CL prescriptions and what they mean
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John Smith
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Andrew MacLean
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Arun
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Thanks Lynn for your answers.
Andrew I think hypermetropia is when you need correction for seeing things in general that are close by. Where as presbyopia is when you only need correction for reading. Which is something that only happens in old age and so is derived from Presbus.
To be honest it doesn't make much sense to me as I would have thought if you cannot read very well, you will not be able to see things that are close by very well either.
Oh well
Andrew I think hypermetropia is when you need correction for seeing things in general that are close by. Where as presbyopia is when you only need correction for reading. Which is something that only happens in old age and so is derived from Presbus.
To be honest it doesn't make much sense to me as I would have thought if you cannot read very well, you will not be able to see things that are close by very well either.
Oh well
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Andrew MacLean
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rosemary johnson
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Andrew asked about presbyopia:
OK, it's a different thing from the type of long-sightedness people can have from an early age.
long-sightedness is because the eyeball is too short, and the lens of the eye forms its image behind the retina. you get reading specs to correct for the eyeball being the wrong length. (Ordinary short-sightedness is where the eyeball is too long and the image comes to a focus in front of the retina, and you wear glasses to move it back.)
Presbyopia (which does indeed derive from the greek presbus, meaning old man) is where the eye loses its ability to "accommodate" - or change the focus from distance to near objects. This is because the eye gets older and less fit and flexible than when it was young.
TYpical first signs are when people of, ahem! more mature years are seen holding their newspapers/books/magazines further away from them, but it can also affect the other end of the scale too as the eye gets less good at adjusting to long distance vision.
ANd that's when the mature people you know start wearing bifocals. Like my dad, for example, who had perfectly oK eyesight untill he was in his late 50s and started wearing bifocals. My mum, who is now 75, has a pair of bifocals for reading/being out and about, and a second par of specs for using the computer/embroidery.
Rosemary
OK, it's a different thing from the type of long-sightedness people can have from an early age.
long-sightedness is because the eyeball is too short, and the lens of the eye forms its image behind the retina. you get reading specs to correct for the eyeball being the wrong length. (Ordinary short-sightedness is where the eyeball is too long and the image comes to a focus in front of the retina, and you wear glasses to move it back.)
Presbyopia (which does indeed derive from the greek presbus, meaning old man) is where the eye loses its ability to "accommodate" - or change the focus from distance to near objects. This is because the eye gets older and less fit and flexible than when it was young.
TYpical first signs are when people of, ahem! more mature years are seen holding their newspapers/books/magazines further away from them, but it can also affect the other end of the scale too as the eye gets less good at adjusting to long distance vision.
ANd that's when the mature people you know start wearing bifocals. Like my dad, for example, who had perfectly oK eyesight untill he was in his late 50s and started wearing bifocals. My mum, who is now 75, has a pair of bifocals for reading/being out and about, and a second par of specs for using the computer/embroidery.
Rosemary
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Andrew MacLean
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I have always had a fascination with language, and in particular with vocabulary: how words got their meaning.
"Emmetropization" is an interesting word. Ali is right to say that it is a very clever process, but the way the word 'grew' is every bit as clever.
Emmet is an old English word. A noun it is almost always used in conjunction with the indefinite article: An Emmet is an ant.
Trope is Greek. It means "to turn". The metaphor, then has to do with one thing turning into a more conveniently shapd version of itself, in a way analogous to the growth of the ant ...
-ization is the suffix that forms a noun from an adjective. Notice ization is always the correct English formation of this suffix. "isation" is French. the source is Latin Izare, and has the same function in latin and Greek izein
"Emmetropization" is an interesting word. Ali is right to say that it is a very clever process, but the way the word 'grew' is every bit as clever.
Emmet is an old English word. A noun it is almost always used in conjunction with the indefinite article: An Emmet is an ant.
Trope is Greek. It means "to turn". The metaphor, then has to do with one thing turning into a more conveniently shapd version of itself, in a way analogous to the growth of the ant ...
-ization is the suffix that forms a noun from an adjective. Notice ization is always the correct English formation of this suffix. "isation" is French. the source is Latin Izare, and has the same function in latin and Greek izein
Andrew MacLean
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Lynn White
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A couple of days away and this thread has developed amazingly!
Just a few additions here: Yes sclerals are completely different from corneal RGP's. I had intended explaining this all at the same time but the thread sort of grew lol I was explaining RGP's (corneal) and soft lenses first because the vast majority of people whether KC or not wear such lenses.
OK - longsightedness(hypermetropia): The confusion arises because when a hypermetrope is young, their focussing system (the lens of the eye) can overcome the effects of a short eye by focussing up as Rosemary said. So this means they can focus up for distance and near but its HARDER for near as in they eye has already used a fair amount of its focussing power just to get distance right.
