visual acuity in young children – what is “normal”?
When people ask what Zoe’s vision is, they’re normally expecting to hear her visual acuity – usually given as 20/20 or the metric equivalent 6/6 – and then they want to know how she compares with other children. I don’t actually know what her uncorrected acuity is, but I was curious about what you might expect a preschooler’s acuity to be.
The Snellen and the Tumbling Eye Charts, both used to measure visual acuity. Image from AllAboutVision.com. (http://www.allaboutvision.com/eye-test/)
Visual acuity is the measurement of how clearly we see at a specific distance, usually 20 feet or 6 meters, though that can vary. It is generally tested in adults with the well-known Snellen eye chart (the one with the big E on top) and with a variety of charts for children. The acuity is usually presented as two numbers that indicate how close a person will need to be to an eye chart to see the letters or symbols clearly, compared to what a person with “normal” vision would see. Let’s say my uncorrected visual acuity is 20/200 – that’s 6/60 in metric – (which it is, more or less, in my right eye). That means that I have to stand 20 feet – or 6 meters – away from the eye chart to read the big E. A person with good vision, on the other hand, could see the E at the top of an eye chart from 200 feet – or 60 meters – away.
It’s worth keeping in mind that visual acuity is not the whole picture (so to speak) when it comes to measuring vision. Visual acuity does not indicate how well the eyes work together, or peripheral vision, or even what the prescription needs to be to correct vision.
For adults, it’s pretty easy to look at the acuity numbers to see how good your vision is: if the first and second numbers are the same, 20/20 or 6/6, that means normal visual acuity. If the second number is smaller than the first, you have better than normal acuity, and if it’s larger than the first your vision is poorer. But for young children, it’s not quite as straight forward. Because children’s vision hasn’t completely developed, a child can have “normal” vision that is worse than 20/20.
In 2003, the American Academy of Pediatrics adopted a policy on Eye Examination in Infants, Children, and Young Adults by Pediatricians. According to those standards, pediatricians should refer any child under the age of 5 with a visual acuity of worse than 20/40 – that’s 6/12 in metric – to an eye doctor. At age 6 and older, they should refer any child with acuity of 20/30 – 6/9 metric – or worse.
More recently, though, a study called the Multiethnic Pediatric Eye Disease Study looked at visual acuity norms in preschool children with the goal of gaining more accurate visual acuity norms for children. The results were published in Optometry and Vision Science in June 2009 (abstract and full citation). They measured the visual acuity of 1,722 children ages 30 to 72 months with no significant refractive errors – so kids that should have good vision. From those measurements they determined the threshholds for visual acuity that would include 95% of the children tested. That means that if the test were done by pediatricians and these guidelines were followed, you’d expect that 5% of children with no refractive error would be referred on to an eye doctor for a follow up. You’d hope that all of the kids with visual problems would also be caught with the testing and also be referred on to an eye doctor. That’s not necessarily the case, the researchers note that children who have “normal” visual acuity may still have visual problems, but that’s a topic for a different post. The nice thing about this study is that it breaks out the age range in to more detail, understanding that vision is still developing significantly in children between the ages of 2 1/2 and 6.
So, according to this most recent study, normal visual acuity for preschoolers may be better defined as:
30 – 35 months: 20/63 (6/20) or better
36 – 47 months: 20/50 (6/15) or better
48 – 59 months: 20/40 (6/12) or better
60 – 72 months: 20/32 (6/10) or better
The American Optometric Association wants to stamp our amblyopia/lazy eye in our lifetimes. That’s why they started a program called InfantSee. Don’t wait for your pediatrician to send you to an optometrist…do it now. Find an eye doctor who will assess your little one’s vision at no cost by going to http://www.infantsee.org today. For the latest in children’s vision research go to http://www.mainosmemos.blogspot.com
Thanks Dominick, I try to pass the infantsee information to all my moms groups and think it is a great program.
I really haven’t stayed on-top of Elly’s visual acuity. In the beginning she was estimated at 20/ 1200 and in a -5.5 perscription. In the last year she has dropped to a -8 perscription. Does the visual acuity change… this is something I will try to remember and ask the vision specialist in the morning.
Elly’s prescription change means the little one became more nearsighted not less. The higher the number the “more” the refractive error amount. As you become more nearsighted usually your visual acuity reduceds until you are given a new pair of spectacles. Then you should see OK. You might want to have a VEP/Sweep VEP (Visually Evoked Potential) done to get a better handle on the visual acuity.
