<div dir="ltr"><div dir="ltr">Ruth - the improbably good resolution acuity of adults must be due to "artifacts". In the Teller stimuli, usually at the edges, in the Cardiff Acuity Cards, unequal line widths seem to be the culprit. As Pete Jones says, it's unlikely that infants and children with reduced visual acuity use artifacts as cues for detection. (This should be verified with data!) One would hope that digital stimuli could be made artifact free, however so far, we have not seen any such stimuli.<div>Chris - An "ecologically valid" test of visual acuity is Cardiff Acuity Cards. Kay picture outlines are created by high-pass line elements. Typical toddlers who are capable are readily tested by asking them to name the pictures. Interestingly, resolution acuity for the Cardiff stimuli is generally consistent with TAC grating acuity across comparable ages. This suggests that TAC and Cardiff Cards both measure resolution acuity. A limitation in our clinical experience and research is that testing Cardiff Card acuity in young infants and patients with very low acuity may be unreliable. </div><div><br></div><div>D. Luisa Mayer, Ph.D.</div><div>Associate Professor</div><div>New England College of Optometry</div><div><br><input name="virtru-metadata" type="hidden" value="{"email-policy":{"state":"closed","expirationUnit":"days","disableCopyPaste":false,"disablePrint":false,"disableForwarding":false,"enableNoauth":false,"persistentProtection":false,"expandedWatermarking":false,"expires":false,"isManaged":false},"attachments":{},"compose-id":"15","compose-window":{"secure":false}}"><div><br></div></div></div><br><div class="gmail_quote" style=""><div dir="ltr" class="gmail_attr">On Tue, Feb 18, 2020 at 9:49 AM Ruth Hamilton <<a href="mailto:Ruth.Hamilton@glasgow.ac.uk" target="_blank">Ruth.Hamilton@glasgow.ac.uk</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Dear Rowan<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Further to your point, our team made some systematic measurements of target vs background luminance for TAC, as well as Keeler Cards for Infants, Lea Paddles
and Cardiff Acuity Cards, and also for a digital test (ipad, Peekaboo). The data are currently being peer reviewed, but we found luminance (and colour) mismatches of differing degrees for all the card-based tests. We also found some improbably good psychophysical
acuities (better than -0.300 logMAR) from some adults tested at 10 m with the card-based tests.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Best wishes<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Ruth<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Dr R Hamilton PhD<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Consultant Clinical Scientist, Paediatric Physiological Measurement<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Royal Hospital for Children, Glasgow, UK<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">+44 141 452 4217<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Secretary, BriSCEV<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><a href="http://www.briscev.org.uk/" target="_blank">http://www.briscev.org.uk</a><u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">@BriSCEV<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">President, ISCEV<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><a href="http://www.facebook.com/ISCEV.org" target="_blank">www.facebook.com/ISCEV.org</a><u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><a href="http://www.linkedin.com/groups/ISCEV-4811521" target="_blank">www.linkedin.com/groups/ISCEV-4811521</a><u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10pt;font-family:Tahoma,sans-serif">From:</span></b><span lang="EN-US" style="font-size:10pt;font-family:Tahoma,sans-serif"> visionlist [mailto:<a href="mailto:visionlist-bounces@visionscience.com" target="_blank">visionlist-bounces@visionscience.com</a>]
<b>On Behalf Of </b>rcandy<br>
<b>Sent:</b> 14 February 2020 13:54<br>
<b>To:</b> Meindert de Vries<br>
<b>Cc:</b> Margaret Woodhouse; <a href="mailto:gislin@jhu.edu" target="_blank">gislin@jhu.edu</a>; <a href="mailto:visionlist@visionscience.com" target="_blank">visionlist@visionscience.com</a><br>
