Dark adaptometry is a diagnostic test that measures the ability of the eye to adjust to low light conditions, which is known as dark adaptation. The test involves exposing the eye to gradually decreasing levels of light until the eye can no longer see an object in front of it. This threshold of visual sensitivity is then recorded and used to evaluate the health of the visual system.
Dark adaptometry is used in the diagnosis and management of a variety of eye conditions, including night blindness, age-related macular degeneration (AMD), and other degenerative retinal disorders. The test is also used to evaluate the effects of medications or other treatments on the visual system.
The dark adaptometry test is performed in a dark room to eliminate any external sources of light that could interfere with the results. The patient is typically instructed to rest their eyes for a few minutes before the test to allow their eyes to adjust to the darkness. The test is performed on one eye at a time, with the other eye covered to prevent it from compensating for the eye being tested.
The test involves exposing the eye to a bright light for several minutes to saturate the photoreceptors in the retina. The light is then turned off, and the patient is asked to report when they can no longer see a small light stimulus placed in front of them. The light stimulus is then gradually increased in brightness until the patient can see it again. This process is repeated several times to determine the threshold of visual sensitivity.
The results of the test are typically recorded as the time it takes for the patient to reach a certain level of visual sensitivity, known as the dark adaptation threshold. Abnormal results may indicate a problem with the visual system, such as a retinal disorder or the effects of certain medications or environmental factors.
Dark adaptometry is a non-invasive and relatively simple test that can provide valuable information about the health of the visual system. It is often used in conjunction with other diagnostic tests, such as visual field testing and electroretinography, to provide a comprehensive evaluation of the visual system.