Help at Work II

[Matthew_]

Are you suggesting we should trace the migration of barns around the world?
It might be interesting. Presumably the further west the barns were constructed the more robust they had to become. If you could find a barn on the mull of kintyre with arabic influences, the barn theory would be established!

[Andrew MacLean]

Not so foolish as you might think

It it could be established that there were Scandanavian influences in the spoken language of Native Americans then the idea that the Americas were first visited by people Viking from North Europe (by way of Iceland, perhaps) would be established.

The fact that on the East Coast of Scotland and in the Northern Ilsles there are distinct Scandanavian influences in the language is actually not a surprise. The sea was a far more easily navigated 'highway' than the land, and it is well known that there was two-way traffic across the North Sea from the earliest times.

Andrew

[Barney]

Interstingly 'bairn' was not originally a Scottish word at all. It is Scandanavian (barn) and means child.

That's very disappointing. You'll be telling us the Chinese invented the bagpipes next. Or even worse, that the English had them afore the Scots.

(http://www.bbc.co.uk/dna/h2g2/A748208)

Not so foolish as you might think

If it could be established that there were Scandanavian influences in the spoken language of Native Americans then the idea that the Americas were first visited by people Viking from North Europe (by way of Iceland, perhaps) would be established.

Or, viewed from a Native American rather than a European perspective, that they visited Scandinavia.

[GarethB]

Tracing the origins of mankind is done through mitochondrial DNA; mitochondria are essentially the power plant of cells and in humans these are passed down through the maternal line.

To the best of my knowledge there are just four distinct genetic types of mitochindrial DNA which has been hypothesised to have only once source!

As i was requested to provide some links, these are the ones I have to hand without dismantling my loft and then hogging the photocpier at work so that I can post links to my web site that is 4 years out of date!

1) The no surgical management of keratoconus continues to play a predominant role in the management of this disorder in a referral population.

Clinical management of keratoconus. A multi center analysis.


2) Thus, we found no effect on endothelial cell density from at least 7 years of daily rigid contact lens wear in eyes with corneal transplants for keratoconus.

Effects of long-term rigid contact lens wear on the endothelium of corneal transplants for keratoconus 10 years after penetrating keratoplasty.


3) CONCLUSIONS: Patients with keratoconus who wear Soft Perm contact lenses have a significantly lower endothelial cell count than those patients with keratoconus who do not wear lenses, or who wear soft toric disposable contact lenses or RGP contact lenses.

Corneal endothelial cell count in keratoconus patients after contact lens wear.


4) Keratoplasty can be delayed or avoided in many keratoconus patients by using contact lenses, especially special design, bispheric lenses. Also, keratoconus eyes often need contact lenses after keratoplasty. This study was over 5 years where 69% did not require keratoplasty, those that did, had keratoplasty on average 3 years after lens fitting.

Keratoconus. Contact lens or keratoplasty?

5) This link is slightly different, but very relevant in that e have discussed cumulative environmental factors with respect to being predisposed genetically to developing KC.

The cascade hypothesis of keratoconus.


6) This site describes in simple terms the types of lenses available to us and how to maximise comfort and hopefully get good lens wear.

Key to successful contact lens wear



I have found this web site to be vast repository of KC studies. http://www.ncbi.nlm.nih.gov

Hope you find these of interest.

[Sajeev]

Gareth, are those the links you was talking about?

If you read them Gareth, they are either comparing contacts in endo cell loss to soft perms, which we know are low in DK or comparing visual accuratcy they give. They are so lame that they are a waist of time to even read in conjuction to why you was quoting them for originally. Also they are short in lenght, not relevant (very much so, that its not worth me typing this post!), and old.

They where not looking in to what we was talking about, in if contacts actually make KC worse.

I thought you said you had studies which say that contacts do not make KC worse?

[GarethB]

Sajeev,

Sorry you feel they are lame, they are only abstarcts which is what you wanted.

As I said the others require emptying my loft, you are welcome to come round and do it for me?

[Sajeev]

Gareth, you make me laugh, your trying sooooo very very hard to say something with out the evidence?!

The abstracts are NOT abstracts to what we was talking about!! I don't know what your trying to do and you are trying too hard to make things "fit" to your liking.

[Ali Akay]

Barney and Sajeev,
It may just be possible that badly fitting non gas-permeable hard lenses could have caused KC in a small number of patients, but it is rather academic now really, dont you think? Unless you are keen to show a link and sue the relevant practice Barney?

When I started fitting lenses, the early gas perms were just coming in and PMMA was still widely used. There were a number of "fitting philosophies" depending on whether the fitter tried to achieve central clearance on the cornea, alignment or touch. As PMMA was not oxygen permeable the fit was less forgiving, you needed the lens to have a fair amount of movement to allow for exchange of tears under the lens bringing fresh oxygen. Most practitioners preferred central alignment or minumum clearance over the cornea, but there was an American method advocating a lot of clearance (I think it was called Bayshore method if I remember correctly).It didnt sound a good idea to have a big pool of tears trapped between the lens and the cornea, but the benefit was better centration when this was difficult to achieve otherwise. It's possible I guess that a lens steeper than the cornea could have resulted in steepening of the central cornea leading to KC in susceptible patients. I've not come across true KC as a result of hard lens wear, but often noticed distorted corneas which would take several months without lenses to recover.

