Type the numbers on your glasses prescription and see a street, a page or your own photo the way your eyes see it without glasses. Free, and nothing leaves your browser.
This is only a simulation. It is not an eye test and not a substitute for an eye exam. Please consult an optometrist or ophthalmologist about your eyes.
Both eyes the same
← nearsighted / farsighted →
Nearsighted: things farther than about 50 cm blur.
0 = no astigmatism
Astigmatism: 0.75 D difference between the two directions.
The line shows the model’s blur direction at the focal point.
The two directions differ by less than 30% in blur here; rotation may be subtle.
Pure sphere: sets SPH and clears CYL and ADD.
Saved only in this browser. Nothing is uploaded.
Drag the picture or use arrow keys to pan; Shift moves farther.
Your sphere, cylinder and axis describe the power and direction of your lenses.
Compound myopic astigmatism
Principal meridians · eye relaxed
Compound myopic astigmatism
SPH + CYL / 2; a power summary, not the same directional blur.
Enclosing 0.25 D steps: −2.50 / −2.25 D
Grades follow the NHC myopia guideline (2026), based on spherical equivalent after cycloplegic refraction. A glasses prescription gives an estimate, not a diagnosis. NHC guideline
The same eyes, at five distances: from a street sign to the phone in your hands.
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Letter heights: street sign 15 cm; shop sign 8 cm; poster 3 cm; computer 3 mm; phone 2 mm.
This is only a simulation. It is not an eye test and not a substitute for an eye exam. Please consult an optometrist or ophthalmologist about your eyes.
Look at the street together. Slide the line to see the clear picture and the picture with blur, then try the buttons to see how the blur grows.
Street · far away · Detail 4×
How far you can see clearly: 50 cm
Model with accommodation relaxed
This is only a simulation. It is not an eye test and not a substitute for an eye exam. Please consult an optometrist or ophthalmologist about your eyes.
Compare the same street sign from 0.00 to −10.00 D, with a 3 mm daylight pupil.
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A street sign 20 m away, letters 15 cm tall.
This is only a simulation. It is not an eye test and not a substitute for an eye exam. Please consult an optometrist or ophthalmologist about your eyes.
It uses geometric optics. Each direction of your prescription puts light out of focus by a known amount, and the size of that blur grows with your pupil. At that scale the smallest line you could read is about as tall as the blur, which matches published acuity data for nearsighted eyes. It leaves out diffraction and the way your brain sharpens what it sees, so treat it as a close illustration, not a measurement.
Nearsightedness can be cancelled by holding things close. Cylinder blur cannot, so some of it stays at every distance. In a lab study, small amounts of astigmatism cost about twice as much acuity as plain defocus of the same strength.
How far your eyes can still refocus for near work. The page estimates it from your age with Hofstetter's average formula; you can set it yourself.
Your pupil opens in the dark, and a wider pupil spreads the same focus error over a larger blur. Pupil size against light level: Watson and Yellott, Journal of Vision, 2012.
Yes. Enter a plus SPH, your ADD and your age, and open the reading scene.
No. Photos, camera frames and your numbers stay in this browser.
I've worn glasses since middle school and gone through dozens of pairs. My prescription barely changed, but every time I got new glasses I couldn't remember my numbers, or even roughly what my prescription was. Every time I looked at the slip, I had to look it all up again.
Later, my son and his friends started wearing glasses one after another. Before he became nearsighted, my son thought it was no big deal. After, he felt the world just wasn't as bright any more.
So I built this site. First, as a useful tool: when you need it, you can understand your numbers right away, without searching, converting or wading through explanations. Second, so the people I care about can see for themselves what nearsightedness and astigmatism do to your vision.
— The maker of Eyesight Simulator
A picture to talk about, with limits you can read.
Is it accurate? It uses geometric optics. Each direction of your prescription puts light out of focus by a known amount, and the size of that blur grows with your pupil. At that scale the smallest line you could read is about as tall as the blur, which matches published acuity data for nearsighted eyes. It leaves out diffraction and the way your brain sharpens what it sees, so treat it as a close illustration, not a measurement.
Why is near still blurry with astigmatism? Nearsightedness can be cancelled by holding things close. Cylinder blur cannot, so some of it stays at every distance. In a lab study, small amounts of astigmatism cost about twice as much acuity as plain defocus of the same strength.
What does my age change? How far your eyes can still refocus for near work. The page estimates it from your age with Hofstetter's average formula; you can set it yourself.
Why is the night street worse? Your pupil opens in the dark, and a wider pupil spreads the same focus error over a larger blur. Pupil size against light level: Watson and Yellott, Journal of Vision, 2012.
Does it work for farsighted and reading glasses? Yes. Enter a plus SPH, your ADD and your age, and open the reading scene.
Is my photo uploaded? No. Photos, camera frames and your numbers stay in this browser.
The acuity comparison is a sanity check on angular scale only; simulated reading performance has not been measured. Accommodation is an average estimate.
Sources: Smith, Relation between spherical refractive error and visual acuity, Optometry and Vision Science, 1991. Raasch, Spherocylindrical refractive errors and visual acuity, Optometry and Vision Science, 1995. Atchison and Mathur, Visual acuity with astigmatic blur, Optometry and Vision Science, 2011. Watson and Yellott, A unified formula for light-adapted pupil size, Journal of Vision, 2012. Rushton, Armstrong and Dunne, The influence on unaided vision of age, pupil diameter and sphero-cylindrical refractive error, Clinical and Experimental Optometry, 2016. National Health Commission, 《近视防治指南（2026年版）》 (myopia grades).
The letters, the lenses, and the people behind the numbers.
Eyesight Simulator
