Section 249 of 440
Complete canonical tutorial. This reader section contains the same teaching body as PWR-066 · Contrast sensitivity. Open the Power dossier.
PWR-066 · SELF GUIDED full tutorial
Judge stripe orientation as contrast falls while keeping luminance and size fixed
Contrast sensitivity can be trained in some clinical settings, but a better test threshold is not generally enhanced vision. This fixture teaches contrast discrimination for one pattern set. The learner begins with obvious stripes, reports orientation before feedback, descends a fixed ladder and retests unfamiliar items. It is not a clinical contrast-sensitivity function and should not be used to clear night driving. The learner also uses catch trials at clearly visible contrast to tell a true low-contrast limit from loss of attention or a habitual orientation response.
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 patch recipe for a helper using a slide or drawing program. Make every patch 8 cm square with ten equal stripes and a mean grey of RGB 128/128/128. Alternate stripe greys by level: 1 = 64 and 192; 2 = 96 and 160; 3 = 112 and 144; 4 = 120 and 136; 5 = 124 and 132; 6 = 126 and 130. Rotate the same stripe tile to horizontal H, vertical V or 45-degree diagonal D; export all patches at one pixel size with no labels visible to the learner.
- Two folded 18-trial keys. Set A is 1H,1V,1D,2V,2D,2H,3D,3H,3V,4H,4V,4D,5V,5H,5D,6D,6V,6H. Set B is 1D,1H,1V,2H,2V,2D,3V,3D,3H,4D,4H,4V,5H,5D,5V,6V,6H,6D. The helper inserts an unscored level-1 catch patch after trials 4, 8, 12 and 16, with concealed H/V/D order.
- A fixed viewing-distance marker and ordinary correction.
- Answer key and trial sheet.
Before you start
- Set comfortable room light and eliminate screen glare.
- Fix display brightness, colour mode, zoom and viewing distance.
- Use the ordinary correction for that distance.
- Do not use the fixture during migraine aura, acute eye symptoms or a photosensitive episode.
3 · The method
Follow these steps in order
- Fix luminance and geometry
Record screen, brightness, room light, patch size and viewing distance.
Why: Contrast depends on background luminance and display behaviour.
Check: All configuration fields are filled.
- Learn orientations
Practise naming the high-contrast horizontal, vertical and diagonal patches.
Why: The response labels must be known before contrast falls.
Check: All practice orientations are named correctly.
- Begin above threshold
Start with an obvious contrast level and view each patch for the same declared time.
Why: Starting easy confirms the task and avoids immediate guessing.
Check: The first two trials are correct without strain.
- Answer before feedback
State orientation and confidence, then reveal the key.
Why: A committed response preserves discrimination data.
Check: Every trial has a pre-feedback answer.
- Descend the ladder
Present the three concealed H/V/D patches at level 1, then levels 2 through 6 in the supplied set order. Give one H, V or D answer per patch and do not skip a level after an error.
Why: A fixed adaptive rule and mixed directions reduce pattern guessing.
Check: Each level has exactly one valid H, V and D trial before the next level begins.
- Stop at repeated uncertainty
Stop after level 6 or earlier for glare, headache, visual disturbance or a missed level-1 catch trial that remains wrong after rest; do not raise brightness or repeat faint patches.
Why: Changing brightness invalidates contrast and chasing faint items adds strain.
Check: The stop reason is recorded.
- Retest novel patterns
After a delay, use a new orientation order at identical settings.
Why: Novel order distinguishes task learning from memorising the sequence.
Check: Settings match and items are unfamiliar.
- Insert visible catch trials
After every four difficult patches, present one clearly visible patch in a concealed orientation. If that catch trial is wrong, pause and mark the preceding difficult group as attention-affected rather than lowering contrast again.
Why: A high-contrast catch trial should remain easy. Missing it suggests fatigue, response-key confusion or a lapse rather than a new contrast threshold.
Check: Catch-trial orientation is correct, or the affected group is labelled and the learner rests before continuing.
