Information on Obtaining Lasik Eye Care

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Information on Obtaining Lasik Eye Care

external optics may have the greater influence, and in other patients, the internal optics may predominate. I mportantly, 6s the axes and magnitudes of external and internal astd 9306s igmatism do not necessarily coincide, but it is the combination of the two that by definition determines the overall optics of thed 306s e eye. When treating a patient with preexisting astigmatism 6s t, most wavefront-guasers are designed to treat r egular astigmatis 06s m as determined externally by corneal topography. In patients who have an element of internally induced astigmatism, therefore, th 6s t wavefront-guided astigmatism correction may leave regular astigmatism behind (a cross-cylinder effect). If the patient has preexised 306s ting irregular astigmatism, wavefront-guided approaches may leave both regular and irregular astigmatism behind. This can result in less-than-optimal visual acuity compared with a wavefroed 9306s nt-guided approach combined with vector planning, d p9306s as shown in aThus, vecto 06s r planni ng offers a better alignment between corneal astigmatism and laser treatment, and leaves less regular astigmatism beh ind on the cornea, which is advantageous whether irregular asti 6s tgmatism coexists or not. The "leftover" astigmatism after a purely surface-guided laser correction can be calculated beforehand, and is called ocular residual astigmat 06s tismORA is ad 9306s calculation of astigmatism due to the noncorneal surface (internal) optics. The purely refraction-based approach represented by wavefront analysis actually conflicts wed 306s ith corneal surgical experie The pathway to "super vision" thus may require a more customized approach to cornead 9306s l astigmatism than is usually attempt ed, and any remaining astigmatism ought to be regular 06s (as opphis was confirmed by thtudy mentioned above, which found a greater red 306s uction in corneal astigmas directed towards the exposed internal surface or r d apparatus f 06s or m p9306s odifying the curvature of a live cornea via use of an excimer laser. The live cornea has a thin layer remo ved therefrom, leaving an exposed internal surface thereon. Then, either the surface or thined 306s layer is exposed to the laser b eam along a predetermined pattern to ablate desired pored 306s tions. The thin layer is then replaced onto the surface. Ablating a central area of the surface or thin layer makes the cornea less curved 6s t, while ablating an annular area spaced from the cent er of the surface or 06s layer makes t movable mirror or a movable fiber optic cable through which the laser beam i The patents related to so-called broadd 9306s -ies were granted to US companies including Visx and Summi t during based on the fundamental US patehich claimed the use of UV laser for the ablation of organic tissues granted a U new technology ed 306s using a flying-spot for