Lynn's FAQ entry

[Sweet]

NO NO NO!!! You can't get rid of it because as i told John when he first put it there i test my vision on it!!!!

I really like it!! And also you never really write small posts anyway!!!!!!!!

So there!! Unless you want to stop being an optometrist you can't give it away!!!! Poking tongue out at you!!!!!!!!!!!

Sweet X x X

[Lynn White]

Just starting some glossary stuff... I am havign trouble copying it over so wuill do a little at a time..

aniseikonia: a difference in the size or shape of two visual images when the images should be the same size and/or shape. Often caused by large differences in spectacle powers/astigmatism between right and left eyes.

astigmatism: a common form of visual impairment in which part of an image is blurred, due to an irregularity in the curvature of the front surface of the eye, the cornea. The curve of the cornea is shaped more like an American football or a rugby ball rather than a normal spherical basketball. Light rays entering the eye there are not uniformly focused on the retina. Rays entering through the more-curved surface are focused before the rays coming through the less-curved surface. The light is focused clearly along one plane but is blurred along the other. The planes are at right angles to each other and this is known as regular astigmatism.The result is blurred vision at all distances. Only part of what you are looking at is in clear focus at any one time.

Astigmatism may be so slight that it causes no problems. Almost everyone has some degree of astigmatism. Significant astigmatism can cause headaches and eye strain and seriously blur vision. Astigmatism may contribute to poor school performance but is often not detected during routine eye screening in schools. It is a refractive error, an error of focusing, that may coexist with other refractive errors like near- sightedness or far-sightedness.

Astigmatism is corrected with slightly cylindrical lenses that have greater light-bending power in one direction than the other. Using these lenses elongates objects in one direction and shortens them in the other, much like looking into a distorting wavy mirror at a circus.

If the two planes are NOT at right angles to one another - then this is called irregular astigmatism and spectacles will no longer correct it because they can only be made with their power planes at right angles to each other.

anisometropia: this is where the two eyes have different powers. This difference becomes significant when there is a large difference between the eyes as it becomes difficult for the brain to merge images form each eye because of magnification differences.

[Lynn White]

Heheh .. I was only trying to be economical!

I suppose this means I just have to write long posts

[Sweet]

This will all be very handy for me and my link role job as i will hopefully understand more! LOL!! Saw a good corneal abrasion last night without it even needing staining and being viewed under the slip lamp! This poor lady got accidently poked in the eye.

Talking of which when testing vision if they are in too much pain to do that i can use which anaesthetic? And it won't cause any problems with a doctor later using a stain will it?

Thanks! Off to get ready for work!

Sweet X x X

[John Smith]

Hi Lynn,

Thanks for these.

One question: "placedo discs" - what are these?

As for the glossary, I'll add your definitions to our existing glossary, which will eventually be linked to the FAQs when they get their own pages.

[Andrew MacLean]

The solution is easy, Lynn

Post longer posts!



Andrew

[Lynn White]

John...

I am not that happy with the astigmatism explanation.. as I said, I just lifted it from an american site and it would help to include diagrams... is that going to be possible?

Placido discs.. again diagrams would be nice hehe.. basically they are concentric circles of light alternated with black projected onto the cornea. On a spherical cornea, they maintain their shape, but on a KC eye they are distorted by the shape of the cone and therefore you can see the contours reflected back.

This is actually the basis of topography... the distorted shape can be mapped like contours on a geographical map of hills. This is then translated into "mapping" where contours of the same height are coloured the same which then means the shape of the cornea can be seen in colour co-ordiantion.

Here's a link that shows pictures of scissoring relexes, placido discs , contact lens fits hydrops etc...

http://www.opt.pacificu.edu/ce/catalog/ ... course.htm

and topography pics...

http://www.geocities.com/HotSprings/Spa ... splay.html

[rosemary johnson]

Gosh, Lynn! You have been busy!

The astigmatism description is fine! - the one thing I'd suggest is to put "like a rugby ball rather than a football" and never mind the American footer or basketball.
Do you still test for astigmatism/correction thereof with one of those rays of spikes a bit like a hedgehog? - is it worth mentioning those, and some of the spikes looking further apart than others?
Rosemary

[Lynn White]

Sweet...

Anaesthetics... well the one to use is proxymetacaine - doesn't sting that much and no, it won't ruin the staining pattern.

We were always taught not to use aneasthetics in cases of abrasions as it slows down healing. At the risk of being jumped on.. all I can say is that no-one who wrote or advocated such a thing ever had a serious corneal abrasion or ulcer!

Having had several corneal traumas myself, I can attest that leaving the eye as it is just gets so painful, photophobic and swollen (because of massive tear production ) that examining the eye becomes impossible. Plus, if it hurts that much, you tend to keep rubbing the eye.. you can't help it!! A touch of anaesthetic immediately calms the whole thing down, reduces swelling ( as tear production goes down) and keeps you hands away from your eyes while a systemic analgesic is taking effect.

Obviously, continued use of anaesthetic is NOT advisable... !!

I remember way back when, I got my very first old fashioned hard lenses.. the optom used anaesthetic to fit them and I thought "OH these are GREAT! Until I got them home and inserted them myself and WHOAH! I could hardly open my eyes...!!

Lynn

[Lynn White]

Rosemary...

I don't use that myself - it's called the astigmatic fan - BUT this is actually a brilliant idea because if I can find a picture of one , I can demonstrate it and also people can check their own astigmnatism on it like they do teh Snellen chart.. so thanks for that...

Mind you... this all relies on me being able to upload pics.. John?