Light attenuation by RPE-melanin in-vivo varies with age and the presence of Stargardt disease.

<p>We calculated the total optical density (OD) of paramacular RPE-melanin versus wavelength of incident radiation with Eqs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172635#pone.0172635.e004" target="_blank">4</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172635#pone.0172635.e006" target="_blank">6</a> based on results of Monte-Carlo simulations. Colored lines indicate attenuation in healthy people of different ages: 20 (red), 40 (green), and 60 (orange). The same is shown for a 20-year old patient with STGD1 (black).</p

Numerical simulation of oxygen uptake by lipofuscin in paramacular RPE in-vivo during exposure to diffuse sunlight.

<p>Oxygen uptake was calculated based on results from a previous investigation of oxygen uptake by isolated human lipofuscin granules [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172635#pone.0172635.ref020" target="_blank">20</a>], after correction for factors affecting retinal exposure levels in-vivo (see text). Results were plotted for healthy people of different ages: 20-year old (red), 40-year old (green), and 60-year old (orange). Results for 20-year old patients with STGD1 are also shown (grey).</p

Monte-Carlo simulation of light scattering and absorption in a thick layer of melanosomes.

<p>In this plot generated by MontCarl, the optical paths (blue lines) of 3000 photons are ray-traced through a relatively thick layer of RPE-melanosomes at the concentration in-vivo. Photons are injected by an infinitely thin light beam at X/ Y = 0/ 0. The X- and Z-axes, respectively, indicate the lateral and vertical (depth) location in the sample. Most photons are either absorbed or scattered back at Z = 30 μm. At the assumed maximum in-vivo layer ‘thickness’ of RPE-melanosomes (3 μm), a small proportion of photons are backscattered or absorbed.</p

Total rates of oxygen uptake by lipofuscin during light exposure.

<p>Rates of oxygen uptake (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172635#pone.0172635.g008" target="_blank">Fig 8</a>) were integrated along the wavelength of incident radiation to obtain the total rate of O₂-uptake, as an indication of cellular oxidative stress in-vivo during exposure to diffuse sunlight (white bars) or during SW-AF imaging (grey bars). X-axes: Age of healthy individuals, or patients with STGD1 (age, 20).</p

Relative contributions of light scattering and absorption by RPE-melanin.

<p>(A) Agreement between Monte-Carlo simulation and theory, plotted based on conditions in the paramacular RPE of a healthy 20-year old person. The optical density (OD) was calculated based on the product of the attenuation coefficient and the melanosome layer thickness (<i>l</i>_melanin). Attenuation by absorption (striped line), scattering (dotted line), and total attenuation (straight line) are plotted separately. The MC results are shown in blue (left Y-axis) and the theoretical result is shown in red (right Y-axis). See text for details. (B) Simulations of a thin (3 μm; blue) and thick (52.5 μm; orange) layer of melanosomes. In case of thicker layers, there is a dominance of the absorption coefficient (<i>μ</i>_{<i>a</i>, melanin}, straight lines) over the backscattering coefficient (<i>μ′</i>_{<i>s</i>, melanin}, striped lines) for all tested wavelengths.</p

Retinal exposure from diffuse solar irradiation compared to excitation light of short-wavelength retinal auto-fluorescence.

<p>At <i>λ</i> = 488 nm the peak height is indicated by single colored dots. Exposures were calculated by Eqs (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172635#pone.0172635.e002" target="_blank">2</a>) and (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172635#pone.0172635.e003" target="_blank">3</a>), respectively. Exposures in ocular media of different ages are plotted; 20 year-old (red), 40 year-old (green), and 60 year-old (orange).</p

Schematic and representative images of measurements in fundus autofluorescence imaging and spectral-domain optical coherence tomography.

<p>Patient 9: area of questionably decreased autofluorescence (QDAF, blue), 1.37 mm²; area of definitely decreased autofluorescence (black), 0.33 mm²; transverse loss of external limiting membrane (ELM-loss, red), 1.75 mm, transverse loss of ellipsoid zone (EZ-loss, blue), 2.24 mm; best-corrected visual acuity, 20/100; <i>ABCA4</i> variants, c.1622T>C;3113C>T:p.[Leu541Pro;Ala1038Val] and c.6316C>T:p.(Arg2106Cys).</p

<i>ABCA4</i> variants in early-onset Stargardt patients from Radboud university medical center (Radboudumc) and Moorfields Eye Hospital (MEH).

<p><i>ABCA4</i> variants in early-onset Stargardt patients from Radboud university medical center (Radboudumc) and Moorfields Eye Hospital (MEH).</p

Yearly progression rate of changes in retinal eccentricity (<i>ε</i>) by visual function, fundus autofluorescence and optical coherence tomography.

<p>Yearly progression rate of changes in retinal eccentricity (<i>ε</i>) by visual function, fundus autofluorescence and optical coherence tomography.</p

Highest potential mean-to-standard deviation ratio (MSDR) for each single outcome measure at different weightings with all possible weight combinations of the other metrics.

<p>MSDRs for best-corrected visual acuity (grey) decrease at increasing weight. MSDRs for transition zones of questionably decreased autofluorescence (blue) increase until 25% weight, but gradually decrease at higher weights. MSDRs for transition zones of definitely decreased autofluorescence decrease at weights higher than 5%. MSDRs for loss of the ellipsoid zone (green) are constant, but decrease substantially at weights higher than approximately 70%. MSDRs for loss of the external limiting membrane (black) decrease at weights higher than approximately 80%.</p