Visual Contrast Sensitivity Screening
See the unseen.
A calibrated, FACT-based test of the contrast your eyes can detect — a function often quietly impaired by mold, Lyme, and biotoxin exposure. The first signal, before the symptoms make sense.
Take the VCS test→Possible biotoxin illness from these exposures
A VCS screen helps flag potential biotoxin illness linked to these common sources.
Damp indoor spaces can harbor toxigenic molds that release inflammatory fragments. Chronic exposure is one of the most common drivers of biotoxin-related illness — and a frequent cause of reduced contrast sensitivity.
Read moreTick-borne Borrelia and common co-infections can affect neurological function. A VCS screen may help flag neurologic involvement worth following up with a knowledgeable provider.
Read moreHarmful algal blooms produce toxins in contaminated water and fish. Exposure can affect the nervous system, sometimes showing up as a measurable contrast deficit.
Read moreCiguatera is a fish-borne toxin; Pfiesteria is an estuarine organism linked to neurotoxic illness. Both are known to affect vision and neurological function.
Read moreSolvents and fumes from paint, adhesives, finishes, and new materials can act as neurotoxins. Prolonged VOC exposure may contribute to measurable contrast-sensitivity changes.
Read moreMercury, lead, and mycotoxins from mold can impair neurological function. A VCS screen can help flag the kind of deficit these exposures tend to produce.
Read moreThe Diagnostic Funnel
From uncertainty to data-backed evidence.
Calibrate
Match the on-screen reference to a card or quarter you have on hand, then settle 18 inches away. The gratings render at the exact physical size your display needs.
Test each eye
Cover one eye, then identify whether each sine-wave pattern runs up, left, or right as the contrast quietly fades across five frequencies.
Read your curve
We plot a contrast-sensitivity curve for both eyes against normal, flag the frequencies biotoxins typically affect, and explain what it means.
What we measure
Five pattern sizes, both eyes, charted against the healthy range.
Your contrast sensitivity is measured at five spatial frequencies — from broad patterns down to the finest detail your screen can render. Each eye is tested independently, and your threshold at each frequency is plotted against the typical healthy range.
Biotoxin-related deficits tend to show as a drop in the mid and high frequencies — the fine-detail end of the chart — rather than across the board. The sample below shows what that pattern looks like.
Sample result · for illustration
Higher = better sensitivity. Notice the dip at the fine-detail end.
- Typical
- Left
- Right
The Geometry of Perception
Why contrast reveals what bloodwork can't.
Many biotoxins are neurotoxins that reach the brain through the olfactory nerve. They reduce capillary oxygen delivery, and the retina's rod cells — which govern contrast — are among the first tissues to show the effect.
The result: neurons that detect fine, high-frequency patterns go quiet while coarse patterns stay intact. The VCS test listens for exactly that asymmetry across five spatial frequencies.
5
spatial frequencies
1.5–18
cycles / degree
~92%
agreement with clinical VCS
The science behind the test
Built on four decades of contrast-vision research.
The FACT (Functional Acuity Contrast Test) methodology your VCScheck screen is based on was developed by Dr. Arthur P. Ginsburg, a vision scientist associated with Vistech Consultants. Ginsburg introduced his contrast-sensitivity chart work in the early 1980s and published the foundational paper, “A New Contrast Sensitivity Vision Test Chart,” in 1984 — the same methodology now used in clinical and research settings worldwide, and the basis VCScheck renders on-screen.
What the FACT chart measures
- ·5 spatial frequencies: 1.5, 3, 6, 12 and 18 cycles/degree
- ·9 contrast levels at each frequency
- ·Sine-wave gratings
- ·Grating orientations: vertical, left, or right
- ·Approximately 0.15 log-unit contrast steps
- ·The lowest contrast correctly identified at each frequency builds your contrast-sensitivity function (curve)
Peer-reviewed source
Ginsburg AP. A New Contrast Sensitivity Vision Test Chart. Am J Optom Physiol Opt. 1984;61(6):403–407.
PubMedThe mechanisms
How biotoxin exposure can affect visual contrast sensitivity
VCS testing can detect subtle changes in how the visual system processes contrast. Several mechanisms may contribute to reduced contrast sensitivity in people affected by biotoxin exposure, especially mycotoxins:
Neuroinflammation
Inflammatory signaling can disrupt normal function within the nervous system, including the pathways responsible for processing visual information.
Mitochondrial Dysfunction
The retina and visual system have very high energy demands. Impaired mitochondrial function can reduce the energy available for normal visual processing.
Reduced Visual Signal-to-Noise
The visual system may become less effective at distinguishing a faint visual signal from its background — exactly the type of function that contrast sensitivity testing challenges.
The simple explanation
Biotoxin Exposure → Inflammation + Oxidative/Metabolic Stress → Disrupted Visual Pathway Function → Reduced Contrast Sensitivity → Detectable by VCS Testing
Important: VCS testing does not diagnose mold toxicity or prove that mycotoxins have damaged the retina. It measures a functional change in visual contrast processing that can occur with neurotoxic and other conditions.
Read the full breakdownResource Sanctuary
Questions, answered plainly.
What is visual contrast sensitivity?+
VCS measures your ability to see faint details at low contrast. It's a non-specific test of neurological function — like an audiometry test, but for vision. Biotoxins can impair it within 24–36 hours of exposure.
Is this a diagnosis?+
No. A VCS test alone is not diagnostic for any specific condition. A positive result suggests a possible clinical or subclinical process and should be discussed with a healthcare provider familiar with CIRS.
How long does it take?+
The VCS portion takes about 5–8 minutes. You'll test each eye separately, covering the other, so plan for a quiet, still moment.
What causes a contrast deficit?+
Many things — nutritional deficiencies, alcohol, medications, and exposure to neurotoxins or biotoxins including mold, Lyme, cyanobacteria, dinoflagellates, and heavy metals like mercury and lead.
Can my whole family use this?+
Yes — everyone is welcome to screen, but each person needs their own account. We track results and per-eye progress individually, so sharing one account would mix people's data and corrupt each person's history and comparison over time. Creating a separate account per person keeps everyone's results private and accurate.
A five-minute window into your neurology.
Calibrate, cover one eye, and let the patterns speak. Your contrast-sensitivity curve appears the moment you finish.
Take the VCS test→