This site provides information about a condition known as "visual snow". It is also sometimes described as "visual static", "grainy vision" or "little white dots" flickering across the entire visual field. Please visit the forum after you've explored the information available here. Remember, you are not alone.

Hallucinogen Persisting Perception Disorder

  • Visual phenomenology of the LSD flashback
    Author: Abraham, HD.
    Journal: Arch Gen Psychiatry 1983; 40: 884-889.
    Abstract: One hundred twenty-three persons with a history of LSD use were studied for the presence of the LSD flashback phenomenon and compared with 40 control subjects. A syndrome emerged that included ten distance visual disturbances. It had lasted for five years in half of the population, was treatable with benzodiazepines, exacerbated by phenothiazines, and precipitated by 19 different stimuli, most commonly emergence into a dark environment. Sensitivity to LSD as determined by flashbacks appears to divide the study sample into three discrete subgroups. There may be a genetic basis to LSD sensitivity.

  • L-5-Hydroxytryptophan for LSD-induced Psychosis
    Author: Abraham, HD.
    Journal: Am J Psychiatry. 1983 Apr;140(4):456-8.
    Abstract: The serotonin precursor L-5-hydroxytryptophan reversed the symptoms of a 23-year-old man suffering from LSD-induced psychosis who participated in a randomized, double-blind crossover study of the drug and a placebo. This finding is compatible with the speculation that some LSD-induced psychotic disorders may be caused by a relative deficiency of CNS serotonin.

  • LSD-Like Panic From Risperidone in Post-LSD Visual Disorder
    Author: Abraham, HD.
    Journal: Journal of Clinical Psychopharmacology. 16(3):238-241, June 1996.
    Abstract: Risperidone, a novel antipsychotic agent, is an antagonist of postsynaptic serotonin-2 and dopamine D2 receptors. In certain individuals, the hallucinogenic drug lysergic acid diethylamide (LSD) is associated with apparently lifelong continuous visual disturbances, characterized in DSM-IV as hallucinogen-persisting perception disorder (HPPD). Because the hallucinogenic mechanism of LSD is known to act in part at postsynaptic serotonin-2 receptors, it is noteworthy that three HPPD patients treated with risperidone reported an exacerbation of LSD-like panic and visual symptoms. We conclude that HPPD may be a relative contraindication for the use of risperidone.

  • Psychelic Drugs
    Author: Abraham, HD.

  • The Psychopharmacology of Hallucinogens
    Author: Abraham, HD; Aldridge, AM; and Gogia, P.
    Journal: Neuropsychopharmacology 14: 285-298, 1996.
    Abstract: Hallucinogenic drugs have been inhaled, ingested, worshipped, and reviled since prehistory. With the purification and synthesis of bontanical preparations and the ensuing discovery of chemically unique agents, hope was raised regarding their therapeutic potential, but this hope has been clouded by an epidemic of abuse and an inventory of adverse effects. This review examines aspects of that controversy, including the history of hallucinogens, epidemiology of current hallucinogen abuse, the association of LSD use with prolonged psychoses and hallucinogen persisting perception disorder, and the efforts to demonstrate the drug's therapeutic efficacy. Human subject ramifications in hallucinogen experimentation are discussed. Future lines of research are suggested in human, animal, and tissue culture paradigms.

  • Stable quantitative EEG difference in post-LSD visual disorder by split-half analysys: evidence for disinhibition
    Author: Abraham, HD; Duffy, FH.
    Journal: Psychiatry Res. 1996 Oct 7;67(3):173-87.
    Abstract: Hallucinogen persisting perceptual disorder (HPPD) may follow the ingestion of LSD or other hallucinogens in a subset of users. It is characterized by chronic, intermittent or constant visual hallucinations of many sorts persisting beyond the period of acute drug effects. We studied 44 LSD-induced HPPD subjects and 88 matched controls to search for spectral and evoked potential differences using quantitative EEG (qEEG). HPPD subjects demonstrated faster alpha frequency and shorter VER (visual evoked response) latency, consistent with prior animal and human data on response to acute LSD administration which suggest LSD-induced cortical disinhibition. AER (auditory evoked response) latency was prolonged consistent with a differential LSD effect upon visual and auditory systems. The exploratory T-statistic significance probability mapping (T-SPM) technique demonstrated HPPD-control differences mostly involving temporal and left parietal scalp regions, confirmed by a split-half analysis. Significant variables were all derived from the long latency flash VER and click AER. None were derived from spectral analyzed EEG data. Canonical correlation between SPM-derived measures and variables reflecting disease severity was highly significant. A between-group stepwise discriminant analysis based upon a full set of qEEG measures demonstrated 87% prospective classification success by jackknifing and 88% success in a separate split-half analysis.

