Endmyopia Wiki - User contributions [en]

Guide talk:Reducing lens complexity

2020-06-16T01:23:37Z

Iceghoul:

==Reduction Example==
{{re|Iceghoul}}I modified your example because it didn't look quite right to me. The differentials weren't consistently 1.25 diopters lower than the normalized and that's why I changed it but if you intended what you had then change it back! Maybe we should use a table to organize the layout...perhaps that will help clarify the example? | [[User:Deadpan|Deadpan]] ([[User talk:Deadpan|talk]]) 22:28, 15 June 2020 (UTC)

{{re|Deadpan}} Okay, that's fine. I usually have to go really low for accurate diffs.

Guide talk:Reducing lens complexity

2020-06-16T01:23:06Z

Iceghoul: /* Reduction Example */

==Reduction Example==
{{re|Iceghoul}}I modified your example because it didn't look quite right to me. The differentials weren't consistently 1.25 diopters lower than the normalized and that's why I changed it but if you intended what you had then change it back! Maybe we should use a table to organize the layout...perhaps that will help clarify the example? | [[User:Deadpan|Deadpan]] ([[User talk:Deadpan|talk]]) 22:28, 15 June 2020 (UTC)

@Deadpan Okay, that's fine. I usually have to go really low for accurate diffs.

Overprescription

2020-06-15T16:59:15Z

Iceghoul:

{{Under_construction}}
'''Overprescription''' is where an [[optometrist]] prescribes more [[diopter]]s than you need to see clearly.

This is easily done, as any perceived benefit from the additional lenses given is often on the fringes of making any real difference in your eyesight. It might be very minor, but once the optometrist is aware there is ''some improvement'' in eyesight, no matter how small, often the additional diopters remain. It is not uncommon for optometrists to correct to more than 20/20, such as 20/15. This may be done to give you the best possible vision at all times, including low light conditions such as night driving. The problem with this is that the majority of myopes spend a lot of time wearing these powerful glasses up close, which contributes to [[hyperopic defocus]].

Standard lens are only available in 0.25D increments, so the optometrist cannot give you the exact strength you need. Rounding towards the weaker strength would introduce (a very slight) [[blur]], so it's not unreasonable (from their perspective) that they might choose to round towards the stronger end.

Overprescription is very easy to correct by wearing less diopters. The wearer never needed those diopters in the first place.

[[Category:Articles]]

Snellen chart

2020-06-15T16:56:16Z

Iceghoul:

{{Under_construction}}
A '''Snellen chart''' is a standard method of measuring [[visual acuity]]. A chart is rated for the distance it should be viewed at, and the lowest line that can be read has a visual acuity result number next to it. The standard distance for Snellen charts is 20 feet or 6 meters. Smaller versions are available for use in smaller indoor spaces. Generally, the [[20/20]] line is the baseline to which your optometrist will aim for your vision correction. The Snellen chart is the most commonly used way of testing if someone has sufficient corrected visual acuity to drive legally. There is no direct correlation between visual acuity and [[myopia]]. Your [[optometrist]] will use the Snellen chart as a reference, to see what refraction will allow you to read the lowest on the chart.

==How to use a Snellen Chart to measure visual acuity==
# Read the documentation that came with your chart to determine what distance it is designed to be viewed at. This is usually 10 feet, 20 feet, 3 m or 6m. It may say right on the chart, on the back, or in the description of the product where you got it.
# Post the chart at eye level
# Make a mark on the floor at the distance the chart is rated for.
# Stand so that your face is above that line.
# Read the lowest line you can see clearly.
# Attempt to read the next line down.
# Have an assistant tell you if you got the letters right or move forward to check. If you got most of the letters right on that line, then the ratio marked for that line is your visual acuity.

==How to use a Snellen Chart with refraction==
{{main|Trial lens kit}}

==Tools==
*[https://www.provisu.ch/images/PDF/Snellenchart_en.pdf Printable Snellen]

==References==
{{reflist}}

[[Category:Articles]]

Measurement

2020-06-15T16:55:46Z

Iceghoul: /* Tools */

{{Under_construction}}

== cm Measurement ==
A simple test for your level of myopia is to hold a ruler up to your eye, and measure how far away you can still read text without [[blur]]. If you measure this distance in centimetres, this is your "cm measurement". The ideal precise measurement is from the surface of your eyeball, but this is obviously not safe, so measure from some facial structure near your eye. Consistency is more important than accuracy, you want to be able to track your small changes over the course of a day, and larger changes over time.

[[Diopters]] = -100cm/cm measurement.

This test is fairly accurate up to about -10 Diopters. This is not corrected for [[vertex distance]], but below -4D vertex distance has no significant effect, and your [[normalized]] lenses should be a little low anyway.

== Trial Refraction ==
If your vision is worse than -10D, you may need a [[trial lens kit]] to measure your own myopia, or you may just stick to professional [[optometrist]] exams.

