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Toric Intraocular Lenses (toric + intraocular_lense)
Selected AbstractsComputerized calculation scheme for bitoric eikonic intraocular lensesOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 3 2003Achim Langenbucher Abstract Despite full correction of the corneal astigmatism with toric intraocular lenses, the retinal image is distorted and the lateral image-object magnification is different in different meridians. The purpose of this study is to describe an iteration strategy for tracing an axial pencil of rays through the ,optical system eye' containing astigmatic refractive surfaces with their axes at random to calculate a thick bitoric lens implant which eliminates image distortion. The capabilities of this computing scheme are demonstrated with two clinical examples. We present a mathematically straightforward computer-based strategy for the calculation of thick bitoric eikonic lens implants. The iteration algorithm is initialized with a spherical front and a toric back surface and stepwise decreases the image distortion by adding cylinder lenses to the front lens surface corrected by the toric lens back surface. Total magnification can be modulated by varying the front-to-back surface power of the thick lens. [source] 4431: Wavefront aberration variations with aspheric toric intraocular lensesACTA OPHTHALMOLOGICA, Issue 2010PJ PISELLA [source] Computerized calculation scheme for retinal image size after implantation of toric intraocular lensesACTA OPHTHALMOLOGICA, Issue 1 2007Achim Langenbucher Abstract. Purpose., To describe a paraxial computing scheme for tracing an axial pencil of rays through the ,optical system eye' containing astigmatic surfaces with their axes at random. Methods., Two rays (,10 prism diopters from vertical and horizontal) are traced through the uncorrected and corrected eye. In the uncorrected eye one specific ray is selected from the pencil of rays, which passes through the pupil center. In the corrected eye any ray can be traced through the eye. From the slope angle, the intersection of the ray with the refractive surface and the refraction the slope angle of the exiting ray is determined and the ray is traced to the subsequent surface. From both rays traced through the eye an ellipse is fitted to the image to characterize the image distortion of an circular object. Example., Assumptions: target refraction ,0.5,1.0D/A = 90° at 14 mm, corneal refraction 42.5 + 3.5D/A = 15°, axial length 23.6 mm, IOL position 4.6 mm, central lens thickness 0.8 mm, refractive index 1.42, front/back surface of the toric IOL 10.0 D/7.14 + 6.47D/A = 101.8°. The vertical incident ray was imaged to (x, y) = (0.0055 mm, ,1.6470 mm)/(0.0067 mm, ,1.6531 mm) in the uncorrected/corrected eye. The horizontal incident ray was imaged to (x, y) = (1.6266 mm, ,0.0055 mm)/(1.6001 mm, ,0.0067 mm) in the uncorrected/corrected eye. The ellipse (semi-major/semi-minor meridian) fitted to the conjugate image of a circle sized 1.648 mm/1.625 mm in an orientation 14.2° in the uncorrected and 1.654 mm/1.599 mm in an orientation 7.1° in the corrected eye. Conclusion., This concept may be relevant for the assessment of aniseikonia after implantation of toric intraocular lenses for correction of high corneal astigmatism. [source] | ||||||||||