I dont think there was a "conspiracy" but obviously the expertise of fitters must have varied greatly, and probably not enough thought was given to possible long term effects. There was a joke about a famous fitter reputed to be the first (and probably only) optician to become a millionaire from fitting contact lenses that if you could make it to the consulting room at the top of the stairs you'd end up with a pair of lenses! I am not suggesting he was a bad fitter, but certainly very prolific, and I dont think there was enough patient education about regular after-care. As Barney said the lenses would last for ever (I've seen lenses over 30 years old) and wearers were often very complacent and bad at looking after their lenses or eyes.

It'd be interesting to know the mechanisms involved if there was a link, was it lack of oxygen, or poor fit, or both,or any number of these combined with a genetic predisposition? But it'd obviously not be possible to carry out such a study now for ethical reasons.

Does it actually matter now? As vast majority of patients (non KC normal eyes) wear soft lenses and fortunately more and more are now wearing silicone based lenses with very high oxygen transmission, it probably doesnt. As far as I know no link has been suggested with normal hydrogel contact lenses which have been around for over 25 years. The point is, most things we do involve a risk, so as long as the practitioners are honest with patients about the risks as known at the time they can have a clear conscience. When prospective patients ask me if there are any risks with contact lenses I always tell them there's an element of risk in putting a foreign body in their eyes, and if they dont want to take any risks they should stay with glasses, but most find the risks low enough to take, and that's their decision.

[Brief edit made by John for legal reasons]

[Sajeev]

Hi Ali thanks for your postings here, they are always good to read, so thanks for taking time out to explain your view on things.

Anyway, I think no ones cares more about their eyes then their owner... so nothing is written is "academic" (in vain/no reason) when its about something as important as vision, or more precisely about possible vision loss.

Slight risk, an higher than slight risk, or no risk at all (that is a common one), or even that contacts stop progression is what those who deal in contacts say, (the contact lens web-sites don't even use one word about this either on their sites). Why is there a wide differance in opinion or policy on this?? Then you have the longest term, with the most ever KCers studied, as with the cleck study, which shows a more clearer picture of what we are dealing with.

NEI study characterizes natural history of keratoconus

Please note the two pages... Anyway if its the fit, why was the fitters in this study not fitting contact lenses properly, when it says the more hours you wear your lens the more chance of scarring, how is the fitting time catered for, which is needed, when on the NHS they don't have the time needed on the whole for this. Why are flat fitting lens given out, when steep fitting lenses the study says was shown to cause less scarring...

Just would like to hear your view's from the other side of the equation.


Best

[Ali Akay]

Sajeev
Firstly, about nonone caring about their eyes more than the patient. It may be true for the majority, but sadly there are an awful lot of patients who do not look after their eyes and ignore the advice given to them, and end up with problems sooner or later. I remember PMMA wearers who never used any cleaning or wetting solution, just wetted their lenses under the tap before insertion and stored them dry; patients cleaning their hard lenses with fairy liquid because it's cheaper!;patients using their saliva as wetting solution!;with soft lens wearers we had a lot of problems in the 80s with patients sleeping in lenses with inadequate oxygen supply and ending up with infections and corneal vascularisation;only a few years ago there was a lot of concern about a very rare but very serious infection called acanthoemeba keratitis which is mainly due to poor hygiene, storing lenses in tap water etc. The list goes on Sanjeev, luckily things are much better now with frequent replacement/disposable lenses.

Why do some practitioners still fit flat, heavy bearing lenses? Good question! Probably because they know no better! One benefit of flat fitting lenses is that they give good vision and fitting can be completed relatively quickly.There's unfortunately a trade off-scarring, but a lot of practitioners sadly see this as a price worth paying, and they feel it's inevitable so perhaps dont try hard enough to prevent it. Patients often get scarring which isnt lens induced as part and parcel of KC, but lens induced scarring is usually easy to spot as it's a perfect circle corresponding to the area of contact between the lens and the cornea, the flatter the lens the larger the diameter of the scar. The odd thing is patients with fairly large lens induced scars can often still see very well in the consulting room, and hence one could feel no harm is done.However this is mainly due to the nature of high contrast test chart used, and patients would usually have symptoms under low contrast or poor light conditions in the real world.

Contact lens fitting has evolved over decades and practitioners tend to stick to what they know works.There is no "universal contact lens fitting manual" that every fitter is obliged to follow. Things are getting better though, and the quality of fittings is much better nowadays. Rest assured practitioners fitting flat lenses do so in good faith.Perhaps we need the professional bodies to provide "good practice" guidelines to their members on this as they do on most other duties we carry out.