What is perimetry?
perimetry is the accurate, quantitative evaluation of the extent of space visible in the patient's periphery when he directs his eyes directly in front of him. Kinetic perimetry includes a moving target, while the perimetry of static threshold uses fixed light points of different intensity. During the eye tests, either a trained perimetrist or an automated system represents stimuli in different parts of the patient's peripheral field to determine the existence and size of the terrain defects. Doctors use information from perimetry to facilitate early diagnosis and provide long -term monitoring of eye diseases or brain lesions. Identifiable patterns of loss of visual field can help locate the process of lesion or disease into part of the eye or brain that is affected.
The natural blind spot in the field of view occurs slightly on the nasal side of the center due to the presence of an optical nerve. Diseases that affect optical nerve such as multiple sclerosis with associated opticouneuritis usually expands the size of physiologicala blind spot. Optical nerves swelling secondary to severe hypertension, brain mass or increased pressure in the skull will also increase the blind spot. Optical nerve tumors such as gliomas or meningiomas, and impact on optical nerve masses, aneurysms or traumatic injuries can also cause the appearance of this defect.
Ophthalmologists regularly incorporate perimetry into the evaluation and care regime for glaucoma. Glaucoma is a condition associated with increased eye pressure, progressive damage to the optical nerve and narrowing of the visual fields. The amount of field loss is associated with the severity of the optical nerve damage. Typical visual field defects that occur in glaucoma include nasal defects, called nasal steps and arc defects that extend the perimeter of the nasal middle line to the physiological blind site. This pattern of loss of visual field coincides with the pattern of nerve fiber layer.
the defects of the field of vision caused by lesions in the brain usually affect the same side of the field in both eyes. For example, a stroke that occurs on the left side of the brain creates a defect in the right field of both eyes. This pattern of loss of the field of vision occurs due to the crossing of the nerve fibers in the optical chiasm, with all the fibers from the same field of view in the opposite part of the brain. These defects are called hemianopia. Shoving to what extent, to which field from each eye corresponds to the non -anticipation field, reflects part of the affected brain, with more identical defects pointing to the rear position of the brain lesion.