How does an autorefractor work?

I have been set an assignment to do about how an autorefractor works.
I would be grateful of any help you can give me.
Regards,
Alistair

(E-Mail Removed) (Alistair Barrett) wrote in message news:<(E-Mail Removed). com>...
> I have been set an assignment to do about how an autorefractor works.
> I would be grateful of any help you can give me.
> Regards,
> Alistair

Dear Alistair,

In order to work properly, I believe that the
accommodation system must be paralyized with
a drug to get an accurate reading your
your refractive status.

I would be curious about that point, since
in some cases you can get an error of
-4 diopters if this is not done correctly
according to one OD on this site.

Best,

Otis
Engineer

"Otis Brown" <(E-Mail Removed)> schreef in bericht
news:(E-Mail Removed) m...

> Dear Alistair,
>
> In order to work properly, I believe that the
> accommodation system must be paralyized with
> a drug to get an accurate reading your
> your refractive status.
>
> I would be curious about that point, since
> in some cases you can get an error of
> -4 diopters if this is not done correctly
> according to one OD on this site.
>
> Best,
>
> Otis
> Engineer

Otis,

An auto-refractor is never to be trusted accurate.
It is a helpful and time saving instrument, nothing less nothing more.
Most of the time accurate which you can tell after you did the normal
refraction work.
This instrument is also handy in cases of verbal difficulties to get a quick
but, in my opinion, rough idea about the amount and type of ametropia.

Jan (normally Dutch spoken)

On Sun, 29 Feb 2004 01:30:24 +0100, Jan wrote:
>
> An auto-refractor is never to be trusted accurate.
> It is a helpful and time saving instrument, nothing less nothing more.
> Most of the time accurate which you can tell after you did the normal
> refraction work.
> This instrument is also handy in cases of verbal difficulties to get a quick
> but, in my opinion, rough idea about the amount and type of ametropia.
>
> Jan (normally Dutch spoken)
I suppose then it's mainly useful with retardates and other individuals
who cannot communicate. In the case of language difficulties, it would be
better to find a translator, even if this is inconvenient.

--
Robert T. Kopp
http://analytic.tripod.com/

"Robert Kopp" <(E-Mail Removed)> schreef in bericht
news(E-Mail Removed)...
> On Sun, 29 Feb 2004 01:30:24 +0100, Jan wrote:
> >
> > An auto-refractor is never to be trusted accurate.
> > It is a helpful and time saving instrument, nothing less nothing more.
> > Most of the time accurate which you can tell after you did the normal
> > refraction work.
> > This instrument is also handy in cases of verbal difficulties to get a
quick
> > but, in my opinion, rough idea about the amount and type of ametropia.
> >
> > Jan (normally Dutch spoken)

> I suppose then it's mainly useful with retardates and other individuals
> who cannot communicate. In the case of language difficulties, it would be
> better to find a translator, even if this is inconvenient.

Again, the auto-refractor is useful to get a QUIK and ALMOST right objectiv
view on the amount and type of ametropia.
In that way it is time saving in "starting" with the subjective measurment
knowing already what you might aspect.
The problem, however, is that you NEVER, without a subjectiv measurment done
afterwards, know if the measurment is the correct one.
BTW, the objectiv measurment could also be done by a much cheaper instrument
called a skiascoop but that takes more time and skill.
In cases of language difficulties it is possible to measure subjectiv by the
use of Landolt rings (a little gap in the ring pointing in different
directions in each other ring) without the help of a translater.
But in this case it is handy to "start" with a measurment done by that
handy instrument called auto-refractor.
One important thing to be mentioned is the impossibility to quantify the
vision aquity by an auto-refractor and this therefore is done afterwards
while measuring subjectiv.

Jan (normally Dutch spoken)

Subjectiv= questioning from the professional and getting answers from the
patient/client after changing glasses in the trial frame or phoropter.
Objectiv= no need from the patient/client to respond when measuring.

"Alistair Barrett" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> I have been set an assignment to do about how an autorefractor works.
> I would be grateful of any help you can give me.
> Regards,
> Alistair

I assume this is a course assignment and your professors would like you to
also learn how to research a topic, not just get an answer from a news
group. Most textbooks on refraction should have a section on auto
refractors and retinoscopy, your optics text will explain optometers, and
you could try MedLine or PubMed (or your school library) to look for the
published articles that describe the development of auto refractors and
describe how they work.

Dr Judy