Hello Welcome to HCM You have sudden onset symptoms like you are about to faint, blurred vision, as if world has paused. The possible reason could be Anxiety disorder and panic, some cardiac pathology especially Angina attacks, or some CNS like Partial seizures etc, Endocrinal abnormality like Hyperthyroid states etc. But as all investigations came normal so there is no need to worry, most likely these symptoms are due to Panic Disorder a type of anxiety disorder. The disorder occurs in episodic manner. Consult a Psychiatrist for expert opinion. Medicines like Paroxetine, Sertraline etc result in improvement. In attacks of severe anxiety then drugs like low dose benzodiazepines can be used. Low dose benzodiazepines like Clonazepam, Alprazolam help in relieving symptoms in times of severe panic attacks. Relaxation exercises, breathing exercises also help in decreasing the symptoms. Thanks, hope this helps you