This patient has a rare condition called visual snow syndrome (VSS). (1) This condition is thought to reflect subcortical network malfunction and cortical hyperexcitability, with the visual cortex being implicated. (2) An underlying cause for VSS has not been identified. Unfortunately, VSS can be quit disabling, and there is no known treatment.
VSS differs from migraine syndromes in terms of neurophysiology and neuroimaging, and they are probably unrelated conditions. (2) Two important considerations in patients with persistent photopsias are cancer-associated retinopathy (CAR)(3) and autoimmune retinopathy. (4) Patients with these conditions often have unusual visual sensations as well as night blindness and ring scotomas. Patients with these conditions, unlike our patients, experience significant visual loss, arterial narrowing, and some anterior chamber and/or vitreous cells. As with our patient, those with CAR and autoimmune retinopathy typically have no or minimal RPE and disc changes. CAR can occur in association with several tumors, most commonly small cell carcinoma of the lung. The visual symptoms of CAR can precede the diagnosis of cancer. Patients in both conditions often have antibodies to certain retinal antigens, but these antibodies can sometimes be seen in asymptomatic individuals. Immunosuppressive treatments for CAR and autoimmune retinopathy have not proven very effective to date.
1. Puledda F, Schankin C, Digre K, Goadsby PJ. Visual snow syndrome: what we know so far. Curr Opin Neurol 2018; 13(1):52-58.
2. White O, Clough M, McKendrick A, Fielding J. Visual snow: Visual misperception. J Neuro-Ophthalmol 2018; 38(4):514-521.
3. Hoogewoud F, Butori P, Blanche P, Brézin AP. Cancer-associated retinopathy preceding the diagnosis of cancer. BMC Ophthalmol 2018; 18(1):285.
4. Grange L, Dalal M, Nussenblatt RB, Sen HN. Autoimmune retinopathy. Am J Opthalmol 2014; 157(2):266-272.