The low vision clinic at Moorfields Eye Hospital in London was established in its current form in 1969 and has grown to become one of the world's largest low vision centers, caring for over 2500 patients each year. A key element of the service provision in the clinic is the prescription of optical low vision devices (LVDs), which are issued on a permanent loan system from the hospital. Since the clinic was inaugurated, LVDs have become more sophisticated, most notably with the introduction of the closed-circuit TV system (CCTV; first used at Moorfields Eye Hospital in 1970) and the recent availability of LED illumination for hand and stand magnifiers (available in the United Kingdom since the late 1990s).
Meticulous records of patient attendances have been kept since the early 1970s in a summary format additional to the patient notes. This summary ledger incorporates the name, hospital number, sex, date of birth, and principal diagnosis of every patient assessed in the low vision clinic; the type or types of LVDs prescribed; and the planned follow up for each patient. In addition, it records whether the visit is a first attendance or a repeat attendance.
Wolffsohn and Cochrane examined the changes in diagnosis and demographics in a low vision clinic in Kooyong, Australia, over a similar length of time. As expected, their paper reported an increase in the number of patients with age-related macular degeneration (AMD), as well as a general aging of the clinic population from 1972 to 1996. By 1998, 13% of patients seen were under 60 years old, with only 4% being under the age of 30. Wolffsohn and colleagues did not measure changes in LVD prescription over time, but in a prospective study in 1998, they found that nearly 60% of patients were prescribed at least one low vision device. The most frequently prescribed devices were illuminated stand magnifiers, bright field magnifiers, and illuminated hand magnifiers.
The type of low vision devices prescribed appears to vary between clinics. Unlike the Kooyong Center described by Wolffsohn (based on data collected in 1998), an analysis of patients seen in 1995 and 1996 by Scott and colleagues reported a large proportion of patients being prescribed spectacle magnifiers and spectacle-mounted telescopes. In contrast, more high addition spectacles were prescribed in a Dutch clinic in 1989 to 1990. These differences do not appear to be the result of changes over time, because all of these analyses were of prescribing habits within a period of 8 years. Furthermore, these differences are not exclusively the result of the country within which the clinic is located. For example, in one clinic in the United Kingdom, the most frequently prescribed devices were illuminated stand magnifiers, illuminated hand magnifiers, and nonilluminated hand magnifiers, whereas in another British clinic, far more spectacle additions and telescopes were used. No studies have been published to date that compare changes in low vision device prescription over time.
The present study retrospectively analyzed the data from the summary ledger for all patients who attended the low vision clinic in 1 month in each of 7 years between 1973 and 2003, with particular reference to the type of low vision devices prescribed.
DISCUSSION
This study has presented longitudinal results of changes in the clinic population and the devices prescribed for patients attending a large state-funded low vision clinic in central London between 1973 and 2003. It is not intended to present a standard of LVD prescription, but merely to provide a historical perspective on the types of low vision devices prescribed in this center. Although we admit that the results presented here may not be surprising to experienced low vision practitioners, we believe that this study is the first to identify changes in low vision prescribing habits over the last 30 years.
Contrary to expectation, the median age of patients in this clinic did not systematically change over the past 30 years, despite the median age of the U.K. population rising by 4 years over this time. This may be, in part, the result of the relatively young age of London's inhabitants compared with the United Kingdom as a whole; London has fewer people over the age of 65 than the rest of the United Kingdom, and there is a net migration of older adults away from London. Furthermore, a number of specialist pediatric ophthalmology and inherited eye disease clinics at Moorfields attract referrals from across the United Kingdom, causing younger patients from outside London to be overrepresented in the low vision clinic. For these reasons, our low vision clinic has a lower median age and has a lower proportion of patients with AMD than other clinics.
The most frequently prescribed LVD in the Moorfields Clinic in each sampled month was the nonilluminated hand magnifier, which accounted for 19% of all devices prescribed. The availability of illuminated hand magnifiers (in particular those with LED illumination) has contributed to the rise in the number of hand magnifiers issued, yet nonilluminated hand magnifiers still represent the bulk of the devices issued. The frequent use of hand and stand magnifiers in our clinic is similar to that reported elsewhere in the United Kingdom and in Australia.