<b>Subject:</b> Re: [visionlist] Teller Acuity Cards<u></u><u></u></span></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Davida Teller, Velma Dobson and their colleagues developed the Teller Acuity Cards to test resolution acuity. To do that, the target must ‘disappear’ when the white and black components of the stimulus can no longer be resolved. This
requires that the mean luminance of the target area is perfectly matched to the mean luminance of the rest of the card. This is hard to do and makes the printing process difficult and more expensive (including visual inspection of each individual card from
extended distance to confirm that there are no visible artifacts beyond the resolution limit). Vanishing optotype tests, such as the Cardiff Cards, use the same principle. Even though the vanishing optotype has a shape that can be recognized, the shape is
defined by a single black & white paired outline that ‘disappears’ to mean luminance when the components can no longer be resolved.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">A test that is constructed to use the forced-choice preferential looking principle (is the target on the left or right of the card?) is critically dependent on having no visible artifact to indicate where the target is once the resolution
limit is passed. This new test appears to have a difference in mean luminance between the target area and background, and therefore it is not a test of resolution acuity. It then becomes a test of detection acuity (can the target be detected using the difference
in luminance?), similar to asking whether we can detect a star against a dark sky. Based on these photographs, it seems very likely that these large targets can be detected easily at the viewing distance that this test would be performed, making it a poor
test of detection acuity.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Any new acuity test should be provided with testing norms that have demonstrated its validity for the population being tested. One easy confirmation of validity in the absence of normative data is to determine the viewing distance at which
an observer can no longer perform the task. If the observer has 20/20 (6/6) acuity, is the card labeled approximately equivalent to 20/20 at the observer's performance limit at the recommended testing distance? Is the card labeled approximately equivalent
to 20/40 (6/12) at the observer's performance limit at twice that viewing distance etc. I am guessing that a typical observer will still be able to do this test at the end of a long corridor and, therefore, that the test is not valid. (Candy, Mishoulam,
Nosovsky & Dobson; IOVS, 2011)<u></u><u></u></p>
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<div>
<p class="MsoNormal"><u></u> <u></u></p>
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<div>
<p class="MsoNormal">I am doing my best to channel Davida and Velma!<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<div>
<p class="MsoNormal"> Rowan<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<div>
<p class="MsoNormal"><span style="font-size:9pt;font-family:Helvetica,sans-serif;color:black">.........................................................................................................................<br>
T. Rowan Candy,<br>
Executive Associate Dean for Academic Affairs,<br>
Professor of Optometry and Vision Science,<br>
Adjunct Professor of Psychological & Brain Sciences<br>
Neuroscience and Cognitive Science Programs<br>
Indiana University<br>
<br>
Phone: (812) 855-9340<br>
<a href="http://www.opt.indiana.edu/people/faculty/candy/index.html" target="_blank">http://www.opt.indiana.edu/people/faculty/candy/index.html</a><u></u><u></u></span></p>
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<p class="MsoNormal"><br>
<br>
<u></u><u></u></p>
<div>
<p class="MsoNormal">On Feb 13, 2020, at 7:52 PM, Gislin Dagnelie <<a href="mailto:gislin@lions.med.jhu.edu" target="_blank">gislin@lions.med.jhu.edu</a>> wrote:<u></u><u></u></p>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<div>
<p class="MsoNormal">Chris and Meindert,<br>
<br>
I definitely agree with Meindert's objection to the cards he presents.<br>
<br>
One thing that is critically important about any card that intends to assess <br>
visual acuity (high-spatial frequency resolution, if you will) through <br>
