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BLUE CONE MONOCHROMACY (BCM) SIMULATION GLASSES
INDEX
DESCRIPTION
INSTRUCTIONS
LIMITATIONS
HOW TO REQUEST BCM SIMULATION GLASSES
APPENDIX 1 – METHOD TO SIMULATE THE VISION OF A SPECIFIC PERSON WITH BCM
APPENDIX 2 – ALTERNATE METHOD TO SIMULATE THE VISION OF A SPECIFIC PERSON WITH BCM
APPENDIX 3 – TECHNICAL DETAILS ABOUT HOW THE GLASSES SIMULATE BCM COLOR VISION
DESCRIPTION
A person with normal vision can use these glasses to simulate Blue Cone Monochromacy color vision by blocking red light and to simulate poor visual acuity.
Main symptoms of BCM include poor ability or inability to distinguish colours, and poor visual acuity, between 20/200 and 20/63 (poor detail vision).
There are 2 versions of the glasses available.
Type 1 – Simulates BCM color vision by blocking red light (made with 2 layers of a red blocking filter ROSCO #2005 Cyan)
Type 2 – Simulates BCM color vision and poor acuity (blurry vision) (made with 2 layers of ROSCO #2005 Cyan and 1 layer of ROSCO #132 diffusion filter)
INSTRUCTIONS
These glasses should be used over any glasses or contacts a normally sighted person uses. This provides a starting point close to 20/20 vision in the US or 10/10 in Europe. You can also use these glasses over a cell phone camera lens to get representative photos of BCM color vision. This is how Figures 3 and 4 above were made.
LIMITATIONS
VISUAL ACUITY: The type 2 glasses are worse acuity (blurrier) than is average for BCM which usually runs between 20/63 and 20/200. The type 2 glasses simulate worst case BCM vision of 20/200 or worse.
This was limited by available diffusion filters. APPENDIX 1 and APPENDIX 2 discuss ways to simulate a specific person’s BCM eyesight. The type 2 glasses will give a good general impression of what worst case BCM vision is like. For normal sighted people trying to understand what a specific person with BCM sees, the methods in the appendices may be worth doing.
COLOR ACCURACY: Not everyone with BCM has exactly the same color vision, depending also by variations in bright light sensitivity, so these glasses may not be an exact match for all individuals with BCM but represent a good simulation.
PHOTOPHOBIA: The glasses cannot simulate the intolerance to light, also called photophobia, that is another major symptom of BCM. Using these glasses over a mobile phone camera and significantly overexposing the image can simulate the additional color loss BCM causes in bright sun without sunglasses. People with BCM feel discomfort in bright light causing them to squint.
NYSTAGMUS: Another symptom of BCM that is not simulated with these glasses is infantile nystagmus, which in some cases persists into adulthood (involuntary rhythmical, repetitive eye movement).
HOW TO REQUEST BCM SIMULATION GLASSES
Please send an email to info@bcmfamilies.org containing the address to send the glasses to and the number of copies. For small orders there are no costs for both shipments in the United States and abroad.
APPENDIX 1 – METHOD TO SIMULATE THE VISION OF A SPECIFIC PERSON WITH BCM
Type 1 red blocking glasses can be used over low cost reading glasses (Figure 5). The reading glasses are used to defocus an image to match the poor acuity of a person with BCM and the Type 1 glasses simulate BCM color vision.
To do this, a normally sighted person and a person with BCM can go to a store that sells low cost reading glasses to test different diopter (strength) reading glasses to find a match for the BCM person’s acuity. In the USA, low cost reading glasses are sold at pharmacies.
A person with normal vision can compare what they can read on distant signs using different diopter reading glasses with what the person with BCM can read. Try different diopter glasses until the normally sighted person is limited to reading the same text size as the person with BCM. It may be useful to print out an eye chart from the internet to take with you to the store. The signs or eye chart being read should be 20 feet (6 meters) or farther away. Diopter values between +1.25 and + 2.5 should typically give the right level of «poor» focus. This will only be true for distant objects. Closer objects will be in better focus which is the purpose of reading glasses. If the normally sighted person wears glasses, the reading glasses should be in addition to (on top of) their normal glasses or contacts. Using these reading glasses plus the Type 1 BCM simulation glasses together will then closely simulate the BCM person’s vision.
If you prefer not to go to a store, Amazon sells bulk reading glasses that are a mix of diopters (powers). At the time of this write-up, Amazon has 10 pairs of reading glasses that vary in diopters from +1.25 to+3.25 for about $20. Search on “bulk reading glasses variety pack” and make sure they are a mix of diopters. Some variety packs are a variety of colors, not diopters.
If you need many pairs of glasses for a class or group demonstration, you can buy bulk reading glasses of a specific diopter. Amazon has several suppliers selling 6 packs of reading glasses for around $13 and eBay has vendors selling 12 packs for $20. Even though these are cheap, they are useful for this purpose. One issue is that screws can fall out of the BOOST EYEWEAR brand glasses shown in the photo in APPENDIX 2.
APPENDIX 2 – ALTERNATE METHOD TO SIMULATE THE VISION OF A SPECIFIC PERSON WITH BCM
You can make your own simulation glasses to match a specific BCM person’s eyesight without the cardboard frames. The ROSCO #2005 filter sheets are available in 20”X24” sheets (508X610mm) for less than $11 (Google search for “ROSCO #2005 sheet”). Narrow double-sided tape can be used to attach 2 layers of this film to the back of reading glasses as shown in Figure 6. The tape is available on Amazon in 2, 3 and 5mm widths (sold as cellphone screen repair tape – $8 to $16 depending on width).
AMAZON and eBay have low-cost bulk reading glasses as noted in APPENDIX 1 if you want larger quantities.
The flatter and more rectangular the back of the lens on the reading glasses, the easier it is to add the filter material.
APPENDIX 3 – TECHNICAL DETAILS ABOUT HOW THE GLASSES SIMULATE BCM COLOR VISION
Figure 7 shows the cone and rod sensitivity for normal vision to different wavelengths of light which the brain interprets as primary colors: blue, green and red. Cones are referenced by vision researchers as S-cones, M-cones, and L-cones for their short, medium, and long wavelength sensitivities. People with BCM have no working green (M) or red (L) cones.
For normal sight, rod cells are only active in low light conditions. In bright light, rod signals are overridden by cone signals.
With BCM, rods are still active even in bright light and the rods are most sensitive to green wavelength light.
