Correlation Between Retinal Nerve Fiber Layer Defect, Neuroretinal Rim Area And Visual Disorder In Primary Open Angle Glaucoma

Glaucoma is commonly defined as a diseases characterized by the elevationof intraocular pressure leading to damage to the optic nerve. Glaucomatous optic nerve damage is usaully detected by measurement of visual field and cup—dis ratio. The manifestation of a field defect may represent a relatively late stage of the disease. The visual loss is virtually irreversible. Recent studies suggest that upto 40% of the optic nerve axans can be lost prior to the manifestation of a detactable visual field defect. Since the size of the disc is variable, the cup—disc ratio provides no absolute quantitative indication of the amount of neural tissue. For this reason, it is important to find the earliest signs for diagnosing the disease at the earliest stage in order to prevent significant optic nerve damage and consequent losses of vision.Since Hoyt reported that photographs of the retinal nerve fiber layer could show glaucomatous abnormalities as subtle losses of nerve fibers in the presence of normal visual fields and optic discs and Littmann described a method for correcting the magnification of the photographic image of any fundus feature. A number of reports suggest that the assessment of retinal nerve fiber layer and the measurement of neuroretinal rim area provide useful cluses to the presence of earliest glaucomatous optic nerve damage. But, identifying incomplete loss of the retinal nerve fiber...