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Abstract Refractive errors as myopia are naturally occurring defects and have required the use of external aids like spectacles or contact lenses. These devices have their own inherent flaws as regard to cosmesis and comfort. Refractive surgery has emerged as a new subspecialty in ophthalmology designed to develop an ideal surgical technique to help people reduce their dependency on their external visual aids. Radial Keratotomy (RK) is one of the early surgical techniques that were used to correct myopia. During the procedure, radial incisions are made in the cornea of the eye with a highly precise diamond blade set to a particular depth. These incisions allow the sides of the cornea to bugle outward and thereby flatten the central portion of the cornea. This brings the focal point of the eye closer to the retina and improves one’s distance vision. RK for myopia was the most commonly performed refractive procedure in the late 1970s and 1980s. Ten years later it was realized that there are many complications occurred with RK and the procedure not safe as it is initially appeared. Excimer laser surface ablation has been used since 1987 to treat myopia, the original procedure was termed photorefractive keratectomy (PRK) in which the epithelium is scraped prior to laser refractive surgical correction, major disadvantage is the great and Summary 181 persistent postoperative pain associated with de-epithelialization., slow visual recovery, and stromal haze, these complications drove to the appearance of LASIK. Laser in situ keratomileusis (LASIK) is the most commonly performed refractive surgery. LASIK is a relatively new procedure that is technically a variation of PRK. The Lasik procedure involves the use of microkeratome to create a hinged flap in the cornea underneath which an excimer laser is used to remove micro amounts of stromal tissue to correct the particular refractive error. The visual rehabilitation, after LASIK is rapid; it’s major limitations include ectasia, flap wrinkles, free caps, incomplete pass of the microkeratome, epithelial ingrowth, flap melt, interface debris, and diffuse lamellar keratitis. Laser subepithelial keratomileusis (LASEK) is a surgical procedure which may reduce the complications of LASIK and PRK. The early results seem promising especially for the potential applications in thin corneas. Alcohol is often used to facilitate removal of the corneal epithelium as a sheet. A hinged epithelial flap is created by peeling the loosened epithelium as a sheet using one of several recently developed surgical techniques. After laser ablation, the flap is repositioned over the ablated stroma. This provides coverage of the lasered stromal bed, and reduces epithelial migration in those patients where the flap adheres to the stroma. Summary 182 LASEK is safe and effective in treating low and moderate degrees of myopia, and eliminates LASIK related flap complications; however there is concern about the probable toxic effects of alcohol on epithelium and underlying corneal stroma. In 2003, Pallikaris described an alternative method for epithelial separation using an instrument called epikeratome, with the use of this device the corneal epithelium can be separated from the underlying stroma without previous preparation with alcohol, the epithelial sheet is then repositioned on the stroma after ablation is complete. This procedure is known as (Epi-LASIK) Epi-LASIK incorporates the advantages of LASIK and LASEK and avoids the potential risk posed by the creation of the LASIK flap, therefore it is possible that the quality of vision would be better in Epi-LASIK treated patients than in LASIK treated patients, meanwhile Epi-LASIK avoids the alcohol related side effects of LASEK, which believes to be associated with less postoperative pain, faster visual recovery and less haze. Femtosecond (fs) laser may offer new possibilities in the field of refractive surgery especially when using the laser as microkeratome. By generating microplasmas inside corneal stroma with femtosecond pulses, it is possible to achieve a cutting effect inside tissue while leaving the anterior layer intact. FS laser is the first bladeless and most accurate modality for corneal flap creation available today. Summary 183 Compared with mechanical microkeratome, fs lasers offer more options for customizing the flap position, shape, diameter & orientation during refractive surgery. In addition, it may be better for creating thin flaps, because it leaves stronger corneas & is likely to cause less denervation kertopathy. Femtosecond Lenticule Extraction (FLEX) is a new form of refractive eye surgery that creates a lenticule from the cornea for removal and a corneal flap, all with a femtosecond laser. In 1708, Herman Boerhaave suggested clear lens extraction (CLE) as means of treating high myopia. A refractive lens exchange (or “clear lens extraction”) refers to the situation where a healthy crystalline lens is removed and replaced by a corrective lens. Accommodative or multifocal IOL can also be used but have varying refractive success. Phakic intraocular surgery is now considered a promising treatment option for patients who suffer from high and extreme. myopia Implantable lenses are similar to the intraocular lenses (IOLs) used in cataract surgery. However, implantable lenses are placed in eyes that retain their natural lens, unlike in cataract surgery where IOLs replace a natural lens that has turned cloudy. The phakic IOL that are used are classified into anterior chamber and posterior chamber pIOL. The anterior chamber can also be classified into angle supported and iris fixated IOL. Phakic intraocular surgery has the advantage of reversibility and the ability to correct high myopia Summary 184 unlike corneal refractive surgery which is limited by corneal thickness. Possible complications include increased chance of a detached retina, loss of endothelial cells, inflammation, infection and cataract. Intrastromal corneal ring (ICR) segment are now an exciting addition to the refractive surgeons. In 1978 Reynolds hypothesized that a ring shaped implants could be introduced through a single, peripheral radial incision in the cornea. Reynolds reasoned that this implant would alter the anterior corneal curvature through expansion or constriction in the diameter of the device, so it can treat myopia. |