Abstract
Purpose:
To develop a novel reflection-based capability of the RetCam® platform for the measurement of macular pigment (MP) optical density (OD) levels and their spatial distributions in infant eyes.
Methods:
Our method is based on the RetCam, a FDA-cleared digital imaging system typically used to inspect the infant retina with white-light, wide-field, high-resolution reflection imaging. We have configured the system to permit reflection based imaging in a relatively narrow spectral region around 485 nm, effectively overlapping the blue-green absorption range of MP. Two-dimensional pixel intensity reflection maps are recorded in which the MP is visible as a region of attenuated reflection. Using a custom software routine, we calculate MPOD levels as the log ratio between reflection intensity pixel areas in the fovea and selected areas in the peripheral retina.
Results:
A clinical trial involved 51 subjects ranging in age from prematurity up to age six. Out of 39 subjects, 37 had a relatively narrow, centrally peaked, MP distribution with circular symmetry, and two subjects had a ring-shaped distribution with near-zero MP level in the center (fovea). Peak MPOD levels varied between 0 and 0.4 in the measured subject population. In all prematurely born infants, MP was found to be absent. On average, MPOD levels increased linearly with age over the first six years of life, eventually reaching levels seen in adults.
Conclusions:
The RetCam® platform can be easily modified for reliable measurements of MP in infants if the imaging is carried out with a spectrally narrow blue light source overlapping the MP absorption range. Compared to white-light imaging results, this leads to increased contrast between foveal image regions attenuated by MP and peripheral regions used as an un-attenuated reference. MP levels are absent in all measured preterm infants, and on average increase linearly with age, reaching levels at age six that approach levels seen in healthy adults. The developed methodology holds promise for future investigations into the role of MP in the developing retina, and in combination with intravenous feeding and/or dietary interventions will make it possible to investigate uptake kinetics and stress factors.
Keywords: 587 macular pigment •
550 imaging/image analysis: clinical •
556 infant vision