Then, as age sets in (ahem!) the eye cannot maintain the near focussing very well. We optoms then often give a patient a distance prescription, to allow the eye to be "normal" for distance, allowing normal focussing for near. However, confusingly, these people generally only use their glasses for reading and refer to them as such. This is becasue they don't actually make distance that much clearer, it just means they see in the distance in a relaxed way rather than having to work at focusing.
When they reach the age of presbyopia, they need extra reading prescription as well, just like anyone else. And reading prescriptions at this age blur distance vision back, as they are just correcting focus at near only. Hence the need for bifocals, multifocals etc.
Andrew. Emmetropia is widely used as meaning perfect correction for distance - ie neither myopia nor hypermetropia. This now has me slightly confused as to word origin with your talk of ants!! I was under the impression emme was derived from greek meaning in proportion. The t belongs to the tropia part of the word which means to turn as you say. Tropia is used in other eye words like esotropia exotropia.
Emmetropisation is truly fascinating and thanks ALi for that explanation. It is so in tersting to try and work out why this goes wrong in certain people and not in others!
Oh and Andrew.. I thought we in the UK used isation not ization, though I do see your point. Certainly, all our tech books use the the isation suffix?
Lynn
Just a few additions here: Yes sclerals are completely different from corneal RGP's. I had intended explaining this all at the same time but the thread sort of grew lol
I was explaining RGP's (corneal) and soft lenses first because the vast majority of people whether KC or not wear such lenses.
OK - longsightedness(hypermetropia): The confusion arises because when a hypermetrope is young, their focussing system (the lens of the eye) can overcome the effects of a short eye by focussing up as Rosemary said. So this means they can focus up for distance and near but its HARDER for near as in they eye has already used a fair amount of its focussing power just to get distance right.
Then, as age sets in (ahem!) the eye cannot maintain the near focussing very well. We optoms then often give a patient a distance prescription, to allow the eye to be "normal" for distance, allowing normal focussing for near. However, confusingly, these people generally only use their glasses for reading and refer to them as such. This is becasue they don't actually make distance that much clearer, it just means they see in the distance in a relaxed way rather than having to work at focusing.
When they reach the age of presbyopia, they need extra reading prescription as well, just like anyone else. And reading prescriptions at this age blur distance vision back, as they are just correcting focus at near only. Hence the need for bifocals, multifocals etc.
Andrew. Emmetropia is widely used as meaning perfect correction for distance - ie neither myopia nor hypermetropia. This now has me slightly confused as to word origin with your talk of ants!! I was under the impression emme was derived from greek meaning in proportion. The t belongs to the tropia part of the word which means to turn as you say. Tropia is used in other eye words like esotropia exotropia.
Emmetropisation is truly fascinating and thanks ALi for that explanation. It is so in tersting to try and work out why this goes wrong in certain people and not in others!
Oh and Andrew.. I thought we in the UK used isation not ization, though I do see your point. Certainly, all our tech books use the the isation suffix?
Lynn
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Andrew MacLean
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Etymology is never an exact scienct. The Greek word is actually Menses, emmena and has to do with balance but only metaphorically. another possible derivation is Latin Mensis meaning Month.
I remain perusaded that my etymology is correct: the word arose at a time in the devlopment of science when all wisdom was thought to be found in the relationships of nature, hence the ant metaphor arises more than once in the developing scientific nature, and was celebrated in the saying "consider the ant, think of her ways" as a model for human social order.
As to "ization", this is correct in English. The OED used to give "isation" as "variant" spelling, sometimes calling it "from French, an affectation", and sometimes "illiterate"
Morse once caught a murderer because he used the "illiterate" form of the suffix and was, in the view of Morse, not the educated man he pretended to be!
Andrew
I remain perusaded that my etymology is correct: the word arose at a time in the devlopment of science when all wisdom was thought to be found in the relationships of nature, hence the ant metaphor arises more than once in the developing scientific nature, and was celebrated in the saying "consider the ant, think of her ways" as a model for human social order.
As to "ization", this is correct in English. The OED used to give "isation" as "variant" spelling, sometimes calling it "from French, an affectation", and sometimes "illiterate"
Morse once caught a murderer because he used the "illiterate" form of the suffix and was, in the view of Morse, not the educated man he pretended to be!
Andrew
Andrew MacLean
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Lynn White
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Well maybe Andrew but I am just going on just what I have learnt from the history of the profession etc...
It was definitely greek origin and not old english, I thought, but I will now research this further!! You see, emmetrope was "coined" a long way before emmetropiz(s)ation, so the anthropomorphism you describe would not have been an issue in the origins of the word.
Yes, I remember that Morse episode well and take your point. Again, I am referring here to common usage amongst my professional colleagues.
Lynn
It was definitely greek origin and not old english, I thought, but I will now research this further!! You see, emmetrope was "coined" a long way before emmetropiz(s)ation, so the anthropomorphism you describe would not have been an issue in the origins of the word.
Yes, I remember that Morse episode well and take your point. Again, I am referring here to common usage amongst my professional colleagues.
Lynn
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