Tussen licht en donker Fysische aspecten van de overgang tussen dag en nachtzien

BSE B210550L / UCL - Université Catholique de LouvainSIGLEBEBelgiu

Choroidal haemodynamics in glaucoma

AIM—Quantification of haemodynamics of the peripapillary choroid in and the assessment of possible differences between normal subjects (N), ocular hypertensive (OHT), primary open angle (POAG), and normal pressure glaucoma (NPG) patients.
METHODS—Video fluorescein angiograms (Rodenstock SLO 101) were made in 22 N subjects, 12 OHT, 48 POAG, and 46 NPG patients. The angiographically derived dye build up curves were described by means of an exponential model. One of the model parameters is the time constant τ theoretically reflecting local blood refreshment time; the blood refreshment time τ is the time needed to replace the blood volume in the choriocapillaris, inversely proportional to the local choroidal blood flow. Other variables are maximal fluorescence (F(dt)) and time of first fluorescence (t(0)). Mean variable values were calculated for disc area and circular areas around the disc.
RESULTS—F(dt) of the disc was significantly lower in the POAG and NPG patients. There was no statistical difference in t(0) between the study groups. The choroidal blood refreshment time was significantly longer in NPG patients and to a lesser extent in the POAG patients compared with the normal controls. The slowest choroidal blood refreshment can be found in the NPG group. The median choroidal blood refreshment times (25th-75th percentile) in the controls, OHT, POAG, and NPG patients were 4.1 (3.7-4.5), 4.4 (3.7-6.4), 5.8 (4.3-6.8), and 7.1 (5.5-9.3) seconds respectively.
CONCLUSIONS—With the help of parametrisation of dye curves, using a one compartmental model, choroidal haemodynamics can be quantified. The blood refreshment time of the peripapillary choriocapillaris was found to be significantly prolonged especially in NPG patients; this may indicate slower choroidal haemodynamics in NPG patients.