4 · Worked example
See the whole method used once
Scenario
Ari views striped patches at 70 cm on one monitor at fixed brightness.
Walkthrough
- Ari records the monitor, brightness, room lamp, patch size and correction.
- They correctly name three high-contrast practice orientations.
- They descend the ladder, answer before feedback and retain every error.
- They stop after three errors across four low-contrast trials without changing brightness.
- At the next session, a novel direction order gives slightly better accuracy at the same middle levels.
- At the midpoint, Ari misses a clearly visible diagonal catch patch, so the preceding four faint trials are labelled attention-affected and are not used as the best level.
Result
The result is improved orientation discrimination for this fixed patch set. It is not a clinical contrast-sensitivity curve or evidence of safer low-light vision. The catch-trial rule prevents a tired response run from being mistaken for a change in visual contrast processing.
5 · Right and wrong
Compare correct or safer execution with the common wrong version
| Moment | Right / safer | Wrong / riskier | Why it matters |
|---|---|---|---|
| Luminance | Keep display brightness and room light fixed. | Increase brightness when a patch fades. | That changes the physical contrast task. |
| Orientation | Mix directions and answer before feedback. | Use a repeating orientation order. | Order guessing can inflate accuracy. |
| Threshold | Use a declared error rule across several trials. | Call one lucky faint answer the threshold. | Threshold-like estimates require repeated choices. |
| Symptoms | Stop for glare, headache or visual disturbance. | Push through because faintness is expected. | Discomfort is not a training target. |
| Claim | Report levels on this display. | Infer safe night driving or clinical recovery. | Display-specific discrimination does not establish function. |
| Visible catch trial | Use an occasional easy patch to confirm attention and response mapping. | Keep descending after an easy patch is missed and call the result poorer contrast sensitivity. | An easy-item miss signals that the trial block, not only contrast, has changed. |
6 · Common mistakes
Spot the error and apply the correction
| Mistake | Fix |
|---|---|
| Increase brightness when a patch fades. | Keep display brightness and room light fixed. |
| Use a repeating orientation order. | Mix directions and answer before feedback. |
| Call one lucky faint answer the threshold. | Use a declared error rule across several trials. |
| Push through because faintness is expected. | Stop for glare, headache or visual disturbance. |
| Infer safe night driving or clinical recovery. | Report levels on this display. |
| The learner repeatedly presses the same orientation key on uncertain patches, creating a response bias. | Count answers by orientation, rebalance the concealed order and pause after any run of four identical responses. |
7 · Practice
Turn the steps into a usable skill
First session
- A helper builds all six RGB stripe levels, exports one H/V/D patch at each level and folds the A and B keys before the learner sees filenames.
- Lock the display mode, brightness, 70 cm distance, room lighting and ordinary correction, then practise H, V and D on level 1.
- Run Set A in its 18-trial concealed order with the four unscored catch patches and one answer before feedback.
- Score H/V/D separately at every level and label any four-trial group before a missed catch as attention-affected.
- After at least 48 hours, run Set B at unchanged settings and compare level-by-level orientation counts rather than declaring a clinical threshold.
Repeat plan
Practise one short ladder on up to two days per week. Use new orders and hold the display constant. Progress means reliable novel-item accuracy, not lower contrast at any cost.
Progress when
- Accuracy improves across several adjacent levels on novel items.
- Orientation errors fall without brightness or distance changes.
- No glare, headache or visual symptom occurs.
Do not progress when
- A device, colour mode or lighting change makes sessions incomparable.
- One-eye difference, persistent blur or contrast difficulty affects daily life.
- The learner uses the score for driving or clinical clearance.
8 · Check the result
Measure what changed
H/V/D orientation accuracy across the six supplied display-grey pairs
How: Record correct/incorrect orientation and confidence by contrast level, plus display, luminance setting, distance and symptoms. Report catch-trial accuracy and response counts for each orientation so an orientation-key bias is visible.
Good result: Both concealed sets reproduce from their keys, easy catch trials remain correct and level-by-level errors are reported at unchanged display settings. Better Set B accuracy is a fixture result, not a contrast-sensitivity threshold or driving clearance.
