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ANALYSIS OF OPTICAL COHERENCE BIOMETRY

ABSTRACT

The earliest cataract surgery is mentioned in Ayurveda, dating from the 5th century BC, showing that Susruta was in India developed specialized instruments and performed the surgery. In the history of ophthalmology, it is endorsed that one successful trial of an IOL implantation has been completed by Sir Harold Ridley in London (St. Thomas Hospital), although the post-operative refractive result was not so quite good, as it was a high myopic effect. In present, the surgical approach is the best successful modality to rehabilitate the patients who are suffering from cataract, by replacing the natural lens with an artificial lens. At the recent time in all over the world, cataract surgery is counted as the most successful and easiest surgery with its excellent result. The ocular biometries have been a milestone with advancement for IOL power calculation to provide maximum visual outcome on the basis of lowest refractive values. The ophthalmic biometries are the procedure for the assessment of different anatomic values of the eye and their estimation for the power of IOL required prior to surgical procedure. Corneal power accounts about two-thirds of the total Diopteric power of the eye so it is an important component for the ocular refractive system. The improper observation of cornea in relation to its power or radius induces mistake in propagation. Corneal curvature is measured by the process of Keratometry which is capable to estimate the central corneal power in Diopter or curvature in mm. It is supposed that the central cornea behaves like a thin spherical lens with on same curvature ratio and index of about 1.3375. The radius of curvature of the cornea relates to the power of cornea with the equation r = 337.5/K. Keratometry readings can be estimate with a variety of instruments. But the mode of estimation either is manual or automated method. Some of the most precious are topography, IOL master, ORBSCAN, Pentacam and OCT (Optical Coherence Tomography). The basic concept is the calculation of magnification from the image size and is directly related to the radius of curvature of the reflecting corneal surface.

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