[Objective measurement of macular optical density]. / Möglichkeiten der objektiven Messung der optischen Dichte der Makula.

Determination of the optical density of the macular pigment may be used for an assessment of the efficacy of oral lutein supplementation in patients with dry AMD. Beside subjective methods like heterochrome flicker photometry, objective methods like the 2-wavelength auto-fluorescence method and the 1-wavelength reflection method are in clinical use today. Both methods show comparable results. For a long-term assessment of the efficacy of oral lutein supplementation, different parameters like mean and maximal optical density as well as the integral over optical density on all pixels ("volume") should be used. The parameter volume often increases also in cases in which other parameters do not change anymore. The 1-wavelength reflection method is used for the newly initiated LUTEGA study. This study will investigate the long-term effects of a fixed lutein/omega-3-fatty acid combination on the optical density in patients with dry AMD.

[Fundus spectrometry in age-related maculopathy]. / Fundusspektrometrie bei altersbezogener Makulopathie.

BACKGROUND: Spectroscopic methods permit the non-invasive detection of fundus pigments by the wavelength-dependent absorption of fluorescence as well as by the fluorescence lifetime. From the relative concentrations of haemoglobin and oxyhaemoglobin, the oxygen saturation can be calculated. The onset of age-related maculopathy might be delayed by a high optical density of xanthophyll. The detection of alterations in fundus autofluorescence points to age-related pathomechanisms (accumulation of lipofuscin, formation of connective tissue). The detection of autofluorescence of redox-pairs of coenzymes results in information about metabolic states at the cellular level, and might make possible an early detection of age-related changes when they are still reversible. METHOD: The evaluation of reflectance spectra, detected by imaging ophthalmo-spectrometry, results in the calculation of oxygen saturation or in the optical density of xanthophyll or of melanin. Fluorescence spectra can be measured also by this technique. For the 2-dimensional determination of the distribution of xanthophyll, a very simple method was developed, requiring fundus illumination by one wavelength only. In the detection of time-resolved autofluorescence, the fluorescence lifetime is used for the determination of endogenous fluorophores. RESULTS: As result of comparing studies between ARM patients and healthy subjects, the consumption of retinal oxygen was increased already in the children of ARM patients. An increasing optical density of xanthophyll was determined after lutein supplementation. Differences in fluorescence lifetime were determined between ARM patients and healthy subjects, but their interpretation requires investigations of cell or of organ model cultures. CONCLUSIONS: The described methods permit in vivo basic investigations of ARM and can be considered as impulses for the development of diagnostic devices.

[Objective determination of optical density of xanthophyll after supplementation of lutein]. / Objektive Bestimmung der optischen Dichte von Xanthophyll nach Supplementation von Lutein.

BACKGROUND: It is thought that a high optical density of xanthophyll has a protective effect against the development of aggregated macular degeneration. The aim of this study was to investigate whether an increase of the optical density of xanthophyll in the macula after a supplementation of lutein can be proven by objective methods. Most methods applied for the determination of the macular pigment require the co-operation of the proband and the ability for foveal fixation. METHOD: Imaging spectrometry and the evaluation of laser scanner images taken at 488 nm will be presented. In contrast to psychophysical methods, both methods are independent of the patients ability for foveal fixation. RESULTS: Even by evaluation of laser scanner images taken as in fluorescence angiography but without inserting the blocking filter, the 2-dimensional distribution of xanthophyll can be determined. In 10 probands taking 6 mg lutein daily over 40 days, an increase of the optical density could be determined at least in some probands. The optical density reached a plateau 30 days after starting the supplementation of lutein. CONCLUSION: The assumed protective effect of xanthophyll against age-related macular degeneration can be influenced by supplementation of lutein under objective control.

Recovery of serum calcium concentrations following acute hypocalcemia in patients with osteoporosis on long-term oral therapy with the bisphosphonate pamidronate.

Bisphosphonates, synthetic compounds that are taken up preferentially by the skeleton and that suppress bone resorption, are currently used in the management of patients with osteoporosis. Long-term uninterrupted administration of low oral doses is the preferred mode of treatment in current clinical trials with newer bisphosphonates. These compounds have, however, a long residence time in the skeleton, and there is no information about their long-term effects on blood calcium homeostasis. We examined the effect of long-term therapy with oral bisphosphonate on blood calcium homeostasis following an acute hypocalcemic stimulus. Twenty patients with vertebral osteoporosis (10 untreated controls and 10 treated with oral pamidronate, 150 mg/day for at least 5 yr) were given intravenous infusions of sodium EDTA, and the concentrations of calcium and PTH in blood were followed for 24 h. Serum calcium concentrations decreased similarly in both groups (maximum decrease 0.21 mmol/L and 0.22 mmol/L, respectively). The recovery of serum calcium concentrations was identical in both groups, and all patients had normal concentrations at 24 h. Plasma PTH increased to a peak of 17.3 +/- 2.5 pmol/L in the control group and to 17.0 +/- 3.1 pmol/L in the pamidronate-treated patients. During the whole study period, there was no difference in either the peak PTH response or in the recovery of plasma PTH values between the two groups. However, when only PTH responses between 60 min and 24 h were examined, there were differences between the two groups. Plasma PTH values, although strictly within the normal range, were significantly higher in the pamidronate-treated patients (P = 0.001). There were no differences in the calcemic responses during this period. Further, there were no detectable changes in immunoreactive PTH-related protein in either group after the EDTA infusions. In conclusion, our study showed that longterm therapy with oral pamidronate does not affect the calcemic response to an acute hypocalcemic stimulus in patients with osteoporosis.