الفهرس 
History of Refractive Surgery and INTACSOnly 14 pages are availabe for public view
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Abstract
Options for visual rehabilitation include spectacle correction, contact lens fitting, refractive keratotomy (RK), photorefractive keratectomy (PRK), laser-assisted in situ keratomileusis (LASIK), and intracorneal rings or Intacs.
The intrastromal corneal ring (ICR) is a device designed to correct mild-to-moderate myopia by flattening the anterior corneal curvature without encroaching on the visual axis. The device is an open-ended PMMA transparent ring with an outer diameter (R2) of 8.1 mm and an inner diameter (R1) of 6.8 mm, and the curvature conforms to that of the cornea. Anterior corneal curvature is changed by using rings of different thicknesses.
Intrastromal corneal ring segments (Intacs microthin prescription inserts), or ICRS, are a more recent design modification of the ICR. The ring segments split the ring into two 150° arcs. The use of ring segments simplifies the implantation procedure.
Another type of Intrastromal corneal ring segments (ICRS) are the Ferrara rings introduced by Pablo Ferrara in 1986. It had proved to be effective in correcting keratoconus due to the 5 mm diameter implantation. The closer the implantation to the visual axis the more effective the segment in correcting Keratoconus.
INTACS are intended for the reduction or elimination of mild myopia (-1.00 to -3.00 D spherical equivalent at the spectacle plane) in patients who are aged 21 years or older, in patients with documented stability of refraction as demonstrated by a change of less than or equal to 0.50 D for at least 12 months prior to the preoperative examination, and in patients where the astigmatic component is +1.00 D or less.
In 2004, INTACS was given humanitarian device approval by the FDA for use in patients with keratoconus. The inserts may now be used to reduce irregular steepening (irregular astigmatism) caused by keratoconus. INTACS inserts help restore clear vision in patients with keratoconus by flattening and repositioning the cornea. INTACS inserts are intended for patients with keratoconus who are no longer able to achieve adequate vision using contact lenses or glasses and for whom corneal transplantation is the only remaining option.
INTACS are contraindicated in high degrees of myopia, hyperopia, or astigmatism, Patients with existing collagen vascular, autoimmune, or immunodeficiency disease, Pregnancy, Patients with previous anterior segment trauma, In the presence of existing ocular conditions, such as recurrent corneal erosion syndrome, corneal dystrophy, or other corneal pathology that may predispose the patient to future complications.