<youtube>n2ku6gJ3z7E</youtube>

== Tools ==
* [https://endmyopia.org/focal-calculator/calc.html EndMyopia lens check Calculator]
*[https://community.endmyopia.org/t/vision-log-tool-for-windows-test-version-current-0-1-3/5945 Varakari's Vision Log Tool]

==References==
{{reflist}}
[[Category:Articles]]

Measurement

2020-06-15T16:49:00Z

Iceghoul: /* Tools */

Measurement

2020-06-15T16:42:49Z

Iceghoul: Reverted edits by Iceghoul (talk) to last revision by Dlskidmore

Measurement

2020-06-15T16:40:22Z

Iceghoul: /* Cm Measurement */

{{Under_construction}}

== Cm Measurement ==
A simple test for your level of myopia is to hold a ruler up to your eye, and measure how far away you can still read text without [[blur]]. If you measure this distance in centimeters, this is your "cm measurement". The ideal precise measurement is from the surface of your eyeball, but this is obviously not safe, so measure from some facial structure near your eye. Consistency is more important than accuracy, you want to be able to track your small changes over the course of a day, and larger changes over time.

[[Diopters]] = -100cm/cm measurement.

This test is fairly accurate up to about -10 Diopters. This is not corrected for [[vertex distance]], but below -4D vertex distance has no significant effect, and your [[normalized]] lenses should be a little low anyway.

== Trial Refraction ==
If your vision is worse than -10D, you may need a [[trial lens kit]] to measure your own myopia, or you may just stick to professional [[optometrist]] exams.

<youtube>n2ku6gJ3z7E</youtube>

== Tools ==
* [https://endmyopia.org/focal-calculator/calc.html EndMyopia lens check Calculator]
*[https://community.endmyopia.org/t/vision-log-tool-for-windows-test-version-current-0-1-3/5945 Varakari's Vision Log Tool]

==References==
{{reflist}}
[[Category:Articles]]

Measurement

2020-06-15T16:39:43Z

Iceghoul:

{{Under_construction}}

== Cm Measurement ==
A simple test for your level of myopia is to hold a ruler up to your eye, and measure how far away you can still read text without [[blur]]. If you measure this distance in centimetres, this is your "cm measurement". The ideal precise measurement is from the surface of your eyeball, but this is obviously not safe, so measure from some facial structure near your eye. Consistency is more important than accuracy, you want to be able to track your small changes over the course of a day, and larger changes over time.

[[Diopters]] = -100cm/cm measurement.

This test is fairly accurate up to about -10 Diopters. This is not corrected for [[vertex distance]], but below -4D vertex distance has no significant effect, and your [[normalized]] lenses should be a little low anyway.

== Trial Refraction ==
If your vision is worse than -10D, you may need a [[trial lens kit]] to measure your own myopia, or you may just stick to professional [[optometrist]] exams.

<youtube>n2ku6gJ3z7E</youtube>

== Tools ==
* [https://endmyopia.org/focal-calculator/calc.html EndMyopia lens check Calculator]
*[https://community.endmyopia.org/t/vision-log-tool-for-windows-test-version-current-0-1-3/5945 Varakari's Vision Log Tool]

==References==
{{reflist}}
[[Category:Articles]]

Guide:Reducing lens complexity

2020-06-15T16:33:05Z

Iceghoul: /* How to reduce lens complexity */

{{Under_construction}}

TODO: this article needs to be expanded for edge cases like already low diopters.

==When to reduce lens complexity==

[[Lens complexity]] is best reduced before getting into the [[low diopters]] range. Ideally, both eyes would be equal before -1.5 [[diopters]]. (TODO: cite an EM source for this)

==How to reduce lens complexity==

'''Make your first reduction a simple [[spherical]] reduction. This will teach you the basics of the [[EndMyopia]] methods.'''

There are two types of reductions:

* <div>A simple reduction is a 0.25 [[diopter]] drop in lense power for both eyes, simultaneously</div>
* <div>An equalizing reduction is a 0.25 [[diopter]] drop in lense power for one eye, the eye with greater correction (more negative)</div>

An equalizing reduction is done to bring the eyes closer to having the same level of correction.

Either type of reduction can be applied to [[spherical]] power or [[cylindrical]] power.

There are three rules for reducing complexity:
# <div>Alternate types of reductions. Simple -> Equalizing -> Simple -> Equalizing...</div>
# <div>Change only spherical or only cylindrical and never both simultaneously</div>
# <div>When equalizing, change both differential lenses and normalized lenses simultaneously to keep the [[focal planes]] in sync.</div>

'''Example'''

Normalized

Left Eye: -3.50 -> -3.25 -> '''-3.25''' -> -3.00
Right Eye: -4.00 - > -3.75 -> '''-3.50''' -> -3.25

Differentials

Left Eye: -2.25 -> -2.00 -> '''-1.75''' -> -1.50
Right Eye: -1.75 -> -1.50 -> '''-1.50''' -> -1.50

==References==
{{reflist}}

==See also==

[[Guide:Resolving double vision]]

[[Category:Guides]]