high-resolution texture filling a contour is that:<br>
1) the average luminance inside the contour is equal to that outside it, and <br>
2) the edges of the contour are filtered, preferably with a raised cosine of a <br>
spatial frequency equal to the fundamental of the texture inside the contour.<br>
<br>
Unless Meindert's photographic rendition is grossly misrepresenting the actual <br>
hues and greyscale levels on the new cards, the cards do not meet the first <br>
requirement: In all cases the average luminance inside the contour is lower <br>
than outside.<br>
<br>
The cards definitely do not meet the second requirement: there is no filtering <br>
around the contour edges<br>
<br>
So I have to agree with Meindert that there are serious problems with these <br>
cards.<br>
<br>
Note, BTW, that the Teller cards do not use filtering around the outside of the <br>
contour either, but this may be less important because of the square contour of <br>
each pattern: black and white bars are equal in area. Still this may lead to <br>
an overestimation of acuity compared to an unconstrained grating<br>
<br>
So while I agree with Chris that there is room for valid alternatives to the <br>
Teller cards, the ones shown here do not appear to meet the minimum <br>
requirements for such an alternative.<br>
<br>
But maybe I'm missing something?<br>
<br>
Gislin<br>
-- <br>
Gislin Dagnelie, Ph.D.<br>
Associate Professor of Ophthalmology<br>
JHU Lions Vision Research & Rehab Center<br>
Johns Hopkins Hospital, Wilmer Woods 358<br>
1800 Orleans St<br>
Baltimore, MD 21287-0023 <a href="http://ultralowvisionlabjhu.net/" target="_blank">http://ultralowvisionlabjhu.net/</a><br>
USA<span> </span> <a href="mailto:gislin@jhu.edu" target="_blank">e-mail: gislin@jhu.edu</a><br>
<br>
<br>
On 13 Feb 2020 at 13:24, Christopher Taylor <<a href="mailto:christopher.taylor@gmail.com" target="_blank">christopher.taylor@gmail.com</a>>
<br>
wrote:<br>
<br>
Why do you believe this test has a fundamental error versus TAC testing? It<br>
is a different test, no more, no less.<br>
<br>
To play devil's advocate, one could claim that Teller Acuity Cards lack<br>
ecological validity because they do not present contours and objects, which<br>
are more important to the visual system during daily living than sinusoidal<br>
or square-wave gratings. That said performance on this test and TAC ought<br>
to correlate and if this new test has other benefits (e.g, faster/easier to<br>
administer, cheaper and more available to purchase, and so on...) and has<br>
appropriate age-norms for the population being screened then might it not<br>
be an advance on traditional TAC testing?<br>
<br>
Best,<br>
<br>
C<br>
<br>
On Thu, Feb 13, 2020 at 9:36 AM Meindert de Vries <<a href="mailto:meindertdevries@visio.org" target="_blank">meindertdevries@visio.org</a>><br>
wrote:<br>
<br>
<br>
<u></u><u></u></p>
<p class="MsoNormal">Dear members ,<br>
<br>
<br>
<br>
Since 1992 I work for Visio, an institution the helps visually impaired<br>
people. We have always been using the Teller Acuity Cards to determine<br>
the visual acuity in children.<br>
<br>
A new test has been presented on the scene, proposing to replace the<br>
Teller Acuity cards, because the TAC are expensive and sometime difficult<br>
to get. I enclose an example picture of the new cards.<br>
<br>
<br>
<br>
>From my perspective and knowledge they have made some fundamental errors<br>
<br>
1. The test seems ambiguous to me, because both object recognition<br>
part of our visual system as well as the much `lower" detection part of<u></u><u></u></p>
<p class="MsoNormal">our<br>
<br>
<u></u><u></u></p>
<p class="MsoNormal" style="margin-bottom:12pt">visual system is triggered by this stimulus<br>
<br>
2. The spatial frequency content of these stimuli (checkerboard<br>
patterns with a distinctive contour) is in the Fourier domain essentially<br>
different from the TAC bar patterns without a contour; nevertheless the<br>
same cycl/cm are used.<br>
<br>
3. In addition to point 2: I think that the contour is a much<br>
stronger stimulus than the checkerboards.<br>
<br>
<br>
<br>
Could anybody reflect on this ?<br>
<br>
<br>
<br>
Most kindley,<br>
<br>
<br>
<br>
<br>
<br>
*drs. M.J. de Vries 69024716001*<br>
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