Section 248 of 440
Complete canonical tutorial. This reader section contains the same teaching body as PWR-065 · Visual acuity. Open the Power dossier.
PWR-065 · SELF GUIDED full tutorial
Identify symbol detail under a fixed display setup without calling it a clinical eye test
Visual acuity can improve in selected amblyopia treatment settings, but this is not a route to superhuman eyesight. The low-risk teachable version is a symbol-discrimination fixture, not home measurement of visual acuity. The learner fixes screen, distance, lighting and usual correction, answers once per row, records errors and repeats with a novel ladder. Clinical visual acuity requires standardised charts and qualified interpretation.
1 · Permission and limits
Know exactly what you may do
2 · Get ready
Gather what you need and check the starting conditions
What you need
- An exact two-ladder construction sheet. A helper makes six rows per ladder at 72, 60, 48, 36, 30 and 24 px in DejaVu Sans or the same available sans-serif font. Each row has four separated groups of five identical arrows except one arrow pointing in the opposite direction; group base directions cycle up, right, down and left. Odd-arrow positions for ladder A, largest to smallest, are [3,5,2,4], [1,4,5,2], [2,5,3,1], [4,1,5,3], [5,2,4,1], [3,1,2,5]. Ladder B uses [2,4,1,5], [5,3,2,1], [4,2,1,3], [1,5,3,2], [2,3,5,4], [4,5,1,2]. The helper folds this position key and labels rows only by size.
- One screen or printed card kept at a marked distance and size.
- Ordinary prescribed glasses or contact lenses.
- A ruler/tape and record for lighting, correction, row accuracy and symptoms.
Before you start
- Use the same eye correction normally used for the selected viewing distance.
- Choose even comfortable lighting without glare and mark the viewing position.
- Do not cover or patch an eye if a clinician has told you not to; record whether one or both eyes are used.
- New or sudden visual loss, eye pain, flashes, a curtain-like shadow or double vision needs prompt eye care, not practice.
3 · The method
Follow these steps in order
- Lock the configuration
Record display, zoom, card size, distance, lighting, correction and whether one or both eyes are used.
Why: Symbol size changes with every one of these choices.
Check: A second person could reproduce the setup.
- Learn the response rule
For each of the four groups on a row, say the odd arrow's position from 1 to 5 before the helper reveals the folded key. Do not revise a blurred answer after feedback.
Why: One fixed question keeps the score about detail discrimination.
Check: The learner gives four position answers on each of two large practice rows and can explain how positions are counted.
- Start with obvious rows
Begin at 72 px and give all four group positions before checking or moving to the next size.
Why: Easy rows establish the task without forcing strain.
Check: Each row has four recorded positions and one confidence rating before feedback.
- Descend one row at a time
Continue toward smaller rows while keeping head and card at the mark and using the same allowed viewing time.
Why: Leaning or zooming makes a smaller symbol larger.
Check: Distance and zoom remain unchanged.
- Use a stopping rule
Stop at the 24 px row or earlier for blur that persists after ordinary blinking, headache, eye pain, nausea or other visual discomfort; never repeat a row to improve its count.
Why: The fixture reports performance by size and does not need a clinical-style threshold chase.
Check: The end reason is 24 px or a named symptom, and no row is replayed.
- Score from the key
Compare the four positions with the folded key, record 0–4 correct for each size and retain every wrong position; do not convert a home row to Snellen or logMAR.
Why: The fixture lacks clinical calibration.
Check: Raw row accuracy and confidence remain visible.
- Retest with a new ladder
After at least 48 hours, use the second ladder in the identical setup.
Why: A new item reduces memorisation of the symbol sequence.
Check: Configuration matches and item order is unfamiliar.
4 · Worked example
See the whole method used once
Scenario
Jules uses two laptop ladders at 60 cm, 100% zoom, desk lamp unchanged and ordinary reading glasses.
Walkthrough
- Jules records screen, zoom, 60 cm distance, lighting and both-eye viewing.
- They answer four odd-arrow positions per row from 72 px to 24 px and lock each row before the helper opens the key.
- They score 0–4 at every size, stop at 24 px without replay and do not convert any row to clinical acuity.
- Two days later they use ladder B at the same 60 cm setup.
- They compare row-level accuracy and symptoms, not a “20/20” label.
Result
Jules becomes more consistent on this symbol fixture. The record does not establish corrected visual acuity or an eye-health change.
