> Source: https://www.thenycoptometrist.com/blog/color-vision-test-nyc (last updated 2026-07-24) # Color Blindness Testing: What a Color Vision Exam Reveals (and What It Can't Fix) **By Dr. Joanna Latek** · Published 2026-07-21 > Most 'color blind' people see color fine, they just confuse certain pairs. A color vision exam pinpoints exactly which cones are affected, why it almost never has a treatment, and where it still matters for licenses and careers. # Color Blindness Testing: What a Color Vision Exam Reveals \(and What It Can't Fix\) Most of the patients who come to me for a color vision exam aren't here because they noticed a problem. They're here because something else requires documentation: a job application, a commercial driver's license, the military, an electrician's apprenticeship. The form says "color vision: pass/fail," and they need an optometrist to fill it in. Others come because their child failed a school screening, or because a parent remembers being told they were "color blind" as a kid and wants to know if their son inherited it. Either way, what most people actually know about color vision is wrong. Let me clear that up first. ## Screening vs a full color vision exam A color vision screening is what happens at a school nurse's office or during a pediatric eye exam. I show a handful of plates from a booklet called the Ishihara test — the ones with numbers made of colored dots hidden inside a field of other colored dots. Someone with normal color vision reads the number. Someone with red-green deficiency sees a different number, or none at all. Screening takes about 60 seconds and answers one question: is there a deficiency, yes or no? A full color vision exam goes deeper. I want to know three things: which type of cone cell is affected, how severe the deficiency is, and whether it's congenital \(you were born with it\) or acquired \(something changed later in life\). Those answers change what I tell you, and sometimes they prompt a bigger workup. The full exam uses more than Ishihara plates. I'll typically use: - **Ishihara plates** — still the front-line test for red-green deficiency. Sensitive, fast, but they only screen for the common forms. - **The D-15 arrangement test** — you get a box of colored caps and arrange them in order. The pattern of errors tells me which axis of color vision is affected and roughly how severely. - **An anomaloscope** — a specialized instrument that mixes a red and a green light and asks you to match a yellow. It's the gold standard for diagnosing the exact type and degree of deficiency, but few offices have one. I use it when the result has to be defensible, for licensing, legal, or occupational decisions. The whole exam takes 20 to 30 minutes. It's painless, there are no drops, and you're not "failing" anything. You're getting measured. ## Red-green vs blue-yellow deficiency — what you actually see Human color vision depends on three types of cone cells in the retina, each tuned to a different range of wavelengths. We call them S-cones \(short, roughly blue\), M-cones \(medium, green\), and L-cones \(long, red\). When all three work, you have what's called trichromatic vision — normal color perception. About 8% of men and roughly 0.5% of women have a hereditary deficiency in either the L or M cones. This is what most people mean by "color blind." It's properly called red-green color vision deficiency, and it ranges from very mild to severe. Most people in this group see color; they just confuse certain pairs. Dark red and dark green look similar. Olive and brown can blur together. A ripe banana and a slightly green one may be hard to tell apart under dim light. Blue-yellow deficiency — called tritan deficiency — is much rarer, affecting well under 0.01% of people, and is more often acquired than inherited. When I see it, I start asking about possible causes: cataracts, certain medications, long-term heavy alcohol use, diabetes, or normal aging changes in the macula. Acquired deficiency can be a clue to something upstream, which is part of why a full exam matters. True monochromacy — seeing the world only in shades of gray — exists but is extremely rare, on the order of 1 in 30,000. If you're reading this, that is almost certainly not you. ## Why "color blind" is almost always a misnomer The phrase "color blind" suggests someone sees the world in black and white. Almost no one with color vision deficiency experiences that. The vast majority see a full spectrum; the spectrum is just compressed or shifted in places. This is why color vision deficiency usually goes undiagnosed until adulthood. A child with red-green deficiency has no reference point for what "normal" color vision is — they call a firetruck red because everyone else does, and the word fits close enough. They learn the