Blue-light reflectance imaging of macular pigment in infants and children

Abstract

Purpose: While the role of the macular pigment carotenoids in the prevention of age-related macular degeneration has been extensively studied in adults, comparatively little is known about the physiology and function of lutein and zeaxanthin in the developing eye. We therefore developed a protocol using a digital video fundus camera (RetCam) to measure macular pigment optical density (MPOD) and distributions in premature infants and in children.

Methods: We used blue light reflectance to image the macular pigment in premature babies at the time of retinopathy of prematurity (ROP) screening and in children aged under 7 years who were undergoing examinations under anesthesia for other reasons. We correlated the MPOD with skin carotenoid levels measured by resonance Raman spectroscopy, serum carotenoids measured by HPLC, and dietary carotenoid intake.

Results: We enrolled 51 infants and children ranging from preterm to age 7 years. MPOD correlated significantly with age (r = 0.36; P = 0.0142), with serum lutein + zeaxanthin (r = 0.44; P = 0.0049) and with skin carotenoid levels (r = 0.42; P = 0.0106), but not with dietary lutein + zeaxanthin intake (r = 0.13; P = 0.50). All premature infants had undetectable macular pigment, and most had unusually low serum and skin carotenoid concentrations.

Conclusions: Our most remarkable finding is the undetectable MPOD in premature infants. This may be due in part to foveal immaturity, but the very low levels of serum and skin carotenoids suggest that these infants are carotenoid insufficient as a consequence of low dietary intake and/or severe oxidative stress. The potential value of carotenoid supplementation in the prevention of ROP and other disorders of prematurity should be a fruitful direction for further investigation.

Keywords: carotenoid; imaging; lutein; macular pigment; zeaxanthin.

Figure 1

Spectroscopic principles underlying macular pigment measurement with the RetCam. The normalized absorption spectrum of primate macular pigment as reported by Snodderly et al. was plotted versus the normalized emission spectra of the RetCam's blue-light and white-light sources as measured by a commercial spectrometer. A correction factor of 1.15 (a) is employed in Equation 1 to compensate for the lower absorbance of MP at the peak of the fundus camera's 480- to 485-nm blue light source relative to the macular pigment's peak absorbance at 460 nm.

Figure 2

Blue light reflectance measurement of macular pigment in subject 7. A fundus reflectance image using 485-nm (blue) excitation light was obtained with a RetCam (upper left). The blue fundus image has three components corresponding to the blue, green, and red chips in the RetCam's internal charge-coupled device (CCD) detector. The blue component was converted to grayscale for all calculations and processing (upper right). A corresponding 3-dimensional pseudo-color MP distribution can then be plotted (lower left) along with a horizontal meridian, nasal–temporal intensity profile running through the center of the fovea (lower right).

Figure 3

Right-left correlation of MPOD measurements of subjects who had both eyes measured.

Figure 4

MPOD versus age.

Figure 5

MPOD versus dietary and serum carotenoids.

Figure 6

Resonance Raman measurement of skin carotenoids versus age.

Figure 7

Resonance Raman measurement of skin carotenoids versus dietary and serum carotenoids.

Figure 8

MPOD versus skin carotenoids measured by resonance Raman spectroscopy (RRS).