الفهرس 
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Abstract
The cornea exhibits viscoelastic properties, which give it the
quality of hysteresis. Corneal hysteresis is an important indicator of the
biomechanical properties of the cornea. The aim of our study was to show
the impact of diabetes on corneal biomechanics.
We used the Ocular Response Analyzer device which measures
CH, CRF, IOPcc and IOPg to detect the changes that occurred in corneal
parameters of the patients with type 2 diabetes since hyperglycemia in
diabetic patients alters the corneal structure by impairing the hydration of
the cornea and homeostasis in the corneal epithelium, stroma and
endothelium.
We conducted our study on control and diabetic patients to detect
the relation between diabetes mellitus and the corneal biomechanics. Our
study was performed on 150eyes of 75 patients as we divided these
patients into three groups. group A involved 50 eyes from 25 healthy
control subjects ,group B involved 50 eyes from 25 diabetic patients with
hba1c <7% and group c involved 50 eyes from 25 diabetic patients with
hba1c >7%.
Our study reported that diabetes leads to an increase in corneal
biomechanics as CH and CRF were elevated with patients of group B
(diabetic patients).
Our explanations to those results were due to hyperglycemia, as
glucose accumulates in collagen proteins resulting in the formation of
covalent cross-linking bonds which lead to increased corneal thickening.
Most probably the patients with hyperglycemia (elevated HbA1c)
showed increase in corneal damping. This increased damping effect was
reflected in a higher CH.
Meanwhile our study correlated both CH and CRF to the duration
of diabetes mellitus and HBA1c in both study groups to show the effect
of diabetes on corneal biomechanics.
Our results revealed a weak positive linear correlation between the
CH and the average duration of diabetes in diabetic group and no
correlation between CH and the average level of HBA1c in control group.
However there was a weak positive linear correlation between CH and the
average level of HBA1C in the diabetic patients in the diabetic group.
For CRF there was a weak positive linear correlation between it
and the average duration of diabetes mellitus in diabetic group and there
was a very weak negative linear correlation between it and the average
level of HBA1c in control group patients. However the correlation
between it and HBA1c in diabetic group was a moderate positive linear
correlation.