Home Interviews Visual Contrast Sensitivity (VCS) Testing: A Valuable Self-Screening Tool for Mold Illness and Treatment Progress

Visual Contrast Sensitivity (VCS) Testing: A Valuable Self-Screening Tool for Mold Illness and Treatment Progress

by Catherine

If you are experiencing health issues and have been exposed to mold in your home or workplace, or you think you may have a mold issue in one of your indoor environments, it is hard to know where to turn for initial symptom assessment and testing without spending lots of time and money on doctors visits that often don’t yield conclusive information. Visual Contrast Sensitivity (VCS) Testing, an online self-assessment of your ability to discern black/white/gray contrast, can help. The test was useful to me in facilitating a connection between my environment and my illness and has continued to be helpful for me in evaluating the effectiveness of my various treatments and new living environments. Thus, I would like to share the details of VCS testing with you today.

Whenever mold exposure is a health concern, the obvious first step should be to address your environment and to figure out whether it has a problem.  There are few tools as helpful as environmental testing with EC3 Mold Screening Test Plates to determine this.  These biologically-based Petri dishes are conclusive in determining the presence of mold. But, when it comes to your body and knowing whether or not it has been or is being affected by mold, there can be confusion and conflicting information. That is where some online tools and self-screening tests can be very useful. While none of these are conclusive without a doctor’s further testing and diagnosis, they can combine circumstantial evidence that can collectively be relied on to make the difficult and elusive mold diagnosis.  Getting diagnosed early can save valuable time and money and is priceless in helping the family manage through any mold hardships impacting their lives.

In my opinion, the best place to start, especially if you are considering medical treatment, is the Free Sinusitis and Mold Sensitivity Evaluation available for FREE at SinusitisWellness.com. It includes questions about both your medical history and home and work environments. Your responses will help to generate valuable information about whether or not your symptoms point to mold as the possible culprit for your health issues. This valuable information can then be used to seek further medical help, or to take practical steps in mold hygiene, or for useful products and follow-up. Since I have already featured this evaluation in a previous post, today I am going to shift my focus to VCS Testing, another self-screening tool, and what it can offer in terms of possible mold exposure insight.

What is the Visual Contrast Sensitivity Test?

The VCS Test is not an eyesight or visual acuity test, but rather a test to see how discretely you can distinguish black/white/grey contrast. Contrast sensitivity testing has been historically useful in cases of cataracts, glaucoma, macular degeneration, and a number of other vision-related concerns. Now, thanks to the research and validation done by Dr. Hudnell, PhD neurotoxicologist of the US EPA, and Dr. Richard Shoemaker, it has also been proven useful in determining potential biotoxin illness. So, while there are no routine lab tests to measure biotoxins, these doctors found that you can measure their effects on the human body, with VCS testing. While not conclusive, The VCS demonstrates deficiencies and specific deficits in people exposed to biotoxins.

But, how?

Many mycotoxins produced by molds are neurotoxins that enter the body via inhalation.  The ultra-sensitive nerves of the olfactory system and its proximity to the brain make neurological symptoms a reality, even with limited exposure.  For sufferers, these symptoms are the most frightening of them all.

When this occurs, the rod cells in the retina (that affect contrast discernment) become useful in evaluating biotoxin exposure and illness, because people with mold/biotoxin illness almost always experience poor circulation at the capillary level. This causes inadequate delivery of oxygen to every cell in the body. The brain is also not getting enough oxygen to work optimally. Thus, the multitude of neurological symptoms associated with mold illness.

The cool thing that these doctors found is that testing the optic nerve and the eye’s ability to distinguish contrast reveals this circulating oxygen decrease, because contrast sensitivity in the retina is immediately affected and testable. Biotoxins in particular were found to affect your ability to see a specific group of the contrast bars on the test accurately. So, in cases where neurotoxicity is present, neurons that detect the smaller bars (high spatial-frequency vision) are functionally impaired, whereas neurons that detect the larger bars (low spatial-frequency vision) are not. In addition, VCS testing gives a measurement at a specific point in time and is infinitely repeatable without harm or invasion to the person being tested. So, if mold illness is found to be your issues, VCS testing can also be helpful when you are looking to gauge improvement, re-exposure, or treatment effectiveness. Thus, the VCS Test is not only a great basic, initial screening tool,  but a great prognosticator as well.

