density of opacities in one example the image analysis system is used to determine the blockage of light transmission by individual opacities for example software can be used with a digital image to detect darker or lighter regions and or gradients between regions an appropriate algorithm can be used to quantify a cross section area of the opacities within the vitreous analysis of the image can also capture an amount of reflectance to calculate a level of opacity translucence of individual opacities in the example of fig2 the cross section area of all opacities would equal an area sum of regions 123 125 127 129 and 131 in one example the image analysis system further defines the visual axis 140 in one example the retina can be detected from features in the image in another example a user can define the visual axis 140 manually using movable boundaries and software in one example the image analysis system further quantifies an amount of the cross section area of the opacities that obstruct a retina in the example of fig2 the cross section area of opacities within the visual axis 140 would include all of region 131 and the portion of region 127 that overlaps the central retina area 112.