الفهرس 
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Abstract
Corneal ring segments are used for correction of Keratoconus.
They consist of polymethyl methacrylate (PMMA) segments; when
surgically placed circumferentially into the periphery of the corneal
stroma, they flatten the central anterior corneal curvature by increasing
the peripheral thickness of the cornea.
The goal of corneal rings implantation is to decrease the corneal
abnormality associated with it, decrease the central corneal curvature, and
improve the visual acuity in affected patients.
The aim of this thesis was to evaluate the safety, efficacy,
predictability, and stability of intrastromal corneal ring implantation in
the management of Keratoconus.
A total of 40 eyes participated in this study; 29 and 11 females. All
patients were diagnosed as keratoconus and had intrastromal corneal ring segment (keraring) implantation.
All patients had careful history taking and thorough preoperative
ophthalmological examination including measurement of visual acuity,
refraction, slit lamp biomicroscopy, fundus examination, intraocular
pressure measurement, and corneal imaging by Pentacam.
Patients were followed up at one day, one week, one month, three
months, and six months postoperatively.
At the end of the follow up period after 6 months, shows that there
was non-significant difference between the studied groups as regarding
preoperative best corrected visual acuity (P>0.05), however,
postoperative BCVA in two segment group was significantly higher than
in 355 ring group.
Postoperative BCVA was found to be significantly higher in both
groups when compared to preoperative one (0.45, 0.71 versus 0.19 and
0.16 in 355 keraring and two segment groups respectively).
The uncorrected visual acuity improved in 90% of eyes, did not
change in 10%, and none worsened (0%). While the best-corrected visual
acuity improved in 94% of eyes, did not change in 6%, and none
worsened (0%).
10 eyes in this study suffered from postoperative complications
segment displacement in one eye in each group, segment extrusion in 1 eye in 355 group. keratitis in 4 eyes in 355 group while one eye in other
group. and corneal vascularization in one eye in each group
Our conclusion is to use the one segment 355 in patients with
more spherical error than cylinder and to use the two segments in
patients with more cylindrical error than spherical.