Re: How to perform retinoscopy

On May 1, 3:31 pm, otisbr...@xxxxxxxxxxxxxx wrote:
Dear Doug,

Subject:  Best Visual Acuity -- METHOD

This is the standard that is preferred by most ODs.

Using a trial lens kit (or Phoropter), and a minus lens -- you do the
following.

Have the person read the Snellen.  OK, 20/70

Now you place a weak minus lens in your trial-lens frame, of -1
diopter.

20/30, OK

You then increase the power (asking 1 or 2 better) until you get the
sharpest
vision possible.

20/20.  OK with a -1.5 diopter lens.

Now let is see if we can do better.  Using a cyl lens, you rotate the
lens
from zero to 90 degrees, looking for that to sharpen the image.

So you get to 20/15 for that person.

You think write the prescription for the Spherical and Cyl and angle.

Enjoy,

On May 1, 3:18 pm, douglas <Protoman2...@xxxxxxxxx> wrote:



On May 1, 9:21 am, "Mike Tyner" <mty...@xxxxxxxxxxxxxx> wrote:

"douglas" <Protoman2...@xxxxxxxxx> wrote

OK, I know how to check the base refractive error, but how do you
check for astigmatism? I know the retinoscope has a protractor on it,

You don't see protractor markings on modern retinoscopes. The markings are
on the phoropter.

I'm pretty sure you use it just for that, but...how?

Once you get a good reflex, you rotate the streak and sweep it in different
directions across the pupil. Many times it's obvious that the streak
neutralizes in one meridian (say, sweeping side-to-side) yet it's way off
90 degrees away, when you sweep up-and-down. That's astigmatism, and the
trick is to determine the maximum and minimum meridians.

If you did both a static cycloplegic and a dynamic non-cycloplegic

Dynamic retinoscopy isn't useful for determining refractive error. Many
doctors never use dynamic and have forgotten how, because it's only valuable
for determining accommodative response and there are other ways to do that.
A few years ago the "Prio system" was pushed out, basically an LCD nearpoint
card with a hole it it, thru which you could do dynamic retinoscopy. It was
gimmicky ("computer vision") and seldom indicated any unique sort of
treatment, but you were obligated to prescripe Prio lenses from it. It
wasn't that much better than a plastic nearpoint card with the same hole.

Retinoscopy is a dying art. Most retinoscopy used to be done to gain a
starting point for subjective refraction, an estimate. Many doctors now use
autorefractors for that, and consequently never pick up a retinoscope. I
wouldn't either, except sometimes I get ahead of my staff and patients
haven't had the autorefraction done yet.

Cycloplegic retinoscopy may be used to help determine latent hyperopia but
dry (non-cyclo) ret is often a good indicator of LH, revealing results that
are a half- or full diopter more plus than the patient's chosen subjective.

Who makes good retinoscopes? Keeler?

Copeland and Welch-Allyn. Don't know the Keeler.

And what's the diff b/w a
retinoscope and an ophthalmoscope?

BIG diff. A ret just generates a streak of light. The streak can be focused
but it's designed to focus an image of the filament (the streak) to the
retina, such that you can see it moving in the pupil.

Ophthalmoscopes are illuminated too, but more important they have an
observation system that lets you see the details of what you're
illuminating. Direct and indirect o'scopes both produce an image of the
retina. In direct scopes, the image is upright and magnified. Indirect
scopes produce upside-down images that are wider-field (less detailed, not
as magnified.)

Can you use a indirect
ophthalmoscope for retinoscopy?

Not very well, I'm not sure it could be done because retinoscopes all focus
the streak in different planes. The ophthalmoscope generates only parallel
light for illumination.

And has any beginning optometry student accidently held the
retinoscope backwards, and temporarily blinded themselves?

Oh sure. Ophthalmoscopes are much brighter.  But with all hand-held scopes,
it's habit to turn it on, then shine it somewhere like your hand or the
wall, to make sure it's working. Putting it to your eye backwards is dumb
but even dumber is getting up in your patient's face then finding the scope
is dead.

-MT

But I'm sure you could use a direct ophthalmoscope for retinoscopy, if
you lacked a retnoscope, would the procedure be any different for
using an ophthalmoscope for static retinoscopy? Which provides better
bva, cyclo, or non-cyclo?- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

That's subjectively. And, according to House, patients lie. So, how do
we use retinoscopy to *objectively* determine our patient's refractive
error? I believe its as follows:

Dim the lights, instill cyclopentolate into the patient's eyes, and
have them look at at a target at optical infinity. You stand 67cm away
from the patient, and set the phoropter to -1.50D --please explain to
me exactly why this is done? To set the effective curvature to zero,
perhaps? And I know that -1.50D is the reciprical of 67cm--, and move
the retinoscope across the pupil. If you see with-motion, add plus
lenses; against-motion, add minus lenses. Stop when the pupil fills w/
light, and there's no motion. Rinse and repeat for all meridians.
Rinse and repeat for the other eye. Subtract -1.50D from the readings
to get the prescription.

How would you use the autorefractor to find an inital starting point
for the static retinoscopy?
.

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