names of colors from context. Often the deficiency only surfaces when a test catches it, or when a specific task — reading a resistor color code, interpreting a weather radar — suddenly gets hard. A useful reframe I offer patients: you're not missing colors. Your brain is making a reasonable guess with slightly less information than someone else's. In most everyday situations, the difference doesn't matter at all. In a few specific ones, it does. There is no medical treatment for congenital color vision deficiency. No drops, no surgery, no glasses that restore the missing cone function. I want to be honest about that up front, because there's a whole marketplace of "color blind glasses" that implies otherwise. A 2022 meta-analysis pooling 16 studies on these devices found insufficient evidence that they meaningfully improve color perception, and a separate 2022 controlled study of 86 patients found no overall improvement on standard clinical color tests — some colors got easier to distinguish while others got harder. Those lenses can shift the contrast between certain colors — making a stop sign pop more clearly against trees, for instance — but they don't give you back what's missing, and many patients find the effect disorienting rather than helpful. They're worth a trial in some cases, with realistic expectations. They are not a cure. ## Careers, licenses, and where color vision matters Most of my adult color vision exams are for occupational reasons. Here's where it tends to come up: - **Commercial drivers \(CDL\), pilots, air traffic controllers** — federal standards require specific color vision thresholds. The FAA, for example, has a list of acceptable tests; passing one means you're done, failing means more testing or a special issuance process. - **Electricians, electronics technicians, plumbers** — color-coded wiring is the obvious example, but the practical issue is often whether you can reliably tell a green indicator light from a red one at a glance. - **Law enforcement, firefighting, military** — each branch and department sets its own standards. Some require normal color vision; others accept documented deficiency with a practical test. - **Some medical and lab work** — less common, but certain specialties and tasks require reliable color discrimination, like reading test strips or identifying stained tissue. If you're headed into one of these fields and you've never been formally tested, get the documentation before you need it. I'd rather you walk into a licensing exam knowing your status than be surprised by it. For kids, the conversation is different. I tell parents: a color vision deficiency doesn't limit much, but it does close a few doors, and knowing early lets a child explore interests without falling in love with a career they can't pursue. It's information, not a verdict. If your child hasn't had a comprehensive eye exam that includes color vision screening, that's the place to start. ## Living well with color vision deficiency For most people, the practical impact of color vision deficiency is small. You learn workarounds: checking the position of a traffic light instead of just the color, reading clothing labels instead of guessing, asking a partner before buying paint. Apps on your phone can identify colors for you when it matters. None of this is dramatic, and most of it becomes automatic over time. If a career or license is on the line, the first step is a proper diagnostic exam — not a screening — so we know exactly what we're working with. Sometimes the result is better than you feared. Sometimes the conversation turns to whether an alternative test or a field-specific practical exam is an option. And sometimes it changes what you pursue. All of those are honest outcomes. What I can't do is wave a wand and restore color vision. What I can do is measure it precisely, document it for whoever needs documentation, and talk honestly with you about what it does and doesn't mean. If that's what you need, I'm happy to help. ## Thinking about color vision testing? I see patients at Eye & Health in the East Village. If you'd like a formal color vision exam — for a license, a career requirement, or just to know for sure — you can book online — usually within the week. _This is not medical advice. Please consult your eyecare professional or schedule an eye appointment today._ --- ### Bibliography Male, S. R., et al. "Color Vision Devices for Color Vision Deficiency Patients: A Systematic Review and Meta-Analysis." Health Science Reports, vol. 5, 2022, e842. Pattie, Callum, Stacey Aston, and Gemma Jordan. "Do EnChroma Glasses Improve Performance on Clinical Tests for Red-Green Color Deficiencies?" Optics Express, vol. 30, no. 18, 2022, pp. 31872-31888. American Optometric Association. "Color Vision Deficiency." aoa.org.