Abstract
Purpose: :
To evaluate the effect of repeated measurements of fundus autofluorescence (FAF; excitation 480 nm, barrier filter 500 nm) and near-infrared-autofluorescence (NIA; excitation 787 nm, barrier filter 800 nm) on the resulting image.
Methods: :
Healthy probands and patients with retinal disorders underwent repeated FAF and NIA imaging using a confocal scanning laser ophthalmoscope (HRA2, Heidelberg Engineering, Heidelberg, Germany) with a 30 degree and 50 degree lens. Images were obtained first with the 30 degree lens and thereafter with the 50 degree lens.
Results: :
In all probands and patients FAF images obtained with the 50 degree lens showed increased FAF intensity in the area previously examined with the 30 degree lens. In contrast, NIA images obtained with the 50 degree lens did not allow to identify the area previously examined with the 30 degree lens. Measurements with either FAF or NIA had no influence on subsequent images obtained with the other method, respectively
Conclusions: :
FAF images are affected by repeated measurements. For the purpose of establishing objective measurement values for comparison between measurements, the measurement technique has to be highly standardized. Obtaining a second image may alter the resolution or contrast contained in the image. The observed effect may indicate prolonged autofluorescence, however, biological effects on the lipofuscin in the RPE cells can not be excluded. With NIA imaging no side effects of imaging and no influence on subsequent images were observed.
Keywords: retinal pigment epithelium • imaging/image analysis: clinical • image processing