الفهرس 
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Abstract
Keratoconus is a degenerative, non-inflammatory disorder of the cornea, characterized by central and para-central thinning and subsequent corneal ectasia. This distortion of the corneal shape, results in irregular astigmatism with associated reduction in vision.
Keratoconus is relatively common, affecting approximately one person in two thousand. It occurs in all ethnic groups worldwide with males and females affected equally .It is usually bilateral, but it is not uncommon to have an asymmetric presentation.
Changes in corneal collagen structure and intercellular matrix, as well as apoptosis and necrosis of keratocytes, exclusively involving the central anterior stroma and the Bowman’s membrane are documented in structurally weakened corneal tissue typical of keratoconus .Mechanisms of this extreme thinning appear to be related to increased proteinase activity, along with decreased proteinase inhibitors .Although all layers of the cornea ultimately may show microscopic alterations, the earliest changes occur in the superficial layers of the cornea (Leibowitz and Morello, 1998).
The diagnosis of keratoconus frequently begins with an ophthalmologist’s assessment of the patient’s medical history, particularly the chief complaint and other visual symptoms, the presence of any history of ocular disease or injury which might affect vision, and the presence of any family history of ocular disease..
If keratoconus is suspected, the ophthalmologist will search for other characteristic findings of the disease by means of slit lamp examination of the cornea. An advanced case is usually readily apparent to the examiner, and can provide for an unambiguous diagnosis prior to more specialised testing( Rabonitz,2004) .Clinical signs include Promenant corneal nerves,Vogt’s striae, The Fleischer ring ,Charleaux sign ,Corneal thinning,Munson’s sign, Rizzuti’s sign and Corneal scarring Hydrops.
Corneal topography is a sensitive method to detect the keratoconus earlier, which helps to take appropriate measures to improve patients’ vision. Also, it can show the configuration of the lesion,. At the same time, it gives a cotraindication for keratoconic patients from undergoing excimer laser keratorefractive surgery (Caroline et al., 2007).
Classification of KC is the first step in approaching the disease because the severity of the disease and the stage at which the patient is diagnosed and treated affect treatment results. KC can be classified either clinical classification or topographic classification or both .
The management of keratoconus varies depending on the state of progression of the disease. In very early cases, spectacles may provide adequate visual correction, but because spectacles do not conform to the unusual shape of the cornea and the resultant induced irregular astigmatism, contact lenses provide better correction. Contact lenses are the mainstay of therapy in this disorder and represent the treatment of choice in 90% of patients (Buxton et al., 1984). Unfortunately, they are not the solution in all cases
For these reasons, between 10-25% of patients with Keratoconus progress to a point where surgical intervention is required. Surgical options include: Intra-corneal ring segment insert (Intacs &Ferrara Rings), Ultraviolet-A/Riboflavin corneal cross linkage (CR3), Lenticular (lens) refractive surgery including refractive lens exchange with toric intraocular lenses & Corneal transplantation (or grafting) including penetrating keratoplasty and Lamellar keratoplasty (Rabinowitz,1998).
Combination of different modalities may be done as CR3 with Intacs, PKP or and toric phakic intraocular lenses for correction of residual myopa and astigmatism following Intacs or PKP (Boxer Wachler et al., 2003).
Introduction of intracorneal rings such as INTACS (Addition Technologies, Fremont, CA), Ferrara rings (Ferrara Ophthalmics, Validolid, Spain) or Kerarings (KeraRing, Mediphacos, Belo Horizonte, Brazil) have provided us with tools for managing keratoconus (Coskunseven et al, 2008).Crosslinking stabilises stromal collagen, increasing the biomechanical stability of the cornea.A combination of these modalities would provide better results because these procedures complement each other.
In our study we have found that ICRS implantation is an effective method for the improvement of UCVA and BCVA in keratoconic eyes. The Keraring is designed to correct corneal surface irregularities, improve UCVA and BCVA, and reduce refractive errors.
However, the addition of CXL to the procedure stops the progression of the disease and provides greater improvements than Keraring implantation alone.