How to Measure Lenses Without a Phoropter
Many parts of the world lack access to adequate and affordable eye care. Yet measuring lens diopter (UK: dioptre) and cylinder is mathematically-precise. It is the reciprocal of the focal length in meters. Measurements are additive, so multiple lenses may be stacked together. With simple calculations and a measuring stick, anyone could look at a chart, fudge some numbers, and order cheap glasses online, check prescriptions, or notice if their eyesight is changing.*
Myopia and Astigmatism Calculator
SPH:
CYL:
Axis:
- Use a desktop computer or large tablet.
- Remove eyeware, or look through lens to be tested.
- Cover one eye while keeping head level.
- Move back from the above diagram until only some lines are clear.
- Click the line that is least blurry.
- If two lines are clear, click between them.
- Use cloth tape or tape measure to get accurate measurements from eye to screen.
Reading glasses: For best results, consult a doctor, try on reading glasses at the store, or view the reading glasses tests at readers.com.
Disclaimer
*For educational purposes only. There is no substitute for visiting an eye professional every two years. They can spot eye diseases that if caught early could prevent serious problems later on. Lens calculations depend on the operator and the quality of measurements. As little as 1/4" makes a big difference.
This electronic document is provided with absolutely no warranty, neither expressed nor implied!
[[ contact ]] class="myButton imaged"
[email protected]
[[ games ]] style="height:18px" class="myButton imaged" #
[[ blackjack 21 ]] class="myButton imaged" title="card game" blackjack.html
[[ find-a-word ]] class="myButton imaged" title="word search puzzle maker" wordsearch.html
[[ crosswords ]] class="myButton imaged" title="crossword puzzle maker" crossword.html
[[ maze generator ]] class="myButton imaged" title="maze widget" amaze.html
[[ game videos ]] class="myButton imaged" //www.youtube.com/playlist?list=PL103CE0161E522511
[[ more games ]] class="myButton imaged" //spins.fedoraproject.org/games/
[[ videos ]] style="height:18px" class="myButton imaged" #
[[ channel ]] class="myButton imaged" //www.youtube.com/themanyone
[[ top videos ]] class="myButton imaged" //www.youtube.com/playlist?list=PL450B634DCEFC261F
[[ game vids ]] class="myButton imaged" //www.youtube.com/playlist?list=PL103CE0161E522511
[[ promotional ]] class="myButton imaged" //www.youtube.com/playlist?list=PL9CFBCB30DAACD82D
[[ nerd science ]] class="myButton imaged" //www.youtube.com/playlist?list=PL19886EB346B7FDBA
[[ programming ]] class="myButton imaged" //www.youtube.com/playlist?list=PLD3F0E68A16FBAB28
[[ music ]] class="myButton imaged" //www.youtube.com/playlist?list=PL185031EE219C3DD8
[[ blender ]] class="myButton imaged" //www.youtube.com/playlist?list=PLBA39F8A451E68BF3
[[ video blog ]] class="myButton imaged" //www.youtube.com/playlist?list=PL5F04A5DEEB16ABE2
[[ music ]] style="height:18px" class="myButton imaged" #
[[ cd on amazon ]] class="myButton imaged" //www.amazon.com/Summertime-Heat/dp/B003C32AUA/ref=sr_1_1?ie=UTF8%26qid=1381990690%26sr=8-1%26keywords=henry+kroll+iii
[[ on itunes ]] class="myButton imaged" //itunes.apple.com/us/album/change-the-world/id359241770
[[ our sites ]] style="height:18px" class="myButton imaged" title="sites we manage" #
[[ thenerdshow ]] class="myButton imaged" title="Free apps, news, videos, and reviews" //thenerdshow.com
[[ anch.org ]] class="myButton imaged" title="All Nations Community Health" //anch.org
[[ fails.us ]] class="myButton imaged" title="Start Your Own Social Media Site Here" //fails.us
[[ comptune.com ]] class="myButton imaged" title="PC Repair and Support" //comptune.com
[[ guarddogbooks]] class="myButton imaged" title="Dad's site" //guarddogbooks.com
[[ hank kroll ]] class="myButton imaged" title="Dad's site" //hankkroll.com
[[ articles ]] style="height:18px" class="myButton imaged" title="news, reviews, and hacks" #
[[ 3D AR ]] class="myButton imaged" title="Our Take on 3D Augmented Reality" 3d.html
[[ audio ]] class="myButton imaged" title="Linux Audio Recording" audio.html
[[ video ]] class="myButton imaged" title="Linux Video Recording" video.html
[[ voice typing ]] class="myButton imaged" title="Enable Voice Typing Everywhere" //github.com/themanyone/whisper_dictation
[[ crack PDF ]] class="myButton imaged" title="crack PDF files" crack%20PDF.html
[[ domes ]] class="myButton imaged" title="geodesic domes" domes.html
[[ fedora ]] class="myButton imaged" title="review of the fedora operating system" fedora.html
[[ high voltage ]] class="myButton imaged" title="adventures in TV repair" high%20voltage.html
[[ hosting ]] class="myButton imaged" title="hosting ad" hosting.html
