The utility of using customized heterochromatic flicker photometry (cHFP) to measure macular pigment in patients with age-related macular degeneration.

The purpose of this study was to assess the utility and validity of using customized heterochromatic flicker photometry (cHFP) to measure macular pigment optical density (MPOD) in patients with intermediate stages of age-related macular degeneration (AMD). The measurement procedure was optimized to accommodate individual differences in temporal vision related to age, disease, or other factors. The validity criteria were based on the similarity of the spectral absorption curves to ex vivo curves of lutein and zeaxanthin and the similarity of spatial density profiles to those measured in subjects without retinal disease. Macular pigment optical density (MPOD) spatial profiles were measured with an LED-based macular densitometer; spectral absorption curves were measured with a 3-channel Maxwellian view system including a monochromator. All patients were characterized via clinical exams and all but 2 subjects from whom data were obtained had masked grading of color fundus photographs using the Wisconsin Age-Related Maculopathy Grading System. Most of the patients were in AREDS category 2 (27%) or 3 (57%). Patients with visual acuity as poor as 20/80 were included, and could perform the task as long as they could see the stimulus. Eighty-one percent of the patients screened were able to perform the cHFP task, and data were obtained from 30 AMD patients. Spatial profiles of MPOD were measured in 19 subjects who could see the stimulus at all tested loci. These profiles were highly similar to those that have been measured with HFP in subjects without retinal disease. The average shape of the spectral absorption curves for the AMD subjects corresponded well to an ex vivo template. These data support both the utility and validity of the cHFP method for measuring MPOD in subjects with intermediate stages of AMD. The ability to measure the retinal response to nutritional intervention is of practical importance for monitoring patients being supplemented with lutein and zeaxanthin in hopes of retarding visual loss and/or disease progression.

Rapid serum carotene loading with high-dose beta-carotene: clinical implications.

The kinetics of serum beta-carotene loading were evaluated to help determine the minimum time required to load fatty tissues, including atherosclerotic plaque and skin, with beta-carotene. Loading atherosclerotic plaque with yellow beta-carotene pigment increases absorption of blue laser radiation, potentially enhancing the selectivity and quality of laser angioplasty. Five healthy volunteers received 300 mg beta-carotene daily (the maximum FDA recommended dose) for 21 days in three divided doses with meals. Serum total carotenoid levels increased exponentially with a 10-day time constant from an average of 1.7-6.5 micrograms/ml (p less than 10(-4]. The skin began to yellow visibly at 10 days and became increasingly yellow for several weeks thereafter, suggesting that augmenting the yellow color of fatty tissues and atherosclerotic plaque with oral beta-carotene may require a minimum of several weeks to attain the maximum effect.