Abstract
Abstract: :
Purpose: Measurements of macular pigment in humans have been made with several physical and psychophysical techniques but have produced variable estimates of its spatial extent. The purpose of the present work was to estimate the spatial extent of macular pigment in young healthy retinas by hyperspectral imaging of the fundus with high spatial and spectral resolution. Methods: The hyperspectral fundus imaging system was adapted from an indirect ophthalmoscope. An area of the retina of about 15 deg was illuminated by light from a xenon lamp filtered by a fast tunable liquid–crystal filter (VariSpec, VS–VIS2–10–HC–35–SQ, Cambridge Research & Instrumentation) with bandwidth about 10 nm. Spectral images of the fundus were acquired sequentially over the spectral range 450–530 nm with a low–noise Peltier–cooled digital camera (Hamamatsu, model C4742–95–12ER) with a spatial resolution of 1344 x 1024 pixels and 12–bit output. The retinas of 25 young healthy subjects, average age 26.6 years, were imaged with this system. The spatial extent of the macular pigment was estimated for each subject from a comparison of the foveal spectral reflectance at each pixel with that of a pixel average in the parafovea. The two–dimensional profile thus obtained was summarized in the horizontal and vertical meridians by the corresponding full width at half height (FWHH). Results: The mean FWHH for the horizontal meridian was 2.7 deg and for the vertical meridian 2.3 deg, each with SEM of about 0.2 deg. Conclusions: Estimates of the extent of the macular pigment obtained by this method are not large and are in general agreement with the smaller estimates reported in the literature, in particular by psychophysical methods (Robson et al., 2003, Vision Res., 1765–1775).
Keywords: macular pigment • imaging/image analysis: clinical • image processing