Spectacle-mounted telescopes are prescribed less frequently in the Moorfields Clinic than in some other centers, and the proportion of spectacle-mounted devices prescribed is falling. As a publicly funded clinic, Moorfields Eye Hospital does have financial restrictions. These pecuniary considerations may contribute to the relatively low numbers of spectacle-mounted devices prescribed; a near spectacle-mounted telescope costs approximately 10 times as much as a nonilluminated hand magnifier.
From the results of a telephone survey, D'Allura and colleagues found that only two thirds of patients who were dispensed with telescopic devices were using them some months later, whereas 89% of those with more simple magnifiers were still using them. It is possible that similar experiences may have been noted by practitioners in the low vision clinic at Moorfields, leading to a reduction in the number of devices prescribed.
The hospital does not supply CCTV systems for patients, hence their absence from the data presented. However, CCTVs are demonstrated in the low vision clinic and patients are given suppliers' information. In addition, schoolchildren have CCTVs supplied by their local education authority. The increased use of CCTVs between 1973 and 2003 may have contributed to the decline in the prescription of spectacle-mounted magnifiers over this time; for patients without a CCTV, the primary requirement of a low vision aid may be to read correspondence, whereas if the patient owns a CCTV for this task, they may require an optical LVD only for use outside the house. An illuminated hand magnifier would generally be more appropriate than a spectacle-mounted device for this purpose. Unfortunately, data on CCTV ownership were not available for analysis.
The two most noticeable changes in LVD prescription evident from this review of 30 years' worth of data are the increase in prescription of the bright field magnifier and the increased use of illuminated hand magnifiers. Although glass “dome” magnifiers have been available for many years, the lighter acrylic bright field magnifier has been manufactured in the United Kingdom since the mid 1980s (Edward Marcus, Low Vision Devices, UK, personal communication, 2004). These magnifiers are now responsible for nearly one fourth of all near low vision devices issued to new patients in this clinic.
Similarly, although illuminated hand magnifiers have been available for many years (they are reported in Faye's textbook from 1984), they have been prescribed in this clinic only since the early 1990s after the introduction of illuminated hand magnifiers with a greater range of magnification. Illuminated devices now account for 40% of all hand magnifiers issued. The recent introduction of LED illumination for hand and stand magnifiers has reduced the number of magnifiers being prescribed with conventional tungsten bulbs.
The importance of ensuring adequate lighting for patients with low vision cannot be underestimated; it has been shown that when reading at home, patients use on average one seventh of the illumination present in the hospital consulting room where devices were demonstrated and that visual acuity is adversely affected by this reduction in lighting.
Although the optimum method for improving lighting is to adapt the light sources in patients' homes, providing illuminated task magnifiers in the clinic will also ameliorate the effects of poor home lighting.
Although the summary ledger is in general well-maintained and legibly written, we concede that there may be errors and omissions within the document. However, there is no evidence that such omissions would be systematic; if anything, they would have caused random undersampling of the data. The fluctuation in the proportion of patients being issued a low vision device may be caused by differences in the prescribing habits of individual staff. However the large number of staff employed by the optometry department should minimize the effect of bias of an individual clinician; in June 2003, for example, 27 different optometrists saw patients in the low vision clinic. The turnover of staff in this clinic is reasonably low; at least three optometrists made entries in the LVA ledger in every year of the study.
The low vision clinic at Moorfields has always been an optometrist-led service; although the authors welcome the move toward multidisciplinary low vision clinics whereby each patient is assessed by a range of low vision professionals, the clinic structure at Moorfields remained unchanged over the 30 years of this study. Although the present study has only sampled the LVA ledger at 5-year intervals, this was deemed necessary in view of the very large number of patients assessed in the Moorfields low vision clinic.
We believe the ledger analyzed in this article to be the largest record of low vision clinic attendances in the world; on current trends, the 100,000th entry on the LVA ledger will be made at some point in mid 2005.
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