For low vision specialists and those who consult them
Monthly Archives: July 2009
July 29, 2009Posted by on
A few weeks ago I wrote about my experiences with the Sony Reader and whether it would be useful for a low vision user. The full post is here, but the punchline was: no, it’s not very useful for people with low vision.
However, I had high hopes for the Amazon Kindle 2. I managed to borrow a Kindle for a few days and performed some of the same tests with it as I did with the Sony Reader. Both devices use a similar size (15cm diagonal) electronic paper display, although the Amazon device is significantly thinner.
The most important function for a low vision user is text size. I had high hopes for the Kindle in this respect: its zoom function has six settings compared to three on the Sony. Unfortunately this does not mean larger text: the maximum text size is the same on both devices at 0.7 logMAR. This means that users without a visual acuity of about 0.3 logMAR (6/12; 20/40) would struggle to read the display for a prolonged period of time.
Interestingly, the minimum size is also the same (0.3 logMAR) so the Kindle just has more graduations of size between these two extremes. Maximum contrast is the same on both devices at about 60% Michelson contrast. This is probably a limitation of the electronic paper technology rather than anything else, so it’s perhaps unsurprising that this is the same.
One area where the Amazon device is far superior to the Sony Reader is in its experimental Text-to-Speech application. This is a relatively good text reader which speaks at about 200 words/minute at its maximum speed. 200 words/minute is slower than many experienced screen reader software users would select, but not far off “normal” book reading speed. Unfortunately the device does not include audio menus, although I understand this is being worked on.
There is some discussion amongst publishers as to whether text-to-speech violates Amazon’s copyright agreement (I imagine this is to do with audiobook rights, although there is a massive difference between automated reading software and a professional audio publication with a trained actor reading text).
So in summary, the Amazon Kindle is probably about as (in)accessible to the visually impaired user as the Sony Reader. If forced to choose between the two I would recommend the Kindle because of its text-to-speech function and I found its menu interface to be more intuitive.
Maybe the next generation of electronic books we accommodate those with low vision by allowing large print sizes?
July 23, 2009Posted by on
One of my friends in web development told me authoritatively “you should use sans serif fonts to make websites easier to read by people with visual problems.” It seems that this is a reasonably widely held view, but the research doesn’t really back this claim up. Indeed, the choice of font is of very little importance on legibility for people with low vision.
In a group of people with low vision, Rubin and colleagues did not find any difference in reading speed between four different fonts provided that character size was properly controlled for (Rubin, Feely, Perera, Ekstrom & Williamson, Ophthalmic & Physiological Optics, 2006). Interestingly, one of those fonts was specifically designed for people with low vision (Tiresias) but this did not really improve reading ability.
In a study of older adults with normal vision reading on a computer screen, another study did not find any difference in reading speed between four commonly used fonts (Bernard, Liao & Mills, Conference on Human Factors in Computing Systems, 2001).
Arditi and colleagues at Lighthouse International in New York have developed a software system for bespoke font construction for people with low vision. Using this system, people can alter many parameters of text such as letter spacing, the type of serifs (decorative elements at the end of each letter, such as those at the end of the top bar in a letter “T” in the Times New Roman font) and ascender or descender height. Whilst there is a significant variability between subjects in the typeface they select, these bespoke fonts do not appear to improve reading above that for common fonts such as Times New Roman (Arditi, Ergonomics, 2004).
Over the 600 year history of printing, typefaces may well have evolved such that the most readable fonts have survived, whilst less readable typefaces such as Blackmore have fallen out of favour.
Advice for web developers: use high colour contrast, high contrast text, use a predictable text format (e.g. left aligned) and most importantly, use good coding practice so that people with screen readers can manipulate the text as they desire. But don’t get hung up on what font to use.
Book review: “Low Vision Rehabilitation: A practical guide for occupational therapists” by Scheiman, Schieman and Whittaker
July 21, 2009Posted by on
This is an excellent overview of low vision rehabilitation which is intended for the Occupational Therapist but would be of equal benefit to educators, low vision support workers, ophthalmic technicians, clinicians new to low vision rehab, or families of people with visual impairment.
