A device for detecting an amyloid protein in an eye of a mammal, the device comprising: a light source configured to emit light to illuminate the eye with at least one of a wavelength of light, a polarization of light or a combination thereof, each appropriate to produce fluorescence in at least an amyloid-binding compound when the amyloid-binding compound is bound to the amyloid protein, an optical unit comprising a photodetector unit for detecting fluorescence emitted from the eye, characterized in that the optical unit further comprises a time correlation single photon count module receiving electrical signals from the photodetector unit indicative of photon counts of fluoresced light from the eye; a processor module configured to determine the time decay rate of fluorescence based on a distribution of photon counts as a function of time channel units; wherein the optical unit is configured to receive light including fluorescence produced as a result of the illumination of the eye and to determine a time decay rate of fluorescence for at least the fluorescence produced by the amyloid-binding compound bound to the amyloid protein, the determining permitting distinguishing of the presence of the amyloid-binding compound bound to the amyloid protein in the eye based at least on the time decay rate, and the light source is configured to emit light of an appropriate wavelength for a peak region of a fluorescent excitation spectrum for the amyloid-binding compound bound to the amyloid protein in the eye, the excitation spectrum having a peak of about 470 nm, the light source being configured to emit the light to illuminate the eye at a wavelength within plus or minus about 20 nm of the peak of the excitation spectrum; the optical unit is further configured to detect light of an appropriate wavelength for a peak region of a fluorescent emission spectrum for the amyloid-binding compound bound to the amyloid protein in the eye, the emission spectrum having a peak of about 580 nm, the optical unit being configured to detect the light from the eye at a wavelength within plus or minus about 20 nm of the peak of the emission spectrum; and the time decay rate is determined for [ -2-(2-(2-methoxyethoxy)ethoxy)ethyl-2-cyano-3-(6-(piperidin-1-yl)naphthalene-2-yl)acrylate]. a light source configured to emit light to illuminate the eye with at least one of a wavelength of light, a polarization of light or a combination thereof, each appropriate to produce fluorescence in at least an amyloid-binding compound when the amyloid-binding compound is bound to the amyloid protein, an optical unit comprising a photodetector unit for detecting fluorescence emitted from the eye, characterized in that the optical unit further comprises a time correlation single photon count module receiving electrical signals from the photodetector unit indicative of photon counts of fluoresced light from the eye; a processor module configured to determine the time decay rate of fluorescence based on a distribution of photon counts as a function of time channel units; wherein the optical unit is configured to receive light including fluorescence produced as a result of the illumination of the eye and to determine a time decay rate of fluorescence for at least the fluorescence produced by the amyloid-binding compound bound to the amyloid protein, the determining permitting distinguishing of the presence of the amyloid-binding compound bound to the amyloid protein in the eye based at least on the time decay rate, and the light source is configured to emit light of an appropriate wavelength for a peak region of a fluorescent excitation spectrum for the amyloid-binding compound bound to the amyloid protein in the eye, the excitation spectrum having a peak of about 470 nm, the light source being configured to emit the light to illuminate the eye at a wavelength within plus or minus about 20 nm of the peak of the excitation spectrum; the optical unit is further configured to detect light of an appropriate wavelength for a peak region of a fluorescent emission spectrum for the amyloid-binding compound bound to the amyloid protein in the eye, the emission spectrum having a peak of about 580 nm, the optical unit being configured to detect the light from the eye at a wavelength within plus or minus about 20 nm of the peak of the emission spectrum; and the time decay rate is determined for [ -2-(2-(2-methoxyethoxy)ethoxy)ethyl-2-cyano-3-(6-(piperidin-1-yl)naphthalene-2-yl)acrylate].