Tobias Buehren

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Accommodation stimulus-response function (ASRF) and its relationship to retinal image quality were investigated using a modified wavefront sensor. Ten subjects were presented with six vergence stimuli between 0.17 D and 5 D. For each vergence distance, ocular wavefronts and subjective visual acuity were measured. Wavefronts were analysed for a fixed 3-mm(More)
PURPOSE To investigate the effects of eyelid pressure on corneal shape and corneal aberrations during reading. METHODS Twenty young subjects with normal ocular health were recruited for the study. The experiment was conducted early in the morning, with subjects instructed not to perform any prolonged reading before the experiment. Corneal topography of(More)
PURPOSE To compare lid-induced changes in corneal optics following reading, microscopy and computer work. METHODS Nine subjects with normal ocular health were recruited for the study. Five subjects were myopic, two were emmetropic, one was astigmatic and one was hyperopic. Corneal topography was measured before and after 60 mins of reading a novel,(More)
We undertook a detailed analysis of the wavefront aberrations of the eyes of 20 young progressing myopes (mean age=22 years; mean spherical equivalent=-3.84 D, range -1.00 to -7.5 D) and twenty young age matched emmetropes (mean age=23 years; mean spherical equivalent=-0.00 D, range +0.25 to -0.25 D). A wavefront sensor was used to measure the ocular(More)
Analysis was undertaken of the retinal image characteristics of the best-spectacle corrected eyes of progressing myopes (n = 20, mean age = 22 years; mean spherical equivalent = -3.84 D) and a control group of emmetropes (n = 20, mean age = 23 years; mean spherical equivalent = 0.00 D) before and after a 2h reading task. Retinal image quality was calculated(More)
PURPOSE Videokeratoscopes provide a wealth of information about the topography of the ocular surface. Although there have been numerous studies of the accuracy and precision of videokeratoscopes with inanimate test objects, little information exists on their precision (repeatability) for real eyes. METHODS To investigate the stability of the ocular(More)
Following our previous work on optimal modeling of corneal surfaces with Zernike polynomials, we have developed a refined bootstrap-based procedure which improves the accuracy of the previous method. We show that for normal corneas, the optimal number of Zernike terms usually corresponds to the fourth or fifth radial order expansion of Zernike polynomials.(More)
PURPOSE To establish repeatability and validity of a partial coherence interferometry (PCI) device in patients with astigmatism. SETTING Industry and university. DESIGN Observational studies. METHODS A prospective study determined the agreement between the IOLMaster 500 PCI device and the Marco 1-position manual keratometer for measurement of mean(More)
PURPOSE To investigate whether there are significant changes in corneal topography during accommodation in normal corneas and corneas that are pathologically thinner due to keratoconus. METHODS A videokeratoscope was modified to present an accommodation stimulus that was coaxial with the instrument's measurement axis. Six subjects with normal corneas and(More)
PURPOSE We aimed to minimize the effect of ocular microfluctuations during videokeratoscopy to improve the qualitative and quantitative analysis of corneal topography. METHODS A technique was developed to measure the tilt, displacement, and cyclotorsion in multiple videokeratographs from the same cornea. This information was used to reposition each(More)