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Visual impairment and activity

In a paper we have recently published we show that in a large cohort epidemiological study, older people who self-rate their eyesight as ‘poor’ or ‘fair’ were twice as likely to be inactive (undertaking moderate physical activity less than once a week) than people rating their eyesight as ‘excellent’. The data presents an association rather than cause and effect. However, there is the potential for lack of physical activity to lead to an increased likelihood of health problems that can cause poor eyesight, such as diabetes. Equally, it can be more difficult for people with poor vision to exercise and be active. In another recent study we showed that ‘physical activity and / or sport’ was the third most challenging activity of daily living for people with the eye condition Retinitis Pigmentosa. Finding ways to help people with poor vision exercise safely therefore has the potential to be extremely valuable. For those with poor vision, I would highly recommend British Blind Sport, for information on a range of different sports. The RNIB website also has a good overview of available resources. One organisation particularly close to my heart is parkrun, who organise free weekly 5k runs around the country (and the world). They are undertaking a project to provide guide runners to people with visual impairment to enable them to take part. I would be more than happy to volunteer as a guide for anyone in the Cambridge area, bearing in mind that as I don’t run very fast I would be much more suited to guiding a beginner!

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Explaining blindness is a struggle

Visual loss caused by Retinitis Pigmentosa (RP) obviously causes difficulty with practical activities in daily life, which we reported in a recent study (Latham et al., IOVS, 2015). However, loss of vision can also lead to significant challenges to emotional health, and we have just published a subsequent paper (Latham et al., PLOS ONE, 2015) to examine what aspects cause greatest difficulty for people with RP.

166 people with RP completed a questionnaire about their emotional health, and the two most difficult items were found to relate to communicating visual loss to other people (specifically, ‘dealing with misunderstandings from others because of your visual impairment’ and ‘explaining to others what you can and cannot see’). We suggest that partly this is because explaining vision loss is very difficult, but is also made more difficult if other people do not have a good understanding of vision loss – perhaps thinking that ‘blind’ means unable to see anything at all, or that only central vision is affected.

Other difficult tasks involved dealing with feelings of frustration and anger, stress and anxiety. There are programs available based on problem-solving approaches that address these topics, which have been shown to be helpful in some groups of older adults with macular degeneration, but we are not aware of any programs of this nature that have specifically targeted people with RP.

Another difficult task was ‘performing daily activities without suffering discomfort in the eyes, such as eyestrain’. Possibly this finding highlights the importance of regular eye examinations or low vision assessments to ensure that spectacles, tints, lighting and low vision aids provide as much support to residual vision as possible to allow tasks to be done as comfortably as possible.

A further key finding was that some groups expressed greater difficulty as a whole with the emotional health tasks, and this included people who use mobility aids, and women. We speculate in the paper as to why this might be, but it may be useful as an indication of who might be in greatest need of help with the emotional consequences of RP. We also found that the difficulty expressed did not depend on how long people has been visually impaired or the severity of visual loss, suggesting that people with RP might need help with the emotional consequences of visual loss at any point.

Many members of RP Fighting Blindness contributed to this research by answering the questionnaire, and we would like to thank you all for your time and enthusiasm for the project. We hope this study is useful and of interest to people with RP, and to those involved in supporting, caring and providing rehabilitation for people with RP.

Visual acuity standards for driving

As a summary of the recent work we’ve done on how an acuity of 6/12 relates to the ability to read a number plate at 20m – both standards for driving in the UK – have a peek at the article in Optometry in Practice this month. The answer is ‘quite well, but not perfectly’, which has implications for optometrists advising patients on their fitness to drive, and for drivers trying to work out if their vision is good enough to meet the standards. With the latter, the first port of call should definitely be to book an eye examination!

The College of Optometrists were happy for this paper to be made available via Anglia Ruskin University’s institutional repository, so can also be viewed here.

Visual difficulties due to RP

We have just published a paper in IOVS outlining the relative difficulties of different visual goals for people with Retinitis PIgmentosa (RP) (Latham et al., doi: 10.1167/iovs.14-16237). The most difficult goals for people with RP relate (unsurprisingly, given the effect of RP on peripheral fields) to mobility, but also to work related activities. There were differences depending on the severity of RP (as given by visual impairment registration status): for those with less severe visual loss, goals relating to communicating with people were relatively more difficult, while for those with more severe loss, goals relating to detailed central visual function (such as reading) were relatively more difficult.

We also looked at the differences in perceptions of difficulty between those with RP and those who support a person with RP. While there was a relatively good match in perceived levels of difficulty, supporters thought people with RP had more difficulty with administrative tasks and domestic chores than those with RP did, and less difficulty with goals relating to communicating with people.

We hope that this paper highlights some areas where people with RP, and their supporters, may benefit from more assistance in addition to traditional orientation and mobility skills. We would highlight work related activities, central visual tasks for those with more severe loss, and difficulties with communicating with people particularly for those with early loss and those supporting someone with RP.

