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Soft Tissue Replacements
Published in Joyce Y. Wong, Joseph D. Bronzino, Biomaterials, 2007
K.B. Chandran, K.J.L. Burg, S.W. Shalaby
Eye implants are used to restore the functionality of damaged or diseased corneas and lenses. Usually the cornea is transplanted from a suitable donor. In cataracts, eye lenses become cloudy and can be removed surgically. Intraocular lenses (IOL) are implanted surgically to replace the original eye lens and to restore function. IOL are made from transparent acrylics, particularly polymethyl methacrylate, which has excellent optical properties. Infection and fixation of the lens to the tissues are frequent concerns, and a number of measures are being used to address them. Transplantation of retinal pigmented epithelium can be used in the treatment of adult onset blindness; the challenge is developing readily detachable or absorbable materials on which to culture sheets of these cells.
Adjustable intraocular lenses: The light adjustable lens
Published in Pablo Artal, Handbook of Visual Optics, 2017
An intraocular lens (IOL) is a surgically implanted, artificial lens designed to replace the natural crystalline lens in the human eye, typically in patients who have developed visually significant cataracts. Since their inception in the late 1940s, IOLs have provided improved uncorrected visual acuity (UCVA) compared to that of the cataractous or aphakic state; however, problems in predictably achieving emmetropia persist as most post–cataract surgery patients rely on spectacles or contact lenses for optimal distance vision.
Tool vibration effect on surface roughness of polymethylmethacrylate in diamond turning
Published in Materials and Manufacturing Processes, 2022
Kuldeep A Mahajan, Raju S. Pawade, Vinod Mishra
The optical components like lens array, cylindrical lens, toric lens, intraocular lenses (IOL) are produced in distinct shapes and geometries, like spherical, aspheric, off-axis, and free-form optics. These components require better surface roughness and higher form accuracy. The single-point diamond turn machining (SPDT) is an efficient process of manufacturing lenses with significantly better form and excellent surface roughness. The surface generated by SPDT is generally dependent on the machining parameters along with material .[1] The vibration occurrence is inevitable in the machining process even though it is an ultra-precision machine .[2]
Effect of Different Spectral Power Distributions on Mesopic Visual Performance with Blue Light-filtering Intraocular Lens
Published in LEUKOS, 2021
EG Vicente, I Arranz, D Galarreta, P Barrionuevo, M Rodríguez-Rosa, S Mar, JA Aparicio, BM Matesanz
The most prevalent age-related illness of the human crystalline lens is cataract, which is an important cause of visual impairment in the elderly (Klein et al. 1992). This opacification results in a wavelength-dependent reduction of the light entering the eye (Labuz et al. 2018) and intraocular scattering, which negatively influences the quality of the retinal image, not only reducing its contrast but affecting its brightness in mesopic conditions (Barrionuevo et al. 2010). This light scattering is defined by the relationship between the size of the opacity particles, their refractive index and the wavelength of the incident light (Méndez-Aguilar et al. 2017). Cataract surgery, with the subsequent implantation of an intraocular lens (IOL), allows old people to recover retinal image quality (Rubin et al. 1993) due to, among other factors, scattering reduction (Labuz et al. 2018). Among the different IOL options available, a blue light-filtering IOL has been widely used in routine clinical practice, though its effect on photoreception and photoprotection is still a matter of review (Davison et al. 2011; Mainster 2010; Zhu et al. 2012). As in the case of photoreception, short-wavelength blocking does not influence photopic contrast sensitivity enough to significantly improve or worsen it, as this curve is mainly determined by long-wavelength light (Wirtitsch et al. 2009). Similarly, mesopic contrast sensitivity was found not to be affected by the spectral properties of a blue light-filtering IOL (Eberhard et al. 2009; Greenstein et al. 2007; Hayashi and Hayashi 2006; Landers et al. 2007; Muftuoglu et al. 2007; Neumaier-Ammerer et al. 2010; Wang et al. 2010). Regarding scotopic contrast sensitivity, Werner reports a loss in scotopic sensitivity of 0.07 logarithmic units after the implantation of a blue light-filtering IOL, an insignificant result considering the 4 logarithmic units range of the scotopic sensitivity (Werner 2005). In terms of color vision, most studies analyzing blue light-filtering IOLs effect on color vision under photopic illumination conditions report no disruption (Cuthbertson et al. 2009; Lavric and Pompe 2014; Leibovitch et al. 2006; Zhu et al. 2012). However, at mesopic conditions, some authors report that blue light-filtering IOLs significantly reduced color vision in the blue-light spectrum (Mester et al. 2008; Neumaier-Ammerer et al. 2010; Wang et al. 2010); meanwhile, others do not reach to the same conclusion (Falkner-Radler et al. 2008). Although Simunovic (2012) states that any impairment in the tritan axis would be much less noticeable if it is compared with the produced by a normal-aged lens.