Abstract
Purpose:
To develop instrumentation for convenient, rapid, quantitative assessment of macular pigment (MP) optical density (OD) levels and their associated spatial distributions in the human retina.
Methods:
We developed a commercial non-mydriatic fundus camera platform for rapid detection of lipofuscin fluorescence (“autofluorescence”), generated in the retinal pigment epithelial layer upon short-pulse xenon flash lamp excitation. Excitation in the 475-495 nm wavelength range, realized with a band pass filter, was used to obtain high spectral overlap with the lipofuscin and MP absorption bands. Two-dimensional fluorescence intensity pixel maps (“AFI images”) were recorded with a high-sensitivity CCD camera at wavelengths above 700 nm - detection conditions under which subject-specific MP characteristics are typically visible as a localized, high-contrast, central image region of attenuated fluorescence. Integrated image processing software compares pixel fluorescence intensities from the peripheral retina with intensities in the macular region, and in this way derives MPOD levels and pseudo-color scaled spatial MP distributions as quantitative measures for individual MP characteristics. The instrument design does not require any patient participation other than viewing an alignment target, and was tested with 17 healthy volunteers and 93 patients with pseudopakic eyes, respectively. All subjects provided informed consent based on institutional review board approval and the tenets of the Declaration of Helsinki.
Results:
High-quality images were obtained in all eyes, demonstrating that MP levels and associated spatial distributions can be conveniently and reliably screened. MP levels in the peak of the distributions ranged typically from 0.10 to 0.90. Subject-specific spatial features of the MP distributions such as ring patterns, shoulders, localized fragmentation, etc. were clearly resolved.
Conclusions:
The developed instrumentation and automated image processing routines provide for the first time a fundus camera based non-mydriatic measurement of autofluoresence-derived MP characteristics in the human retina. Permitting convenient, rapid, objective MP measurements in clinical as well as field settings, the methodology is well suited for age-related macular degeneration research as well as for screening of MP levels and their associated spatial distributions in response to nutritional interventions.
Keywords: 465 clinical (human) or epidemiologic studies: systems/equipment/techniques •
587 macular pigment •
582 ipofuscin