The direct compensation method allows for an accurate (standard deviation below 0.05 log unit) determination of intraocular light scattering between 3.5 and 25 deg of scattering angle and is suitable for untrained subjects. The method was used to study population behaviour and individual variation in 129 volunteers between 20 and 82 yr of age, visual acuity equal to or better than one and no apparent eye pathology. The results indicate straylight to increase with the 4th power of age, doubling at 70. In addition to the age dependence, there was great variation between individuals. Part of this is due to negative correlation with pigmentation.

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Light scattering for normal and cataractous lenses from 21-86 yr old donors was measured in vitro. As expected, scattering increased with severity of cataract. Scattering decreased with angle according to a power law. This corresponded to the power law finding for functional straylight measurements in early-cataract patients using white light (power around -2). In vitro, straylight increased monotonically from 700 nm (power around -2.3) towards 400 nm (power around -2.0). For extreme cataracts the angular dependence flattened at small angles. The present results suggest that the structures dominating in light scattering differ not by scattering type but by number, and that they are not very small compared to wavelength. The present results were used to specify the separate effects of light absorption and light scattering on lenticular light transmission.