Archive | January 2011

Vision 2011 – abstract 3

This is the abstract of the paper I will be presenting in Concurrent Breakout session 10 on Monday 21st Feb, 4.15 to 5.30pm. Unluckily, this is the same time Daryl will be presenting abstract 2 below so if both are of interest a choice as to which one to go to might need to be made!

 

READING FUNCTION WITH AND WITHOUT LOW VISION AIDS

Keziah Latham PhD MCOptom 1A,B; Daryl R. Tabrett BOptom MCOptom 1A,B

1. Anglia Ruskin University, Cambridge, UK

A. Department of Vision & Hearing Sciences

B. Vision & Eye Research Unit

Purpose: People with impaired vision usually read with the assistance of low vision aids to magnify print. When assessing reading ability, practitioners often assess reading function in a standardized way without the use of magnifiers. What is the relationship between reading with and without magnifiers? Can magnifier aided reading performance be predicted from standardized assessment of visual function?  

Methods: 100 people who had recently attended a low vision clinic and reported difficulties in everyday life due to vision participated. ‘Uncompensated’ visual function using habitual correction and an appropriate add was assessed for distance visual acuity (VA), contrast sensitivity (CS), and visual fields. MNRead charts were used to assess acuity, critical print size and reading speed in ‘uncompensated’ conditions and also ‘compensated’ by using habitual low vision aids. 

Results: 78% of subjects could resolve a print size of N5 or better with their magnifier, as compared to 32% without. Those unable to achieve N5 with a magnifier were predicted with 87% accuracy by a combination of uncompensated reading acuity of worse than 0.9logMAR, and a CS of 1.05logCS or worse. Mean uncompensated acuity reserve (critical print size: acuity) was 1.74:1, tending to be larger for those with better acuity. Mean compensated acuity reserve was 2.2:1, with 18% of those achieving N5 acuity with a magnifier having an acuity reserve greater than 3. These subjects could not be predicted from the visual functions assessed. Compensation with magnifiers did not significantly affect reading speed (t=0.4, p=.69).

Conclusions: Compensating for impaired vision with magnifiers improves access to smaller print, but does not influence maximum sentence reading speed. Predicting a patient’s acuity response to magnification can be achieved by assessing uncompensated reading acuity and CS. However, the size of print allowing best reading speed with a magnifier is not always predictable from the acuity.

 

Vision 2011 – abstract 2

Daryl will be presenting this paper on Monday 21st Feb 4.15-5.30pm in the Concurrent Breakout session 8.

FACTORS INFLUENCING SELF-REPORTED VISUAL FUNCTION IN THE VISUALLY IMPAIRED

Daryl R. Tabrett BOptom MCOptom 1A,B; Keziah Latham PhD MCOptom 1A,B

1. Anglia Ruskin University, Cambridge, UK
A. Department of Vision & Hearing Sciences
B. Vision & Eye Research Unit

 Purpose: Self-reported visual function assessment instruments are regularly used in clinical and research settings as patient reported outcomes to assess the perceived visual abilities of the visually impaired. Previously, vision loss severity as assessed by clinical measures of visual function has only moderately predicted self-reported visual function. Other psychosocial aspects have been suggested to relate to self-reported visual ability. This study assesses the relative roles of visual and non-visual factors in influencing self-reported visual function in people with vision loss.

Methods: One hundred adults with visual impairment were administered the Activity Inventory to assess self-reported visual ability. Clinical visual function assessment included habitual distance visual acuity, near reading performance, contrast sensitivity, visual fields and depth discrimination. Psychosocial constructs assessed were personality (five factor model), social support, depression and adjustment to vision loss.

Results: All measures of clinical visual function except depth discrimination significantly correlated with self-reported visual function in univariate analyses, as did all psychosocial constructs except personality, where neuroticism was the only significantly related trait.  Multiple regression analyses indicated that a clinical measure of acuity, near reading performance and visual field function, along with psychosocial aspects of depression and adjustment best predicted self-reported visual function explaining approximately 70% of variance in responses.

Conclusions: The results suggest that self-reported visual function in the visually impaired is not only significantly influenced by vision loss severity but by non-visual psychosocial aspects as well. These findings have implications for the future interpretation of patient reported assessments of visual function. Since psychosocial predictors could explain unique variance not accountable for by the degree of visual impairment it may be feasible to improve perceived and possibly actual visual function by other means in addition to vision enhancement. 

 

Vision 2011 – abstract 1

The Vision 2011 meeting in Kuala Lumpur is now coming up fast! This is the abstract of the work that I’ll be presenting in Concurrent Symposium 4 on Wed 23 Feb, in the 11-12.30 session. The symposium is ‘New Developments in Research and Rehabilitation’ and has been organised by Ruth van Nispen of the VU University Medical Centre, Amsterdam.

READING MEDICINE LABELS WITH IMPAIRED VISION

Keziah Latham PhD MCOptom 1A,B;  Daryl R. Tabrett BOptom MCOptom 1A,B; Claire Usherwood BOptom MCOptom 1A; James Schaitel BOptom 1A; Sam Waller PhD 2

1. Anglia Ruskin University, Cambridge, UK
A. Department of Vision & Hearing Sciences
B. Vision & Eye Research Unit
2. Department of Engineering, University of Cambridge, UK.

Purpose: Reading pharmacy medicine labels is a task that is important and difficult for people with impaired vision to do. We have previously shown that objective assessment of reading medicine labels is influenced by the specific task used, and that the task variants we created appeared to be easier to read than subjects’ own medicine labels. In this study, we sought to determine the format of typical UK pharmacy labels, and to compare their legibility to those constructed to best practice guidelines.

Methods: 28 sample labels were obtained from 7 high street pharmacies. Experimental labels were constructed reflecting a typical pharmacy label, a label constructed to Design for Patient Safety (DfPS) guidelines, and a large print label. Twenty normally-sighted subjects read labels under habitual conditions (mean VA -0.14logMAR), and under two conditions of simulated visual impairment (mean VA +0.41 and +0.69logMAR). Outcome measures were speed and accuracy of label reading.

Results: Mean font size for directions on the sample labels was 9.3±0.8 point, rather than the recommended minimum size of 12 point. In the mild visual impairment condition, using the DfPS label improved accurate reading speed by 58% over the typical label. In the moderate visual impairment condition, 65% of subjects were able to see sufficient of the directions to be able to take the medication appropriately with the DfPS label, as compared to 20% with the typical label.

Conclusions: The UK pharmacy labels in this sample did not fully meet DfPS guidelines. With unimpaired vision, label design had little impact on legibility. However, the results provide evidence that preparing pharmacy labels according to best practice guidelines improves their legibility for those with impaired vision, and strengthens the argument for conformance to DfPS guidelines.