Glossary of terms - community draft

Hi there fine Meowers,

In this post Jake requests us to help Endmyopia with a nice and compact glossary of terms, designed to give newbies a compact reference to the terms that we utilize. Please add to and edit the following definitions if you feel like helping ol’ uncle Jakey out a little here.

Have a look here (thanks @Cateye) to get an idea of what it should end up looking like:

We use two categories, general eyesight terminology and Endmyopian specific:

Endmyopia specific (thanks @mag):

  • Active focus - The process of looking at an object or text that is slightly beyond your eyes’ (together with any corrective lenses) maximum focus distance (i.e. slightly blurry) and in a relaxing way, waiting for your eye to clear up the blur. Note: you may have to train your eyes to be able to do this first.

  • Ciliary spasm - A contraction of the ciliary [see: ciliary muscle] in which a thickened state of the lens lingers following a period of close-up vision. Absent ciliary relaxation, the lens is unable to refocus on objects situated at a greater focal distance, thereby producing a state of myopia.

  • Ciliary muscle - A smooth fibrous muscle internal to the eye which surrounds the flexible lens. Through both contraction and relaxation, the ciliary function changes the shape of the lens, thereby changing the distance upon which the eye can properly focus.

  • Differentials - As “normalised” but lenses reduced further in refractive power such that you can only see as far as your most common screen distance leaving a small amount of blur.

  • Distance to blur - The distance you can see JUST before objects/text start to become blurry.

  • Focal point/Focal plane - The distance at which an object (or, in the case of focal plane, a flat surface perpendicular to the line of sight) appears to be in proper focus to the viewer. This distance is a function of the particular shape of the lens within the eye at the moment of viewing and will also be affected by the shape and strength of any corrective lenses placed between the eye and the object (or surface) being viewed.

  • Full prescription - The lenses prescription that allows you to see to “infinity”/the horizon without any blur. Using this prescription things you see should not become blurry at any distance, only smaller. With these, your viewing distance is limited only by subject size/eye resolution, not by blur.

  • Normalised - Lenses (glasses or contacts) that have a refractive power lower than your full prescription but high enough to provide distance vision with only a small amount of blur (enough to practice active focus). “Small amount” is subjective and is different for each person.

Eyesight in general (thanks @HectorVazquezPeralta) :

  • Accommodation - the ability of the eye to flex the lens in the eye and change focal distance.

  • Circle of least confusion - The geometric area of light focus inside the eye that is the best compromise for astigmatism correction. This is approximately located at the point light focus of your “spherical equivalent” (sphere + cylinder/2) would be, but is a circle instead of a point.

  • Myopia - (more commonly known as shortsightedness) is, as contrary as what we have been taught, a refractive state in which a person who suffers from it isn’t able to see things clearly at the distance.

  • Myopic /hyperopic defocus - Myopic defocus is when images are blurry because you’re nearsighted. Hyperopic defocus is when images are blurry because you’re farsighted. Defocus can be accentuated or canceled with lenses. A person with good vision wearing plus lenses would introduce myopic defocus.

  • Pseudo myopia - or NITM (Near Induced Transent Myopia) is the previous stage for lens induced myopia. The pseudo myopia is just a symptom caused by the strain generated from an excessive amount of work seeing something up close, generally Computers or Smartphone screens.

  • Spherical equivalent - Sphere power + 1/2 of cylinder power. This approximates the same total lens strength without astigmatism correction.

  • Presbyopia - The inability to change your natural lens focus due to normal age related lens stiffening.

  • Hyperopia - Farsighted

Please feel free to make these better, comments below for discussion purposes. I would like to get some input on the question of whether we need to add eyesight problems to the general list, thinks like cataract, glaucoma, retinal detachment come to mind, vote on it in this poll please:

  • Add eye health related terms to the glossary
  • Don’t add them, it’ll make for too long of a list
  • Add them, but under it’s own header
  • I’m impartial

0 voters

@Laurens: I’d like to start by adding the following terms (and cross references):

-optician - a technician that fits and dispenses glasses and contacts, in many locations this is a licensed profession.
-eye doctor
-Anisometropia (diopter ratio)
-Astigmatism/cylinder correction - a plus spherical lens focuses light on a point, a cylinder lens focuses light in a line. If you see directional smear blur, you will probably be prescribed a cylinder in your glasses.
-prism - a lens that changes the angle of all light passing through it, meaning that looking straight ahead you’ll see an image off to the side.
Often used to treat lazy eye/amblyopia.
-axis - the angle of the cylinder correction
-plus lens
-minus lens
-cylindrical lens
-accommodative amplitude (I never spell that word right)
-ciliary spasm/accommodative spasm
-crystalline lens
-ciliary muscle
-peripheral retina
-color blindness
-night myopia
-night blindness
-dark adaptation
-dark focus
-contrast ratio
-diopter gap
-overcorrection (has two meanings)
-contact lens
-focal length
-refractive error
-refractive state
-trial frame
-add power
-cycloplegic refraction
-subjective refraction
-final refraction
-intraocular pressure
-refractive surgery
-blur adaptation
-accommodative lag and lead
-Accommodative reserve
-pupillary distance
-index of refraction

I’ll think of more, too.

