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The red reflex refers to a reddish reflection that is observed when an eye doctor shines a light into a patient’s healthy eye. This reflex is produced when the light from the doctor’s instrument, called an ophthalmoscope, travels through the pupil and is reflected back from the cells of the retina at the back of the eye. The clear transmission of this reddish light indicates that the eye is healthy, whereas the lack of a red reflex or the presence of spots or asymmetries between the two eyes can indicate a variety of different eye abnormalities.
A red reflex test is recommended for all infants and should ideally be performed for the first time between the first two weeks and two months of life. The test should then be repeated periodically as needed throughout the child’s early life. Most of the abnormalities detected by this test have dramatically improved outcome if detected early, and for this reason, this test is mandated by law in some states. The test should be performed in a darkened room and the doctor should shine the light into an infant’s eye from a distance of approximately one foot (.3 m).
The most common abnormalities seen in this test are the production of white light and/or whitish spots or no light at all, rather than the typical reddish color. This usually indicates that something abnormal in the eye is blocking the transmission of light through the pupil and to the retina. The absence of light is usually caused by some type of bleeding, or hemorrhaging, in the eye, but may also be caused by any large foreign object in the eye that prevents light transmission. An asymmetrical result may be a sign of serious developmental abnormalities, but it may also simply indicate that the two eyes have quite different refractive errors.
Abnormal white color or white spots can be caused by cataracts or glaucoma. They may also be caused by retinal abnormalities like infections in the retina or retinal detachment. All of these conditions can threaten the infant’s sight, and for this reason, any kind of red reflex abnormality should be dealt with immediately.
Another abnormality that may cause whitish light or spots in the red reflex test is the presence of retinoblastoma, or a tumor of the eye that usually occurs in young children. This tumor has a tendency to occur in families, but it can also occur in children who have no family history of this condition. It may be possible to remove this tumor by laser surgery, although larger and aggressive tumors may result in eye loss if this is the only way to stop the cancer. The outcome for retinoblastoma is usually good if caught before the tumor has had a chance to spread outside of the eye, but the prognosis is less favorable after spreading.