Difference between revisions of Trial lens kit

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Medical: If you have any vision problems not compensated for by refraction, go see your [[optometrist]].
Medical: If you have any vision problems not compensated for by refraction, go see your [[optometrist]].


= Minimalist Trial Lens Kit =
== Minimalist Trial Lens Kit ==
A small kit that will allow you to test small changes to your wearing lenses would be:
A small kit that will allow you to test small changes to your wearing lenses would be:
* +/-0.25 and +/-0.5 [[#Flippers]]
* +/-0.25 and +/-0.5 [[#Flippers]]
Line 11: Line 11:
* [[Snellen Chart]]
* [[Snellen Chart]]


= Trial frames =
== Trial frames ==
Trial frames are frames which you can mount trial lenses in and wear like glasses.  They come in many forms, they may have lots of adjustments or come in fixed PD widths.  Using a frame with the correct PD is important so the wearer is looking through the optical centers of the lenses.  Adjust the frame for the best comfort and so the wearer is looking through the optical center of the lens.  A trial frame that holds four lenses and has axis adjustment is best.
Trial frames are frames which you can mount trial lenses in and wear like glasses.  They come in many forms, they may have lots of adjustments or come in fixed PD widths.  Using a frame with the correct PD is important so the wearer is looking through the optical centers of the lenses.  Adjust the frame for the best comfort and so the wearer is looking through the optical center of the lens.  A trial frame that holds four lenses and has axis adjustment is best.


== Placing lenses in the trial frame ==
=== Placing lenses in the trial frame ===
Always place the strongest lens in the stack closest to the eye to reduce the effects of [[vertex distance]].  Line up the lines on [[cylinder]] lenses with the [[axis]] of [[astigmatism]].  There may be a dial that helps rotate the cylinder lens.
Always place the strongest lens in the stack closest to the eye to reduce the effects of [[vertex distance]].  Line up the lines on [[cylinder]] lenses with the [[axis]] of [[astigmatism]].  There may be a dial that helps rotate the cylinder lens.


= Flippers =
== Flippers ==
Flip lenses are designed to be hand held in front of the trial lens or customary lenses and test plus vs minus at a set power.  Can be used to determine if the customary lenses need tweaking up or down.  They may be monocular or [[binocular]]  They are also used in [[vision training]].
Flip lenses are designed to be hand held in front of the trial lens or customary lenses and test plus vs minus at a set power.  Can be used to determine if the customary lenses need tweaking up or down.  They may be monocular or [[binocular]]  They are also used in [[vision training]].


= How to test myopia with a trial lens kit =
== How to test myopia with a trial lens kit ==
You will use the sphere lenses for this test.
You will use the sphere lenses for this test.
This is a very extensive topic
This is a very extensive topic
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* [https://youtu.be/j48PMpFKxBo Trial Frame Refraction: More Than Just “1 or 2?”]
* [https://youtu.be/j48PMpFKxBo Trial Frame Refraction: More Than Just “1 or 2?”]


= How to test Astigmatism =
== How to test Astigmatism ==
Testing for [[astigmatism]] is tricky, and you should master testing for myopia first.  Errors such as being off by 90 degrees are common.
Testing for [[astigmatism]] is tricky, and you should master testing for myopia first.  Errors such as being off by 90 degrees are common.


== JCC Lens ==
=== JCC Lens ===
The JCC Lens has two cylinders at opposite angles and powers.  By holding the lens in different ways over a trial cylinder lens, you can determine if the angle or power of the cylinder lens should be changed.  (This is the part of the refraction test where the doctor is happy if both options are equally blurry.)
The JCC Lens has two cylinders at opposite angles and powers.  By holding the lens in different ways over a trial cylinder lens, you can determine if the angle or power of the cylinder lens should be changed.  (This is the part of the refraction test where the doctor is happy if both options are equally blurry.)
* [https://youtu.be/ba4ck7oYauY JCC - Example 1 Emily 2/4]
* [https://youtu.be/ba4ck7oYauY JCC - Example 1 Emily 2/4]


== Stenopeaic Slit ==
=== Stenopeaic Slit ===
A stenopeaic slit is just an opaque disk with a slit in it.  By putting the slit at different angles and taking standard myopic refraction, one can calculate the angle and power cylinder needed.
A stenopeaic slit is just an opaque disk with a slit in it.  By putting the slit at different angles and taking standard myopic refraction, one can calculate the angle and power cylinder needed.
* [http://www.journalrepository.org/media/journals/OR_23/2018/Feb/Chowdhury822018OR39503.pdf Stenopeaic Slit: A Diagnostic and Refractive Tool]
* [http://www.journalrepository.org/media/journals/OR_23/2018/Feb/Chowdhury822018OR39503.pdf Stenopeaic Slit: A Diagnostic and Refractive Tool]