It starts with a very clear introduction to epidemiology of visual impairment, basic anatomy and optics, and the pathophysiology or common causes of low vision. Whilst this overview would be insufficient for an optometry student revising for exams, it ensures that the intended reader is not left behind by terms in the rest of the book.
The second section presents the optometric and occupational therapy models of low vision evaluation. The bulk of the book, rather optimistically entitled “treatment”, covers optical low vision devices, nonoptical devices, electronic magnifers, environmental modifications and computer technology in low vision rehab. It also includes an excellent chapter on diabetes self-management which is often overlooked in other textbooks. The final section describes pratice management for the low vision practitioner.
I have some reservations over the section entitled “treatment”; as low vision professionals we are able to ameliorate some of the difficulties people with visual impairment experience but I really don’t think it’s fair to say that we treat anything. This may sound like a pedantic point, but I think it is misleading to our clients/patients/service users if they think they are being referred for a low vision “treatment”. I was also disappointed to see quite heavy used of low vision simulation photographs in the text: I think it is now reasonably well accepted that a photo of a scene with a black pattern in the middle is not a realistic simulation of vision with a macular scotoma, for example.
However, these are minor gripes about what remains an extremely readable, useful overview of low vision rehabilitation which may well find readers beyond its intended audience.
July 17, 2009Posted by on
In my last post I mentioned that traumatic brain injury (TBI) is an increasingly important cause of visual impairment in the USA, in particular in returning servicemen. As it happens, a paper in the July Optometry & Vision Science by Brahm and colleagues discusses this issue in depth.
It is important to realise that although military personnel from the Iraq and Afghanistan conflicts are the most publicised group of people with TBI, in the USA 650,000 cases of TBI are caused every year by road crashes and falls.
Brahm and colleagues examined data from 68 inpatients with moderate-severe TBI and 124 outpatients with mild TBI. All were veterans.
Of those with severe TBI (inpatients), 22% had vision of worse than 20/70 (6/21), with 3% of the sample having no perception of light.visual impairment of but had at least light perception; of 20/100 (3/60) to PL; and 6% had visual acuity between 20/100 (3/60) and 20/70).
About one-third of the inpatients and 3% of outpatients had visual field loss with most of these being hemianopia defects.
A very large proportion of the population reported reading difficulties (87% of outpatients; 66% of inpatients) which may be caused by other ocular and oculomotor problems identified in this study, including convergence insufficiency, accommodative insufficiency, strabismus and saccadic dysfunction.
The paper has really emphasised to me that TBI is a very varied diagnosis which probably encompasses many different conditions. I was particularly interested to learn about the large number of civilians who may also have this condition. Encouragingly, a relatively high proportion of the TBI population would appear to have visual problems which could be helped with low vision rehabilitation, and I imagine that this is an area we will hear more about in the coming years.
July 13, 2009Posted by on
I am looking forward to two low vision conferences in the next six months.
In September, I’ll be making my first trip to the Envision Conference in San Antonio, Texas. This is a multidisciplinary meeting which is aimed at clinicians, rehab workers and researchers interested in visual impairment. Although I will only be at the meeting for one day (the Friday, when I’m speaking), the whole programme looks very interesting. I am particularly looking forward to hearing Greg Goodrich speak about traumatic brain injury (TBI) related vision loss in survivors of the Iraq and Afghanistan conflicts. I have yet to see any patients with TBI in clinic (I think it is better recognised in the US than the UK) but, unfortunately, this is likely to become a more common problem for us.
Then in November I will be attending the American Academy of Optometry meeting in Orlando, Florida. The low vision stream here looks particularly strong, with a low vision stream running continuously through the meeting. I haven’t had chance to fully preview the programme yet, but it looks like there are some high-quality speakers presenting on interesting topics.
