Sunday, August 16, 2015

Update on the Danish optical device

I ran a few images of devices ... 

that might have been found in a Danish opticians office past Elin over the weekend.  Here is the one that she said seemed most-like the one she remembered.   This is a keratometer from the 1950s.   

In particular, it was a monocular device.  The biggest difference is that Elin recalls seeing blue and red rings, a bit like the duochrome test.  

One optometrist's page tells us that the duochrome test is often red-green, but that blue may be substituted for green on occasion.  That same page also tells us that circles are sometimes used in the test, and they're called Verhoeff's Circles.  

Don't know if this will solve the Challenge or not, but I thought I should give you this additional clue! 

Search on 


  1. I saw this thing too. It hardly seems to me to be a fun thing for kids to play with, nor even adults for that matter. Astigmatism surely is not that interesting. Is it?

    jon tU

    In case you missed it, my Danish Doctor has asked around without success--but is still working on it

  2. This image looks a lot like this tool and is known also as a Ophthalmometer. I queried [before the keratometer]

    Which leads me to ask if when using the tool did she look directly into the scope close up? The tool above would likely have a head rest based on my finding. There are some other older tools as well at this site that might help.

  3. This one has the chin rest directly under the scope

  4. I was referred to and heard back from Dr. David Goss, Professor of Optometry at Indiana University and Editor of Hindsight: Journal of Optometry History.

    "The description of concentric red and blue circles suggests to me that this was a device that demonstrated the cobalt blue filter test, also known as the cobalt disc test. Cobalt blue filters absorb light in the middle range of the visual spectrum and transmit red and blue light. The test makes use of the chromatic aberration of the eye. On this test, a white spot of light is directed through a cobalt blue filter. Persons with significant amounts of myopia (nearsightedness) will see red circle with a blue circular border around it. Persons with significant amounts of hyperopia (farsightedness) will see a blue circle with a red circular border around it. An oval may be seen in significant amounts of astigmatism.

    It is not used as a clinical test today, but a description can be found in books on refractive procedure or visual optics from a few decades ago, such as Visual Optics, 5th ed., vol. 1, by Emsley (1953, p. 101) or Clinical Refraction, 3rd ed., by Borish (1970, pp. 793-794). A fairly detailed description of the test can be found on pages 145-148 in a 1909 book by Thorington ( I hope this helps."

    If this sounds familiar to Elin, the "cobalt blue filter test" may be the technique being used. But Dr. Goss didn't say anything about the "instrument" through which people would look. I'll ask him if it was a simple tube-type viewer, or something more elaborate, like a keratometer/ophthalmometer.

  5. Good day. Thanks for the answers you got from outside the online, almadenmike and Jon tU.

    I am also looking forward to read the answer. With "cobalt blue filter test" words tried to find new answer and no luck so far. Just other name for Keratometers= ophthalmometer.

    With [cobalt blue ophthalmometer 1940 denmark optician stores] images. Results show and old ophthalmometer

    Early 1900's F. A. Hardy & Co. Ophthalmometer-Optical Examination Device Odditie

    Out of topic. I was reading first SearchReSearch posts. It is very interesting. Glad you post with us, Fred! And also I was thinking about my "six degrees of separation" to be able to find Dr. Russell's site. It is kind of magic.

    Have great week

  6. Here is what Dr. Goss had to say about how the cobalt test would be viewed:

    "My guess is that the instrument that Elin described included just a tube with perhaps a simple lens system for viewing the light passing through the cobalt blue filter. It may in fact have looked like the tube portion of the keratometer that you referenced - one component of a keratometer is a telescopic system for viewing the reflection of an image from the surface of the cornea.

    "Her description does not sound at all like the duochrome (or bichrome) test. In that test, black letters or black Verhoeff circles are viewed against a background of red on one side of the chart and against a background of green on the other side of the chart. So it involves black circles (or letters), and the red and green are backgrounds which are side by side and not circular.

    "I have viewed the colored circles produced by a cobalt blue filter. Myopia and hyperopia can be simulated with plus and minus lenses. The colors are quite striking, so I can see how it would catch the interest of passersby."

  7. I think Dr Goss is very close to the target. I tried the translate and search too with nothing even close.


  8. After reading Dr. Russell's answer:

    [1950 danish ophthalmometer]

    Gives good possible results. Still need to read them. Quick reading with Ctr-F "Astigmatism", says:

    "Ophthalmological eye care in the 1950s...Refraction and prescription of glasses took up a substantial part of the time. Refraction was performed subjectively with the Snellen letters at 6 m using fogging, cross-cylinder and astigmatic fan. Objective methods were the ophthalmometer (Javal-Schiøtz and Helmholtz principle) and sciascopy (retinoscopy)...

    Also, wrote to European Society of Ophthalmology after finding them with [danish ophthalmological society] with no answer yet.

    1. This past weekend I also send the query to the Optisches Museum der Ernst-Abbe-Stiftung Jena in Germany and the European Council of Optometry and Optics.

      The museum contact wrote back that they'll respond within two weeks, and the ECOO contact said she's forwarded the question to their Danish and German members.

      I'll post the reponses that I receive.

    2. I've just heard back from the Harold Kohn Vision Science Library at SUNY College of Optometry. Dr. Jay Cohen also says the test in question appears to be the "Cobalt Disc" and sent me a scan of p. 714 from the 1998 book "Clinical Refraction" (editor: William J. Benjamin) that describes it. He said he knew of no photos of the test apparatus and that it has not been in clinical use since the 1950s. The scanned article said the Bichrome/Duochrome tests do at least as well, and are much better for "color deficient" subjects.

      (Note: "Clinical Refraction" can be found on Google Books (, but there are no previews.)

    3. Almadenmike, Dr. Russell this is the image that I found with Almadenmike post.

      ["cobalt disc" optician] in Images. No Url, just that image in the results