The red reflex refers to the reddish-orange reflection of light from the eye's retina that is observed when using an ophthalmoscope or retinoscope from approximately 30 cm / 1 foot. This examination is usually performed in a dimly lit or dark room.
Many eye problems may be detected by this test, such as:
Newborns are regularly screened for retinoblastomas with an ophthalmoscope (see also: Retinoblastoma#Diagnosis).
According to Bates' Guide to Physical Exams, retinal detachment would result in the absence of red reflex in the affected eye.
Simultaneous red reflex test
The simultaneous red reflex test is used to view both reflexes at the same time. This can help determine if the patient has normal ocular alignment. In order to perform this test the patient and physician are normally approximately 2 to 3 feet away from each other.