Jonny Olsson

A package for the statistical analysis of visual fields

We have devised a package for the statistical analysis of computerized visual fields. It is based on a new mathematical model of the normal visual field and intended to facilitate interpretation of single fields and to illustrate changes over time in consecutive threshold fields. Single field analyses include maps showing pointwise total and pattern deviations from the age-corrected normal reference field. These maps are displayed both numerically, in dB, and as noninterpolated greyscaled probability maps illustrating the statistical significance of measured deviations. These probability maps help emphasize shallow, but significant, depressions in the paracentral field while frequently occurring false positive deviations occurring in the midperiphery are de-emphasized. Visual field indices, summarizing the deviations of height (Mean Deviation) and shape (Pattern Standard Deviation and Corrected Pattern Standard Deviation) of the measured field are weighted according to the normal variance among healthy individuals and printed out together with level of statistical significance. For follow-up the programme contains several different options. These range from an Overview format where threshold printouts and probability maps from several tests are printed in reduced size, but without any reduction of data, on a single sheet of paper, to a box plot format where the development of the field is shown with an intermediate degree of data reduction and a format employing a high degree of data reduction: graphs over visual field indices over time. If five or more tests are available a linear regression analysis of Mean Deviation is automatically performed. The programme will become available in the Humphrey Field Analyzer.

Reliability parameters in computerized perimetry

The distribution of results of perimetric reliability tests, false positive and false negative answers, fixation losses and short-term fluctuation, was studied in a material of 84 healthy normal subjects, randomly selected from the population, and in 45 patients with glaucoma. All subjects were tested with the 30–2 programme of the Humphrey Field Analyzer. We further investigated the influence of perimetric reliability on the measured visual field, as expressed by the visual field indices Mean Deviation and Pattern Standard Deviation. Sample multiple correlation coefficients were calculated for a number of combinations of reliability parameters and visual field indices.

Comparison of excess costs of care and production losses because of morbidity in diabetic patients.

OBJECTIVE To assess and compare excess costs of care and production losses because of morbidity in diabetic patients and the general population of a Swedish community. RESEARCH DESIGN AND METHODS Costs of production losses were calculated from medical and social insurance records on sickness benefit days (short-term illness) and premature retirement (permanent disability) in people with diabetes and in the entire population of the community (a municipality comprising a town and rural surroundings, with 28,000 inhabitants). Care costs included those of consultations and inpatient care, as well as costs of insulin, oral antidiabetic medications, other drugs, test material, and treatment devices, and they were obtained from patient records, the health care administration, and the statistics of community pharmacy sales. RESULTS Of the diabetic patients < 65 years of age, above which both diabetic and nondiabetic people get retirement pension, and sickness benefits cease, 62% of those on insulin treatment in each gender had insulin-dependent diabetes mellitus (IDDM). All insulin-treated non-insulin-dependent diabetes mellitus (NIDDM) patients were > 40 years of age. Both the insulin-treated and the non-insulin-treated diabetic patients were prematurely retired twice as often as the average population and had twice as many inpatient days. The insulin-treated subjects also had twice as many sickness benefit days. The excess costs of production losses as a result of morbidity in people with diabetes were about

Spatial analyses of glaucomatous visual fields; a comparison with traditional visual field indices

7,000 per individual and year. The corresponding excess costs of inpatient care were

Quantile Estimation from Repeated Measurements

800. The therapeutic expenditures for control of diabetes were about

Use of calcium channel blockers and beta blockers as antihypertensives in relation to mortality in type 2 diabetes patients: a population‐based observational study

600 per individual and year. If converted to U.S. conditions, the costs of lost production as a result of excess morbidity (< 65 years of age) would be

Normal variability of static perimetric threshold values across the central visual field

12 billion and

A new generation of algorithms for computerized threshold perimetry, SITA

9 billion for people with insulin-treated and non-insulin-treated diabetes, respectively. CONCLUSIONS If improved metabolic control by intensified treatment would reduce excess morbidity in both IDDM and NIDDM, the predominant costs of production losses imply that intensified antidiabetic treatment might save costs.

The effect of perimetric experience in normal subjects.

Abstract Interpretation of numeric automated threshold visual field results is often difficult. A large amount of data is obtained for every single field tested. Various approaches to summarize this data have been suggested, most commonly the mean and standard deviation of departures from age‐corrected normal threshold values. These visual field indices differ substantially from subjective field interpretation where spatial relationships are important. We have previously devised two methods for automated field interpretation which take spatial information into account ‐ regional up‐down comparisons and arcuate cluster analysis. We now studied the merits of using these new spatial methods and compared them to traditional visual field indices for discrimination between normal and glaucomatous field results. Central static 30° field results in 101 eyes of 101 normal subjects and 101 eyes of 101 patients with glaucoma were discriminated using logistic regression analysis. The best field classification was obtained with a spatial visual field model combining up‐down differences and arcuate clusters. The advantages of the spatial model were confirmed in an independent material of 163 eyes of 163 normal subjects and 76 eyes of 76 patients with glaucoma where eyes with large field defects had been removed. In this material the spatial model gave 87% sensitivity and 83% specificity while the best non‐spatial model gave 82% sensitivity and 80% specificity. Visual field interpretation in glaucoma may be significantly enhanced if detection is focused on circumscribed field loss rather than on averages of differential light sensitivities and similar indices which do not take spatial relationships into consideration.

Visual field interpretation with empiric probability maps.

Abstract Quantile estimators for a nonparametric components of variance situation are proposed consistency and asymptotic normality are proved. Situations with different numbers of measurements for different subjects are considered. Measurements on separate subjects are assumed to be independent, whereas measurements on the same subject have a fixed dependence. The estimators are obtained by inverting weighted empirical distribution functions. An “optimal” estimator and a simple estimator based on within-subject averages are studied. Small-sample properties are studied by simulation as an illustration the estimators are applied to give normal limits for differential light sensitivity of the human eye.