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The sight test fee Little evidence to support conclusions
Little evidence to support conclusionsEDITOR, - D A H Laidlaw and colleagues' paper on the effect of the sight test fee precipitated a predictable furore in the media.1 I was disappointed to see that the authors had included data from 1988 when predicting future referrals. They admit that 1988 was an exceptional year for sight tests. They then justify inclusion of those data by calculating that the actual number of referrals did not fall outside the confidence interval for the prediction. Including data that are higher than expected because of the impending introduction of the sight test fee cannot be justified. It is to be expected that fewer tests were done in 1989 because extra tests had been done in 1988.
The table shows a recalculation of the predicted number of referrals, 95% confidence intervals, and 95% prediction intervals (which are more appropriate than confidence intervals when results are
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Relevant Article
- The sight test fee: effect on ophthalmology referrals and rate of glaucoma detection
- D A H Laidlaw, P A Bloom, A O Hughes, J M Sparrow, and V J Marmion
BMJ 1994 309: 634-636.[Abstract] [Full Text]
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