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Anterior segment imaging has made tremendous strides since the introduction of slit lamp biomicroscopy. When the slit illumination device [1] of Swedish ophthalmologist Allvar Gullstrand was combined with Czapski 's binocular microscope in 1916, a major advance was marked as more accurate three-dimensional visualization and localization of anterior segment pathology became possible. Subsequent advances...
Biaxial microincision clear corneal phacoemulsifica-tion was a new method which made the corneal incision smaller; it was described by Shearing in 1985 [1]. This procedure uses separate irrigations with an irrigating chopper and sleeveless phacoemulsification tip, and also requires pulsed phacoemulsification energy. The minimization of the incision is a consequence of a natural evolution of...
In 1991, Hara and co-workers were the first to publish the idea of inserting an endocapsular ring into the capsular bag [1]. They used a closed ring made of soft silicone with a groove on its inner surface for the loops of the intraocu lar lens (IOL). The ring was thought not only to main tain the circular contour of the capsular bag equator, but also to withhold lens epithelial cell (LEC) migration...
In 5 B.C., Sanskrit manuscripts first described couching, the procedure by which a needle is placed into the eye and an opa lescent lens pushe d into the vit reous cavity in order to clear the visual axis. In 1748, Jacques Daviel performed the first extracapsular cataract extraction, and then, in 1967, Charles Kelman invented what is known today as phacoemulsification, considered by many in the Western...
Astigmatism is an optical aberration caused by the toricity of an optical system. If two meridians of an optical system with the least and highest refractive power are positioned perpendicular to each other, the resulting aberration is defined as regular astigmatism. Instead of one focal point, regular astigmatism results in two perpendicular focal lines and a circle of least confusion (Fig. 5.1)...
The introduction of wavefront technology in ophthalmology has provided important insights on the effect of cataract and refractive surgery on the optical properties of the eye. In the field of cataract surgery, a primary area of interest has been the role of spherical aberration on modifying quality of vision. Positive spherical aberration occurs in an optical system when marginal rays are focused...
Higher-Order Aberrations, and Higher-Order Aberration Correction Can Induce Spherical Refractive Error (Aberration Interaction) Based on the plethora of reports in the literature, refrac tive surgical procedures often reduce spherical and cylin drical (lower-order) aberrations but have a tendency to induce higher-order aberrations (HOA) in a variety of refractive surgeries. APPLEGATE and coworkers...
By “accommodation” is understood the change of the eye's optical power to facilitate focusing on objects at different distances. Hermann von Helmholtz whose description of the accommodative mechanism from the year 1855 is still valid in all major parts wrote in his Handbook of Physio logical Optics: “There is no other portion of physiological optics where one finds so many differing and contradic...
As the population segment between the ages of 45 and 55 grows, so will the demand for presbyopic correction. Current technolog y is well equipped to meet the visual demands of young patients with refractive error and older patients with cataracts. However, the options for those that fall between these extremes (i.e., the presbyope) are still evolving. Presbyopia results from a decrease in the accommodative...
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