1.
[Limits of the confocal laser-scanning technique in measurements of time-resolved autofluorescence of the ocular fundus].
Schweitzer, D, Hammer, M, Schweitzer, F
Biomedizinische Technik. Biomedical engineering. 2005;(9):263-7
Abstract
GOAL: The 2-dimensional measurement of the time-dependent autofluorescence has in combination of confocal laser scanner technique and time correlated single photon counting the potential for the investigation of the metabolism state at the eye ground. It was to be examined, to what extent these measurements are influenced through the auto-fluorescence of the crystalline lens. MATERIAL AND METHOD The time-dependent auto-fluorescence was measured on eyes of 21 patients with age-related macular degeneration (AMD) and of 26 healthy subjects in 40 degrees fundus images. The experimental set-up used, was developed at the eye clinic of the University of Jena. In this scanning laser ophthalmoscope, the fundus was excited at 446 nm by pulses of 100 ps full width at half maximum and 40 MHz repetition rate. The auto-fluorescence was detected with a time resolution of 25 ps for wavelengths > 500 nm. The dynamic auto-fluorescence of each pixel was approximated by a tri-exponential model function. In order to determine the influence of the fluorescence of the crystalline lens, healthy eyes and eyes were compared with implanted artificial intra-ocular lenses. For comparison the frequency distributions were used, which the decay times t1, t2 and t3 in the fundus images had been calculated with. RESULTS Clear differences were shown in the frequency distributions of the fluorescence lifetimes between AMD-patients and healthy subjects, It resulted, however, from a crucial analysis that the fluorescence of the crystalline lens is not suppressed by the confocal laser scanning principle sufficiently. In particular the long lifetime t3 is overlapped by the fluorescence of the crystalline lens of about 4.6 ns. To the complete suppression of the influence of the lens fluorescence in measurements of the time-resolved fundus auto-fluorescence it is suggested to combine the confocal laser scanning technique with the principle of the aperture diaphragm division. CONCLUSION In order to be able to determine the capability of measurements of the time-dependent fundus auto-fluorescence as diagnostic tool exactly, the influence of the crystalline lens is to reduce through the combination of confocal laser scanning ophthalmoscopy with the principle of the aperture diaphragm division diversely.
2.
[Blood concentration of homocysteine, vitamin B (12), and folic acid in patients with exudative age related macular degeneration].
Nowak, M, Szapska, B, Swietochowska, E, Wielkoszyński, T, Marek, B, Kos-Kudła, B, Kajdaniuk, D, Głogowska-Szelag, J, Siemińska, L, Ostrowska, Z
Klinika oczna. 2004;(3 Suppl):429-30
Abstract
PURPOSE Recent studies have shown a relationship between elevated levels of Hcy and vascular disease including cerebrovascular accidents and myocardial infarctions. Elevated Hcy plasma is considered as an independent risk factor for atherosclerosis and trombosis. MATERIAL AND METHODS This study included 30 patients with diagnosed exudative form of AMD. We evaluated plasma homocysteine levels, by high performance liquid chromatography and red blood cell folic acid, plasma folic acid and plasma vitamin B12 concentration by radioassay method. RESULTS The plasma concentration of Hcy in AMD patients had significantly increased when compared with control group. We found not significant decrease of the plasma vitamin B12, red blood cell folic acid and plasma folic acid concentration in AMD group, when compared with the control group.