Tests for glaucoma
Special tests for glaucoma
Field charting:
Field of vision describes the side vision when one is looking straight ahead. The testing of the extent of the side vision is important in the diagnosis and follow up of several disease including glaucoma, and diseases relating the eye with the brain (neuroopththalmology). The test is usually done on computerized machines (Humphrey field analyzer). The machine is programmed to test several points, sometimes repeatedly with varying illumination. The test may take time depending upon the defect in a given patient. The computer has inbuilt software that enables comparison of the field charting on repeat testing of the same patient.
Optic disc photography:
Optic disc is the only part of the optic nerve visible to the eye doctor in the back of the eye. The appearance of the disc gives valuable information to diagnose and treat conditions such as glaucoma. It is important to be able to compare the appearance of the disc over a period time in cases of chronic glaucoma. This is made possible by several techniques- one of which is the photography of the disc using the fundus camera.
GDx nerve fibre analyzer:
This recent innovation allows measurement of the thickness of the nerve fibre layer, which is the part of the retina that is first affected in the disease of glaucoma. The nerve fibril layer defect is detected long before any defect is noted in the function of the eye including the field examination. This test may help in the early detection of significant damage caused by glaucoma and help in the follow up of these patients. The test involves the use of scanning laser that passes through the nerve fibre layer and in the process undergoes a process called retardation. By measuring the extent of retardation the machine calculates the thickness of the nerve fibre layer.
Ultrasound biomicroscopy (UBM):
This is an advanced technology in ultrasonography, which permits high-resolution pictures of the front of the eye. The technology enables the measurement of the angle of the eye, which is otherwise not accessible for measurement. The angle of the eye is the path through which the fluid in the eye finds access outside. The angle can become closed in certain individuals. This propensity to closure of the angle can be more adequately predicted using this advanced testing. Following injury to the eye, sometimes abnormal communications develop leading to excess drainage of fluid and resulting soft eyes. These abnormal sites can be best identified by UBM.
