Methods and apparatus for detection of carotenoids in macular tissue

An apparatus for measuring macular pigments, comprising:

• a first light source that generates light at a first wavelength;
• an optional second light source that generates light at a second wavelength that is different from the first wavelength;
• delivery means for directing light sequentially from the first and second light sources onto macular tissue of an eye for which macular pigment levels are to be measured;
• detection means for collecting light emitted from the macular tissue, the collected light comprising lipofuscin emission from the macular tissue at two excitation wavelengths;
• and
• quantifying means for determining intensities of the lipofuscin emission at the excitation wavelengths, and determining the macular pigment levels in the macular tissue from the differing lipofuscin emission intensities in the macula and peripheral retina.

A method for measuring macular pigments, comprising:

• providing at least one light source that generates light at a wavelength that produces an autofluorescence lipofuscin emission and a Raman response with a wavelength shift for carotenoids to be detected;
• directing light from the light source onto macular tissue of an eye for which macular pigment levels are to be measured, the light from the light source having an intensity that does not substantially alter macular pigment levels in the macular tissue;
• collecting light emitted from the macular tissue in a first optical channel, the collected light in the first optical channel comprising lipofuscin emission from the macular tissue at two wavelengths, including a first excitation wavelength that overlaps both the macular pigment and lipofuscin absorption range, and a second excitation wavelength that is longer than the first excitation wavelength and lies outside the macular pigment absorption range but still excites lipofuscin emission;
• quantifying the lipofuscin emission intensities at the first and second excitation wavelengths;
• determining the macular pigment levels in the macular tissue from the differing lipofuscin emission intensities in the macula and peripheral retina;
• collecting light scattered from the macular tissue in a second optical channel, the scattered light in the second optical channel including elastically and inelastically scattered light, the inelastically scattered light producing a Raman signal corresponding to carotenoids in the tissue;
• filtering out the elastically scattered light;
• and
• quantifying the intensity of the Raman signal.

An apparatus for measuring macular pigments, comprising:

• at least one light source that generates light at a wavelength that produces an autofluorescence lipofuscin emission, and a Raman response with a wavelength shift for carotenoids to be detected;
• a first optical channel;
• a second optical channel;
• delivery means for directing light from the autofluorescence lipofuscin emission to the first optical channel, and directing scattered light containing a Raman signal to the second optical channel;
• a first optical detector for collecting light from the first optical channel;
• a second optical detector for collecting light from the second optical channel;
• and
• quantifying means for determining intensities of the lipofuscin emission from the first optical channel, and determining Raman signal intensity of the scattered light from the second optical channel.