Saturday, August 31, 2013

Visual processing speed slows down as we age, making driving less safe - how to measure it and how to improve it

We slow down as we age.  But can we get some of our youthful speed back, at least with respect to visual processing?  Will treating visual processing weakness make older adults safer drivers? A new article in the September 2013 issue of the journal Vision Research suggests that the answers to these questions is "yes".

With respect to eyes and vision, the need for reading glasses is a common vision change that few manage to escape as they age. Another change, that is not as well known is changes in our visual processing speed.  

Changes in visual processing speed affect all aspects of our daily life.  Slower visual processing can make us generally inefficient as we are slow to take in and react to our visual world.  It can also make us prone to accidents.  

What can we do about declining visual processing speed? There is research that suggests that with the appropriate training, therapy and practice, visual processing speed can be improved for for many activities of daily living such as driving.  

One way to test visual processing speed is a protocol developed by doctors of optometry called Useful Field of View (UFOV).  It consists of a computer-generated series of three tests. The results are categorized into areas of visual processing weakness:

  • rapid visual processing, 
  • selective visual processing, and 
  • divided attention. 
If weaknesses are found, they can then be addressed with specific vision therapy or training based on the protocol for the UFOV.  The results can then be measured and they usually affect the speed with which older adults can perform everyday visual tasks, with the result of, hopefully, decreasing the risk of accidents.

The results of UFOV illustrate the difference between legal driving and safe driving.  Legal driving requirements are based on visual acuity - how clearly you see at various distances and whether you have the necessary peripheral vision.  Legal driving tests do not assess how useful your vision is to the task of driving. Safe driving is impacted by the driver's speed of visual information processing. The law has not caught up to vision science yet, but it is only a matter of time.

For people that have weak visual processing speed and who want to improve, developmental optometrists at our Vancouver eye clinic such as Dr. M.K. Randhawa, offer therapy programs to improve visual processing speed.  Car accidents can radically change your life for the worse, anything that can be done to avoid them is welcome.

Related articles:

Monday, August 26, 2013

Macular degeneration and depression

A new study published in the Canadian Journal of Ophthalmology found that a 21.3% patients with a macular degeneration demonstrated severe symptoms of depression. The study also found that patients who lived with others had a lower prevalence of depression, which suggests the need to help ensure that patients with macular degeneration have adequate support and live in an environment that mitigates the risk of depression.

It is not surprising that severe depression is common among patients with macular degeneration, as the disease impairs vision to an extent that it reduces a person's quality of life.

This is normal vision:

Depression and age related macular degneration

 This is vision with macular degeneration:

Macular degeneration treatment in Vancouver, BC.

At our Vancouver eye clinic, we find that maximizing a patient's remaining vision can improve quality of life and reduce depression.  Visit for more information on how low vision devices can help the visually impaired.

This is not the first study to link vision and mental health. See the following related articles:

Sharp Vision Sharp Mind 
Feb 09, 2012

Depressed? Anxious? Maybe your eyes are too dry
Apr 20, 2012


Can J Ophthalmol 2013 Aug 01;48(4)269-273, J Jivraj, I Jivraj, M Tennant, C Rudnisky

Saturday, August 17, 2013

Eye injuries from party foam, silly string and artificial snow

Eye injuries are the most common cause of blindness in kids.  And the most common cause of eye injuries is sports.  But a new study published in the June 2013 issue of the journal Cornea puts the spotlight on chemical eye injuries resulting from contact with "silly string," "party foam," or fake snow.

The study looked all patients who came to two particular hospitals with eye injuries over a two year period.  Around 100 patients had come with injuries related to party foam.

All patients suffered from chemical conjunctivitis (100%).  Chemical conjunctivitis is also kown as chemical pink eye or "toxic pinkeye".  It can also be caused by getting smoke, liquids, fumes, or chemicals in the eye. Chemical conjunctivitis can look like this:

Image: Wikipedia

79% of patients had superficial punctate keratopathy, which involves the death of small groups of cells on the surface of the cornea (the clear layer in front of the iris and pupil). Symptoms of superficial punctate keratopathy include the following redness, watering, and sensitive to light and decreased vision.

The study authors observed that 85 patients were seen in 2007 compared wit only 11 in 2008. The authors claim that the reduction was directly attributable to increased public awareness because of media coverage (newspapers, radio, and national TV) on the dangers posed by silly string.

Chemical eye injuries of the kind caused by silly string are usually easily treated in the optometrist's office.

We hope that this blog post will increase awareness and therefore contribute towards the prevention of this eye injury.


Party Foam-Induced Eye Injuries and the Power of Media InterventionCornea 2013 Jun 01;32(6)826-829, A Abulafia, F Segev, E Platner, B Simon

Silly string image: Jake Garn,, used with permision.

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Wednesday, August 14, 2013

Myopia control in children and spectacle lens design - how the right lenses can keep your eyes from getting worse

We have written extensively on the very big problem of mypoia and myopia progression.  Not only is it problematic that a child's vision gets more and more blurry as myopia progresses, it also puts the child at higher risk of developing glaucoma and retinal detachments, both of which can cause permanent vision loss.

So far, the best treatment for slowing and even stopping myopia progression is orthokeratology.  A number of studies have shown that orthokertology is effective:

Orthokeratology slows or stops the progression of myopia in children July 6, 2013

Study suggests that young children may benefit from orthokeratology February 14, 2013

New study confirms orthokeratology for slowing myopia progression January 30, 2013

Orthokeratology is shown to be safe for correcting myopia in chidlren Aug 11, 2012

Orthokeratology is shown to be effective in correcting astigmatism and myopia Jun 18, 2012
New study supports orthokeratology for myopia control and for astigmatism correction Jan 10, 2012 

As children's eye doctors we are very interested in treatments that can slow or stop the progression of myopia.

A new study published in July 2013 in the journal Investigative Ophthalmology & Visual Science suggests that the right spectacle lens design can slow the progression of myopia.   The study was titled "Peripheral Defocus and Myopia Progression in Myopic Children Randomly Assigned to Wear Single Vision and Progressive Addition Lenses".

The researchers looked at eighty-four myopic children between the age of 6 and 11 years with myopia that was measured between -0.75 and -4.50 diopters.  They were randomly assigned to wear single vision lenses or progressive addition lenses (often called "progressives" or "no-line bifocals").  The researchers then took measurements to investigate the association between peripheral defocus and the one-year change in central myopia.

The study concluded that the progressive lenses caused a myopic shift in peripheral defocus. Superior myopic defocus was associated with less central myopia progression. This suggests that lens designs like progressives that result in peripheral myopic defocus can potentially be used to slow myopia progression. 

However, orthokeratology is still the most effective way to slow myopia progression and is the only treatment that has been shown to stop myopia progression.


Invest. Ophthalmol. Vis. Sci. 2013 Jul 09;[EPub Ahead of Print], DA Berntsen, CD Barr, DO Mutti, K Zadni

Investigative Ophthalmology & Visual Science
Peripheral Defocus and Myopia Progression in Myopic Children Randomly Assigned to Wear Single Vision and Progressive Addition LensesInvest. Ophthalmol. Vis. Sci. 2013 Jul 09;[EPub Ahead of Print], DA Berntsen, CD Barr, DO Mutti, K Zadnik