Thanks @Dlskidmore for your great additions to these terms!


Myopic /hyperopic defocus
Circle of least confusion
Spherical equivalent
Maybe the types of astigmatism


Also, I would say DON’T add health-related eyesight problem terms to the glossary. Not because it’ll make it too long, but because illnesses/conditions require longer explanations, sometimes whole articles. This is a glossary of terms where the definition is at most one paragraph but preferrably one sentence. That format doesn’t fit with explanation of diseases requiring whole articles. Plus these things are probably better explained elsewhere than we could do here


True, but we’d just add a short description.So people immediatle know that it’s a different condition from myopia. Maybe add a link.


maybe but it also gets into the domain of medical advice which Jake likes to avoid… I mean if we start defining diseases in our own terms isn’t that kind of like medical advice?

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Just put them in the section “other eye-relatd health conditions”, and list them. Maybe add wikipedia definitions in 1 short sentence. If we’re quoting wiki, we’re safe :smiley:
I just think it’s important, so non-english-fluent-people, the ones that keep silent here, have a quicker way to understand what is EM related, and what is totally different.


OK we’ll just have to agree to disagree on this one :wink:


The term I’ve used and heard most of my life is nearsighted (vs shortsighted).


In the UK more people use short-sighted. Maybe near-sighted is more common in the US


Yea, I would have to disagree on the medical conditions part. As @Lajos says, we don’t want to get into medical stuff. For one side, Endmyopia isn’t the place where people want or need to come and get medical specific advice from, and for the other, it can get tricky in terms of getting the mainstream all over us.

Maybe in the future it will become a possible option, but right now I don’t think is the case.

Btw, if no one here knows me (which probably is the case lol) I’m the guy behind the marketing stuff of Endmyopia. :stuck_out_tongue:

So @Laurens and everyone, if we could avoid getting into medical stuff, it would be better. :smiley:


In the US, the term “short-sighted” typically refers to one’s ability to consider the longer term consequences of near term actions. It’s kind of a put-down to call someone short-sighted. :roll_eyes: So, perhaps best to include all such terms lumped together as examples of global terminology for the same condition.


Ok, silly question here, but …

I’m happy to help construct the glossary. But it’s not obvious to me how to go about contributing. Is there a shared document somewhere? Or do we just post our definitional offerings up within this thread? Or some other thread? :man_shrugging:

Just need a tap in the right direction. (Probably the same reason I could never find the Rough Guide, either).


On the very top, Laurens’ first post, you shoulbe be able to edit it. Below his post, whre you can like the post, there’s an edit icon. (though maybe not, if you’re just started here, depending on automated user trust level)


well in the UK it’s used for that too. One is physical short-sightedness, the other is metaphorical / figure of speech

Yeah let’s stick to defining EM-specific terms plus functional terms related to the functioning of a normal eye

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added a few definitions. Feel free to constructily criticize :wink:

@FMR please put yours in alphabetical order

Ok, we are open to possibilities also.

The main issue is avoiding the mainstream to be on top of us.

But… ok, as I have seen from the results in the poll, maybe it could help doing it.

It definitely still needs to be discussed, though.

What do you think, @jakey?

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I personally would tend towards leaving them out for now. One, we don’t deal with medical issues (dicey enough as it is) . And two, let’s not overwhelm ourselves with holding the world on our shoulders. As a starting point people come here and don’t know what active focus means - also be easier for them to find these terms with a manageably sized list. :slight_smile:

Can always keep adding and get into the other things later on.

My two cents.


Ok, I must be really dense here, but I still cannot seem to find the actual draft glossary itself - just a series of links to thread topics talking about it. (Then again, I still never found the Rough Guide document either.)

If I were to attempt to contribute to this glossary where would I find the actual working document itself?


That’s a good point.
We are just contributing with writing the terms here and it’s meanings, but yeah, that’s a good idea.

Let me talk with @Laurens and @jakey about this.

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