Color vision tests for seafarers and pre-employment medicals: what to expect

For a lot of Filipino families, a medical result decides a career. Seafaring, aviation, the uniformed services, electrical and technical trades — all of them screen colour vision, and the applicant usually finds out on the day.

Here is what the test is, what it means, and what an optical store can and cannot do about the result. We would rather you heard the straight version from us than a hopeful version from somewhere else.

Why these jobs test colour vision

Safety-critical work runs on colour coding. Navigation lights at sea are red, green and white, and reading them correctly at night is how a watchkeeper knows which way another vessel is heading. Signal lights, warning indicators, resistor bands and wiring are all colour-coded. Where a mistake is dangerous, the standard exists.

How the test is done

The most common screening method uses pseudoisochromatic plates — the pages of coloured dots with a number hidden inside, usually referred to as Ishihara plates. Someone with normal colour vision reads one number; someone with a red-green deficiency reads a different one, or none at all.

Some medicals go further. A lantern test shows small coloured lights the way they would appear at a distance at sea, and is used in maritime and aviation contexts. An arrangement test asks you to put coloured caps in order and grades how severe a deficiency is rather than just detecting one.

Two practical notes. Lighting matters — plates are meant to be read under proper daylight-balanced light, and a poorly lit room can produce a misleading result. And the test is done with your normal distance correction on, so bring your glasses.

What a colour vision deficiency actually is

The retina contains three types of cone cell, tuned to different parts of the spectrum. In colour vision deficiency, one type is absent or shifted, so certain colours become hard to tell apart. Red-green deficiency is by far the most common form and is inherited, carried on the X chromosome — which is why it affects men far more often than women. The commonly cited figure is roughly one in twelve men.

It is not blindness. Most people with it see colour perfectly well; they confuse particular pairs. Many go their whole lives without knowing until a medical exam tells them.

The part nobody wants to hear

Inherited colour vision deficiency cannot be corrected. There is no lens, no coating, no treatment that restores normal cone function. Tinted filters marketed for colour vision change how certain colours are perceived by altering the light reaching the eye — they do not repair anything, and they are generally not permitted during official testing. Wearing one to a medical is likely to invalidate the result rather than pass it.

Anyone selling you glasses that promise to pass a colour vision medical is selling you a false result and a wasted fee. We will not do that.

What is still worth doing

Plenty. Colour vision is one line on a medical form, and the rest of it is very much within your control.

• Get your distance acuity right. Uncorrected refractive error fails more applicants than colour vision does, and unlike colour vision it is fully correctable.
• Get tested before the official medical. Knowing your colour vision status in advance means you choose your path rather than being surprised by it.
• Check the specific standard. Requirements differ by role, by rank and by the authority setting them. A deficiency that rules out one deck position may be acceptable in another department entirely. Ask the agency or the licensing body for the exact standard rather than assuming the worst.
• Have your general eye health checked. Some colour vision changes are acquired rather than inherited — and an acquired change, particularly in one eye only, is a medical finding worth investigating.

Know your result before the day

Book a Vision7 eye test at your nearest Vision Express store. The exam confirms your distance and near acuity, checks how your eyes work together, and screens the health of the eye — the parts of a pre-employment vision standard that are actually fixable, sorted out well before you sit the official medical.

If you need correction to meet an acuity standard, ask for the Shamir Opulens Exact at the counter — it is cut to your own measurements, which is what gets you the sharpest achievable distance vision rather than merely adequate vision on test day. If you work long hours on screens between contracts, ask about the Essilor Blue Light Single Vision instead for everyday comfort.

Every pair carries a 1-year warranty, free lifetime ultrasonic cleaning and free lifetime custom fitting and adjustment. Many prescriptions are ready in 30 minutes.

This article is general information. Colour vision standards are set by the relevant licensing authority or employer — confirm the exact requirement for your role with them.