How Do I Take a VCS Test?

In the past, you could go to a doctor’s, naturopath’s, or holistic practitioner’s office to be tested. This definitely constrained people’s ability to use the VCS as an early indicator of exposure, because it still required taking the step to seek medical advice prior to test access. Later, Dr. Shoemaker offered the test on his SurvivingMold.com site for a fee. Now, the VCS test is available for FREE, or for a small donation with analytics or if repeat testing is needed at VCStest.com. This is great news for anyone curious about testing or wanting to take a first hassle-free step towards figuring out whether or not mold or other biotoxin-related exposures may be causing their health issues. With this free initial testing model, you can immediately receive a quantitative “Positive” or “Negative” answer as to whether or not you are displaying a visual contrast deficiencies possibly indicative of mold or biotoxin illness. With that information, you can choose to seek further medical advice and/or testing.

VCSTest.com: How Is It Different and How Does It Work?

VCSTest.com was started to help those suffering with biotoxin illness figure out why they’re sick, which ultimately helps them to recover, so they can get back to living.  The site offers a calibrated, accurate online contrast sensitivity test based on the FACT (Functional Acuity Contrast Test), which was developed almost 4 decades ago and has been used in medical research and clinically ever since.  The FACT uses a series of tilted sine-wave gratings (sets of parallel bars) to determine contrast sensitivity at five spatial frequencies. The person being tested will go through a series of test images calibrated at various gratings and answer each time as to whether the image they are viewing has its parallel bars pointing left, right, or up.

According to the site’s founder and developer who is a technologist and a physicist (by training and at heart, anyway), “Our test is accurate – and relied on by thousands of doctors – because we’ve developed a calibration system that allows us to tailor it to each individual user by accommodating their display size and pixel density, the desired test distance, and the infinite combinations of display types and settings, video cards and settings, operating systems and settings, and web browsers and browser configurations.  Using the calibration information, we collect from the user, we generate test images in software (on the fly) specifically for that person, so that the test images displayed are the correct size and have the correct contrast levels.   Calibration is extremely important; without it, you can’t have accurate results.  As far as I know, there are no other accurate FACT-based online contrast sensitivity tests.”

VCSTest.com offers its test to anyone interested in checking their contrast sensitivity but focuses on contrast sensitivity testing as it relates to a number of serious health conditions. The majority of its users are generally suffering with one or more forms of chronic illness related to exposure to biotoxins, like those produced by many molds and by the pathogens responsible for Lyme disease and its common coinfections.

Also, according to the site’s founder and developer, there are definite benefits of using the test, especially when symptoms initially begin:

“By looking at contrast sensitivity at 2 spatial frequencies in particular, we can tell with a high degree of probability (there’s a ~2% false positive rate and a ~8% false negative rate, according to the research behind the test) whether or not someone is likely suffering from the effects of exposure to biotoxins.  This bit of information then helps our users and their doctors determine what might be behind their illness.  It’s important to note that contrast sensitivity testing isn’t (and can’t be) diagnostic, but only works as a screen; this means that you can’t definitively diagnose any condition using it, but you can get a good idea whether and where you might have a problem so you know to look deeper (for instance, with an environmental assessment and/or challenge, basic blood labs, etc.).  Many who use our test are suffering from complex, multi-symptom, multi-system illnesses, and they’re looking for something that might help them figure out what’s going on.  The test can also be used to track and gauge recovery progress over time by taking it regularly and comparing test scores.

Because we also know that financial difficulties go hand-in-hand with chronic illness, we offer the test on a free-or-by-donation basis, which means that we initially offer a free test with limited results and ask for a donation for more detailed results and/or to take the test again. If a user can’t donate, we’ll upgrade results and provide additional testing for free if they send us an email.”

While the test is generally pass/fail, you can look at the biotoxin scores and the charts that are generated to determine whether – and to what degree – your contrast sensitivity has changed (hopefully for the better).  (This is when using the VCS can be very valuable after diagnosis and during treatment.) The maximum biotoxin score is 18 in each eye and 36 for both eyes.  A comparison of how you’ve scored on consecutive tests, as a fraction of those totals, can be used as a rough indicator of how you’re doing.  For instance, if you score a 20 out of 36 (55%) on your first test and 25 out of 36 (69%) when you retest a few weeks later, you know your contrast sensitivity has improved and that whatever you’re doing is likely working. On the other hand, if your scores stay the same or get worse, you might want to consider doing something else.  At VCStest.com, test scores are plotted on a chart on the website, which makes tracking progress easier. (Note: This ability to chart your scores over time is available for a small donation.)

