The College of Optometrists

I am finding my final Rx with esp. myope px's is being under-minused by about +0.75DS, compared to their previous RX history:

(1) Am I pushing the plus too much!.. but I've been taught at Uni to do that, as long as they still see to their best acuity.- In my case all these underminused myopes still see 6/5...and I do keep the young myopes on the duochrome-green.. on the +1.00 they are about 6/12

(2) I have been testing at my pre-reg place for about 5 months ... and have not had any px return complaining yet!!

(3) My supervisor feels i'm pushing the plus too much!! and shouldnt rely on the +1.00 ..

sorry - this sounds a real muddle! It does not matter ifthey windup on the green or the red - as long as they are satisfied with the final Rx. Yep - my uni stressed max plus - as though accomodating was a sin - but it is more subtle than that. You can have 6/5 sharp and 6/5 hazy - I know which I want - the sharp one!

Try using a very tiny line - they struggle to read 6/6 - so put them on 6/5 - now it is only the odd letter. Now add and subt 0.25 - and you will find your end point is easier to get - and won't blur them (or the tiny line will be even more blurry!). Ask them if its nice and sharp. It could be yr testing distance is too small for you.

2) - not neccessarily - they could have gotton a second opinion elsewhere.

3)try what yr supervisor suggests - there is no law that says they have to have max plus. Infact over plussing creases more rechecks than over minusing. good luck! try borrowing 'clinical pearls in refractive care' by Len Werner and Leon Press - very good. palf

palfi, i wish you were my supervisor !!

Thank you palfi.. 6/5 is the lowest line on my snellen chart and I will try isolating specific letters on this line to see if px prefers -0.25DS...

but, what about the other +0.50DS?? ..since I seem to be consistently out by about +0.75DS..

I will measure the Testing dist. to ensure 6m... incidently, my superviser uses a projector screen in his room (one where you have to do the subjective in the dark) will that make a difference??

Have you tried binocular refraction using a +1.50DS in the fogged eye? This ensures sufficient fog even if you are slightly over minused and allows you to forget about +1.00 test. You can largely forget about duo as well (not all together!).

Anyway who says you are overplussing when nobody has complained?

:-)

let me offer some more ideas which may help. Before you begin, think of a strategy for yr px, ie if myopic, they nearly all have 6/6 and like it clear. If hyperopic then if young - minimum plus which alleviates symptoms keeps it clear and lenses thin. But hyperopic/ pre- presbyopic more plus for comfort.

Also make two New Years promises NOW :

(1) I promise only to use the minimum of lens changes to get the final Rx. Then during yr day work out yr average lens changes and try and reduce this number. This will force you to think about every lens presentation and help you stop duplicating (confusing) and also presenting lenses too small for the px to appreciate(really asking for problems!). I can say more - but will leave it for you to explore!

(2)I promise to re-invent my own way of doing cross-cyl, sph checking etc - to make it easier. And along with this I will invent suitable questions. This is also to explore. I promise to play with all the techniques to find the best for me and try breaking all the rules 'till I am satisfied.

(2a) I also promise to test my own eyes with these new personal techniques - so you can be yr own judge!

My technique is to cover the other eye. Get them to read what they can. I usually start by saying 'what is the chart like, please?'.

Then I use large sph + & - to check

ie 6/12 -- add + 0.5 - 0.5 'what does that do?' - or 'how does this change it?'. I don't mess abt with small change unless I am near the end.

If its okay to + - 0.50 I do XCyl. 'which gives the better picture?, or 'does this improve things?'

I don't flog the XCyl usually, just a couple of flicks, or just plonk it over then whip it back agn in various angles. If it is getting better - I then drop that first eye and do the other eye (to rest first eye).

When that's done, again only roughly, put a + 0.75 fog over second eye and start to refine first eye. Then switch +0.75 fog and refine second eye. I refine by pushing them onto a really tiny line (they usually swear at this point - and then make a reasonsble stab at reading it) +0.25 and -0.25 twirl used to maximise clarity. 'Is it really clear now? ' if yes - open both eyes and they say wow. Then paddle between eyes to check both eyes sharp. Sometimes I check on bichrome if I feel really lost. (personaly, I try to make the cyls 90 and 180 if I can get away with it (to reduce risk of spex distortions and cyl intolerances - you would be surprised that tolerance some people show to cyls - but this is a 'dodgy area' and needs practice(cyls are not cast in stone either!!).

But my extra check is that I do monoc accom push up test - and both eyes should have the same depth of focus given no pathology or major anisometropia. So If one eye has 4ds accom and the other 3.5ds - I recheck my distance ballance agn.

My room is only 3 metres long - direct chart - no mirror - but I know that 'sharp' is -0.50 back from the 'just hazing' point. (so, I can also use that).

For kids I always use a +1.00 lens which drop to 6/9 - 6/12. there is an intersting study in this moths OPO.

On the whole I tend to direct the px and keep to the point. I rarely chat to them.

Don't forget that the depth of focus of the eye is often +-0.25 anyway.

Wow!!...thanx palf..

If you are testing at 3m, the px is accommadating by 0.33D, so you need to subtract 0.25 from your final result, this could account for some of the extra plus your getting.

Thanx godzilla, I agree...however my testing room is the traditional snellen chart with the mirror at 3m. Its my supervisor who uses the projector screen in his testing room.

I have remeasured the testing room and it is definitely 3m from from the px's eye level (sitting on the testin chair) to the mirror. Since, the snellen testing unit is on the wall, at the back of the testing chair. Then the testing room must be 6m.

I have since spoken to my supervisor and we are incorporating a 6/4 line to fine tune the final Rx and I'm doing Binocular Refn on most of my pxs. And Palfi I will take on the 2.5 new year resoln. you have set me.

Many thanx..

I found a projector chart gave me consistant (and complained about)over plus of .75 to 1.00 dioptres. yes testing in the dark may make a difference, pupil size varies apart from anything else. Keep trying though, and don't beat yourself up so much, you are doing fine, by being so thoughtful

yea - well said samadd! - every testing room has its own flavour - wierd isn't it! I like trad snellen charts - but have a projector now.

Oh I have thought of more points - do what you have to do - and leave the rest alone - ie :go cautiously!

Get the book from college library - its worth a read.

And as samadd says - don't sweat the small stuff - you are really doing fine!

Lets know how you get along

prof palf

Thanx,will do...