Analyzing refractive data

Purpose: To provide a general approach to the analysis of refractive data that overcomes the shortcomings of traditional treatments and can be easily adapted to most spreadsheets. Setting: Corneal Service, Royal Liverpool Hospital, Liverpool United Kingdom, and Optometric Science Group, Rand Afrikaans University, Auckland Park, South Africa. Method: The basis of the analyses is the dioptric power matrix. Using a hypothetical sample of data on pre-event and post-event refractions, the calculation of the mean pre-event and post-event refractions and the effect of an event on the refractive outcome, for example the refractive surgical effect, are illustrated. The most important statistics, the mean and the variance-covariance of refractions, and the formal testing of hypotheses on the mean are provided. Results: The method of analysis demonstrated how an event such as cataract surgery, occlusion treatment of amblyopia, or anisometropia can be evaluated in terms of refractive outcome. Hypothesis testing, showed how the significance of this effect may be demonstrated. Conclusions: This standardized method of analyzing and reporting refractive data enables a quantitative analysis and statistical hypothesis testing of the complete refractive data. This approach has generalized applicability in a range of commonly encountered contexts such as the refractive change after cataract and refractive surgery, corneal transplantation, and treatment for amblyopia or the significance of anisometropia. The method is relatively straightforward and can be adapted to most conventional spreadsheets. (C) 2002 ASCRS and ESCRS.