Hi there my 7 year old daughters VA is 3/19 (metres), everything that i see on the internet is is always referred to from 6 metres distance. Is there a way to convert her VA of 3/19 to the 6 metre distance? cheers Belinda
Hi Belinda, You should be able to just multiply both numbers by 2, so 3/19 would be 6/38.
This is such wonderful info. I can’t believe Stella, at 28 months, has one eye at 20/20. I remember being told, before she had glasses, that her visual acuity was above average for her age. But after that, the left eye’s acuity started going down, but now it’s back up to 20/30. Like you said, visual acuity is just one piece of the puzzle. It’s all so confusing yet fascinating.
hi ann,
My kid who is 5 1/2 years old has visual acuity of 6/9 or 20/30. From the above it looks like this should be acceptable below 6 years. Does that mean they dont require glasses?
Thanks,
Man
My son is almost 6 years old, and I was told by an optometrist that he is farsighted. Giving us a correction of +2 ou, for reading. But then the doctor mentioned that sometimes this is normal, so if my son doesn’t have any problems to leave it alone.
I don’t know what do. Is it normal? should I get my son reading glasses?
Farsightedness or hyperopia is a bit trickier than nearsightedness (myopia) and astigmatism. With farsightedness the vision system is never at rest. For instance when we look far away our focusing system should be resting….and then turned on as we look closer and closer. With farsightedness you have to continually focus for all distances all the time. What is “normal” for a child with farsightedness will vary with age and visual demands. For a child who is six years of age I would consider +2.00 right on the edge of where I might recommend glasses. Does the child have any other vision problems? Blurred vision, headaches, eye turns, etc? If not I might wait before prescribing glasses. The other thing to remember that our academic curriculum has shifted downward significantly…children are being taught to read and reading at much earlier ages. This is not necessarily a good thing…especially if the child has farsightedness….which can make reading very difficult. When in doubt….seek a second opinion. Beware that doctors will vary widely when it comes prescribing…especially for hyperopia…..and MDs do not tyically prescribe as often as ODs. For a doc who could give you a good second opinion, I would suggesting go to the College of Optometrists in Vision Development at http://www.covd.org and click on their Dr. Locator button in the upper right field. Hope this helped a bit.
Thank you so much, Dr. Maino, that was a fantastically clear and helpful explanation. I feel like I’m always learning something when you post here!
Sent from my iPhone
Thank you so much, this really helped. You are basically said the same thing as the optometrist, you are my second opinion.
My son doesn’t have any other problems such as, crossed eye, headaches, poor school performance; about the blurry vision I don’t think he would know any different. Anyways, he is in kindergarten, doing great in school and reading above grade level. So, I am just going to wait and see.
Thank you again,
Rossana
Hi my daughter has just turned 5 yrs old, I booked her for a routine eye test, my daughter has no complaints with near or far distance, how ever when optometrist did ret it showed her right eye was -4.50ds and le -3.00ds, on snellen chart she managed to read 6/9 with out refraction, with refraction le -1.50ds she read no better on chart but he was adiment that le prescription is -1.50ds with a +1.00ds blur le was 6/12+, in re with over refraction of -3.00ds she saw 6/10, again over refraction did not make her read any better. The optometrist has rebooked her for another day a morning test, to do the eye test again, and to refer her to the hospital, I am very concerned on what the outcome will be. concerned mum
Your daughter has a fair amount of myopia (nearsightedness) that could cause amblyopia (lazy eye). The visual acuity without refraction seems much too good to be true unless your child was squinting….in any case, I might take the visual acuities with a large grain of salt. Did the doc use dilating/anti-focusing drops and then re-check not only the eye health but also the amount of nearsightedness present? Bringing your little one back for a re-check is a good idea….don’t know why she would need a referral to a hospital at this point. If she has amblyopia…once the prescription is verified the best thing to do (as shown by research clinical trials) is to put a pair of glasses on her for full time wear and then to follow her closely. If the glasses do not get her to the visual acuity we would like, then more aggressive therapy is needed (optometric vision therapy…check out http://www.covd.org). Keep me posted on her progress.
my daughter is 4yrs old. her vision is 6/6 in rt eye and 6/9 in left. auto raf gave the cylindrical power of -2.5 in left eye and -.75 in rt eye. shud i go for dialatation test.her binocular vision is 6/6.