Criteria for cataract surgery: the role of visual acuity and visual function
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford OAX 6AW and Department of Internal Medicine, Division of General Medicine, University of Michigan, Ann Arbor, Michigan, USA
- Center for Practice Management and Outcomes Research, Veterans Affairs Health Services Research and Development Field Program, PO Box 130170, Ann Arbor, MI 48113-0170, USA.
The paper presented by Crabtree et al in this issue of the BJO (p 519) represents yet another contribution to the growing literature on the assessment of visual function in ophthalmic patients from a variety of different settings.1-8 To date, the majority of such studies have centred on comparing the postoperative gains in visual function and visual acuity as a result of cataract surgery.9-13 Not unexpectedly, such studies have suggested that a strong correlation between visual acuity, a largely objective measure, and visual function, a relatively more subjective measure of vision, exists. For the most part too, such studies have found that visual function questionnaires are highly setting and population dependent, and that what might work in the United States just about works in England, but doesn’t work at all in India, even though they are all rooted in vision. But what to do with the resulting information contained in the burgeoning plethora visual functioning indices?
Both the current (p 519) and previous authors have raised the question of utilising such visual function questionnaires in conjunction with traditional visual acuity measures, as a means of prioritising who gets listed for cataract surgery.6 8-11Underpinning the much contested and hotly debated subject of who should receive cataract surgery is, of course, the magnitude of the cataract backlog operating within any one country. Globally it is estimated that cataract accounts for at least 17 million blind people.14In the United States, however, with one of the highest number of ophthalmologists per population, the cataract surgical threshold is lower than in countries with distinct shortages of ophthalmologists. Under such circumstances of limited resources which can be devoted to reducing the backlog of unoperated cataract, the prioritisation of cataract surgery assumes that patients with some, as yet undefined, combination of poor visual acuity and low visual function scores will be given cataract surgery first. The difficulty of this approach is apparent—namely, overestimation of a patient’s visual functioning status. In fact, if such a system were to be implemented, there would be tremendous incentive for patients to artificially suppress their own visual function scores to ensure a place on the cataract surgery list. Any effort to maintain fairness in the delivery of publicly sponsored cataract surgery should seriously reconsider any attempt to prioritise cataract surgery upon the basis of patient perceived valuations of their own visual capabilities. Rather, the whole area of vision function requires much more refinement and study as to how it might be used, if at all, in any attempt to prioritise cataract surgery either in whole or in part in the place of clinical measures, most notably visual acuity. Although efforts to uncover the ways in which visual function measures might be used to prioritise cataract surgery are laudable goals, equal if perhaps not more substantive gains might be derived by increasing the existing number of people capable of performing cataract surgery, a course of action which prepares ophthalmology to meet its biggest challenge of the coming millennium—the sustained provision of high quality, cost effective, cataract surgery on a global scale.
