There are many causes of blindness in cats, and they can look different, and are treated differently.
For instance, a cat with retinal detachments will have big dilated pupils, where you can see hardly any of the iris (colored part) of the eye. Retinal detachment can be caused by high blood pressure, which in turn can be caused by kidney
disease, or by hyperthyroid disease. Sometimes you see bright spots, like the ones you describe.
A cat with cataracts will also be blind, but instead of big dilated pupils, you will see a glassy appearance. Cataracts can be treated with surgery.
If your cat has gone suddenly blind, he should be checked by a veterinarian as soon as possible; the longer he is blind, the less chance of getting the vision back. There is some hope of restoration if this just happened, and is due to something treatable like hyperthyroidism
or high blood pressure. I hope you can get some answers soon, and wish you a good outcome. Rebecca