A modified Hartmann-Shack aberrometer for measuring stray light in the anterior segment of the human eye

To examine the use of a modified Hartmann-Shack wave front aberrometer (WASCA; Carl Zeiss Meditec AG, Germany) to measure objective stray light caused by forward light scatter from the anterior segment of the human eye. HELIOS Klinikum Erfurt/Institute of Biomedical Engineering and Informatics, Ilmenau University of Technology, Germany. Scatter parameters, including the Michelson contrast and cross-sectional area at half height (CAHM) were examined in Hartmann-Shack images from ten subjects with a cataract in one eye and an intraocular lens (IOL) in the other. The parameters were compared between each eye. Light scatter was then measured in 40 healthy subjects (age range, 23-75 years) with spherical ametropia ranging from -0.25 to 0.25 diopters. The subjects were divided into three age groups; 23-35, 36-50, and 51-75 years. Light scatter was also measured using four alternative methods. CAHM and contrast were significantly different between the eyes with the cataract and the IOL (P = 0.007 and P = 0.004, respectively). CAHM (r = 0.557, P < 0.001) and contrast (r = -0.467, P < 0.001) were both significantly correlated with age. There were significant differences in CAHM and contrast between the age groups. The modified wave front aberrometer can be used to measure stray light, although its diagnostic sensitivity in individual patients must be improved.