Vision Screening & Rough Spectacles Power Estimator
Educational screening tool with zoom control, calibration,
eye-by-eye check, and result summary
⚠️ Screening tool only — not a prescription
Choose zoom, calibrate your screen, test each eye, and get a rough
estimate.
This app helps with a basic visual screening workflow. It lets the
user choose a zoom factor, calibrate the display against a real
card, view distance/near optotypes, try a blur-power adjustment,
screen for possible astigmatism, and see a rough result summary.
Zoom selector
Screen calibration
Left / right eye test
Power estimate slider
Astigmatism screening
Important
This is not a medical device and not a prescription generator.
Do not use this to order glasses or change an existing
prescription.
Stop if you feel eye strain, headache, dizziness, or discomfort.
Children, people with eye disease, recent surgery, or sudden
vision loss should seek professional care.
1
Warnings
Read and accept safety and accuracy limits.
2
Calibration
Match the card shape to a real bank card.
3
Optotype check
Pick the smallest clearly readable line.
4
Blur slider
Find the rough lens value that looks clearest.
5
Astigmatism + Results
Check if some directions look darker or sharper.
Step 1 — Safety and usage
Start only after reading the warnings. This tool can help with
basic screening, but it cannot provide a valid prescription.
⚠️ Do not use these results to order spectacles, change
prescription, or self-diagnose eye disease.
Not a medical device
Approximate values only
Professional exam still required
Step 2 — Screen calibration
Place a real bank card, ATM card, or similar card against the
screen. Use the slider until the on-screen rectangle matches the
real card size. Standard bank card size is about
85.6 mm × 53.98 mm.
Move until the on-screen card matches your real card
exactly.
Step 3 — Optotype line test
Pick the smallest line that is still clearly readable
E F P T O Z
L P E D
Zoom preview follows your selected factor
Distance mode: about 3 meters / 10 feet
Testing: Left eye
E F P T O Z
Step 4 — Rough spherical correction finder
Move the slider until the shown text looks clearest. This provides
only a rough estimate. Negative values suggest possible myopia.
Positive values suggest possible hyperopia or near-focus support.
Approximate blur adjustment
Testing: Left eye
C L E A R
0.00 D
Range: −8.00 D to +5.00 D in 0.25 D steps.
The app cannot accurately measure cylinder power, axis, or full
prescription requirements. Use this only as a rough self-screening
guide.
Step 5 — Astigmatism screening and results
Look at the dial below. If some directions appear darker, sharper,
or more distinct than others, there may be a possibility of
astigmatism. This is only a screening hint.
⚠️ These are approximate values. Consult an eye specialist.
Left eye
—
No estimate saved yet.
Right eye
—
No estimate saved yet.
Possible astigmatism screening
Not marked
No screening note yet.
Overall message
Professional check advised
Use this only as a preliminary indication. A full exam is
needed for exact spectacle power.
Complete the steps above to generate your screening summary.
Important warnings before using this tool
Please read carefully. This tool is for basic screening and
educational use only.
Primary disclaimer
This tool is NOT a medical device and does NOT provide a valid
eyeglass prescription.
It is only for basic vision screening and educational purposes.
Results may be inaccurate due to screen size, brightness,
viewing distance, lighting conditions, and user input.
Always consult a qualified optometrist or ophthalmologist for a
proper eye examination and prescription.
Accuracy limitations
This tool cannot accurately measure astigmatism cylinder power
and axis.
It cannot assess eye disease, binocular vision, or exact
prescription needs.
Any values shown are rough estimates only.
Usage conditions
Use in a well-lit room.
Maintain the instructed viewing distance.
Keep screen brightness comfortable.
Test one eye at a time when required.
Improper setup can lead to incorrect results.
Stop immediately if uncomfortable
Stop if you feel eye strain, headache, dizziness, blurred
vision, or double vision.
Do not continue if you feel uncomfortable.
High-risk users should not rely on this
Do not rely on this tool for children.
Do not rely on it if you have diabetes, known eye disease,
recent eye surgery, or sudden worsening of vision.
Seek professional medical advice instead.
Result interpretation
Do not use the results to order glasses online.
Do not use them to change an existing prescription.
Do not self-diagnose vision problems using this app.
Liability notice
By using this tool, you acknowledge that the results are
approximate and that the creators are not responsible for
decisions made based on these results.