The Focusing Test: What Your Amplitude of Accommodation Number Means
Your Focusing Test at a Glance
The focusing test checks how strongly your eyes can sharpen an object held close to your face. The amplitude of accommodation is the most focusing power your eyes can add for near vision, created when the lens inside each eye changes shape, and it is measured in units called diopters 1. Your eye doctor compares your number against what is typical for your age, not against a single fixed target.
A higher number means your eyes can focus on closer objects with less effort. Because the lens stiffens over the years, focusing power falls steadily with age, so a teenager and a 55-year-old are held to very different standards 2. One low reading on its own is a clue to look further, not a diagnosis.
If your number sits near the expected range and near work feels fine, you usually need to do nothing. If it is low and reading or screens are a daily strain, ask whether reading glasses or focusing exercises would help. A focusing power that falls short of age norms is called accommodative insufficiency, and it is one of the more common focusing problems in school-aged children 3.
What Amplitude of Accommodation Actually Is
Seeing something near takes active work inside the eye. A small muscle inside the eye lets the lens become rounder and stronger, adding the extra focusing power needed to keep close objects sharp 1. The closer the object, the more focusing power your eyes have to supply to hold it clear.
Amplitude is simply the ceiling on that effort: the strongest your eyes can focus before an object blurs. The number comes from the near point of accommodation, the closest distance you can hold something and still see it clearly, converted into diopters 4.
As a rough example, a near point of 10 centimeters works out to an amplitude of about 10 diopters. The shorter the near point, the higher the amplitude.
Losing focusing power over time is normal, not a disease. Presbyopia is the natural, age-related loss of near focus that everyone develops, usually becoming noticeable after about age 45 as the lens grows harder and less flexible 5. This is why the same low number can be perfectly normal at 50 yet worth a closer look at 15.
How to Prepare for the Focusing Test
Bring the glasses or contact lenses you normally wear for reading and screens. The test is often run both with and without your correction, so your doctor can see how your eyes perform in everyday conditions. Wear your usual lenses to the visit rather than an old spare pair.
Focusing can feel harder when your eyes are tired, so try to arrive reasonably rested rather than straight after hours of screen work. Mention if you have been reading heavily that day. The test itself is quick, usually only a few minutes for each eye, and good room lighting helps.
Tell the examiner about any eyestrain, headaches, blur, or trouble concentrating during reading, and when those happen. Mention your medications and any health conditions too. This background helps your doctor read the number in context instead of in isolation.
What Happens During the Test
This is the most common version, and it is quick and comfortable. In the push-up (Donder) method, a small target is slowly moved toward your eye along a device called an RAF ruler until it first turns blurry, and that near point is converted into your amplitude 4. You simply say the moment the letters or picture stop looking sharp.
Some doctors use lenses instead of moving a target closer. In the minus-lens method, steadily stronger lenses are placed in front of the eye until the target blurs, and this approach tends to read about 2 diopters lower than the push-up method 4. Both methods are painless, and nothing touches the eye.
The amplitude number is often just one part of a wider focusing check. Your eye doctor may also test accommodative facility, how quickly you can shift focus using flip lenses, and use dynamic retinoscopy to watch how your eyes respond to a near target 4. Together these give a fuller picture than any single number can.
Understanding Your Results
Your result only means something next to an age benchmark. A common rule of thumb, Hofstetter's formula, estimates the minimum expected amplitude as 15 minus one quarter of your age, and the average as 18.5 minus 0.3 times your age, in diopters 2. For a 10-year-old, for instance, the minimum works out to about 12.5 diopters.
A number under the benchmark is followed up, not feared. Accommodative insufficiency is typically diagnosed when the measured amplitude is at least 2 diopters below the minimum expected for a person's age, together with symptoms during near work 2. Your doctor weighs the number alongside how your eyes actually feel while reading.
An in-range result is reassuring, but it is not a clean bill of health for the whole eye. Because the push-up test relies on your own report of first blur, it can overestimate true focusing power, and a normal number does not rule out every eye or vision problem 4. If symptoms continue despite a normal result, tell your doctor, because the cause may lie elsewhere and deserves its own check.
Risks, Reliability, and What Comes Next
The focusing test carries no physical risk. Nothing touches the eye, the basic push-up test needs no drops, and you can pause at any time. The main limitation is simply that tired or distracted eyes can give a lower reading than your true best.
A single measurement is a snapshot, not a verdict. Push-up amplitude readings vary with attention, fatigue, and the depth of field of the eye, so doctors often repeat or combine tests rather than trust one figure 4. A borderline result is frequently rechecked on another day before any conclusion is drawn.
Low focusing power is usually very manageable. Accommodative insufficiency is commonly treated with reading (plus) lenses and with vision therapy exercises such as lens flippers, and near-work symptoms often ease with treatment 6. Your doctor will tailor the plan to your age, symptoms, and daily demands rather than promise any one result.
