See a neuro-ophthalmologist. Find one at www.aao.org Use the search feature and read the many postings about visual snow. I don't comment much on visual snow because frankly I have not had patients complain of it nor is there much research on the subject.
JCH III MD
Hello Hulabana, to participate in a survey addressing visual snow and other persistent perception problems please contact ***@****. He is a neurologist and psychiatrist making a study in the topic. He will send you a survey that may help in finding out more about the possible causes in your case (BTW tumours are really rare as a cause of persistent visual snow, other diagnoses are much more frequent) so that you can take these informations with you with your next visit to a doctor at your place.
Dang, I didn't realize I couldn't post an email address. If you do google "Those With Visual Snow, you should be able to find the forums dedicated to this, as well as the survey.