This does not prove: Record a full contrast-sensitivity function or validated bounded threshold at declared luminance and correction; do not substitute chart acuity or subjective sharpness.
Self-check
- Can you demonstrate “Learn orientations”? All practice orientations are named correctly.
- Can you demonstrate “Answer before feedback”? Every trial has a pre-feedback answer.
- Can you demonstrate “Retest novel patterns”? Settings match and items are unfamiliar.
- When a visible catch patch is missed, can you explain why the nearby faint trials must be held out instead of being interpreted as a contrast limit?
9 · Stop, adapt or get help
Keep the safety boundary practical
Stop and get help
- Stop for eye pain, migraine aura, nausea, headache, persistent afterimage or sudden visual change.
- Seek urgent eye care for sudden vision loss, new field loss or painful red eye.
- Arrange professional testing when contrast problems affect mobility, faces or driving.
Accessibility and adaptations
- Use spoken orientation answers or switches without adding a speed score.
- Increase the physical patch size only as a declared new accessibility configuration.
- Provide non-glare surrounds and breaks while keeping the tested contrast values unchanged.
10 · Evidence and limits
Why these instructions are here
- primary research
Controlled perceptual-learning research supports task-specific contrast-sensitivity change in amblyopia.
Perceptual learning improves contrast sensitivity and visual acuity in adults with anisometropic amblyopia - primary research
Primary research reports transfer from contrast training to a defined motion task, showing that transfer must be measured rather than assumed.
Training in contrast detection improves motion perception of sinewave gratings in amblyopia
Limits
- Record a full contrast-sensitivity function or validated bounded threshold at declared luminance and correction; do not substitute chart acuity or subjective sharpness.
- Unsupported claim: See through darkness.
- Unsupported claim: Make every visual task sharper.
- Unsupported claim: Repair the retina by gaming.
- A home display cannot provide a clinical contrast-sensitivity function or prove safe performance in traffic or dim environments.
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
- Primary empirical supportLimiting / 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.
Fix luminance and geometry
Record screen, brightness, room light, patch size and viewing distance.
Contrast depends on background luminance and display behaviour.
All configuration fields are filled.
I’m stuck on this step
Reset: Re-read this authored instruction — “Record screen, brightness, room light, patch size and viewing distance.” — and its success check, then attempt only this step.
Possible snag: Increase brightness when a patch fades.
Correction: Keep display brightness and room light fixed.
Stop / get help: Stop for eye pain, migraine aura, nausea, headache, persistent afterimage or sudden visual change.
Learn orientations
Practise naming the high-contrast horizontal, vertical and diagonal patches.
The response labels must be known before contrast falls.
All practice orientations are named correctly.
I’m stuck on this step
Reset: Re-read this authored instruction — “Practise naming the high-contrast horizontal, vertical and diagonal patches.” — and its success check, then attempt only this step.
Possible snag: The result from “Practise naming the high-contrast horizontal, vertical and diagonal patches.” does not yet meet this declared check: All practice orientations are named correctly.
Correction: Return to the start of “Learn orientations”, reduce complexity or pace, and repeat only the part needed to satisfy: “All practice orientations are named correctly.”
Stop / get help: Stop for eye pain, migraine aura, nausea, headache, persistent afterimage or sudden visual change.
Begin above threshold
Start with an obvious contrast level and view each patch for the same declared time.
Starting easy confirms the task and avoids immediate guessing.
The first two trials are correct without strain.
I’m stuck on this step
Reset: Re-read this authored instruction — “Start with an obvious contrast level and view each patch for the same declared time.” — and its success check, then attempt only this step.
Possible snag: Call one lucky faint answer the threshold.
Correction: Use a declared error rule across several trials.
Stop / get help: Stop for eye pain, migraine aura, nausea, headache, persistent afterimage or sudden visual change.
Answer before feedback
State orientation and confidence, then reveal the key.
A committed response preserves discrimination data.
Every trial has a pre-feedback answer.