  • Visual Function in Past Users of LSD: Psychophysical Findings
    Author: Abraham, HD; Wolf, E.
    Journal: Journal of Abnormal Psychology. 97(4), Nov 1988, 443-447.
    Abstract: Twenty-four subjects with a history of use of the hallucinogenic drug, LSD, 2.3 years prior to being studied were found on psychophysical testing to have impairments of visual function when compared with a matched control group. The LSD group had depressed critical flicker frequencies (p<0.0001) and reduced sensitivity to light during dark adaptation (p<0.0001). Peripheral visual fields appeared to be predominantly affected. Drug effects were noted with other abused substances as well, but LSD effects predominated over six other types of abusable substances. We conclude that LSD exerts continued effects on visual function at least 2 years following exposure to the drug.

  • Hallucinogens, Designer Drugs, and Inhalants
    Author: Abraham, HD.

  • EEG coherence in post-LSD visual hallucinations
    Author: Abraham, HD; Duffy, FH.
    Journal: Psychiatry Res. 2001 Oct 1;107(3):151-63.
    Abstract: LSD use in certain individuals may result in chronic visual hallucinations, a DSM-IV syndrome known as hallucinogen persisting perception disorder (HPPD). We studied 38 HPPD subjects with a mean of 9.7 years of persistent visual hallucinations and 33 control subjects. Measures of local and medium distance EEG spectral coherence were calculated from all subjects. Coherence, a measure of spectral similarity over time, may estimate cortical coupling. In the eyes-open state in HPPD subjects, widespread reduction of coherence was noted. However, upon eye closure, the occipital region demonstrated augmented regional coherence over many frequencies but with reduced coherence of the occipital region to more distant regions. This occipital coherence increase correlated with previously reported shortened occipital visual evoked potential latency for HPPD subjects. We speculate from coherence and known clinical and psychophysical data that, in HPPD, there is widespread cortical inhibition in the eyes-opened state, but localized and isolated occipital disinhibition upon eye closure, a state known to facilitate hallucinatory experiences. An analogy is drawn to findings in the interictal and ictal epileptic focus. In HPPD, we speculate that occipital EEG hypersynchrony resulting from increased regional coherence, when coupled with relative isolation of visual cortex, especially upon eye closure, facilitates hallucinations and illusions.

  • Adverse consequences of lysergic acid diethylamide
    Author: Abraham, HD; Aldridge, AM.
    Journal: Addiction. 1993 Oct;88(10):1327-34.
    Abstract: The continued endemic use of hallucinogenic drugs, and of LSD in particular, raises concern regarding their short and long term adverse consequences. The epidemiology of LSD abuse is reviewed suggesting an increase in LSD use among the young as the prevalence rates for other substances continues to fall. Evidence supports the association of LSD use with panic reactions, prolonged schizoaffective psychoses and post-hallucinogen perceptual disorder, the latter being present continually for as long as 5 years. Evidence does not support claims of genetic disorders arising from hallucinogens. In light of the foregoing, current data confirm earlier findings of long lasting psychopathology arising in vulnerable individuals from the use of LSD. A hypothetical long term molecular mechanism of adverse effects is proposed.

  • A Chronic Impairment of Colour Vision in Users of LSD
    Author: Abraham, HD.
    Journal: Br J Psychiatry. 1982 May;140:518-20.
    Abstract: Forty-six users of the hallucinogen lysergic acid diethylamide were compared with 31 controls on a test of colour discrimination an average of two years after their last exposure to the drug. Controls performed better than users, and LSD users without flashbacks performed better than users with flashbacks. An analysis of variance between the three groups was significant at P less than 0.001. This study suggests that some users of LSD may have a sustained or irreversible impairment in colour discrimination.

  • Hallucinogen persisting perception disorder: what do we know after 50 years?
    Author: Halpern, JH; Pope, HG Jr.
    Journal: Drug Alcohol Depend. 2003 Mar 1;69(2):109-19
    Abstract: 'Flashbacks' following use of hallucinogenic drugs have been reported for decades; they are recognized in DSM-IV as 'Hallucinogen Persisting Perception Disorder (Flashbacks)', or HPPD. We located and analyzed 20 quantitative studies between 1955 and 2001 examining this phenomenon. However, many of these studies were performed before operational criteria for HPPD were published in DSM-III-R, so they are difficult to interpret in the light of current diagnostic criteria. Overall, current knowledge of HPPD remains very limited. In particular (1) the term 'flashbacks' is defined in so many ways that it is essentially valueless; (2) most studies provide too little information to judge how many cases could meet DSM-IV criteria for HPPD; and consequently (3) information about risk factors for HPPD, possible etiologic mechanisms, and potential treatment modalities must be interpreted with great caution. At present, HPPD appears to be a genuine but uncommon disorder, sometimes persisting for months or years after hallucinogen use and causing substantial morbidity. It is reported most commonly after illicit LSD use, but less commonly with LSD administered in research or treatment settings, or with use of other types of hallucinogens. There are case reports, but no randomized controlled trials, of successful treatment with neuroleptics, anticonvulsants, benzodiazepines, and clonidine. Although it may be difficult to collect large samples of HPPD cases, further studies are critically needed to augment the meager data presently available regarding the prevalence, etiology, and treatment of HPPD.

