know how to get him some cool shades?

Hi there.here's an exerpt from Pet Education.com:

Cats with Strabismus (Cross-Eyed) by

Race Foster, DVM

Marty Smith, DVM

Strabismus is a term used to describe the abnormal positioning or direction of the eyeball. Normally, the eyeball is held in place and moves from side to side and top to bottom under the influence of small muscles which attach directly to the eyeball. Occasionally one muscle may be longer or stronger than the muscle located on the opposite side. This causes the eyeball to veer off in an abnormal direction. One or both eyes may be affected. If both eyes deviate towards the nose, the pet is referred to as cross-eyed. This is common in Siamese cats and is called medial or convergent strabismus. The eyeballs may deviate away from the nose, just the opposite of being cross-eyed, and this is called divergent strabismus. This is common in Boston Terriers and is inherited in this breed.

Strabismus can also occur as a result of injury to some of the nerves going to the eye muscles. In addition, it may be seen if the cat or dog has a disease of the vestibular system. The vestibular system is part of the ear and is what helps the cat (and us) keep our balance. If the vestibular system is not functioning normally, the cat may feel as though he is spinning, and his eyes will move abnormally to try to adjust to that.