الفهرس 
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Abstract
keratoconus is a condition in which the cornea assumes a conical shape as a result of non inflammatory thinning of the corneal stroma. The corneal thinning induces irregular astigmatism, myopia, and protrusion leading to mild to marked impairment in quality of vision. It is a progressive disorder ultimately affecting both eyes although only one eye may be affected initially.
Management of KC has advanced during the last few years and still in progress. The management modalities could be divided into interventional and non interventional modalities.
Interventional procedures including procedures that weakens the cornea and procedures which reinforce the cornea however it is more logic to reinforce a thin cornea as in keratoconus rather than weakening it .
Interacorneal ring segment implantation is a technique, originally designed to correct low degrees of myopic errors .As interacorneal ring segment placement does not involve the direct manipulation of the central cornea or tissue removal ,the normal prolate surface asphericity of the cornea is preserved.
This prospective study was carried out on 35 eyes of 33 patients having keratoconus attending the outpatient clinic of Mansoura ophthalmic center during the period from February 2010 to November 2011. The aim of the study was to evaluate the safety and the efficacy of the intracorneal ring in the treatment of keratoconus .
Patients with confirmed keratoconus diagnosis either clinical or topographic diagnosis whose keratometric reading less than 60 diopter, corneal pachymetry at the site of incision more than 400µm, clear corneal center, contact lens intolerance and their age more than 18 years old were included in the study. Patients with any associated ocular pathology or corneal opacity were excluded from the study.
All patients underwent complete history taking, base line evaluation included assessment of the UCVA, BCVA, slit lamp examination, refraction, pachymetry at the site of incision, corneal topography and keratometry.
Informed consent were signed by each patient. The patients were implanted by symmetrical Intacs segments (Addition technology, inc) using a standard technique with mechanical channel dissector. The incision was done at the axis of the steepest keratometry. The nomogram provided by the manufactures were used to choose the suitable ring.
Postoperative evaluation was done at 1month, 3 months and six months postoperatively included slit lamp examination, UCVA, BCVA, refraction, spherical equivalent and changes in keratometry. Postoperative complications (if occurred) were recorded and photographed.
It was found that the UCVA improved from preoperative mean of 0.12±0.13 to 0.22 ± o.15 at six month postoperative with P=0.002. BCVA improved from preoperative mean of 0.17 ± 0.14 to 0.32 ± 0.16 at six month postoperative with P=0.0. Spherical refractive error improved from -6.25 ± 3.7 to -2.2 ± 1.3.The mean cylinder improved from -5.8 ± 2.5 to -3.7 ± 1.7. The mean spherical equivalent improved from -8.5 ± 5.5 to -4.07 ± 1.9 .The k1 decreased from 53 ± 3.8 to 50.4 ± 4.8, K2 decreased from 49.14 ± 3.5 to 46.9 ± 4.1 with a P value <0.05 at the six month postoperative. The I-S asymmetry decreased from 7.75 ± 4.2 to 5.5 ± 4.1 at six month postoperative with P value =0.053.
It was concluded that the intracorneal rings cause significant improvement in the UCVA, BCVA, spherical error ,cylinder and the spherical equivalent. Intracorneal rings can also cause significant improvement in K1,K2. Changes in I-S asymmetry were considered statistically insignificant.
Group of complications were encountered in the cases of the study(ring migration ,neovasculrisation, ring deposits). However most of the complications were considered visually insignificant. Explantation of the ring was done in one case due to superficial migration and foreign body sensation.
Conclusions
• The intracorneal ring implantation is considered a moderately invasive, safe and effective technique in improving the vision of keratoconus patients.
• The intracorneal ring should be limited to a group of keratoconus patients whose K readings <60D, who are CL intolerant and the PKP is needed to be postponed.
• The intracorneal rings can’t eliminate the disease but it only decreases the corneal steepening causing a limited improvement in the UCVA, BCVA and the refraction..
• Preoperative detailed patient counseling, discussing the patient expectations and that they almost will need visual rehabilitation after Intacs implantation (glasses or C.L) is mandatory before surgery.
• The visual outcome and the degree of patient satisfaction is still unpredictable.
• Additional procedures (e.g CXL & PRK) can improve the visual outcome of the Intacs
• Further follow up is needed to draw out the final effect of Intacs on the natural progression of keratoconus and to determine if they influence the clinical indications and the outcome of keratoplastic procedures.