الفهرس 
Optics of astigmatismOnly 14 pages are availabe for public view
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Abstract
Astigmatism is a refractive error in which the power of astigmatic eye varies in different meridians. Astigmatism is classified into regular, oblique and irregular astigmatism. Most astigmatism is corneal in origin.
A detailed preoperative patient evaluation is of critical importance in achieving successful outcome following refractive surgery. Thorough history and meticulous examination are very important prior to surgery.
Corneal topography is one of the most important tool in evaluations candidates for refractive surgery. Patients with irregular cornea are poor candidates for refractive surgery.
Several techniques of incisional corneal surgery have been used to correct astigmatism including , transverse keratectomy, arcuate keratotomy and limbal relxing incisions.
Excimer laser refractive surgery techniques are the most effective surgical procedures in correction of astigmatism .
The corneal ring segments are designed for implantation inside the cornea. Two commonly used corneal ring segments are currently available, INTACS (intrastromal corneal ring segments) and KERA ring. The most exciting development in intacs technology is the application of the device for treatment in therapeutic indications such as keratoconus.
Toric IOLs are another modality in treatment of regular astigmatism in patients with cataract. Postoperative rotaion of the toric IOL is a significant problem.