5 · Right and wrong
Compare correct or safer execution with the common wrong version
| Moment | Right / safer | Wrong / riskier | Why it matters |
|---|---|---|---|
| Distance | Keep the marked viewing distance. | Lean closer on difficult rows. | Moving closer enlarges the symbol. |
| Display | Keep screen, zoom and brightness fixed. | Zoom or switch devices mid-test. | A display change creates a new task. |
| Answer | Commit one response before the key. | Study the answer and then report certainty. | That trains the item rather than measures discrimination. |
| Stop | End after the declared errors or discomfort. | Squint and repeat until the row is memorised. | Strain and repetition distort the score. |
| Claim | Call it odd-symbol discrimination at this setup. | Call the row clinical acuity or superhuman eyesight. | The fixture is not a calibrated eye chart. |
6 · Common mistakes
Spot the error and apply the correction
| Mistake | Fix |
|---|---|
| Lean closer on difficult rows. | Keep the marked viewing distance. |
| Zoom or switch devices mid-test. | Keep screen, zoom and brightness fixed. |
| Study the answer and then report certainty. | Commit one response before the key. |
| Squint and repeat until the row is memorised. | End after the declared errors or discomfort. |
| Call the row clinical acuity or superhuman eyesight. | Call it odd-symbol discrimination at this setup. |
7 · Practice
Turn the steps into a usable skill
First session
- Have a helper construct ladders A and B from the six sizes and folded position keys before the learner sees either ladder.
- Set 100% zoom, mark 60 cm, record lighting, ordinary correction and the font actually used.
- Practise counting odd-arrow positions on two unscored 72 px groups, then run ladder A once from 72 to 24 px without replay.
- For every size, score all four positions, retain errors and record confidence and symptoms.
- After at least 48 hours, run concealed ladder B with the same font, zoom, distance, lighting and correction.
Repeat plan
Use at most two ladders per session, two sessions per week, with a new item order. Progress only by better novel-ladder consistency at the same setup; clinical treatment follows an eye professional.
Progress when
- Novel-ladder accuracy improves at fixed distance and size.
- Confidence better matches correct answers.
- No leaning, zooming or discomfort occurs.
Do not progress when
- The setup cannot be held constant.
- Visual symptoms, headache or eye strain appear.
- A clinical vision problem or prescription change is suspected.
8 · Check the result
Measure what changed
Odd-arrow position accuracy at each of six non-clinical display sizes
How: For each ladder and size, report correct positions out of four, the four original responses, confidence, font, pixel size, zoom, viewing distance, correction, lighting and symptoms. Compare A and B size by size; never convert the result to clinical units.
Good result: Both ladders are completed under matched settings and the size-by-size record can be reproduced from the folded keys. Any difference is described as fixture performance, not a visual-acuity pass or prescription result.
This does not prove: Use calibrated logMAR or equivalent acuity with declared correction and test conditions; acuity does not establish contrast, field, search, depth, low-light or functional safety.
Self-check
- Can you demonstrate “Learn the response rule”? The learner answers two large practice rows correctly.
- Can you demonstrate “Descend one row at a time”? Distance and zoom remain unchanged.
- Can you demonstrate “Retest with a new ladder”? Configuration matches and item order is unfamiliar.
9 · Stop, adapt or get help
Keep the safety boundary practical
Stop and get help
- Seek urgent eye care for sudden vision loss, a curtain/shadow, new flashes/floaters with loss, severe eye pain or new double vision.
- Stop the fixture for headache, nausea, eye pain, persistent blur or visual distortion.
- Arrange an eye examination when everyday vision changes, one eye differs unexpectedly or correction no longer works.
Accessibility and adaptations
- Use large practice symbols and a screen reader for instructions while keeping the visual response itself unchanged.
- Use a chin/forehead distance marker only if comfortable and non-restrictive.
- Allow pointing, speech, switch or eye-gaze responses; motor speed is not scored.
10 · Evidence and limits
Why these instructions are here
- primary research
Primary research in adults with amblyopia found task-specific changes in contrast sensitivity and visual acuity under controlled training.
Perceptual learning improves contrast sensitivity and visual acuity in adults with anisometropic amblyopia - primary research
A controlled study found no added fluoxetine benefit, illustrating that perceptual learning findings do not justify medication or universal enhancement claims.
Fluoxetine does not enhance the effect of perceptual learning on visual function in adults with amblyopia
Limits
- Use calibrated logMAR or equivalent acuity with declared correction and test conditions; acuity does not establish contrast, field, search, depth, low-light or functional safety.