My Experience and How I use VCS Testing

I was initially given my first VCS test at my naturopathic doctor’s office. It indicated that I had been exposed to mycotoxins.  My first score was 55%. Then, I was periodically given it to make sure things were still going well with my treatment. I also tested after our remediation and we were living in our home again to make sure I was not still being exposed. I now take the VCS test online from time to time now just to check in and make sure I am still doing well.

(Note: As I have learned, my experience is extremely common.  I’ve heard from many people who’ve used the test to help figure out why they’re sick, then over time to track their recovery, and then again when their circumstances change–when they move, etc.–to determine whether the changes or their new environment are a problem for them.  There are also people who are extremely sensitive to mold who take the test daily to make sure their environment is safe and to track treatment progress.)

To close, I am going to take you through my most recent experience of taking the test online at VCStest.com, so that you know what to expect and what your results will look like, should you decide to take it.

This is my actual test and my actual results, because I want to be completely transparent with you about healing from mold illness. As you can see, it is an ongoing process. Full disclosure: I had been feeling a little “off” again. I had begun to experience symptoms of ulcerative colitis and was feeling fatigued. I took the test, and sure enough, it indicated that my percentages are still a little off. Because of access to this information, I reached out to Dr. Dennis with my results. I am following his recommendations on further testing and supplements and will track my progress here on the blog.

My VCS Test

To begin, you login to your account or create a login if it is your first time to the site.

Then, you will be directed through test instructions and calibrating your test to give you the most accurate results.

All of the calibration steps are easy to follow and to understand. You are even given advice along the way if your computer doesn’t seem to be a good fit for the test.

Once the test begins, you will be asked to cover one eye at a time. will go through a series of images for each eye.

You will go through a series of contrast images for each eye.

Once you have completed testing on both eyes, you will receive your results.

To explain the results a little better, the charts plot your contrast sensitivity test for each eye.  The left axes represent contrast sensitivity, the right axes represent percent contrast, and the bottom axes represent the spatial frequency of the parallel bars in the test images in cycles per degree (CPD); the closer the bars, the higher the spatial frequency.

Each plotted circle represents an image from your test, and its position corresponds to its contrast level and spatial frequency.  The biotoxin columns – 6 and 12 CPD (columns C and D) – are outlined in blue.  A green-filled circle indicates that you answered correctly when asked to identify the tilt of the bars, whereas a red-filled circle indicates that you answered incorrectly.  The black ‘tails’ point in the direction the bars in the test images were tilted in your test, and where you answered incorrectly the red tails point in the direction you indicated.

The gray line represents the contrast sensitivity curve (average, both eyes) over the tested range of spatial frequencies among healthy individuals in the published research, and the red line is the curve formed by connecting the circles representing the highest contrast sensitivity images correctly identified at each spatial frequency.   Higher contrast sensitivity numbers are better, and if the red line is generally above the gray line you outperformed healthy research subjects.  If, on the other hand, the red line dips substantially below the gray line at any point, you may have a health-affecting condition and should consider seeing your healthcare provider.

My Results: The Breakdown


My results indicate I was able to discern the tilt of the bars in the test images 77 times out of 90, for a ‘Total Score’ of 77, or 86%.    As indicated above, my right visual system generally performed better than my left.

My positive results suggest that I may be suffering from a condition affecting my visual contrast. Thus, I should see my healthcare provider. I will say, though, that my results are decidedly better than my results 2 years ago of 55%.


In the biotoxin columns – 6 and 12 CPD (columns C and D) – which are generally considered most relevant and suggestive of biotoxin-related illness, you answered correctly 31 times out of 36, for a ‘Biotoxin Score’ of 31, or 86%. Since the test is essentially PASS/FAIL, a score of less than 100% is not ideal.

My results suggest the likely presence of biotoxins, and/or that I could have other health issues or neuropathology.