Persistent Migraine Aura

  • Diffusion- and perfusion-weighted MR imaging in persistent migrainous visual disturbances
    Author: Jager, HR; Giffin, NJ; Goadsby, PJ.
    Journal: Cephalalgia. 2005 May;25(5):323-32.
    Abstract: Pathological changes on diffusion-weighted MR scans had been described in hemiplegic migraine and perfusion changes had been demonstrated in typical migraine aura with radio-isotope studies and, more recently, MR perfusion imaging. However, there is relatively little knowledge of the pathophysiology of long-lasting migraine aura and its possibly variant phenotype, visual snow. Our aim was to investigate with advanced MR techniques whether patients with long-lasting visual disturbance showed regional alterations in cerebral water diffusion and perfusion. We have studied four patients using MR perfusion and MR diffusion imaging. Two patients had typical visual aura and two had a primary persistent visual disturbance (visual snow phenomenon). All patients had normal conventional structural MR imaging. MR diffusion-weighted images were acquired with a b-value of up to 1000 s/mm2. From the diffusion weighted images we generated maps of apparent diffusion coefficient (ADC), which were inspected visually and used for ADC measurements of predefined regions of interest, which included the visual, frontal, insular and temporal cortices. MR perfusion imaging was performed using a bolus tracking technique with dynamic susceptibility-weighted images. Colour coded maps of relative cerebral blood volume, mean transit time and bolus arrival time were generated, as well as time-signal intensity curves over the anterior, middle and posterior cerebral artery territories. The maps of the ADC and above perfusion parameters appeared symmetrical in all patients with no evidence of decreased water diffusion or cerebral perfusion in the occipital regions, or elsewhere. There was no statistically significant difference between the ADC measurements of the primary visual cortices and other cortical regions. Our findings suggest that regional changes in cerebral water diffusion and perfusion do not play an important part in the pathophysiology of persistent migraine aura or primary persistent visual disturbance.

Lyme Disease

Other

  • Central disorders of vision in humans
    Author: Girkin, CA; Miller, NR.
    Journal: Surv Ophthalmol. 2001 Mar-Apr;45(5):379-405.
    Abstract: Over the past 20 years, researchers have discovered over 30 separate visual areas in the cortex of the macaque monkey that exhibit specific responses to visual and environmental stimuli. Many of these areas are homologous to regions of the human visual cortex, and numerous syndromes involving these areas are described in the neurologic and ophthalmic literature. The focus of this review is the anatomy and physiology of these higher cortical visual areas, with special emphasis on their relevance to syndromes in humans. The early visual system processes information primarily by way of two separate systems: parvocellular and magnocellular. Thus, even at this early stage, visual information is functionally segregated. We will trace this segregation to downstream areas involved in increasingly complex visual processing and discuss the results of lesions in these areas in humans. An understanding of these areas is important, as many of these patients will first seek the attention of the ophthalmologist, often with vague, poorly defined complaints that may be difficult to specifically define.

  • Practical evaluation and diagnosis of headache
    Author: Marks, DR; Rapoport, AM.
    Journal: Semin Neurol. 1997;17(4):307-12.
    Abstract: Establishing an open and honest physician-patient relationship is essential for the proper evaluation and management of headache disorders. Obtaining a complete headache and medical history is the most important part of the initial diagnostic evaluation. This history should include information about headache onset, pain intensity, character of the pain, presence of aura, associated autonomic symptoms, and trigger factors. Special attention must be paid to the frequency of analgesic use, both prescription and over-the-counter, to identify analgesic rebound headache. A thorough neurologic examination must also be performed; if it is normal, there is usually no need for special tests. Headaches are classified as either primary or secondary. Primary headaches have no structural or metabolic cause, while secondary headaches are caused by an underlying pathologic or metabolic process. Migraine, tension-type, cluster, and analgesic-rebound headaches are all primary headache disorders. Secondary headaches are caused by conditions such as increased intracranial pressure, pseudotumor cerebri, subdural and intracerebral hematomas, hypertension, meningitis, temporal arteritis, Lyme disease, and brain tumors. Accurate diagnosis of headache is essential to determine the appropriateness of further testing and to guide proper treatment of the patient's condition.