الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
As the cornea play important rule in vision, so it is important to understand the anatomy and physiology of cornea. Corneal ectasia and keratoconus are non-inflammatory disorders in which cornea is thinning, deformed and biomechanical weakening which result in visual impairment secondary to stromal scarring due to progressive distortion and bowing of the cornea in keratoconus and ectasia, rigid or complex curvature contact lens is needed to achieve good vision. Furthermore, keratoconus tends to progress over second and fifth decades of life and can lead to intolerance of contact lens, corneal transplantation in (10% - 20%) of cases. Treatment available to patients with keratoconus and ectasia include (intra-stromal corneal ring segment implantation), keratoplasty and collagen cross-linking.
Collagen cross-linking has emerged as a promising technique to slow or stop the progression of keratoconus as well as post-LASIK ectasia. In the procedure riboflavin (vitamin B2) is administered in conjunctiva with ultraviolet A (uva, 365 nm). The interaction of riboflavin and UVA causes formation of reactive oxygen species leading to the formation of additional covalent bonds between collagen molecules with consequent biomechanical stiffening of the cornea.
Eligible criteria includes age (14 to 45 years), thinnest corneal pachymetry higher than 400 µm with no central corneal scarring and maximum corneal curvature not exceed 60D. The disorder should be progressive in nature worsening in the last 6-12 months.
Topical anaesthesia is applied, then the central corneal epithelium is removed followed by application of Riboflavin eye drops every minute for 30 minutes, then the eye is exposed to UV-A light with energy for 30 minutes. At the end of treatment the cornea is flushed with BSS and, antibiotic eye drops are applied and a bandage contact lens is inserted.
The main advantages of CXL are being less invasive, inexpensive, no stitches or incisions & easy, more suitable as a first choice for form fruste keratoconus & patients with Intacs. C3-riboflavin is effective for stabilizing keratoconus.
Severe complications are not to be expected because the treatment parameters are far below all known damage thresholds, complications include a foreign body sensation, Corneal haze, Delayed reepithelialisation, Dryness of the eyes, Corneal oedema, Corneal infection.
Conclusion
C3-R treatment alone or combined improved vision and, the ability to permanently strengthen the inherently weakened cornea. It is a major advance in the management of these cases. C3-R treatments provide real hope for many patients with keratectasia and keratoconus. C3-R is safe with high success .