When to Call Your Eye Doctor
The focusing test itself is not an emergency test, and low focusing power is not an urgent danger. Even so, a few eye symptoms need same-day care no matter what your focusing number is. Call an eye doctor or seek urgent care the same day for sudden vision loss, a curtain or shadow over part of your sight, a sudden burst of new floaters or flashes of light, or sudden eye pain with redness.
Book a routine eye exam if near work is a regular struggle. Blurred near vision, eyestrain, headaches, and reduced reading endurance are the common symptoms of a focusing problem such as accommodative insufficiency 3. In children this can look like avoiding homework, losing their place while reading, or tiring quickly at near tasks.
An optometrist or ophthalmologist performs and reads this test. Checking how the eyes focus, move, and work together is a standard part of a comprehensive eye examination 7. If a focusing or eye-teaming problem turns up, your doctor may suggest glasses, exercises, or a follow-up plan.
Common Questions About the Focusing Test
No. The focusing test is painless and non-invasive. In the usual push-up method, you look at a small target that moves closer while you say when it blurs, and nothing touches your eye. The minus-lens version simply places lenses in front of you. You may feel your eyes working a little as you strain to keep the target clear, but that effort is normal and passes at once.
Not long. The focusing measurement itself usually takes only a few minutes, often a minute or two per eye. It is commonly folded into a longer comprehensive eye exam that also checks your prescription, eye movements, and eye health. If your doctor repeats the test or adds related focusing checks, plan for a little extra time, but the focusing part alone is short.
It depends heavily on your age, because focusing power drops as you get older. Hofstetter's rule of thumb sets the minimum expected amplitude at 15 minus one quarter of your age in diopters, so a 20-year-old would expect at least about 10 diopters and a 40-year-old at least about 5 2. Your doctor compares your reading to this age-based range rather than to one universal number.
Not exactly, though they overlap. A low number can be normal aging (presbyopia), which reading glasses address, or it can be accommodative insufficiency in a younger person, which may call for glasses or focusing exercises. Presbyopia is the expected age-related loss of near focus after about age 45, while a low number in a child or young adult is judged against age norms 5. Your doctor decides which pattern fits.
Long stretches of near work can leave your eyes tired and make focusing feel harder in the moment, and heavy same-day reading can lower a single reading. That is one reason doctors sometimes recheck a borderline result on another day. Screen habits are worth mentioning at your visit, but a genuinely low amplitude is measured against age norms and is not explained by tiredness alone.
Some decline with age is expected and normal for everyone. Because the lens gradually hardens with age, near focusing power falls over the years, which is what leads to presbyopia in mid-life 5. That does not mean a problem is looming; it means the benchmark your doctor uses shifts with age, and glasses easily make up the difference when near focus fades.
More Questions About Your Focusing Number
For some focusing problems, yes. Accommodative insufficiency is commonly treated with plus (reading) lenses and vision therapy exercises such as lens flippers, and near-work symptoms often improve with treatment 6. Exercises will not reverse normal age-related presbyopia, though, since that comes from the lens hardening. Your doctor can tell you which situation you are in and whether therapy, glasses, or both make sense for you.
Seeing far away and focusing up close are different skills. A child can have sharp distance vision yet struggle to sustain near focus, which shows up as trouble reading rather than trouble seeing the board. Accommodative insufficiency is one of the more common focusing problems in school-aged children and often appears as reading fatigue or avoiding near work 3. A full eye exam sorts out what a screening flagged.
Not for the basic focusing measurement. The push-up and minus-lens tests do not require dilating or numbing drops. Your doctor might use drops for other parts of a comprehensive exam, such as dilating your pupils to check eye health, but those are separate from the amplitude measurement itself. Ask ahead if you want to know whether drops are planned for your visit.
- How does my amplitude compare to what is expected for my age?
- Do my symptoms match my focusing result, or should we look further?
- Would reading glasses, vision therapy, or both help me most?
- Should we recheck a borderline number on another day?
- Are there other focusing or eye-teaming tests I should have?
- StatPearls, NCBI Bookshelf (2024). Accommodative Insufficiency (StatPearls).
- StatPearls, NCBI Bookshelf (2024). Accommodative Insufficiency (StatPearls).
- StatPearls, NCBI Bookshelf (2024). Accommodative Insufficiency (StatPearls).
- StatPearls, NCBI Bookshelf (2024). Accommodative Insufficiency (StatPearls).
- National Eye Institute (NEI) (2023). Presbyopia.
- StatPearls, NCBI Bookshelf (2024). Accommodative Insufficiency (StatPearls).
- American Optometric Association (AOA) (2024). Comprehensive eye exams.