الفهرس 
Corneal anatomyOnly 14 pages are availabe for public view
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Abstract
The cornea is a transparent, avascular tissue, which covers the anterior one-sixth
of the eye, the central portion of the anterior corneal surface acts as the sphero
cylindrical convex mirror.
Corneal refractive surgery aims to alter the refractive power of the cornea by
changing its shape to decrease dependency on eyeglasses or contact lenses.
Keratorefractive procedures include incisional, Surface Ablation, LASIK,
Femto LASIK, Refractive lenticule extraction, Intrastromal Corneal Ring
Segments. Corneal refractive surgery mostly acts on the anterior cornea,
Corneal curvature and thickness are remodeled for inducing refractive changes,
Also it altered the corneal biomechanical properties.
Corneal thickness is an important factor in determining whether the patient
is suitable for refractive surgery and identifying the optimal refractive
procedure, Corneal thicknesses are measured by, Pentacam, anterior segment optical
coherence tomography (AS-OCT), ultrasound pachymetry, Orbscan measurements,
and noncontact specular microscopy.
IOP measurement is important parameters in the glaucoma classification,
diagnosis, follow-up and treatment of and ocular hypertension. The Corneal
thickness is the local factors that influence the measurements.
IOP measurement by several methods as Goldmann Applanation Tonometer
(GAT) , The Perkins applanation tonometer, Non-contact air puff tonometer (NCT) ,
Tono-pen (TP) hand tonometry, The rebound tonometer (RT; I-Care), The Diaton
tonometer, Dynamic contour tonometry (DCT), Pneumatonometer, Ocular
Response Analyzer (ORA) , Corvis ST (CST), Ocuton S.
Corneal refractive surgery ablates of the corneal tissue that induces
changes in the corneal curvature, central corneal thickness (CCT), and cornealSummary
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rigidity, These changes alter the postoperative IOP and make the IOP
assessment is unreliable.
Corneal refractive surgery decrease IOP due to the quantity of tissue
removed, IOP reduction after Corneal refractive surgery was significant and
correlated with preoperative IOP, CCT, and The spherical equivalent of the
attempted correction.
The main objective is to study the role of central corneal thickness in the
estimation of Intraocular pressure after Corneal refractive surgery , One
hundred and fifty eyes of seventy-five patients diagnosed clinically to have
refractive error were selected. Their ages ranged from 19-42 years. 50 eyes
operated using the Femto-LASIK group[1], 50 eyes operated using the Lasik
group [2]. and 50 eyes operated using the PRK group[3]. Central corneal
thickness was measured for all patients before and after the operation. IOP
measurement was performed for all patients before and after the operation one,
three and six month
Overall, measured IOP is underestimated after Corneal refractive surgery,
There are highly significant decreases in IOP postoperatively and in follow up
period among Femto LASIK, LASIK groups at 1,3 and 6 months. In the PRK
group there is a highly significant decrease in IOP in the follow-up period after
3 and 6 months but, little significant difference after one month of the operation.