eye disorders
Primary Open Angle Glaucoma
Symptoms and Signs of Primary Open Angle Glaucoma
Early primary open-angle glaucoma symptoms are uncommon. Usually, the patient becomes aware of visual field loss only when optic nerve atrophy is marked; the typically asymmetric deficits contribute to delay in recognition. However, some patients have complaints, such as missing stairs if their inferior visual field has been lost, noticing portions of words missing when reading, or having difficulty with driving earlier in the course of the disease. Examination findings include an unobstructed open angle on gonioscopy and characteristic optic nerve appearance and visual field defects. Intraocular pressure (IOP) may be normal or high but is almost always higher in the eye with more optic nerve damage. The optic nerve head (ie, disk) is normally a slightly vertically elongated circle with a centrally located depression called the cup. The neurosensory rim is the tissue between the margin of the cup and the edge of the disk, and is composed of the ganglion cell axons from the retina. Characteristic optic nerve changes include Increased cup:disk ratio (particularly an increasing ratio over time) Thinning of the neurosensory rim Pitting or notching of the rim Nerve fiber layer hemorrhage that crosses the disk margin (ie, Drance hemorrhage or splinter hemorrhages) Vertical elongation of the cup Quick (ie, sharp change in the course of angulations in the exiting blood vessels [called bayoneting]) Thinning of the neurosensory rim (optic nerve or retinal nerve fiber layer) over time alone can be diagnostic of glaucoma regardless of the IOP or visual field and is the initial sign of damage in 40 to 60% of cases. In other cases, the initial sign of damage is some visual field change. Wedge-shaped dark areas may develop, reflecting damage to the retinal nerve fiber layer. Visual field changes caused by lesions of the optic nerve include Nasal step defects (which do not cross the horizontal meridian—an imaginary horizontal line between the upper and lower parts of the visual field) Arcuate (arc-shaped) scotomata extending nasally from the blind spot Temporal wedge defects Paracentral Scotomata None In contrast, deficits of the more proximal visual pathways (ie, from the lateral geniculate nucleus to the occipital lobe) involve quadrants or hemispheres of the visual field; thus, deficits do not cross the vertical meridian. 