Quantitative cataract measurement

Abstract

Abstract Purpose: To provide an overview of the impact of cataract on optical image transfer and the possibilities to measure cataract quantitatively. Methods: The current paper reviews strategies for how limitations of the imaging transfer of the eye originating from the lens can be quantitatively measured. Results: The diameter of the pupil should be standardized in comparisons of optical image transfer. In vitro, aberrations and light scattering can be measured directly as point spread function characterized by Strehl ratio. Also, the effect of stray light, resonant absorption and aberrations can be measured directly. All, in vivo techniques require consideration of the impact of the cornea on the optical image transfer. Further, if psychophysical sensing is used, the image transfer of the total visual system depends on the optical transfer and the neurosenory transfer. Slit lamp microscopy with slit illumination, optionally improved with Scheimplug projection, or alternatively with retroillumination provides quantitative geographic information about the distribution of emission of light scattering, but inconsistently correlates to the image transfer. Visual acuity measures high contrast resolution. Cataract causes loss of contrast sensitivity, mainly due to scattering and stray light. The effect of stray light can be sensed psychophysically. The point spread function and aberrations in the optical system can be measured with double pass technique. Conclusions: Cataract can be measured quantitatively as reduction of optical transfer of the eye which is limited by aberrations, light scattering, stray light and resonant absorption.