Rob G L van der Heijde

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The purpose of this study was to determine the shear compliance of human crystalline lenses as a function of age and frequency. Dynamic mechanical analysis was performed on 39 human lenses, ranging in age from 18 to 90 years, within the frequency range of 0.001-30 Hz. The lenses were stored at -70 degrees C before being measured. The influence of freezing(More)
PURPOSE To obtain the shape of the posterior corneal surface in a healthy population, using Scheimpflug photography corrected for distortion due to the geometry of the Scheimpflug imaging system and the refraction of the anterior corneal surface. METHODS The posterior corneas of 83 subjects, ranging in age from 16 to 62 years, were measured in the(More)
PURPOSE A change in surface area of the capsular bag and a change in volume of the lens can indicate whether a change in the shape of the lens during accommodation is due to the compressibility or the elasticity of the lens material. METHODS 3D magnetic resonance imaging (MRI) was used to image the complete shape of the lens in a group of five healthy(More)
Knowledge about geometric properties such as shape and volume and Poisson's ratio of the nucleus can be used in the mechanical and optical modeling of the accommodation process. Therefore, Scheimpflug imaging was used to determine the shape of the human lens nucleus during accommodation in five subjects. To describe the shape of the nucleus, we fitted a(More)
We present a comparison between measurements of the radius of the anterior and posterior lens surface, which was performed using corrected Scheimpflug imaging and Purkinje imaging in the same group of participants (46 for the anterior lens, and 34 for the posterior lens). Comparisons were also made as a function of accommodation (0 to 7 D) in a subset of 11(More)
PURPOSE To determine the precision and reliability of retinal thickness measurements with an optical coherence tomograph (Stratus OCT 3; Carl Zeiss Meditec, Dublin, CA) and a retinal thickness analyzer (RTA; Talia Technology Ltd., Neve-Ilan, Israel) in foveal, parafoveal, and perifoveal areas. METHODS Three measurements of all areas were performed within(More)
A ray-tracing procedure was applied to corrected Scheimpflug photography measurements to determine the spherical aberration of the anterior and posterior surfaces of the cornea. It was found that the total spherical aberration of the cornea increases slightly with age. The spherical aberration of the posterior corneal surface is negative at a young age and(More)
PURPOSE The purpose of this study is to demonstrate the performance of a topographer (the VU topographer, prototype development, VU University Medical Center, Amsterdam, The Netherlands) that uses a color-coded stimulus pattern to reconstruct both the rotation-symmetric and nonrotation-symmetric shape features of the anterior corneal surface. METHODS(More)
PURPOSE To experimentally verify the suggestion of Gullstrand (1909), i.e., that the equivalent refractive index of the human lens increases with accommodation. METHODS The left eye of five subjects was focused on different accommodation stimuli, while the right eye was imaged with Scheimpflug photography in order to obtain the shape of the lens and(More)
PURPOSE A pseudo forward ray-tracing (PFRT) algorithm is developed to evaluate surface reconstruction in corneal topography. The method can be applied to topographers where one-to-one correspondence between mire and image points can be established. METHODS The PFRT algorithm was applied on a corneal topographer designed and constructed at the VU(More)