الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Higher order aberrations persist as one of the more challenging refractive complications. It represent distortion acquired by a wavefront of light when it passes through an eye with irregularities of its refractive components for example corneas which had previous radial keratotomy (RK) procedure, cross linked Keratoconic eyes,decentered LASIK treatment and corneal trauma.
Wavefront technology represents a paradigm shift in the way optical aberrations can be measured, described, and treated. Measurement of the eye’s wavefront aberration is becoming an important goal in clinical ophthalmology and plays a critical role leading toward the optical correction of these ocular aberrations.
Wavefront-guided LASIK (WFG) LASIK is a variation of the surgery in which the excimer laser is instructed to ablate a sophisticated pattern based on measurements from an aberrometer. The Hartmann -Shack aberrometer, which is one of the most commonly used aberrometers, has been used for several years. It measures the shape of the wavefront that is reflected out of the eye from a point source on the fovea. An array of microlenslets is used to subdivide the outgoing wavefront into multiple beams which produce spot images on a video sensor. The displacement of each spot from the corresponding nonaberrated reference position is used to determine the shape of the wavefront. It is formed of 240 lenslets (low-resolution aberrometer). This limited number of lenslets narrowed the ability of the aberrometer in detecting fine details of the eye wavefront especially in irregular corneas. Optimizing the Hartmann-Shack aberrometer to increase the dynamic range and at the same time increase the lenslet number into 1257 without sacrificing measurement sensitivity improved spot quality, gave better detection of highly aberrated eyes with subsequent improvement in treating higher order aberrations.
The aim of this work was to assess the use of high definition Hartmann Shack aberrometer in diagnosis and treatment of highly aberrated eyes.
The present study included a total of 20 eyes from 18 patients divided into three groups, Group A eleven post cross linked Keratoconic eyes ,Group B: included five post LASIK decentration eyes and Group C included four post radial keratotomy eyes.