What contrast sensitivity can and cannot answer
Someone may read black letters on a white chart but still miss a curb in dim light or a face in shadow. An old glasses prescription, dry eye, cataract, glaucoma, retina or optic-nerve disease, migraine, concussion, medicine, fatigue, lighting, and screen setup can lower contrast. Calling one home failure mold exposure may delay eye or nerve care.
Visual function
It tests faint targets, not sharp black letters
Contrast sensitivity can reveal difficulty with low-contrast edges, faces, steps, glare, or dim scenes even when high-contrast acuity looks good.
Many explanations
A low result does not name a disease
Correction, dry eye, cataract, glaucoma, retinal or optic-nerve disease, multiple sclerosis, migraine, concussion, medicines, fatigue, age, and test setup can all matter.
What this test does not answer
A building needs exposure evidence
A health screen cannot identify mold, a mycotoxin dose, or a safe building. Water damage, moisture, inspection, and medical findings answer different parts of the concern.
These conditions need their own exams and tests: mold illness, CIRS, Lyme disease, concussion, MS, cataract, glaucoma, migraine, and brain inflammation. A proper eye exam checks the visual causes. Get the building and exposure evidence checked separately.
Save this test
Save the setup with the score
My Fog keeps the device, lighting, glasses or contacts, each eye, symptoms, and follow-up together. A repeat can then show whether the same visual task changed under similar conditions.
Repeat only when the same method and setup answer a useful question. Do not repeat until a pass appears.
How do age, vision, lighting, device, and test setup affect the result?
Age, literacy, vision correction, pregnancy, pupil size, eye disease, neurologic illness, and the test platform change what a score means. Sex, age, or life stage cannot establish that mold is causing the symptoms.
Infants and children
Adult letter or grating screens and adult internet norms may not fit a child's attention, language, development, or vision. Use pediatric optometry or ophthalmology and an age-appropriate test when a child struggles to see faces, steps, classroom material, or dim objects.
Teenagers and adults
Check the current prescription, contact lenses, dry eye, migraine, concussion, screen exposure, medicines, and neurologic symptoms. A repeated home failure is a reason to examine vision, not evidence that a building caused brain fog.
Women, pregnancy, and postpartum
The 2026 mold study excluded pregnancy, so its accuracy figures do not apply. New blurred vision, flashes, severe headache, high blood pressure symptoms, or neurologic change during pregnancy or postpartum needs direct obstetric and eye or neurologic assessment.
Men
There is no separate male home-screen cutoff and no male mold interpretation. Treat sex as research context. Go by the named method, correction, age, eye findings and symptoms, not a made-up cutoff.
Older adults
Cataract, glaucoma, macular disease, reduced pupil response, low light, glare, medicines, and neurologic illness become more common with age. Contrast difficulty can affect steps, faces, reading, and driving even when a standard acuity chart looks fairly good.
How to test without making the screen meaningless
Use the instructions for the exact test. Record its name, chart or website, device, screen size, resolution, browser zoom, test distance, room light, date, and time. Say whether you tested each eye or both together.
Wear the glasses or contact lenses normally used for the test distance unless an optometrist or the test manual tells you otherwise. Keep them on even if an online page says otherwise. Note blur, dirty lenses, dry eye, or a recent prescription change.
For a home screen, turn off automatic brightness and night color changes. Avoid glare, set the required brightness and zoom, and measure the stated distance. Use the same device and room for a repeat. An uncalibrated screen cannot match a clinical chart reliably.
Test one eye at a time when the method calls for it. Cover the other eye without pressing on it. Take the planned rest between eyes. Stop if covering an eye causes pain, marked dizziness, or an unsafe balance problem.
The 2026 biotoxin study used its handheld chart at 40 to 45 cm. It required corrected vision of at least 20/50, equal light, and separate testing of each eye. Digital tests ran in an eye clinic at about 300 to 500 lux. A home setup is different.
Skip testing during a migraine aura, severe eye strain, bad dry eye, fever, intoxication or exhaustion, unless you need a result from that episode. Save the symptom and episode beside the score.
Get urgent care for sudden vision loss, a dark curtain, a new blind area, or flashes with many new floaters. Severe eye pain, double vision with weakness, a severe new headache, facial droop, speech trouble, or one-sided weakness also needs urgent care.
Choose what you want the test to check
Use a home screen to notice a possible visual-function problem, not to diagnose mold or CIRS. Use a standardized clinical chart when an eye professional needs a graded score tied to a defined method.
Set the viewing conditions
Use the required correction, lighting, distance, device calibration, screen settings, and eye order. Record them before starting so a repeat is a fair comparison.
Respond without guessing a cause
Keep naming the letter or stripe direction until the method says to stop. A wrong answer measures performance in that setup; it does not reveal what caused it.
Save each eye and each method
Keep right eye, left eye, binocular result, spatial-frequency rows, score or pass/fail, correction, symptoms, and test conditions separate. Do not convert an online score into a Pelli-Robson value.
Use the result to choose a next check
A repeat failure under valid conditions supports an eye examination. Exposure concerns need a separate building history and inspection; neurologic symptoms need the examination that fits them.
How to understand a VCS result
Start with the named method. A Pelli-Robson log score, a spatial-frequency curve, and an online pass/fail result are not interchangeable. Read the result beside correction, eye, distance, lighting, device, symptoms, and repeat conditions.
Within this method's expected result
Within the named method's expected result under valid conditions
This suggests no clear contrast deficit on that test in that setup. It does not rule out mold exposure, CIRS, eye disease, neurologic disease, or real difficulty under glare or low light.