Of course, I will keep you all updated through blogging and twittering from each meeting…
July 10, 2009Posted by on
The major purpose of my US trip was to spend some time in the Minnesota Laboratory for Low Vision Research, Dr Gordon Legge’s lab at the University of Minnesota. Dr Legge’s particular interest is in reading with visual impairment and he is unquestionably a world expert in this field.
A significant contribution which Dr Legge has made is the seminal Psychophysics of Reading series of papers (recently published in book form as Psychophysics of Reading in Normal and Low Vision: amazon.com link; amazon.co.uk link). He also developed the MNREAD reading speed test which has become the gold standard for measuring reading in people with low vision.
Gordon’s lab has recently purchased a MP-1 micoperimeter and I was pleased to be able to share some of my experiences with this instrument with the people in the lab, and I also gave a teaching session on the MP-1.
We had a very interesting series of discussions about what exactly constitutes a preferred retinal locus (the retinal area repeatably used for fixating a target by people with central vision loss) and how this can be defined. We also had some stimulating discussion about the role of artificial scotomas in rehabilitation research – to what extent can simulated central vision loss mimic the performance of people who have “real” central vision loss caused by macular disease or other conditions? Expect more on these topics in future blog posts…
July 2, 2009Posted by on
This item will be of particular interest to researchers thinking of where to submit their next paper, and for people who read journal articles on low vision.
The 2008 Journal Impact Factors have been announced. The impact factor of a medical or scientific journal relates to how many times each article is cited by other articles, on average. If a journal is full of cutting-edge research then many people will cite it, and the impact factor will be high. If no-one reads it, or if the research it contains isn’t important, it will have a low impact factor.
Very high impact factor journals tend to be the general medical and scientific journals which attract a large number of submissions (so they can be selective) and a large number of readers. Near the top of the tree are New England Journal of Medicine (impact factor: 50), Nature (31) and Science (28).
I’ve summarised below some of the journals which low vision research is published in…
Ophthalmology: 5.30 (2/41 ophthalmology journals)
Investigative Ophthalmology and Vision Science: 3.58 (4/41)
Retina: 3.48 (5/41)
Journal of Vision: 2.95 (9/41)
British Journal of Ophthalmology: 2.86 (10/41)
Eye: 2.06 (17/41)
Vision Research: 2.05 (18.41)
Optometry and Vision Science: 1.58 (22/41)
Ophthalmic & Physiological Optics: 1.00 (37/41)
Impact factor is only one measure of journal quality, and for many of us the readership is more important (if I wanted my paper to be seen by vision scientists I would rather submit to Vision Research or Journal of Vision than Ophthalmology, for example). But most of us, I suspect, send our best work to journals nearer the top of this list to start with.
Sorry if this isn’t directly interesting to those of you who read this blog from outside the science community: I will have something more clinically interesting for my next update.
July 2, 2009Posted by on
I just received a message from Optolec announcing a fall in price of their Compact+ video magnifier (in the US it’s now $595 – no news on whether the UK price is falling yet).
I like handheld video magnifiers – they are a nice mechanism for providing relatively high magnification, with minimal distortion, and contrast manipulation. The current generation have largely got over the problems of image smear and excess heat, and are relatively affordable. Perhaps most importantly, some of them (the SmartView and Compact+ spring to mind) actually look quite cool.
Having said that, I think that they can still not replace optical magnifiers for many tasks. Many people seem to prefer using a relatively low power hand magnifier for shop prices (maybe a +12D Eschenbach folding magnifier, or a +24DS COIL LED Illuminated Hand magnifier). An appropriately prescribed optical magnifier can still be less bulky and far quicker to use.
For example, a patient I saw relatively recently had already purchased multiple electronic devices — including a head mounted device (JORDY 2, I think, at a cost of several thousand pounds), but wanted something to be able to see the spine of books in a bookshop. He was absolutely delighted with a +12D non-illuminated hand magnifier (net cost about 60 pence ($1; €1). Although technology is great, don’t overlook the simple solutions.