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Optics and refractive errors
Published in Mostafa Khalil, Omar Kouli, The Duke Elder Exam of Ophthalmology, 2019
Nemat Ahmed, Omar Kouli, Mostafa Khalil, Obaid Kousha
This is a test that uses chromatic aberrations of the eye to refine the best vision sphere following optical correction. The test is comprised of black letters positioned on two backgrounds, red and green. As red is a longer wavelength than green, it will focus behind the retina, while green will focus in front of the retina.
Optical and visual metrics
Published in Pablo Artal, Handbook of Visual Optics, 2017
Measures of optical quality (aberrations) and optical performance (image quality, contrast transfer, etc.) are objective methods (Figure 18.1). While the final arbiter of image quality is the human viewer, these efforts to define objective metrics can be useful for many applications. Along with the eye, the optical performance of correcting lenses (contact, ophthalmic, and intraocular lenses), used increasingly more frequently, must be considered for understanding how the images are formed at the retina. Thus, for optical design the manufacturer needs some merit functions to achieve the quality requirements. The aberrations of the eye and their effects on retinal image quality have long been of interest. Further, the link between vision and ocular optical quality has enjoyed a renewed attention. How the complex interactions of aberrations impact visual performance is being systematically investigated by looking at correlations of objective and subjective estimates. Also, new objective metrics that incorporate some neural characteristics of the visual system have been proposed recently that correlate better with clinical measures of visual performance.
The short term effect of trehalose and different doses of sodium hyaluronate on anterior corneal aberrations in dry eye patients
Published in Cutaneous and Ocular Toxicology, 2021
Yener Yildirim, Cemal Ozsaygili, Bekir Kucuk
In the literature, some studies showed that the HOAs of the patients with dry-eye were found to be improved after the instillation of artificial tears22,23 whereas, a study24 showed that HOAs increased significantly 1 min after the instillation of 0.3% SH and returned to baseline at 10 min. In addition, a study19 showed that all HOAs remained stable to baseline after the 0.18% hypotonic SH instillation. Although several studies have been conducted to evaluate the optical aberrations in dry eye patients using the artificial tears, there is no previously published study comparing the short-time effect of three different artificial tears (0.15% SH − 0.20% SH − Trehalose + 0.15% SH) on ocular aberrations in dry eye disease.
Comprehensive Evaluation of Retinal Image Quality in Comparing Different Aspheric to Spherical Intraocular Lens Implants
Published in Current Eye Research, 2019
Xuan Liao, Xiuqi Haung, Changjun Lan, Qingqing Tan, Baiwei Wen, Jia Lin, Jing Tian
The demand for cataract patients to improve the vision-related quality of life has promoted the evolvement of surgical techniques and materials over the past century. Modern cataract surgery, routinely combined with posterior chamber intraocular lens (IOL) implantation, has shifted over from a visual restorative treatment to a refractive procedure.1,2 To date, artificial IOL has been available not only to replace natural crystalline lens and compensate for defocusing error, but also mimic specific physiologic properties and improve retinal image quality. Unfortunately, almost all of IOLs affect ocular aberrations in some manner. Spherical aberration (SA) is one of the most important aberrations of the eye. In the young phakic eye, the virgin corneal positive SA is at least partially compensated for by lenticular negative SA, resulting in low ocular aberrations overall.3 The minimization of aberrations should physically contribute to the optimization of optical quality and functional vision of eye. With aging, however, the lenticular SA changes from negative to positive, losing the compensatory capacity for cornea and thus decreasing the overall visual and optical quality of eye. Conventional spherical IOL, similar to aged crystalline lens, has a positive SA which adds to corneal positive SA. Given this, aspherical IOL or aberration-free IOL, with one or both optimized surface curvatures in their optical zones, are designed to simulate optically the characteristics and functionality of the young transparent crystalline lens and counterbalance for the intrinsic positive asphericity of the prolate cornea.4
“For Mass Eye and Ear Special Issue” Adaptive Optics in the Evaluation of Diabetic Retinopathy
Published in Seminars in Ophthalmology, 2019
Omar AbdelAl, Mohammed Ashraf, Konstantina Sampani, Jennifer K Sun
There have been several wavefront analysis methods proposed to measure optical aberrations of an eye. The Shack–Hartmann Wavefront Sensor (SHWS) is widely considered to be the best available approach to measure aberrations in the human eye. Junzhong Liang and Donald Miller, led by David Williams, built the world’s first AO retinal camera in the 1990s, leveraging the potential of SHWS technology for ophthalmic applications.28,29 In the SHWS, light is propagated through a lenslet array; each lenslet focuses the light beam onto a spot on a charge-coupled device (CCD) camera.39,40 Aberrations within the beam change the position of the focused light, and this displacement of the spots on the CCD is used to reconstruct the wavefront.