ABSTRACT
The method of near-field goniophotometry is used ever-increasingly to acquire detailed luminance information about various luminaires. It overcomes certain limitations of its predecessor, the widely used and thoroughly standardized far-field goniophotometry, and provides further opportunities to expand the scope of the measurement, but also introduces a new set of limiting factors. The aim of this paper is to examine the effect of positioning uncertainties on near-field goniophotometric measurements' results. For this, a simplified ray tracing model is constructed computable in closed form as stacked matrix equations, in order to reduce the computation time as much as possible. The model is then fed to a simulated goniophotometric measurement, loaded with various uncertainties according to the Monte Carlo method. Finally, the resulting uncertainties are derived from statistical analysis of the output in both the near and far fields. Various metrics are tested as potential criteria for acceptance, including correlation and repeated measures ANOVA tests, both faring well until the angle of incidence of the rays is below 55°, the ANOVA test being more sensitive to sampling and rejecting systems with 0.1° angular error and above, while the same results still pass the correlation test until 0.5°. Converted far-field results are compared to the standardized requirements, indicating the necessity of similar mechanical precision.
ABSTRACT
PURPOSE: To analyze the preoperative results of multifocal electroretinography (mfERG) in the fellow eyes of patients with idiopathic unilateral macular hole and to evaluate the usefulness of this method in predicting the likelihood of macular hole formation in the fellow eye. METHODS: Over a period of 5 years, 80 eyes of 40 patients (mean age, 64.9 years) with unilateral idiopathic macular hole were examined. The diagnosis of idiopathic macular hole was confirmed by optical coherence tomography (OCT). The fellow eyes were intact in all cases. All patients underwent vitreoretinal surgery. Before the surgery, both eyes of the patients were examined by mfERG. During the follow-up period, the 40 fellow eyes were also observed by OCT, and the changes in the vitreofoveal attachment were investigated. The preoperative response densities and ring ratios of mfERG were analyzed in both eyes, and discriminant analysis was used to calculate the best separator function. RESULTS: Preoperative mfERGs demonstrated significantly lower mean response densities in the central area of the 40 eyes with macular hole than in the fellow eyes. During the follow-up period, macular hole was diagnosed in 13 fellow eyes by OCT. The preoperative values of the mfERGs in these eyes were significantly lower than in the other 27 cases. The mfERG ring ratios were significantly lower in the fellow eyes in which macular holes developed than in those that remained intact. CONCLUSIONS: The analysis of ERG in the fellow eyes of patients with macular hole seems clinically useful. The lower amplitude may forecast the propensity for subsequent development of a macular hole. Patients with low central ERG amplitude and lower ring ratios in the healthy fellow eyes should have stricter follow-up.