Setup or result is uncertain
Near a method cutoff or collected with uncertain correction, distance, lighting, calibration, fatigue, dry eye, or guessing
Repeat only if the question matters and you can fix the conditions. An eye professional may choose a standardized chart rather than another home pass/fail screen.
Reduced contrast or failed screen
Reduced contrast or a failed screen under valid conditions
This shows a visual-function finding, not its cause. Arrange an eye examination, review neurologic and medicine context, and investigate a building separately when the exposure history supports it.
The common handheld mold chart did not distinguish the groups
The study's experimental digital test reached 85% to 100% sensitivity and 60% to 80% specificity, while commercial digital tools had only 20% to 40% specificity. It involved 28 selected cases and 30 controls under controlled conditions. Those figures do not validate a home mold diagnosis.
See research details
Keep each value beside its method, population, and clinical question.
Older functional literature associates scores below about 1.5 with visual impairment and below about 1.05 with disability. These are method-specific visual-function values, not mold or CIRS thresholds and not conversions for a home grating test.
The design does not establish population screening accuracy or prove that mold caused a low result. The Shoemaker handheld chart did not distinguish the groups.
Low specificity means many people without the selected case definition can screen positive. The experimental test was not commercially available and required calibrated equipment and technical support.
A health screen and a building assessment answer different questions. Use moisture history and qualified inspection for the building and clinical evaluation for symptoms.
Contrast loss can coexist with normal high-contrast acuity and an ocular-surface or screen-use problem. A mold label can't replace an eye exam.
What you can do after a failed screen
Use the screen to describe a visual problem and improve the next appointment. Do not use it as a shortcut from brain fog to mold treatment.
Fix the simple viewing problems
Clean your glasses and use the right prescription and test distance. Control glare, use steady light, treat known dry eye as advised, rest tired eyes, and record migraine or screen-strain timing. Do not repeat the test until you memorize it.
Book an eye exam when the deficit repeats
Bring the result for each eye to an optometrist or eye doctor. Ask for checks of vision, glasses strength, eye surface, lens, retina, optic nerve, visual fields, pupils, and clinical contrast when useful. Different eye and nerve problems need different follow-up.
Investigate the building as a building
Record leaks, flooding, visible dampness, odors, rooms, dates, and whether symptoms change by location. Repair active moisture and use qualified inspection when needed.
Know the urgent eye and neurologic signs
Get urgent care for sudden vision loss, a curtain, a new blind area, flashes with many floaters, or severe eye pain. Double vision with weakness, a severe new headache, facial droop, speech trouble, or one-sided weakness also needs urgent care.
Do not start binders, antifungals, supplements, restrictive diets, expensive testing, or major remediation from a VCS result alone. Do not delay an eye examination, neurologic review, or urgent care while repeating an online screen.
What to save for an eye or medical visit
Keep these together
- Test name, version, chart or device, screen settings, brightness, zoom, distance, and lighting
- Glasses or contacts, right-eye, left-eye and binocular result, spatial-frequency rows, score and pass/fail
- Blur, dry eye, glare, migraine, fatigue, screen time, medicines, concussion, neurologic and location timing
- Eye examination, acuity, refraction, ocular surface, lens, retina, optic nerve, fields, pupils, and clinician interpretation
- Water-damage history, moisture or inspection findings, and what changed by location without treating VCS as exposure proof
Question for the visit
“Ask whether the result reflects a real contrast deficit, whether the home setup was valid, which eye or neurologic cause needs checking, and whether a building question should be investigated separately.”
Sources for Visual Contrast Sensitivity Test
Contrast definition, Pelli-Robson method, functional values, reliability, visual disability, age, lighting, and clinical quality.
Twenty-eight selected cases, 30 controls, four test methods, controlled setup, accuracy ranges, handheld failure, and study limits.
Greater than 95% consensus against VCS diagnosis of indoor mold exposure because evidence is insufficient.
Computer vision syndrome, ocular surface, Pelli-Robson and peripheral contrast testing despite normal corrected acuity.
See each claim's sources
procedure
Contrast sensitivity measures the lowest contrast at which a target can be distinguished from its background and is different from high-contrast visual acuity.procedure
Pelli-Robson testing at 1 m uses three-letter groups, 0.15 log contrast steps, and credit for at least 2 of 3 letters at a level.range
Pelli-Robson values below about 1.5 have been associated with visual impairment and below about 1.05 with disability, as method-specific functional values rather than mold thresholds.context
The 2026 biotoxin study compared 28 selected cases with 30 controls, included cases ages 27 to 60, excluded pregnancy, and used controlled optometry-lab testing.limitation
The Shoemaker handheld chart did not significantly distinguish the selected exposed and control groups in the 2026 study.limitation
The experimental test ranged from 85% to 100% sensitivity and 60% to 80% specificity with maximum LR+ 4.0, while commercial digital tests ranged from 80% to 95% sensitivity and 20% to 40% specificity with LR+ 1.25 to 2.5.procedure
The study required at least 20/50 corrected acuity, monocular testing, 40 to 45 cm for the handheld chart, controlled lighting, and calibrated digital equipment.limitation
The 2023 AWMF indoor-mold guideline reached greater than 95% consensus that VCS should not be used to diagnose indoor mold exposure because evidence is insufficient.context
A 2026 study assessed contrast and ocular-surface measures in 55 adults with computer vision syndrome and 55 controls despite 6/6 best-corrected acuity, showing that screen and eye-surface context can coexist with normal acuity.