Note: Biotoxins that can affect contrast sensitivity at 6 and 12 CPD include:  venom from animal or insect stings or bites, toxins produced by many species of mold, cyanobacteria, dinoflagellates (particularly Pfiesteria and Ciguatera), parasites, and the pathogens responsible for Lyme disease and its common co-infections, and others. Poor contrast function at 6 CPD is also correlated with both use of cigarettes and tobacco products and exposure to certain volatile organic compounds, while contrast function at 12 CPD is correlated with cigarette and tobacco use. I do not smoke, so I must focus on the other things that could be affecting these markers.


My results do not indicate that I suffer from nutritional deficiency or related conditions.


Contrast function at 18 CPD (column E) is often affected in cases of biotoxin illness and is often used to measure progress during biotoxin illness treatment, as contrast sensitivity at this spatial frequency generally improves faster than at other spatial frequencies.  It is also correlated with a number of risk factors, including use of cigarettes and other tobacco products, alcohol consumption, blood lead level, exposure to certain volatile organic compounds, and age and socioeconomic status.

Your 18 CPD results are below the average among healthy research subjects and given your results at 6 and/or 12 CPD (columns C and D), it appears more likely you may suffer from biotoxin illness.

Note that both those experiencing a Jarisch-Herxheimer, or detox reaction, and Lyme sufferers undergoing treatment with Cholestyramine and/or Welchol often have impaired contrast function at 12 and 18 CPD (columns D and E) – and also generally feel worse. For me, this could likely be the case, because when I took the test, I was actively using a charcoal binder and a liver-focused detox supplement.

Dr. Dennis’s Recommendations

Since I no longer live in close proximity to Dr. Dennis, I sent him my results via email. It is important to note that since the VCS is merely a screening tool, further diagnostics should ALWAYS be done prior to any treatment. That being said, I have a definite mold illness history, for which he treated me. Here is his response:

“These results don’t look that bad considering where you were testing before. This could still be an old exposure and mean nothing. Let’s do some further testing to have a better picture.

I will order a blood draw to do TGF beta1 inflammation marker & IgG mold levels in your blood.

In the meantime, make sure your diet consists of less refined carbs more complex carbs from whole food sources, like fruits and vegetables. Add some (8 drops) of CitriDrops Dietary Supplement to 4 ounces of water 2 times day, a probiotic, and 1 tsp brain octane (MCT oil) per day. Also take Glutathione 2 times per day.

We will reevaluate when we have all of your results.”

I hope this post has broken things down and answered any questions you may have had about VCS testing. Have you done VCS Testing? Was it helpful? I want to hear from you.










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Kim Becker - 8:14 pm

Great info on VCS testing! I am currently in treatment with Dr Andrew Heyman and take the VCS monthly from the Surviving Mold website. I’m going to start taking it from VCSTest.com as well, and see how they compare.

I have visited your website many times and had no idea Dr. Dennis was your father until today! I am a patient at his clinic. He is a godsend to those of us who deal with mold sickness.

Catherine - 1:42 am

Hi Kim,

Thank you so much for writing. I am his daughter. I include that info in the About Me section, but I don’t think most folks read it. For so long I did not buy into the mold thing. Then I got very sick. Life has a strange way of reconnecting us when it counts. I actually find the VCS Test very helpful. It was what first pointed me to viral activation and nutritional deficiencies from my ulcerative colitis. I was in a mold-free environment, but still scoring low on the VCS in certain areas. It has been a tool for the military for decades to pinpoint toxic exposures. It amazes me that more docs don’t use it as a evaluation tool. I hope you are well and are healing. Take care!

Rebecca Paul - 11:04 pm

hi I have had cateract surgery and my lens are monovision. Will that affect my results?

Catherine - 1:43 am

Hi Rebecca,

You may have to take it at a doc’s office. There are provisions for many different things with the VCS test. I am just not exactly sure about this one.

Cecile - 11:16 pm

Hi, thank you for sharing your experience! Is it possible to ask what things or item or experience can affect the VCS test? For example, section E, can it be relationships, California fires…etc. thank you

Catherine - 5:30 pm

Hi, Cecile,
Well, you have to look at the overall results to get the best idea. In E, things like alcohol, tobacco use, stress, and even treatments like use of certain binders or having a Herx reaction can make you dip. If the dip in E coordinates with your results in columns C and D, then it is more likely that your E results are from some sort of exposure, like biotoxins or the fires, etc. Does that help? The VCS is very helpful, but must be used with further testing and patient history to provide any diagnostic info. Thank you for reading and for your question!


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