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DIT FAF EXAM WITH CORRECT ANSWERS 100 % VERIFIED!!
FAF
used to record fluorescence that may occur naturally in the eye or accumulate as a byproduct of a disease process
autofluorescence used to distinguish this type of fluorescence from that which occurs from administration of fluorescent dyes such as fluorescein or indocyanine green
fluorophores chemical structures that possess fluorescent properties when exposed to light of an appropriate wavelength
Fluorescence occurs when these molecules absorb electromagnetic energy, excites them to a higher energy state→ triggers the emission of light at wavelengths longer than the excitation source.
In the Eye Exhibit natural (measurable/significant) fluorescence lipofuscin pigments in the retina, Optic nerve drusen, astrocytic hamartomas,
aging crystalline lens (vs. 'normal' crystalline lens)
RPE
Single layer of polygonal cells, Located between the choroid & neuro-sensory retina, Multiple functions
RPE multiple functions responsible for phagocytosis and lysosomal breakdown of pigmented outer segments of photoreceptors,
allows the renewal process necessary to maintain photoreceptor excitability
RPE lipofuscin contains at least ___ different fluorophores 10
Retinoid Fluorophores emission spectra green, golden yellow, yellow-green, and orange-red
Lipofuscin the major source of fundus autofluorescence,
aging and ocular disease
LF can be made to fluoresce by a fairly broad range of wavelengths, about 500 to 800 nm, Peak emission about 630 nm (600 - 610 nm),
After excitation the molecule will spontaneously release a photon of light of a somewhat longer wavelength
lipofuscin is a dominant macular fluorophore
lipofuscin absorption absorbs blue light with a peak excitation wavelength of 470 nm, emits yellow-green light at a peak wavelength of 600-610 nm
Melanin an ocular pigment located in the both RPE cells and in uveal melanocytes, rimary fluorophore in near-infrared
autofluorescence
melanin in the fundus is distributed primarily in the fovea, macula, and periphery
melanin peak excitation 787 nm
melanin on conventional FAF absorbs the short-wavelegth excitation beam (decreasing the overall autofluorescent signal)
Lipofuscin based autofluorescence is also known as blue autofluorescence (BAF), short wave autofluorescence (SWAF), or simply (fundus) autofluorescence. FAF; AF
Melanin based autofluorescence is also known as near- infrared autofluorescence. (NIRAF)
FAF Images
Both BAF and NIRAF can be differentiated from the red-free images by
he darker appearance of the optic disc and retinal blood vessels compared to the red-free images.
Commercially available FAF systems include fundus cameras, confocal scanning laser ophthalmoscopes (cSLO), ultra-widefield technologies
Limitations/challenges of FAF
Signal strength: Low signal strength (two orders of magnitude less than the peak signal of fluorescein angiography), Interpreting the image: variable quality and intensity, phenomenon of photoreceptor bleaching. Pt discomfort from blue-light excitation beam. Lacking formal studies demonstrating the specific safety/adverse effects of FAF
FAF utilizes the fluorescent properties of lipofuscin within the RPE to create an image
Lipofuscin byproduct of
lysosomal breakdown of photoreceptor outer segments
Density map of lipofuscin' SWAF brighter areas representing regions of increased lipofuscin density, many retinal pathologies often lead to RPE dysfunction and an accumulation of lipofuscin, abnormal patterns of AF act as markers for retinal disease
Common conditions - FAF usefulness Retinal Dystrophies, macular telangiectasis, pharmacologix toxicity, AMD
retinal dystrophies Viteliform dystrophy (Best's disease), Stargardt disease, cone and cone-rod dystrophies
hyperfluorescent Areas of excess lipofuscin (LF) accumulation
Fresh intraretinal and subretinal hemorrhages,
Intraretinal and subretinal lipid,
Fibrosis, scar tissue, or borders of laser scars,
Retinal vessels,
Luteal pigment (lutein and zeaxanthin)
increased FAF(SWAF) signal commonly due to lipofuscin accumulation in the RPE, presence of other fluorophores not in the RPE: drusen - (including those in the optic nerve head) or older hemorrhages, lack of absorbing material, artifactsLipofuscinopathies
Lipofuscinopathies including Stargardt disease, Best disease, and adult vitelliform macular dystrophy
Age-related macular degeneration RPE in the junctional zone preceding enlargement of occurrence of geographic atrophy
Subretinal fluid leading to separation of the outer segments of the photoreceptors from the underlying RPE, which leads to improper outer segment turnover
Disease Markers lines of evidence suggest that excessive lipofuscin accumulation represents a common downstream pathogenetic pathway in various hereditary and complex retinal diseases
Changes in the FAF signal may allow for an estimate of the extent of damage, diagnose sequalae such as secondary CNV (choroidal neovascularization), learn more about the inflammatory process, possibly anticipate future problems caused by disease
Clinical applications noninvasive diagnosis, monitoring disease progression, explaining visual loss (Explaining visual symptoms)
FAF provides functional information about retinal cells useful for almost any fundus disorder.
Choroidal nevus overlying drusen, hypoautofluorescence, location within the choroid, causing deep shadowing overlying tiny drusen, and no subretinal fluid on OCT
Pigmented choroidal melanoma ipofuscin (orange pigment)-is a risk factor for tumor growth, FAF photography: ipofuscin is not observed clinically, subretinal fluid - hyper
Retinal dystrophies and degenerations show abnormal autofluorescence
retinal dystrophies such as retinitis pigmentosa demonstrate areas of both hyper- and hypofluorescence, a sign that the retina is 'burning out'
Hydroxychloroquine maculopathy A ring of hyper-autofluorescence along with parafoveal dark areas will be visible, especially true in moderate and later stages
Damage from hydroxychloroquine and chloroquine toxicity appears to primarily affect the perifoveal photoreceptors, with secondary damage to the RPE
early hydroxychloroquine and chloroquine toxicity changes are noted on SD-OCT and mfERG, increased AF is seen with FAF likely due to early RPE dysfunction.
late finding of hydroxychloroquine and chloroquine toxicity include atrophy and decreased AF.
Retinal Detachment Hyperfluorescence in areas immediately adjacent to a retinal detachment can demarcate its extent
Central serous chorioretinopathy (CSC) extent seen with autofluorescence, not just in the area of the subretinal fluid but also in other parts of the macula or even the other eye
Adaptive optics SLO describes the use of wavefront sensors to sense aberrations of ocular optics, and to use deformable mirrors to compensate for the aberrations to enhance retinal imaging
