For low vision specialists and those who consult them
Monthly Archives: March 2010
March 25, 2010Posted by on
My Apple iPhone is one of my favourite gadgets, and I was interested to see that there is now a magnifier app known as ‘iCanSee’ available through iTunes for 59p (or 99¢).
It has a zoom function which claims to magnify up to 4x, although when I tested it the maximum magnification setting only equated to 2x at the closest working distance which did not blur the image. The autofocus works pretty well on my 3GS (I don’t think other versions of the iPhone have focusing cameras so the app may not work as well on those). On my phone it focuses down to a minimum distance of about 10cm and the motion blur when the phone is moved along a line of text isn’t bad at all. I should mention that it’s pretty unusable unless you enable the full screen mode. It’s also pretty good for distance magnification, although it’s much harder to hold a phone steady than a monocular telescope.
It’s a shame it doesn’t have any image processing abilities, like contrast reversal or contrast enhancement, as I imagine the iPhone processor should be fast enough to allow this. It’s also a shame that higher magnification isn’t possible.
At present I think the app will be more useful to presbyopes who have forgotten their reading glasses than to people with visual impairment. However I think we will see more sophisticated software like this in the future: the next generation of electronic magnifiers will probably ‘piggyback’ onto existing technology rather than requiring new hardware. After all, I’ve yet to see an electronic magnifier company produce anything as attractive as an iPhone…
March 17, 2010Posted by on
Last week’s edition of the British Medical Journal had a good review article on treatment of age-related macular disease. I’d recommend it as an overview to anyone who is interested in this topic, but there is a serious oversight (to my mind): there is no mention at all of the role of low vision services. This is particularly concerning as the journal’s primary audience is general practitioners (family doctors) who may well be consulted by patients for whom AMD treatment is not appropriate. The authors go so far as to mention that many people with AMD will not be able to perform visual tasks (after treatment) but make no further suggestion as to what should be done at that stage.
Together with some colleagues, I have written a letter to the journal to point out this oversight: it should be available on the BMJ website but to save you the effort of trying to find it I’ve duplicated our letter below.
We read with interest the excellent review paper by Chakravarthy which provided a clear overview of pharmacological treatment for age-related macular degeneration (1). However we were concerned that the role of low vision clinics was not mentioned in this article.
Intensive low vision services, which include the prescription of optimal spectacle correction, optical and electronic magnification, and advice on strategies to maximise residual vision, have been shown to improve visual ability in people with macular disease with an effect size equal to a visual acuity improvement of 8 lines of visual acuity (2). Even a single one-hour consultation in a hospital based low vision service improves quality of life by a similar amount to a treatment which restores 5 lines of visual acuity (3).
As Chakravarthy highlights, even after treatment which successfully restores retinal structure, many people still experience difficulty with critical visual tasks such as reading and face recognition. These are tasks with which low vision rehabilitation can assist (4) yet there is evidence that people who have received such treatment are less likely to be referred to low vision clinics (5).
We urge colleagues to ensure that referral to a low vision clinic is made for those people with macular disease where treatment is not indicated and for those where treatment does not restore the visual function to pre-disease levels.
Michael Crossland PhD MCOptom
Angela Rees MD MRCOphth
Gary Rubin PhD
Professor of Ophthalmology
1. Chakravarthy U, Evans J, Rosenfeld PJ. Age related macular degeneration. British Medical Journal 2010;340:526-30.
2. Stelmack JA, Moran D, Dean D, Massof RW. Short- and long-term effects of an intensive inpatient vision rehabilitation program. Arch Phys Med Rehabil 2007;88(6):691-5.
3. Pearce E, Crossland MD, Rubin GS. The efficacy of low vision device training in a hospital based low vision clinic. British Journal of Ophthalmology 2010;In Press.
4. Margrain TH. Minimising the impact of visual impairment. Low vision aids are a simple way of alleviating impairment. British Medical Journal 1999;318(7197):1504.
5. Sunness JS, Schartz RB, Thompson JT, Sjaarda RN, Elman MJ. Patterns of Referral of Retinal Patients for Low Vision Intervention in the Anti-Vegf Era. Retina-the Journal of Retinal and Vitreous Diseases 2009;29(7):1036-39.
March 11, 2010Posted by on
I have just read an interesting paper by Yu and colleagues from Minnesota in the most recent edition of Journal of Vision. I don’t often review papers based on people with good vision in this blog but I think it has some useful implications for people with some forms of visual impairment.
In it, the authors compare reading speed for text presented in four different forms. The first form is conventional, horizontally arranged, left-to-right words. They then look at text rotated 90º clockwise or anticlockwise (the same as rotating a book so the spine is horizontal). The final form is ‘marquee’ text where words are vertical but characters are the correct orientation,
For their most natural condition of extended lower case text, they find (unsurprisingly) that reading is quickest for conventional text. Roatating text clockwise or anticlockwise makes reading about half as fast, and the marquee form is slower still: it reduces reading speed to about one third of normal values.
Interestingly, rotating text clockwise gave slightly (although not statistically significantly) faster reading speeds that rotating anticlockwise. The authors speculate that reading top-to-bottom may be more natural than reading bottom-to-top.
Why is this relevant to a low vision blog? Well, as the authors point out, if someone with no central vision from macular disease uses retina to the side of their macula, rotating text may be a useful strategy so that letters do not fall into the non-seeing region. It shows that a simple page rotation is probably more useful than manipulating text into ‘marquee’ format.
What the authors don’t discuss (I was disappointed to notice) is people with hemianopia (where half of the visual field is missing, usually as a consequence of stroke or brain injury). In my clinical experience many people with hemianopia find text rotation useful, so that a whole line is visible at one time. This work shows that this simple rotation of text may be more useful for these people than any more complicated text manipulation approaches.
March 2, 2010Posted by on
Many people in the field of vision rehabilitation are concerned with ensuring that low vision services are available to as many people as possible. But does every visually impaired person want to receive low vision services?
I must confess that I had not given this question much thought: like many of my colleagues I assume that low vision clinics should be accessible by everyone, and would argue strongly that every person with visual impairment should be assessed in a low vision clinic at least once. However, a recent post on the AAO vision rehab mailing list has made me question this. Dan Roberts, the director of MD Support, has surveyed a small group of people with AMD who have not received low vision rehabilitation. He identified 18 people who had not received low vision rehab, and asked them why they hadn’t been to a low vision clinic. To quote directly from his report:
1 (6%) did not know Low vision rehab (LVR) was available.
4 (22%) knew LVR was available, but were not encouraged to pursue it.
5 (28%) were encouraged to pursue LVR, but felt it unnecessary, either because of still-satisfactory vision or knowledge gained from other resources.
4 (22%) were encouraged to pursue LVR, but couldn’t afford it.
4 (22%) found LVR sessions too inconvenient, due to distance or time.
This small survey shows that the barrier to accessing rehab is not entirely due to lack of awareness or accessibility but simply that some people are not interested in pursuing vision rehabilitation.
Of course this is a very small sample of a very self-selecting group (those who subscribe to a macular disease email list, who are likely to be better informed than the general population). All of the subjects had internet access and sufficient vision to use a computer (presumably without Zoomtext or other text enlargement software). And, consistent with other studies, some people were indeed found to be discouraged by the cost of low vision rehabilitation or the distance to the clinic.
This survey could be seen as evidence that we don’t communicate the benefits of vision rehabilitation to potential service users clearly enough. However, the point remains that not every visually impaired person wants to attend a low vision consultation.