Low Vision News

For low vision specialists and those who consult them

Monthly Archives: December 2009

lowvisionnews.org – the first six months

As the year draws to a close, I have been looking at the stats for this blog. Since starting on June 24th 2009, there have been 2,021 visits to the blog posts – an average of 58 readers per post.

The top five most visited posts (excluding the ‘about’ page) were:
2008 Journal impact factors
Sony Reader: a missed opportunity for low vision users
Opinion piece: Low vision care in a state funded health system
What is the future of assistive devices for the visually impaired?
2009 Conference previews

I have had some very interesting emails and discussions with people who have read the blog: professionals and service users; researchers and clinicians. In 2010 I will continue posting research and conference news of interest to low vision specialists and people with visual impairment.

Any suggestions for future posts, or comments on the frequency of posts (initially two posts per week, now generally one post each week) will be gratefully received – the “comments” section is open.

Finally, I wish every reader of lowvisionnews.org a very happy new year.

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Journal article: Perceptual learning increases reading speed (in young control subjects reading with peripheral retina)

There is an interesting article in this month’s Vision Research by Yu and colleagues which examines training reading performance in the peripheral retina of people without eye disease. The idea of this study is to see whether training may be useful for people with macular disease who must use their peripheral retina to read.

The authors recruited university students and trained them to read with an eccentric part of the visual field (10ยบ below the centre of the vision) for one hour a day for four days. This training consisted of either reading words presented one at a time; making a judgement over whether three letters were a word or not (a lexical decision task – eg. “is ‘twe’ a word?”); or identifying letters which appeared on a screen. They also had a control group who did not receive any training.

Reading speed increased after all of the training procedures – with a mean improvement in reading speed of 72% in those who practiced reading words with peripheral retina; 54% in those who practised identifying letters; and 39% in those who performed the lexical decision task. This improvement transferred to letters of a different size and to different (nontrained) locations of the peripheral visual field.

Does this mean that this training would be useful for people with macular disease? Not necessarily. The subjects performing this experiment had good central vision and were much younger than most people with macular disease. More significantly, this would have been the first time that they read with peripheral retina: those with macular disease are forced to use their peripheral retina all of the time and may already be “trained” to read as well as is possible with noncentral retina.

I think the most important finding from this study is that that the lexical decision making task seems to increase reading speed. It would be very exciting if this type of task improved reading for people with macular disease as this word/nonword judgement is something which could be easily performed by patients at home using a laptop computer. I look forward to seeing more work from this group on whether the effect is as strong in people with eye disease as it is in their subjects with good vision.

Implanted miniature telescopes: science fiction here today?

A telescope for people with macular disease which can be implanted in the eye, which isn’t visible to others and leaves you with both hands free, sounds great to most people. It even sounds a bit like science fiction – a world away from most low vision devices which are hand-held magnifiers which have been used for centuries. Surely everyone with macular disease should have the implantable miniature telescope (IMT) implanted as routine?

I am a little more reserved. Whilst it’s true that visual acuity improves when the telescope is implanted, by three lines on average, this comes at the expense of a restricted visual field and reduced light getting through to the retina. We know that people with macular disease find cataract surgery useful even when there’s not a visual acuity increase (reference) – presumably because they appreciate the extra light which reaches the retina in this case. It seems odd to implant a device which significantly reduces the amount of light getting through the eye’s optics, even if that does give a small improvement in visual acuity.

It is important to note that in all of the studies to date, the improvements reported have been measured after a very intensive rehabilitation programme which includes eccentric viewing training and careful instruction in the use of these telescopes. To date no studies have been published which show the improvement in visual acuity without the implanted telescope, but with such close contact with a rehab worker. As the device is only in early stages of clinical trials, it isn’t appropriate to yet have a randomised controlled trial (RCT) of the IMT, but I eagerly await the results of a well conducted RCT on this subject.

Finally, it is not completely risk free as a procedure: two of the subjects in the safety trial (1%) required a corneal transplant following the implant. There also the risks of retinal detachment and infection from any surgical procedure on the eye.

I have no doubt that some people who have the IMT or other intraocular telescopes implanted find them useful and have a good outcome. I also concede that I am fairly conservative when it comes to new treatments and tend to remain sceptical for longer than some of my colleagues do.

Now for the disclaimer: I have no commercial interest in the IMT or its competitors. The IMT may well be the best option for you: this blog post is purely my own (naturally sceptical) opinion. If you are considering this procedure your ophthalmologist and optometrist are by far the best people to seek advice from.