Contrast Sensitiviy Test for Tablets

Contrast Sensitivity Function

What is the ClinicCSF Test?

The ClinicCSF is a Professional APP for measuring the Contrast Sensitivity Function with Sinusoidal Gratings.

Who Developed the ClinicCSF?

The ClinicCSF has been entirely designed and programmed by Optometrist Researchers. 

Who is the ClinicCSF recommended for?

The ClinicCSF is recommended for the clinic use by Optometrist or Ophthalmologist. 

Version 1.0.2. Only for Tablets (Please, don´t buy to use on smartphones)

  • Sinusoidal Grattings as stimulus.
  • 4 basic spatial frequencies (3,6,12,18 c.p.d).
  • Sound Feedback.
  • Comparison of results with normal age ranges.
  • A Fixation Mask to recognize where the stimulus is
  • Results showed on a Figure with normal values for different ages.
  • Stimulus generated after calibration with Spyder4Elite on IPad 2 and IPad Retina.
  • It offers the possibility to personalize the contrast levels of the sinusoidal grating and generate your own Calibrated Software. (Please contact with us to know more about this advanced option - Best option for researchers).

What is the Contrast Sensitivity Function?

Contrast in Sinusoidal Gratings

Contrast Sensitivity is a psychophysical measurement of Visual Function. It is defined as the inverse of the minimum quantity of contrast that an observer would be able to detect. A general definition of spatial contrast is that it is a physical dimension referring to the light-dark transition of a border or an edge of an image that delineates the existence of a pattern or object. Contrast is defined as the ratio of the difference in the luminance of these two adjacent areas to the lower or higher of these luminance values (Owsley, 2003).

There are two common ways in vision for expressing contrast. These ways are associated with the different kinds of Clinical Test. The Michelson contrast usually applies to periodic patterns such as Sinusoidal or Square Grattings. At the left image we show a Clinic CSF stimulus calculated by Michelson Contrast. In other way, no periodical patterns as optotypes are presented on spatially extended white backgrounds, contrast is tipically defined as luminance of the background (Lmax) minus of the luminance of the letter (Lmin), divided by the luminance of the background (Right Image). For measuring Visual Acuity at Low Contrast, please visit Amblyopia Visual Acuity Test for Tablets.

How we calculate Contrast Sensitivity for IPad and other Tablets?

For the design of psychophysical clinical test with computers or portable devices as Tablets or Ipads, it is very important to translate digital color levels of screen (RGB) to Luminance and Chromatic Coordinates values (CIE). This process could be achieved with different devices such as spectroradiometers or colorimeters. The prizes of those instruments could differ highly.

We have measured the chromatic characteristics of the devices for which Clinic CSF is available with the Spyder4Elite Colorimeter. We developed visual stimulus considering the obtained values with the chromatic measurements of the screen. We assume that the same models not should differ so much between them. I would like to thank ColorLab developers from University of Valencia particularly to M.J. Luque because Clinic CSF uses their free Matlab Toolbox. The visual stimulus package is external loaded by the software so it has the possibility for Researchers to load their own stimulus and contrast values (Please fill contact form for further information about this). 

The Clinic CSF has been developed with Matlab (to generate visual stimulus) and ActionScript 3.0 to implement the pshychophysical methods into Tablets and IPad. We also use MadComponens to generate menu and Screen Results so I would also thank Daniel Freeman for sharing their project with us. 

 

General Procedures with the ClinicCSF.

The ClinicCSF can be used to evaluate Visual Performance with Normal Optics (Glasses) or Corrective Contact Lenses. Also you could evaluate Visual Pathways, this process could undergone some changes depending on the needs of the Experimenter.

  • Patient should take the best correction in glasses if you want to evaluate Visual Pathways.
  • Test is performed in monocular vision unless you want to examine Visual Performance in Binocular Visión.
  • Distance between patient and Tablet should be 2 meters.
  • The Optometrist should explain the test process to the patient. Noting that sometimes will not see the stimulus.
  • The Optometrist should press the button indicating the response of the patient. If the patient refers not seeing, Optometrist should press any of button alleatory.
  • Test automatically calculates the next contrast and spatial frequency to present. Optometrist should only worry about motivate patient to blink after each response until the test is completed and the results window is showed.

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People in this conversation

  • Guest - serena speaker OTR SCLV

    Can this test be used at any closer distance than 2 meters. I am a low vision occupational therapist that performs testing in the home. Most of my clients prefer 16 cm near test distance. Is this possible with this test?
    I am presenting CSF program at USA national conference, Envision Conference, sept 12, 2015 in Denver. I would like to add this test to the range of tests that participants will be exposed to for use in their practices. Investigation indicates that I will need to add a non-glare filter to the iPad screen to eliminate the glare factor. What are your thoughts?

    from Brenham, TX 77833, USA
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  • Dear Serena,

    I appreciate your comment, the test has been designed to be presented at 2 meters of distance and if you present it at less distance you will be assessing a lower spatial frequency range. I believe in standardization therefore I do not recommend this test for low vision patients because it has not been designed for this population. Anyway, I am working in other tests for the future that may be interesting for this population.

    With regard your second question you should consider this:
    1.- I developed ClinicCSF to be presented at mesopic vision with no overlights that may reflect in the screen.
    2.- If you use a glare filter you have to calibrate the screen with that filter and nowadays there is not any app that offers you the possibility to insert your own calibration data measured with a colorimeter as Spyder4Elite (I am working now on that).

    Please, feel free to contact with me by contact form in order to anwer any other particular question or by LinkedIn https://es.linkedin.com/in/manuelrodriguezvallejo/en

    It will be a pleasure to answer all your questions

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