- Unsupported claim: Train eyesight beyond human limits.
- Unsupported claim: Throw away glasses.
- Unsupported claim: Cure every lazy eye.
- Home symbol performance does not diagnose amblyopia, set a prescription or replace calibrated clinical acuity testing.
Open the complete canonical research register
- Primary empirical supportLimiting / contraryPerceptual learning improves contrast sensitivity and visual acuity in adults with anisometropic amblyopia
Y. Zhou; C. Huang; P. Xu; L. Tao; Z. Qiu; X. Li; Z.-L. Lu · 2006 · Primary research
- Primary empirical supportLimiting / contraryFluoxetine does not enhance the effect of perceptual learning on visual function in adults with amblyopia
H. J. Huttunen; J. M. Palva; L. Lindberg; S. Palva; V. Saarela; E. Karvonen; M.-L. Latvala; J. Liinamaa; S. Booms; E. Castrén; H. Uusitalo · 2018 · Primary research
- Primary empirical supportLimiting / contraryImproving vision in adult amblyopia by perceptual learning
U. Polat; T. Ma-Naim; M. Belkin; D. Sagi · 2004 · Primary research
- Primary empirical supportLimiting / contraryRandomised trial of three treatments for amblyopia: Vision therapy and patching, perceptual learning and patching alone
R. Hernández-Andrés; M. Á. Serrano; A. Alacreu-Crespo; M. J. Luque · 2025 · Primary research
- Limiting / contraryTraining in contrast detection improves motion perception of sinewave gratings in amblyopia
F. Hou; C.-B. Huang; L. Tao; L. Feng; Y. Zhou; Z.-L. Lu · 2011 · Primary research
- Primary empirical supportLimiting / contraryPerceptual learning improves contrast sensitivity, visual acuity, and foveal crowding in amblyopia
M. Barollo; G. Contemori; L. Battaglini; A. Pavan; C. Casco · 2017 · Primary research
Read the complete evidence interpretation on the Power dossier.
Tutorial delivery controls
Learn, adapt, troubleshoot and resume
Progress is saved only in this browser on this device.
Step-by-step learner mode
Each activity includes its success check, a nearby accessible alternative and an “I’m stuck” correction path. Alternatives preserve the target where possible; when they change the task, Titan labels them as related rather than equivalent.
Lock the configuration
Record display, zoom, card size, distance, lighting, correction and whether one or both eyes are used.
Symbol size changes with every one of these choices.
A second person could reproduce the setup.
I’m stuck on this step
Reset: Re-read this authored instruction — “Record display, zoom, card size, distance, lighting, correction and whether one or both eyes are used.” — and its success check, then attempt only this step.
Possible snag: Zoom or switch devices mid-test.
Correction: Keep screen, zoom and brightness fixed.
Stop / get help: Seek urgent eye care for sudden vision loss, a curtain/shadow, new flashes/floaters with loss, severe eye pain or new double vision.
Learn the response rule
For each of the four groups on a row, say the odd arrow's position from 1 to 5 before the helper reveals the folded key. Do not revise a blurred answer after feedback.
One fixed question keeps the score about detail discrimination.
The learner gives four position answers on each of two large practice rows and can explain how positions are counted.
I’m stuck on this step
Reset: Re-read this authored instruction — “For each of the four groups on a row, say the odd arrow's position from 1 to 5 before the helper reveals the folded key. Do not revise a blurred answer after feedback.” — and its success check, then attempt only this step.
Possible snag: Study the answer and then report certainty.
Correction: Commit one response before the key.
Stop / get help: Seek urgent eye care for sudden vision loss, a curtain/shadow, new flashes/floaters with loss, severe eye pain or new double vision.
Start with obvious rows
Begin at 72 px and give all four group positions before checking or moving to the next size.
Easy rows establish the task without forcing strain.
Each row has four recorded positions and one confidence rating before feedback.
I’m stuck on this step
Reset: Re-read this authored instruction — “Begin at 72 px and give all four group positions before checking or moving to the next size.” — and its success check, then attempt only this step.
Possible snag: The result from “Begin at 72 px and give all four group positions before checking or moving to the next size.” does not yet meet this declared check: Each row has four recorded positions and one confidence rating before feedback.
Correction: Return to the start of “Start with obvious rows”, reduce complexity or pace, and repeat only the part needed to satisfy: “Each row has four recorded positions and one confidence rating before feedback.”
