The red reflex is elicited in the Brückner test, a pediatric screening tool often used by primary care doctors and pediatricians to detect abnormalities of the eyes and ocular diseases. Originally described as a “transillumination” test, Brückner found that the red reflex was useful in detecting strabismus and amblyopia in young children. The red reflex from the retina is a quick and non-invasive test used to identify opacities in the visual axis, such as a corneal abnormality or cataract, as well as abnormalities in the posterior segment of the eye, such as retinoblastoma.
A red reflex should appear red, orange, or yellow and be symmetric across both pupils. Eliciting a normal red reflex requires transmission through a transparent optical media, including the tear film, cornea, aqueous humor, lens, and vitreous body. An abnormal or absent red reflex can indicate sight and life-threatening pathology, including congenital cataracts, retinal abnormalities, retinoblastoma, strabismus, or refractive errors. Abnormal red reflex requires urgent referral to an ophthalmologist. Currently, the American Academy of Pediatrics policy recommends eye examinations for neonates and children from birth to 2 years of age at specific intervals during the newborn examination and well-child visits.
The red reflex test uses an ophthalmoscope or retinoscope, with the examiner standing approximately 1 to 2 feet away from the patient. The direct ophthalmoscope should be set at “0,” and the examiner directs the light onto both eyes simultaneously. The pupils will become illuminated as light reflects off the back of the retina and through the aperture of the scope. The examiner should then move closer also to assess each eye individually. For the pupils to be large enough for light to enter, the examination should be performed in a dark or dimly lit room.
If pupils are not large enough to allow light to enter into the eye, this will result in an absent red reflex. Performing the examination in a darkened room and starting with the smallest diameter beam of light setting on the ophthalmoscope are two techniques that can be used to help in this condition. Topical medications to dilate the pupil, such as tropicamide, cyclopentolate hydrochloride, and phenylephrine, can also be used. There are specific, suggested dosages for children of different ages.
The validity of the red reflex examination has been the object of extensive study in the literature with varying results. Overall, the Brückner test has shown to be a sensitive and specific marker for amblyopia, anterior and posterior segment opacities, and strabismus in children. Results do vary with different equipment as well as the expertise of the examiner and may result in a high number of false negatives leading to unnecessary referrals.
The purpose of vision screening is to identify patients with ocular abnormalities that may require urgent referral to an ophthalmologist for potential sight and sometimes life-saving treatment. Vision system screening in neonates, infants, and children includes several components and should occur during each well-child visit. Vision screening should begin with the detection of risk factors requiring a thorough review of family and personal ocular history. Premature birth, cerebral palsy, down syndrome as well as a family history of strabismus, retinoblastoma, congenital cataracts, or genetic diseases are critical risk factors to consider.
The eye examination should evaluate the following: external structures of the eyes, including the eyelids, motility, eye muscle balance, pupils, and red reflex. The red reflex test can be performed relatively quickly as well as noninvasively, which is useful for evaluating an apprehensive child. This test has shown to have high sensitivity for testing abnormalities in both the anterior segment and posterior segments of the eye, and a normal red reflex can rule out intraocular pathology. In contrast, an abnormal reflex indicates the need for an ophthalmologic referral for comprehensive evaluation.
To be considered normal, a red reflex should be seen in both eyes symmetrically and equivalent in color, intensity, and clarity. An absent or black reflex may indicate an obstruction that is preventing light from reflecting back to the examiner. An absent red reflex can result from cataracts, corneal scars, or vitreous hemorrhage. Debris over the surface of the eye may also cause a black reflex, so the examiner should ask the patient to blink and check for the red reflex again. Examiners should be aware of the routine topical application of the prophylaxis erythromycin eye ointment and try to avoid examining the red reflex within approximate time to the ointment application.
Abnormalities associated with abnormal red reflex can be grouped into two categories;
The first one is leukokoria ( white reflex), which can result from the following:
The second group includes conditions that result in an abnormal pattern of red reflexes, such as:
The American Academy of Pediatrics and American Academy of Ophthalmology recommends screening eye examinations for all newborns as well as children at specific intervals of age during office visits. The eye exam is an essential part of assessing neonates because the prognosis of ocular disorders in children is highly dependent on early detection and referral. [Level 5] The neonatal eye screen involves the use of an ophthalmoscope to check the red reflex as well as a careful observation of anatomic structures and visual behavior. If undetected, ocular disorders in children can result in permanent vision loss and, rarely, death. Early screening is also crucial for the critical period of development in neonates and infants. A vision screening can occur in the pediatrician or primary care office, in the school nurse office, or even in the emergency department. Implementing a standard way of screening vision in children in the primary care setting has demonstrated to be the most effective method of detecting vision problems promptly. It is essential to follow up with children who get referred to make sure a pediatric ophthalmologist has adequately evaluated them.
There are validated instrument-based screening devices available that images the red reflex to detect a refractive error, amblyopia, and strabismus in children without pharmacological pupillary dilation. These automatic instruments, such as the photo-screeners and autorefractors, are easy-to-use and can be implemented in the primary care setting as a part of reliable and sensitive vision screening.
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