A particular thank you to all the members of RP Fighting Blindness who took part in this study – we hope that what we have found will be useful to you, and a summary will be on its way to you as soon as possible!

Visual standards for driving

We have just published a paper in BJO which examines the relationship between the two UK visual acuity standards for driving: the ability to read a number plate at 20m, which has been a longstanding visual requirement for driving in the UK, and the ability to read 6/12 on a letter chart, which was introduced as a standard in 2012 to bring the UK into line with European directives.

There is not perfect equivalence between the standards: some drivers will be able to read a number plate but not the appropriate line on an acuity chart, while others will achieve the test chart requirement but not be able to read a number plate. These findings have implications for assessment of visual adequacy to drive, particularly for police officers and driving test instructors who assess the ability to read a number plate, and for optometrists and doctors who assess the visual acuity of drivers.

Latham K, Katsou MF, Rae S. Advising patients on visual fitness to drive: implications of revised DVLA regulations. Br J Ophthalmol doi:10.1136/bjophthalmol-2014-306173.

The effect of trial frames on adaptive gait

We have recently published a paper in ‘Gait & Posture’ examining whether the use of trial frames when correcting the vision of participants in adaptive gait studies might in itself alter adaptive gait. We found that this is indeed the case, and that wearing a full or half-eye trial frame made participants more cautious in an obstacle crossing task.

Timmis MA, Turner K, Latham K. The effect of trial frames on adaptive gait. Gait & Posture, 2014. DOI: 10.1016/j.gaitpost.2014.10.021

Measurement of the patient’s perspective

I have had a paper accepted for the upcoming special issue of Optometry and Vision Science on ‘Measurement of the patient’s perspective’. My contribution is ‘Evaluation of an Emotional Support Service for the Visually Impaired’, and a link to the paper will be available soon. The study examined the effect of a peer group emotional support service run by Cam Sight on visual quality of life (as assessed with Frost’s VCM1). The service was most beneficial to those with initially poorer visual quality of life, who showed significant improvements in visual quality of life that were maintained for 6 months after the service provision (effect size 0.92). The questionnaire items which became and remained easier were feeling lonely or isolated due to eyesight, feeling sad or low due to eyesight, and feeling worried about general safety outside the home. The study adds to the evidence that group based programmes can be effective in supporting people with visual impairment, particularly those who are depressed or have poor visual quality of life.

Vernier acuity and autism

We have just had a short report published in Molecular Autism: Latham K, Chung STL, Allen PM, Tavassoli T, Baron-Cohen S. Spatial localisation in autism: evidence for differences in early cortical visual processing. Molecular Autism 2013, 4:4 doi:10.1186/2040-2392-4-4.

We know that people with autism spectrum conditions (ASC) perceive the world differently to people without autism, but it isn’t clear where these differences start to arise and whether they are solely perceptual or if there are also differences in basic visual processing. We’ve previously shown (Tavassoli et al., Vision Research 51:1778-1780, 2011) no differences in visual acuity, limited at the retinal level, in autism. In this study we have examined line vernier acuity in autistics and controls, a task thought to be determined in the early stages of cortical visual processing. Whilst there was no difference between the responses of ASC subjects and controls in an abutting vernier task, ASC subjects showed slightly better thresholds than controls on a separated vernier task and a much stronger relationship between abutting and separated thresholds, suggesting that (unlike in controls) the 2 tasks might be mediated by similar mechanisms.

I hasten to add that this preliminary study needs further exploration. But we think that this finding is rather interesting, and suggests the possibility that vision in autism might start to differ at the level of basic cortical visual processing rather than being restricted to higher level perceptual differences.

Adjusting to vision loss – paper available

Tabrett and Latham, Adjustment to vision loss in a mixed sample of adults with established visual loss. IOVS, 53:7227-7234, 2012 is now available!

Adjusting to visual loss

Daryl and I have just had a paper accepted in Investigative Ophthalmology and Visual Science (Tabrett & Latham, Adjustment to vision loss in a mixed sample of adults with established visual impairment) that looks at the factors that are related to how well someone adjusts to being visually impaired. As outcome measure, we used our AS-WAS questionnaire (Acceptance and Self-Worth Adjustment Scale, OVS 87:899, 2010), which is a refined version of the Nottingham Adjustment Scale. Factors associated with the poorer adjustment were higher levels of depressive symptoms, higher scores on the personality trait of neuroticism and lower scores on the personality trait of conscientiousness. This suggests  that as clinicians, we would do well to try and identify people who may well adjust poorly to visual impairment in order to try and put the appropriate support in place from an early stage. Factors that weren’t associated with the level of adjustment included the severity of visual loss, and the duration of visual impairment. This suggest that people wth VI could benefit from support in adjusting to life with visual impairment at any point following diagnosis, and regardless of the level of visual loss. A link to the early view paper will follow soon.