== JCC vs Stenopeaic ==  
=== JCC vs Stenopeaic ===  
The use of a Stenopeaic slit vs a JCC lens seems to be cultural.  Most US doctors will use JCC lens, while middle eastern doctors prefer the stenopeaic slit.  The stenopeaic slit may be more useful for very high astigmatism.  Both tests work for low to moderate astigmatism and it's more about how your doctor was trained which he/she will use.  For DIY types, the stenopeaic slit is easy to make at home and is compatible with the simpler cm [[measurement]] when a full trial lens kit is not available.
The use of a Stenopeaic slit vs a JCC lens seems to be cultural.  Most US doctors will use JCC lens, while middle eastern doctors prefer the stenopeaic slit.  The stenopeaic slit may be more useful for very high astigmatism.  Both tests work for low to moderate astigmatism and it's more about how your doctor was trained which he/she will use.  For DIY types, the stenopeaic slit is easy to make at home and is compatible with the simpler cm [[measurement]] when a full trial lens kit is not available.


= Pinhole =
== Pinhole ==
The pinhole accessory in many trial lens sets may help distinguish between refractive issues and medical issues.  If the vision does not improve or gets worse with use of the pinhole lens, this is an issue that should be addressed by an [[optometrist]].
The pinhole accessory in many trial lens sets may help distinguish between refractive issues and medical issues.  If the vision does not improve or gets worse with use of the pinhole lens, this is an issue that should be addressed by an [[optometrist]].



Revision as of 16:08, 11 June 2020

A trial lens kit is a set of lenses of various powers and usually a frame shaped like a pair of glasses but with mounting points for the lenses. The number of lenses and powers will vary by what kit you buy. If you are a very high myope, try to find a kit that includes powers close to your prescription.

Legal: Check your local laws before performing any trial lens tests on someone other than yourself. This may require a licence in your jurisdiction.

Medical: If you have any vision problems not compensated for by refraction, go see your optometrist.

Minimalist Trial Lens Kit

A small kit that will allow you to test small changes to your wearing lenses would be:

Trial frames

Trial frames are frames which you can mount trial lenses in and wear like glasses. They come in many forms, they may have lots of adjustments or come in fixed PD widths. Using a frame with the correct PD is important so the wearer is looking through the optical centers of the lenses. Adjust the frame for the best comfort and so the wearer is looking through the optical center of the lens. A trial frame that holds four lenses and has axis adjustment is best.

Placing lenses in the trial frame

Always place the strongest lens in the stack closest to the eye to reduce the effects of vertex distance. Line up the lines on cylinder lenses with the axis of astigmatism. There may be a dial that helps rotate the cylinder lens.

Flippers

Flip lenses are designed to be hand held in front of the trial lens or customary lenses and test plus vs minus at a set power. Can be used to determine if the customary lenses need tweaking up or down. They may be monocular or binocular They are also used in vision training.

How to test myopia with a trial lens kit

You will use the sphere lenses for this test. This is a very extensive topic

HowTos

=Lecture Format Videos

How to test Astigmatism

Testing for astigmatism is tricky, and you should master testing for myopia first. Errors such as being off by 90 degrees are common.

JCC Lens

The JCC Lens has two cylinders at opposite angles and powers. By holding the lens in different ways over a trial cylinder lens, you can determine if the angle or power of the cylinder lens should be changed. (This is the part of the refraction test where the doctor is happy if both options are equally blurry.)

Stenopeaic Slit

A stenopeaic slit is just an opaque disk with a slit in it. By putting the slit at different angles and taking standard myopic refraction, one can calculate the angle and power cylinder needed.

JCC vs Stenopeaic

The use of a Stenopeaic slit vs a JCC lens seems to be cultural. Most US doctors will use JCC lens, while middle eastern doctors prefer the stenopeaic slit. The stenopeaic slit may be more useful for very high astigmatism. Both tests work for low to moderate astigmatism and it's more about how your doctor was trained which he/she will use. For DIY types, the stenopeaic slit is easy to make at home and is compatible with the simpler cm measurement when a full trial lens kit is not available.

Pinhole

The pinhole accessory in many trial lens sets may help distinguish between refractive issues and medical issues. If the vision does not improve or gets worse with use of the pinhole lens, this is an issue that should be addressed by an optometrist.

References