[[ kernel ]] class="myButton imaged" title="building a fedora kernel rpm" kernel.html
[[ maze ]] class="myButton imaged" title="how our maze generator works" maze.html
[[ omnitech ]] class="myButton imaged" title="hacking WinCE GPS" omnitech.html
[[ responsive ]] class="myButton imaged" title="Responsive Web Design" responsive.html
[[ rooting ]] class="myButton imaged" title="Rooting Android Phones" rooting.html
[[ scite ]] class="myButton imaged" title="review of the scite text editor and ide" scite.html
[[ social media ]] class="myButton imaged" title="social media and business" social%20media.html
[[ solar cooker ]] class="myButton imaged" title="build a solar cooker for $1" solar%20cooker.html
[[ trig or treat ]] class="myButton imaged" title="happy Pythagorean Halloween" trig%20or%20treat.html
[[ wine ]] class="myButton imaged" title="how to run windows programs on Linux" wine.html
[[ zotero ]] class="myButton imaged" title="zotero: an indespensible research tool" zotero.html
[[ python ]] style="height:18px" class="myButton imaged" title="python development" #
[[ master control ]] class="myButton imaged" title="the ultimate multimedia controller and test center" master%20control.html
[[ freespeech ]] class="myButton imaged" title="speech recognition" freespeech.html
[[ crowbar ]] class="myButton imaged" title="twitter app" //code.google.com/p/crowbar/
[[ drive lister ]] class="myButton imaged" title="show Linux disk devices" fedora.html#Drive
[[ greenhorn ]] class="myButton imaged" title="python code inspector" //code.google.com/p/greenhorn/
[[ javascript ]] style="height:18px" class="myButton imaged" title="javascript development" #
[[ voice typing ]] class="myButton imaged" title="Online Editor with Voice Typing" ckeditor/plugins/speech/edit_help.html
[[ find-a-word ]] class="myButton imaged" title="word search puzzle maker" wordsearch.html
[[ big num calc ]] class="myButton imaged" title="big number calculator" calculator.html
[[ blackjack 21 ]] class="myButton imaged" title="card game" blackjack.html
[[ crosswords ]] class="myButton imaged" title="crossword puzzle maker" crossword.html
[[ more calculators ]] class="myButton imaged" title="various calculators" calculators.html
[[ social icons ]] class="myButton imaged" title="social media sharing" social%20icons.html
[[ js editor ]] class="myButton imaged" title="javascript editor" editor.html
[[ block art ]] class="myButton imaged" title="javascript editor" blocks.html
[[ eye test ]] class="myButton imaged" title="measure astigmatism and myopia" EyeTest.php
[[ firstpage ]] class="myButton imaged" title="Content Management System (CMS)" firstpage/
[[ gitblog ]] class="myButton imaged" title="Use GitHub as a blogging platform" gitblog/
[[ morse code ]] class="myButton imaged" title="Morse Code translator" morse%20code.html
[[ binary code ]] class="myButton imaged" title="Binary Code translator" binary.html
[[ bit rot ]] class="myButton imaged" title="ROT-13 ciphers" bit%20rot.html
[[ decrypt0r ]] class="myButton imaged" title="Easy cipher decryption" decrypt.html
[[ font fun ]] class="myButton imaged" title="Facebook fonts" fontfun.html
[[ snow ]] class="myButton imaged" title="Snow background" snow.html
[[ amaze ]] class="myButton imaged" title="maze widget" amaze.html
[[ artify ]] class="myButton imaged" title="artify the web" artify.html
[[ c, c++ ]] style="height:18px" class="myButton imaged" title="c development" #
[[ py embedding ]] class="myButton imaged" title="Embedding Python 2.7 on Linux x86_64 and Windows64 (wine)" embedding%20python.html
[[ gstreamer-1.0 ]] class="myButton imaged" title="Cross-compiling Gstreamer 1.0 with Mingw64" gstreamer.html
[[ gtk+ ]] class="myButton imaged" title="Cross-compiling GTK+ with Mingw64" GTK+.html
[[ platypus ]] class="myButton imaged" title="speech recognition for Linux, with wine" platypus.html
[[ motion tracker ]] class="myButton imaged" title="live video motion tracking" motion%20tracking.html
[[ asheron's call ]] class="myButton imaged" title="Asheron's Call bots" decal.html
[[ tape ]] class="myButton imaged" title="tape files together" gitblog/?a=themanyone&p=tape
[[ more... ]] class="myButton imaged" title="more c programs" c%20programs.html
[[ page styles ]] style="height:18px" class="myButton imaged" #
[[ circuits ]] class="myButton imaged" javascript:setActiveStyleSheet('preferred');
[[ easter ]] class="myButton imaged" javascript:setActiveStyleSheet('easter');
[[ evening ]] class="myButton imaged" javascript:setActiveStyleSheet('evening');
[[ club mix ]] class="myButton imaged" javascript:setActiveStyleSheet('clubmix');
[[ daylight ]] class="myButton imaged" javascript:setActiveStyleSheet('light');
[[ clover ]] class="myButton imaged" javascript:setActiveStyleSheet('clover');