Subjects and methods

Data were collected over a 6 month period from October 1997 to March 1998 from all new referrals to the Cardiff University low vision clinic. This clinic provides low vision services in South Wales to patients referred by the University of Wales College of Medicine.

Each patient had a low vision assessment. This involved the taking of history and symptoms, detailed questioning about the patients' visual requirements, assessment of their visual performance, refraction and an evaluation of the effect of magnification on their reading vision., This information was used to help to identify a suitable low vision aid.

Visual performance was evaluated using the Bailey-Lovie logMAR chart. This chart has a number of advantages over the conventional Snellen chart and is particularly well suited to evaluation of impaired vision.14 In particular, it is possible to equate acuities obtained at different distances. This advantage is less relevant in assessments of near vision performance because it is seldom necessary to recalculate reading acuity for different distances. Therefore, reading performance was determined using the reading test types as approved by the Faculty of Ophthalmologists. This standardised text uses the Times New Roman typeface and is a widely accepted functional test of reading acuity.14

All new referrals were accompanied by a letter from the referring ophthalmologist stating the diagnosis. Information about the patients' ocular condition along with their age, sex, visual acuity before and after refraction, and their reading performance with reading spectacles both with and with out an appropriate low vision aid was recorded. The data were analysed on computer using a software package (spss Ver 7.5).

Results

In total data were collected from all 168 new referrals to the low vision clinic over the 6 month period of this investigation. The biographical characteristics of the patients are summarised in Table1.

Although the low vision clinic saw patients from almost all age groups (range 12–103 years) the vast majority (83%) were over retirement age (65 years). The mean age of low vision patients was 76 years.

For ease of interpretation data about visual performance recorded using the Bailey-Lovie logMAR chart were converted to the equivalent Snellen fraction and are also presented in Table 1. Patients attending the low vision clinic for the first time had a mean binocular visual acuity of only 6/36. Refraction improved binocular VA by one line or more in only 59 subjects. For this group the mean improvement in VA equated to an improvement from approximately 6/36 to 6/18.

Figure 1 shows that only 23% of new referrals to our low vision clinic could read standard newsprint sized text (N8) on arrival at the clinic, indeed 40% were unable to read large print (N14). After provision of suitable low vision aids there was a marked increase in the number of people who could read. Almost nine out of 10 people with impaired vision were able to read standard sized newsprint (N8 or better) with the appropriate low vision aid. Low vision aids significantly improved reading ability (Wilcoxon signed rank test, two tails, p<0.0001).

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Figure 1

Pie charts showing the fraction of new referrals who could read newsprint (N8 or better) with reading spectacles but without the use of a low vision aid (left) and the fraction that could read with a low vision aid (right).

Of those people whose vision improved to N8 or better 58% had ARMD, 6% had glaucoma, 6% diabetic retinopathy, and 5% myopic degeneration. This distribution is almost identical to the original sample. The mean presenting visual acuity and reading vision of this group was 6/48 (range 1/60 to 6/9) and N17 (range N48 to N9) respectively.

Table 2 describes the types and powers of the magnifying devices used to bring about the improvement in reading ability. All devices were supplied on a loan basis free of charge in accordance with guidelines on best practice.9

Discussion

The results of this study clearly show that low vision aids are an effective means of improving reading ability in people with impaired vision. The improved reading performance addresses the primary complaint of the majority of patients with ARM and it is perhaps for this reason that previous studies examining the effectiveness of low vision aid provision have reported that more than eight out of 10 patients reported a benefit from attending a low vision clinic.12

The observation that the pathology profile of the group whose vision was improved to N8 or better, was virtually identical to the original sample suggests that the benefit of low vision aid provision is not dependent on underlying pathology.

In common with many eye clinics, this study only evaluated reading performance in terms of ability to read N type print rather than reading speed or duration (reading fluency was noted descriptively but such data are not readily amenable to analysis—for example, “N10 with ease”). However, even if text of a particular size cannot be read fluently for long periods thus allowing reading for pleasure, it still provides access to essential material—for example, bills and bank statements which equate to about N8.

The vast majority of people who attend a low vision clinic for the first time have a significant degree of visual impairment; almost eight out of 10 are unable to read normal print and almost seven out of 10 have a binocular visual acuity below 6/18. This finding is of some concern because people with such poor vision are likely to experience considerable difficulty in performing many daily tasks. Furthermore, these difficulties are likely to have been experienced for some time because many of the causes of visual impairment progress slowly and insidiously. Undoubtedly, there are many people in the community whose visual loss goes unrecorded.15 16 There may be several reasons why people with impaired vision do not attend the low vision clinic at an earlier stage, the patient may fail to recognise the degree of visual impairment,17 fear of treatment,18 the stigma of blindness,19 and differences in ophthalmological referral criteria.20 An additional reason might be that, because there is no treatment for conditions such as age related maculopathy, it is perceived that little can be done to help people with impaired vision. This study clearly shows that this is not the case and that low vision aids help people with impaired vision to read.