Passed the school screening, still can't see the board: screening vs. eye exam

A school vision screening and an eye examination are different things, and passing the first does not cancel the second. A screening is built to sort a hall full of children quickly into “probably fine” and “worth a proper look”, and it trades accuracy for that speed. The best-studied instrument screener, checked against full examinations, correctly flagged about 88 of every 100 children who had the conditions it looks for and correctly cleared about 78 of every 100 who did not.1 Evidence: MODERATE Put the other way round: roughly one child in eight with the very problem the device exists to find walks out with a pass. If your child passed in the autumn and is now leaning towards the board, the slip of paper is not evidence that nothing is wrong. It is a prompt to book the examination that was due anyway.

I am a father, not a doctor. Here is what the screening checked, what it structurally could not see, and roughly how often a real examination should happen.

What a screening is for

Parents misread the slip in two directions. One reads passed and files the subject under done. The other reads referred and spends a fortnight convinced their child has been diagnosed with something. Neither happened.

A screening sorts a queue. An examination finds out what is going on inside one child’s eyes. The first is a net with a mesh; a pass is not a clean bill of health, and a referral is not a diagnosis, just a note that somebody should look properly.

Do take the screening you are offered. It is usually free, it catches children who would otherwise be found years later, and in many places it is the only eye care many children ever get. Passing it is simply not the same as being examined.

What the net misses: long sight, one weak eye, two eyes that do not work together, and eye length

Most school screenings test distance vision, which is sensible and is nowhere near the whole eye.

Long sight. A child’s focusing muscle is far stronger than an adult’s. A long-sighted child can hold that muscle tight, read a distance chart cleanly and still find a page of print exhausting. In a large study of preschoolers with uncorrected long sight — children nobody had flagged — early literacy scores came in about four points below their classmates’, and eight and a half points below when near vision was affected too.5 Evidence: MODERATE The only reliable way to measure long sight in a child is a refraction done after drops that switch the focusing muscle off, which the International Myopia Institute treats as the reference standard in children for precisely this reason.7 Evidence: STRONG No corridor screening does that.

One weak eye and one good one. Two eyes make a single picture, and a good eye covers for a struggling one completely. A child with one weak eye can read the chart with both eyes open and sail through, unless each eye is tested on its own. Astigmatism — an eye that focuses unevenly, so a letter is sharp one way and smeared the other — hides in the same place, behind a good partner eye or a chart read quickly from a distance.

How the two eyes work together. An examination checks what each eye does while the other is covered, and tests depth perception. That is where a turning eye gets caught. A chart on a wall does not look for it.

The length of the eye. No screening measures it, and it is the number that decides a short-sighted child’s future. The 2025 IMI summary names the best single predictor of a child about to become short-sighted — the refraction, measured with the focusing muscle switched off — and says that tracking it alongside eye length is the heart of managing a child at risk.6 Evidence: STRONG Instrument screeners hunt mainly for the risk factors for a lazy eye, not for the speed of a growing eye. A child can pass every year and still be on the slope.

Who runs your school’s screening, at what age, with what equipment, and whether anybody follows up the result varies by country and often by district. I cannot describe yours; the questions below are how you find out.

The number you will see quoted, and why I do not use it

Alongside all of this you will meet a figure: screenings miss “up to 60 per cent” of vision problems, or “up to 75 per cent”. I went looking for the study behind it. The trail ends on professional-association web pages, each quoting a different number and none citing peer-reviewed work.8 Evidence: LIMITED The honest version does not need a percentage: a screening is a net, nets have holes, and the section above tells you roughly where they are.

The same scepticism applies to eye charts printed at home and apps that test a child on the sofa. None of them measures a refraction, looks at a retina or measures the length of an eye. The only result they can give you that is worth anything is a fail. A pass at home is a feeling, not information.

How often, in three lines

The people who ought to agree on a schedule do not, so here are the three positions in a line each. The American Academy of Pediatrics, with the eye surgeons and children’s eye specialists, describes a ladder: inspection and red reflex in the newborn nursery, instrument screening from about twelve months, and chart-based acuity testing from about four.2 Evidence: STRONG The American Optometric Association asks for a full examination at six to twelve months, at least one between three and five, one before school starts and one every year after that; the guideline is being rewritten.4 Evidence: MODERATE The US Preventive Services Task Force, which sets a deliberately high bar, says screen at least once between three and five and that under three there is not enough evidence either way.3 Evidence: STRONG

They are answering different questions — whether screening every child at a given age has been shown in trials to change how they see years later, versus what the child in front of you should have — which is why the answers differ. The common ground is enough for a parent: at least one proper vision check between three and five whether or not anything looks wrong, more often once a child is short-sighted, and the interval your own examiner gives you written down and kept.

The referral that leaks, and what to say at school

A referral only works if somebody acts on it. In a trial of school eye screening in Kenya, about 54 per cent of children referred for an examination reached one, against about 22 per cent in comparison schools — and even the better programme lost half the children it had found.9 Evidence: MODERATE Everything of value happens in the weeks after the letter comes home, and that part is yours.

A school can also see something you cannot. A teacher watches your child work beside thirty others for six hours a day, a comparison group you will never have at home. So ask to be told: if your child is squinting at the board, copying from a neighbour or edging the chair forward, you would like to know.Evidence: EXPERIENCE And when a school’s answer is to move a child to the front row, treat that as a sign, not a fix; a child at the front can read the board with an eye that needs a prescription for another whole term.

When you are told, book an examination. Not a lamp, not a seat change, not a fortnight of watching at the kitchen table. If what you are noticing is on the short list of six urgent signs, book this week.

Two questions to ask at the appointment

Was each eye tested on its own? You want two numbers, not one. A single result for both eyes together is exactly how one weak eye hides.

Was the refraction done with drops — and if not, why not? A specific reason is fine. “We don’t tend to” deserves a follow-up question, because without drops a child’s focusing muscle can hold a long-sighted eye in focus straight through the test.

The next time a screening slip comes home, read it this way: a referral means book now, and a pass does not cancel the check that was already due. For what happens once you are in the room, and what else to ask before you leave, see what happens in a child’s eye exam.

Drawn from Chapter 12 and Chapter 13 of Children's Eyesight Problems, second edition. Report a correction.