May 2015

Eye on Vision May 2015 Newsletter

In this issue:

 


 

 

 

This month in Eye on Vision Video

 

 

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I want to take a moment to say THANK YOU to everyone who came by to visit Amy and me at our booth in Denver at ARVO earlier this month. It’s always at the top of our list of favorite meetings and was such a exciting and energized time for us. I could fill page after page writing about all the fun and friends we were able to see, interesting people we met, conversations we had and events we attended. 

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We even got a lesson from Dr. Robert Enzenauer, MD on why pirates wore eye patches after a discussion about Patti Pics being chosen for Penny the Pirate. That was funny, embarrassing and memorable.

 Much of the time our booth felt like a busy airport where old and new VIP friends made a quick landing to say hello, share stories, exchange information, collaborate on new projects and much more. Sometimes there were only seconds to say “Hi, I’m late for (_______) but there’s something I have to talk to you about and I’ll be back later,” while barely breaking pace as they dashed by.

We love hearing about how our products are used in research, clinical settings and clinical trials. ARVO is “the” meeting where that all comes together in high doses. It’s so rewarding to have the privilege of serving all the individuals we do in this vast, multi-faceted world of vision care and research. Again we were honored to be chosen to work on several new groundbreaking  projects that will be keeping things interesting and challenging for the next several months. We look forward to sharing more about them, when it’s appropriate to do so.

Our new LED ETDRS Cabinet had an amazingly warm reception from everyone.  The features, quality and construction earned two thumbs up unanimously, from dozens of people, including those at governmental agencies whose opinion, acceptance or approval is very relevant.

Many visitors at our booth took interest in the LuxIQ as well and identified it as a great device to vary and control lighting at near distance for research and trials. 

There’s so much more to say but I must stop at some point. Thank you again to everyone who stopped by. It was a great pleasure to see you again. To those we missed we hope to see you at next year’s meeting or one of the others we’ll be attending before then.

 Best regards,

 

Ed Kopidlansky Jr.
President
Precision Vision

P.S. Want to know why Pirates wore eye patches? Click here to read interesting eye fact #6 in our article on Healthy Vision Month.

 

 

Drs. Legge and Massof Receive Prestigious Award from

The Helen Keller Foundation

 

Precision Vision would like to congratulate Dr. Gordon Legge, Creator of the MN Read Chart and Dr. Robert Massof for being this year’s recipients of the Helen Keller Prize for Vision Research. Presented at this year’s ARVO Gathering the Prize was created in 1994. The Prize Selection Committee  includes scientists and research physicians who are leading figures in the international vision research community.

 

In creating and awarding the Helen Keller Prize for Vision Research, the Helen Keller Foundation for Research and Education  hopes to open the eyes of the world, not only to the need for vision research, but to the critical need to support that research in order to secure for future generations the precious gift of sight.

 

 
In Celebration of Healthy Vision Month
 

As many of you know May is Healthy Vision Month. Brought forth by the National Eye Institute the event emphasizes the importance the proper care and protection of your eyes through the following:

  • Getting a Dilated Eye Exam
  • Living a Healthy Lifestyle
  • Knowing your Family History
  • Using Protective Eyewear
  • Wearing Sun Glasses 
 
In celebration of this event Precision Vision scoured the web to find interesting factoids about your eyes.  What follows is our list of 10 interesting eye facts for your enjoyment and edification

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  1. The highest visual acuity ever measured (to the authors knowledge) was in an unnamed Aborigine man. His visual acuity was 6/1.5, meaning that he could read a chart from 6 meters away as well as someone with “normal” vision could read it from 1.5 meters away. (source: James Pitt, Quora.com)
  2. An Eagle has a visual acuity of 20/4. That means that what a human with 20/20 eyesight can see clearly at 20 feet, an eagle can see it with the same clarity at 100 feet. (source: improveeyesighthq.com)
  3. Our eyes have an imperceptible reflex that prevents our vision from blurring as we move. New research from John Hopkins Medicine describes how the wire-like projections of specialized nerve cells find their way from the retina to plug into the correct part of the brain. (source: John Hopkins Medicine)
  4. Our eyes are made up of over 200 million parts. (source: Lenstore.co.uk
  5. If the eye was a digital camera its resolution would be 576 megapixels. (source: clarkvision.com)
  6. The reason Pirates wore eye patches had nothing to do with missing an eye, and everything to do with being able to see when they moved from the broad daylight of a ship’s deck to the near darkness below decks. (source: Mentalfloss.com)
  7. The entire length of all eyelashes shed by a human in their life is over 98 feet with each eye lash having a life span of about 5 months. (source: dicoveryeye.org)
  8. Carrots don’t make your eyesight better. That was a bit of misinformation spread by the British during WWII to cover up their R.A.D.A.R technologies from the Nazis. (source: washingtonpost.com)
  9. Eyeglasses or contact lenses prescribed for general use may not be adequate for use with computer video display terminals (VDT). Special occupational lenses prescribed to meet the unique demands of VDT work may be needed. (source: American Optometric Association
  10. The American Association for Pediatric Ophthalmology and Strabismus (AAPOS) recommends that vision screenings should be conducted for children as early 3 months of age. Especially if the infant does not track well after 3 months of age or the infant has an abnormal red reflex or history of retinoblastoma in a parent or sibling.(source: aapos.com

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In our next Ask PV we look at a very frequently asked question:

Q: Early contrast tests used sine-wave gratings; in 1988 Pelli and Robson introduced their chart based on letter recognition.  Which is the preferred one?

