الفهرس 
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Abstract
Primary open-angle glaucoma is one of the leading causes of blindness world wide . The death of retinal ganglion cells in POAG is reflected by increased cupping of the optic disc, loss of nerve fiber layer and functional visual field defect.
Conventional clinical tools (e.g ophthalmoscopy) are subjective and show great variability even with experienced observers. The interpretation of nerve fiber layer photographs is influenced by the examiner experience and the amount of melanin in the patients pigment epithelium. It also depends on the age of the patient. The shiny looks of the retina prevent viewing of the RNFL reflex in younger individuals. Blue light improves the visualization of the retinal NFL, but in older patients with yellow discoloration of the lens, the clinical evaluation of the NFL is limited because of filtering of blue light through cataractous lens. The neuro-retianl rim and the optic disc show considerable inter individual variability .
Perimetry has been considered to be the global standard in the diagnosis of glaucoma. However a disadvantage of standard perimetry is that the first visual field defects appear only after the death of a significant proportion (25% - 40%) of ganglion cells and nerve fibers .
Therefore more sensitive tests that detect early retinal ganglion cell changes in glaucoma would be useful .
Optical coherence tomography OCT is one promising technology that has been developed to access tissue thickness in vivo, such as that of the retinal nerve fiber layer . OCT permits high resolution cross sectional imaging of biological tissue using light. OCT utilizes low coherence interferometry and near infrared low coherence light to achieve a resolution of approximated 10 microns in the eye. OCT enables non contact and non invasive imaging of the optic nerve head (OHN) and nerve fiber layer .
VEPs are used primarily to measure the functional integrity of the visual pathways from retina via the optic nerves to the visual cortex of the brain.
We studied 30 eyes of 16 subjects, the eyes were classified into 2 groups: group I included 9 eyes (with cup / disc ratio equal or less than 0.5 ) and group II included 21 eyes (with cup / disc ratio more than 0.5)
All eyes underwent a full field ophthalmic, OCT and pattern VEP.
OCT results showed significant reduction of RNFL thickness in glaucoma and glaucoma suspect eyes in the majority of quadrants as well as in the average RNFL thickness p < 0.001.
the pattern VEP of early and advanced glaucomatous patient with variable cup /disc ratio and reported affection of the VEP by causing both reductions in amplitude and increases in latency. And by statistically analysis of the results that there were no statistically significant differences between C/D ratio groups and any of the VEP measurements (p>0.05).