The Manitoba Cataract Waiting List Program prioritizes patients for cataract surgery on the basis of functional impairment (VF-14), potential loss of work, potential loss of a driver's licence and time spent waiting.1 We would argue that a prioritization system comprised of multiple independent components, some medical and some social, cannot be validated by a single “objective patient-derived outcome measure.” We would also argue that as long as each component is reasonable and has been objectively validated where possible, the overall result is reasonable.
We chose the VF-14 as our ranking tool for functional impairment in Manitoba precisely because it has been objectively shown to be a highly consistent, valid measure of functional impairment caused by cataracts2 and has been shown in outcome studies to be a robust predictor of change in patients' satisfaction with their vision.3 International studies have demonstrated it to be reliable and responsive to change in visual function.4,5,6,7 Two of the 14 questions in the VF-14 relate to driving: we do not believe this is a heavy bias. If anything, the VF-14 is biased against visual impairment in the workplace because the questions were specifically selected to review a broad spectrum of vision-dependent activities in everyday life.2
We do not believe it is necessary to subject the additional points we awarded for potential loss of work to an outcome study. The ophthalmologists in our community made a value judgement that they wished to continue giving priority to patients who risked losing their jobs because of visual impairment. Similarly, most ophthalmologists tended to give priority to patients at risk of losing their driver's licence and wished to maintain this pattern of practice. (This has been subjected to outcome analysis: most studies looking at Snellen acuity after cataract surgery have shown a >>90% rate of attainment of 20/40 acuity, the threshold for a driver's licence.8)
Giving points for time spent on the waiting list might encourage surgeons to manipulate the system if all patients were pooled together. However, in the Manitoba Cataract Waiting List Program each surgeon's waiting list is kept separate; all patients are assessed by the same criteria, but data are pooled only for statistical analysis. This separation of the waiting lists eliminates any reason to manipulate the system given that all members of the department share operating room time equally.
Sanmugasunderam and Romanchuk also argue that the length of time spent waiting for surgery should not affect a patient's prioritization if his or her functional impairment remains unchanged, unless the wait produces clearly proven morbidity. Surgery is booked when the cataract reduces visual function to a level that interferes with everyday activities.8 This has been shown to have negative implications for general health9 and has led some jurisdictions to set maximum reasonable waiting times for different levels of functional impairment.10,11
Sanmugasunderam and Romanchuk state that our program is “just a consensus model.” We would argue that the consensus component of the model is an integral reason for its success. It was through consensus that we agreed upon the criteria to measure. We then selected the most objectively validated tools and agreed upon a relative scoring system. Another jurisdiction might go through the same process and come up with different criteria or a different scoring system. We feel that surgeons are more likely to accept the process if they have been involved in creating it.
Signatures
Lorne Bellan
Misericordia Health Centre Winnipeg, Man.
Mathen Mathen
Misericordia Health Centre Winnipeg, Man.
References
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