Enhancing the knowledge in fundus autofluorescence of optic nerve head drusen assessed with broad line fundus imaging technology.

Abstract

The concept of retinal autofluorescence (AF) came to light in the 1970s when an autofluorescent signal of optic nerve head drusen (ONHD) was noted prior to the injection of fluorescein dye [1]. Nowadays, several devices offer distinct methods for acquiring short-wave fundus autofluorescence (SW-FAF) images, all of them being clinically useful in assessing the presence of lipofuscin, a naturally occurring ocular fluorophor which reflects the general health of the photoreceptor and retinal pigment epithelium (RPE). Each device provides a different image acquisition method; thus, discrepancies exist in the images obtained. For example, fundus cameras feature a high-energy white flash that streams through a wideband excitation filter and a series of mirrors and apertures to obtain images. On the other hand, confocal scanning laser ophthalmoscope (cSLO) emits a single wavelength, which will only excite fluorophores that absorb light with a peak excitation near that specific wavelength [2]. Broad line fundus image (BLFI) technique is a hybrid of both cSLO and traditional fundus photography. By utilizing line scanning illuminationwith light-emitting diodes (LEDs) and an aperture confocal to the illumination, this system illuminates and detects retinal images in two wavelength ranges: fundus autofluorescence (FAF)-Blue (435–500 nm) and FAF-Green (500–585 nm) [3]. Both are categorized as short-wavelength, but it is well known that green light can reach deeper layers of the retina, being absorbed less by the luteal pigments of themacula, and allowing a better definition of lesions in the underlying RPE. ONHD are a form of calcific degeneration in some of the axons of the optic nerve that may give a swollen-looking appearance, and are usually formed early in life. ONHD are diagnosed with fundoscopic examination, but some casesmay require B-scan ultrasonography, AF, and optical coherence tomography (OCT) to confirm the lesion [4]. The features of ONHD in FAF imaging are well described in many previous publications [4], [5]. Yan et al. [4] recently described the peculiarities of ONHD in FAF-Blue and -Green by using a cSLO system from two different devices. Despite a considerable amount of meaningful information, we were unable to find a description of FAF imaging in ONHD using BLFI technology in the literature. We have recently observed a noticeable disparity in the