Computer modelling of a cataract waiting list

Abstract

AIM—To compare three different strategies for determining admission dates for patients awaiting cataract extraction after scoring for visual impairment.
METHODS—357 patients attending for assessment for cataract surgery were scored for visual impairment. These scores were used as a basis for ranking patients into three impairment strata. A computer simulation was used to compare 3 years' operation of different admission strategies—a first come first served booking system, a triage booking system, and a waiting list system in which admissions were strictly ordered according to priority stratum. Differences in priority weighted delays before treatment were analysed.
RESULTS—Both the triage system and the priority based waiting list system gave considerable reduction in priority weighted delay compared with a first come first served admission policy. The percentage reduction achieved (30%-60%) is strongly influenced by the number of weeks fully booked when the booking systems are introduced. The priority weighted delay of the triage system, where booking decisions were made at the time of the outpatient assessment, was consistently and substantially outperformed by the priority based waiting list system where the decision to allocate an admission date was delayed as long as possible.
CONCLUSIONS—There is considerable scope for reducing delays to high priority patients if simple rules are used to determine admission dates. Using these rules, booking patients at the time of the outpatient assessment gives substantially less benefit in terms of reducing delays to high priority patients than if the decision about the admission date is deferred.



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Figure 1  .

The operation of the triage priority booking system, allocating patients to different booking zones according to their priority score.

Figure 2  .

Distribution of the visual impairment scores.

Figure 3  .

Comparison of total priority weighted delay incurred over 3 years of operation of the treatment scheduling systems. Curves represent best fit quadratics through clusters of 10 points each representing an independent simulation.

Figure 4  .

Percentage reduction in priority weighted delay in comparison with first come first served booking system. Each point represents 3 years' operation of the system for different periods fully booked at the initiation of the simulation.