Stop / get help: Seek urgent eye care for sudden vision loss, a curtain/shadow, new flashes/floaters with loss, severe eye pain or new double vision.
Descend one row at a time
Continue toward smaller rows while keeping head and card at the mark and using the same allowed viewing time.
Leaning or zooming makes a smaller symbol larger.
Distance and zoom remain unchanged.
I’m stuck on this step
Reset: Re-read this authored instruction — “Continue toward smaller rows while keeping head and card at the mark and using the same allowed viewing time.” — and its success check, then attempt only this step.
Possible snag: Lean closer on difficult rows.
Correction: Keep the marked viewing distance.
Stop / get help: Seek urgent eye care for sudden vision loss, a curtain/shadow, new flashes/floaters with loss, severe eye pain or new double vision.
Use a stopping rule
Stop at the 24 px row or earlier for blur that persists after ordinary blinking, headache, eye pain, nausea or other visual discomfort; never repeat a row to improve its count.
The fixture reports performance by size and does not need a clinical-style threshold chase.
The end reason is 24 px or a named symptom, and no row is replayed.
I’m stuck on this step
Reset: Re-read this authored instruction — “Stop at the 24 px row or earlier for blur that persists after ordinary blinking, headache, eye pain, nausea or other visual discomfort; never repeat a row to improve its count.” — and its success check, then attempt only this step.
Possible snag: Squint and repeat until the row is memorised.
Correction: End after the declared errors or discomfort.
Stop / get help: Seek urgent eye care for sudden vision loss, a curtain/shadow, new flashes/floaters with loss, severe eye pain or new double vision.
Score from the key
Compare the four positions with the folded key, record 0–4 correct for each size and retain every wrong position; do not convert a home row to Snellen or logMAR.
The fixture lacks clinical calibration.
Raw row accuracy and confidence remain visible.
I’m stuck on this step
Reset: Re-read this authored instruction — “Compare the four positions with the folded key, record 0–4 correct for each size and retain every wrong position; do not convert a home row to Snellen or logMAR.” — and its success check, then attempt only this step.
Possible snag: The result from “Compare the four positions with the folded key, record 0–4 correct for each size and retain every wrong position; do not convert a home row to Snellen or logMAR.” does not yet meet this declared check: Raw row accuracy and confidence remain visible.
Correction: Return to the start of “Score from the key”, reduce complexity or pace, and repeat only the part needed to satisfy: “Raw row accuracy and confidence remain visible.”
Stop / get help: Seek urgent eye care for sudden vision loss, a curtain/shadow, new flashes/floaters with loss, severe eye pain or new double vision.
Retest with a new ladder
After at least 48 hours, use the second ladder in the identical setup.
A new item reduces memorisation of the symbol sequence.
Configuration matches and item order is unfamiliar.
I’m stuck on this step
Reset: Re-read this authored instruction — “After at least 48 hours, use the second ladder in the identical setup.” — and its success check, then attempt only this step.
Possible snag: Call the row clinical acuity or superhuman eyesight.
Correction: Call it odd-symbol discrimination at this setup.
Stop / get help: Seek urgent eye care for sudden vision loss, a curtain/shadow, new flashes/floaters with loss, severe eye pain or new double vision.
Correct versus incorrect execution
These accessible process diagrams are built from the tutorial’s own right/wrong teaching. They are not anatomical illustrations and do not add technique beyond the canonical tutorial.
Keep the marked viewing distance.
Lean closer on difficult rows.
Keep screen, zoom and brightness fixed.
Zoom or switch devices mid-test.
Commit one response before the key.
Study the answer and then report certainty.
End after the declared errors or discomfort.
Squint and repeat until the row is memorised.
Call it odd-symbol discrimination at this setup.
Call the row clinical acuity or superhuman eyesight.
Method-structure checklist
10 of 10 structural checks present
- Ordered, Power-specific instructions — present
- Every activity has a success check — present
- Materials or supplied records are declared — present
- Measurement or assessment rule is present — present
- Tutorial-specific troubleshooting is present — present
- Stopping or escalation boundary is present — present
- Every activity has an adjacent alternative — present
- Correct-versus-incorrect comparison is present — present
- Evidence context is bound to the Power record — present
- Planning metadata is present — present
The method-readiness band and presence checklist assess tutorial presentation and are separate from evidence quality for the underlying Power. They are automated editorial aids, not human approval.
Manual editorial sign-off: Pending. This tutorial must not display a human-approved state until an identified editor signs the exact content hash.