I am sorry to hear that your kitty is having this problem.
I would be most concerned about a problem in the lens of the eye, most likely a cataract. In a young kitten, this can frequently be addressed surgically if the retina is working normally.
You can get some idea of the function of the retina by flashing a bright light into the eye and seeing whether the pupil gets smaller. If it does, it implies that the retina has some function.
Here is a link to an article on cataracts:
I hope this helps!
As always, if you have further questions or concerns, please don't hesitate to ask them using the "reply" function.
The pictures on that page, now that I look at them, show only mature cataracts that affect the entire lens. Cataracts can be partial and only affect one section of the lens such as you describe.
I am glad to hear that he has good function and seems visible.
This being the case, if he seems comfortable, there is not likely to be anything that needs to be done unless something changes.
I would always encourage you to have him evaluated by your veterinarian or a veterinary ophthalmologist.