 

To answer this question we polled three world renown experts on the subject matter: Dr. August Colenbrander, Dr. John Robson and Dr. Ian Bailey:

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August Colenbrander, MD:

Early studies of human contrast sensitivity were built on studies for the design of lens systems.

For such studies, including studies of the optics of the eye and the correction of refractive error, sine-waves are often preferred because they have advantages for calculations.

 

However, when attention is broadened to the entire visual system and eventually to visually-guided behavior, we must consider not only the optics of the eye, but also the characteristics of the photoreceptors and the effects of neural processing, which starts in the inner retina, and continues in the visual cortex and in higher visual centers.

 

Repetitive patterns, such as gratings, are common in man-made objects, but not in natural scenes.  Fuzzy edges, as in sine-wave gratings, are not common in natural scenes either.  It is highly unlikely, therefore, that the neural system would have evolved to detect sine-waves.

An important function of the retina is edge detection and edge enhancement; thus the detection of sharp edges, as in letters on Pelli-Robson and Mars cards, appears to be closer to the detection and interpretation of natural forms than is the detection of sine-wave gratings.  It thus may be a better predictor of the ability to perform Activities of Daily Living (ADL). 

John Robson, MA, PhD, ScD:

Measurement of the contrast threshold for sine wave gratings of many different spatial frequencies allows a subject’s complete “contrast sensitivity function” to be explored directly.  However, there is little evidence that this time consuming measurement  provides a clinically more useful assessment of the subject’s visual capabilities than can be obtained more expeditiously and precisely by conventional measurement of acuity together with measurement of  contrast sensitivity for a test pattern whose visibility is  dependent upon the peak value of the subject’s contrast sensitivity function.

It would in principle be possible to measure a subject’s peak contrast sensitivity using a sine-wave grating of appropriate spatial frequency, but grating test patterns do not lend themselves to incorporation into the robust and rapid psycho-physical procedures that are important for practical testing in a clinical setting.  Speed and robustness can most easily be obtained by using a “many-alternative forced choice” psycho-physical method where the subject is required to identify which of many alternative test targets is being presented.   

Such a procedure cannot in practice be satisfactorily implemented using grating patterns. However, a procedure with 10 or more alternatives is conveniently implemented using letters (of appropriate angular size) with which most subjects are extremely familiar and can easily name.  The importance of the many-alternative identification  procedure was recognized by Hermann Snellen when he designed the first acuity charts and it is the adoption of this procedure with 10 or more different letters in contrast sensitivity charts such as the Pelli-Robson and Mars cards which primarily accounts for their reliability.  

Ian Bailey, OD, MS, FBCO, FAAO
There is a special sweetness about the mathematical approach of analyzing the light distribution within a visual scene in terms of “Fourier” sinusoidal components, and then using the observer’s contrast sensitivity function (CSF) to predict the visual percept- that is, how the scene will be seen. However, this theory often fails to predict the visual capabilities or difficulties of observers with damage to the neural components of the visual system. Macular degeneration is an obvious example.

The major practical problems that patients have as a result of impaired contrast sensitivity are related to mobility and orientation. Being able to detect objects and navigate efficiently largely depends of the visual detection of borders or edges. Contrast sensitivity tests should determine thresholds for edge detection and this means that test targets for detection or recognition should have sharp visual edges. The widely used Pelli-Robson test and the Mars test do this by having their test targets as letters or numbers of relatively large angular size.

With such targets, the contrast threshold for detection is similar to that for recognition. If you can see that it is there, it might take time but you probably recognize the shape.
Testing contrast sensitivity with sinusoidal targets of low spatial frequencies may have some value in predicting how well the observer might be able to see some things like undulations in the surface of a walk-path, using CS tests that have sharp edges has more broad relevance to understanding and predicting functional abilities at real world tasks, especially orientation and mobility.

 

Update from Nepal Mercy Clinic
I am sure you are all aware of the devastating earthquakes that rumbled through Nepal on April 25, 2015 that killed more than 8,000 people while leaving over 18,000 injured.  In an attempt to find out if these quakes affected the remote Mercy Clinic we reported on in last month’s Eye on Vision we found this Facebook posting from TEAM| The Evangelical Alliance Mission whom Ted and Rachel MacKinney, featured in last month’s article are members. In the post  dated April 25th:

For more information on TEAM and the Nepal Mission please go to their Facebook page at: https://www.facebook.com/TheEvangelicalAllianceMission.

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