I’m stuck on this step
Reset: Re-read this authored instruction — “State orientation and confidence, then reveal the key.” — and its success check, then attempt only this step.
Possible snag: Use a repeating orientation order.
Correction: Mix directions and answer before feedback.
Stop / get help: Stop for eye pain, migraine aura, nausea, headache, persistent afterimage or sudden visual change.
Descend the ladder
Present the three concealed H/V/D patches at level 1, then levels 2 through 6 in the supplied set order. Give one H, V or D answer per patch and do not skip a level after an error.
A fixed adaptive rule and mixed directions reduce pattern guessing.
Each level has exactly one valid H, V and D trial before the next level begins.
I’m stuck on this step
Reset: Re-read this authored instruction — “Present the three concealed H/V/D patches at level 1, then levels 2 through 6 in the supplied set order. Give one H, V or D answer per patch and do not skip a level after an error.” — and its success check, then attempt only this step.
Possible snag: Infer safe night driving or clinical recovery.
Correction: Report levels on this display.
Stop / get help: Stop for eye pain, migraine aura, nausea, headache, persistent afterimage or sudden visual change.
Stop at repeated uncertainty
Stop after level 6 or earlier for glare, headache, visual disturbance or a missed level-1 catch trial that remains wrong after rest; do not raise brightness or repeat faint patches.
Changing brightness invalidates contrast and chasing faint items adds strain.
The stop reason is recorded.
I’m stuck on this step
Reset: Re-read this authored instruction — “Stop after level 6 or earlier for glare, headache, visual disturbance or a missed level-1 catch trial that remains wrong after rest; do not raise brightness or repeat faint patches.” — and its success check, then attempt only this step.
Possible snag: Push through because faintness is expected.
Correction: Stop for glare, headache or visual disturbance.
Stop / get help: Stop for eye pain, migraine aura, nausea, headache, persistent afterimage or sudden visual change.
Retest novel patterns
After a delay, use a new orientation order at identical settings.
Novel order distinguishes task learning from memorising the sequence.
Settings match and items are unfamiliar.
I’m stuck on this step
Reset: Re-read this authored instruction — “After a delay, use a new orientation order at identical settings.” — and its success check, then attempt only this step.
Possible snag: The result from “After a delay, use a new orientation order at identical settings.” does not yet meet this declared check: Settings match and items are unfamiliar.
Correction: Return to the start of “Retest novel patterns”, reduce complexity or pace, and repeat only the part needed to satisfy: “Settings match and items are unfamiliar.”
Stop / get help: Stop for eye pain, migraine aura, nausea, headache, persistent afterimage or sudden visual change.
Insert visible catch trials
After every four difficult patches, present one clearly visible patch in a concealed orientation. If that catch trial is wrong, pause and mark the preceding difficult group as attention-affected rather than lowering contrast again.
A high-contrast catch trial should remain easy. Missing it suggests fatigue, response-key confusion or a lapse rather than a new contrast threshold.
Catch-trial orientation is correct, or the affected group is labelled and the learner rests before continuing.
I’m stuck on this step
Reset: Re-read this authored instruction — “After every four difficult patches, present one clearly visible patch in a concealed orientation. If that catch trial is wrong, pause and mark the preceding difficult group as attention-affected rather than lowering contrast again.” — and its success check, then attempt only this step.
Possible snag: The learner repeatedly presses the same orientation key on uncertain patches, creating a response bias.
Correction: Count answers by orientation, rebalance the concealed order and pause after any run of four identical responses.
Stop / get help: Stop for eye pain, migraine aura, nausea, headache, persistent afterimage or sudden visual change.
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 display brightness and room light fixed.
Increase brightness when a patch fades.
Mix directions and answer before feedback.
Use a repeating orientation order.
Use a declared error rule across several trials.
Call one lucky faint answer the threshold.
Stop for glare, headache or visual disturbance.
Push through because faintness is expected.
Report levels on this display.
Infer safe night driving or clinical recovery.
Use an occasional easy patch to confirm attention and response mapping.
Keep descending after an easy patch is missed and call the result poorer contrast sensitivity.
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.