If you are reading this, then the chances are that you view the world through a clear glass. An eyesight good enough to navigate the world with or without the help of glasses or contact lenses.
But for the unlucky few who suffer from Visual snow syndrome (VSS), this same reality is a visual mess with their perception being constantly and persistently covered by a grainy filter of varying intensity. This visual disturbance is the primary characteristic of VSS; which is defined as a rare condition that exhibits a persistent visual phenomenon on a person’s visual perception that is similar to an analog television static4. Always having their visual field covered with a grainy filter is detrimental to the patients of VSS, and you may be inclined to think that much research has been done to understand this disorder but that is not the case. Because of its rarity, only limited research has been conducted on VSS with less than 10 studied cases in the literature before 2014, and its underlying mechanisms are not yet understood.
Rising interest in understanding VSS
In recent years, however, the understudied nature of VSS is slowly but surely changing with about 200+ studies now dedicated to it. This increase in research interest has shed some light on its underlying mechanisms and opened many doors for future research. One of the main findings of VSS in the last decade is the two ways in which VSS presents itself; primary and secondary. Primary VSS cases are characterized as a sudden onset of VSS symptoms without any underlying explanation. On the other hand, secondary cases are associated with a prior underlying cause of either drug abuse or head trauma6. The drugs that are thought to induce secondary VSS are marijuana and other hallucinogenic drugs such as LSD, MDMA, mescaline, etc. This association of prior drug abuse with VSS is significant such that it allows us to study the neural mechanisms of these drugs and use those findings to narrow down brain regions of interest for VSS. For instance, hallucinations induced by LSD are known to work by affecting the neural connections in the thalamus5. This finding along with the previous association of VSS with LSD can be used to target the thalamus as a brain region of interest and study it to understand its underlying mechanism. Furthermore, recent research into VSS has also found a connection between VSS and other neurological disorders such as tinnitus (persistent ringing noise), palinopsia (afterimage), and nyctalopia (impaired night vision)1. Similar to the significance of previously described drug association, this presentation of VSS together with other neurological disorders can be used as a guideline to study the brain region of interest for the cause of VSS.
What causes VSS?
Despite the recent interest and numerous new studies dedicated to VSS, the underlying cause for this disorder is still unknown. What is known however is the fact that VSS is not caused as a result of faulty eye and its parts but due to a neurological disorder of the visual processing areas in the brain cortex2. When Lauschke et al., 2016 performed both ophthalmic (relating to the eye) and neurological examinations in patients with VSS, they observed no ophthalmic problems with patients reporting 6/6 in vision and other eye tests. This finding pointed towards a neurological problem for the cause of VSS, which they were then able to narrow down to a fault in the central color-dependent processing of the brain. Furthermore, they also highlighted an increase in the firing of neurons in the thalamus, resulting in a thalamocortical dysrhythmia as a possible cause for VSS. This involvement of the thalamus in VSS echoes the previous finding of how secondary VSS presents itself as a result of hallucinogenic drug abuse that alters the normal functioning of the thalamus. A more general look into the brain regions that are different in patients with VSS compared to controls has identified alterations in gray matter volume in various brain regions such as the temporal lobe, parahippocampal gyrus, and other limbic and temporal structures7.
Treatments for VSS
As mentioned throughout the article, the lack of research on the basic biology of VSS has caused a shortage of effective treatment strategies. To date, no conclusive treatment option has been obtained from a scientific trial, and most of our treatment strategies are acquired from individual case report studies tailored to the need of the individual patient. For instance, there are cases where the severity of VSS has been decreased through the use of drugs such as lamotrigine8, and amitriptyline9. Additionally, the use of non-medicine strategies such as tinted lenses, and distraction has also been shown to improve the severity of VSS for some patients3. However, findings from these studies cannot be generalized as they were individual case studies and were only found to be helpful at an individual level.
In conclusion, the rise of interest in studying VSS as a neurological disorder has shed new and intriguing insights into it. This has resulted in many theories and hypotheses for the causes of VSS that can be further studied in more detail. Such future direction for studying VSS can be in the form of “VSS as a cause of the difference in the gray matter”, and “Parahippocampal involvement in patients with VSS”. Nevertheless, if this trend of increased research continues, then the mystery of this rare disorder may soon be unraveled with an accurate understanding of its working mechanisms and the availability of proper treatment options. Even though this possibility is far in the future, a general treatment for VSS is sure to help those unlucky few suffering from this detrimental disorder.