By Minna Saslaw, MD.
Case 1: At a 4
year WCC visit the visual acuity testing shows 20/30 vision in both eyes,
do you refer to ophthalmology? Would you refer if the R eye was 20/20 and
L eye 20/40?
Answer: When testing
visual acuity, each eye should be tested separately and then together. Referral
criteria include vision of 20/50 or worse in 3-5 year old children and for
children 6 years of age or older 20/40 or worse, OR a two-line difference
between eyes even within the passing range (e.g. OD 20/20 and OS 20/30).
If a child is unable to perform the tests on two separate occasions they
should be referred to an ophthalmologist.
If a child is uncooperative the testing should be attempted
again in 4-6mos. The most commonly used methods are the tumbling E, Allen
picture test, LH symbol test or HOTV test for younger children and Snellen
charts or numbers for children 6 yrs and older. (see appendix 1 in reference
1 and Figure 1)
Case 2: During
a 1mo weight check visit a parent is concerned because the eyes sometimes
appear cross-eyed what do you say? What would you say at the 6mo visit?
The same parent asks when can the baby see and if he can see colors?
Answer: Disconjugate
eye movements can be normal in the first 3 months of life as long as the
baby is able to fix briefly on close objects 8-12inches away e.g. parent’s
face when being held. Shining a light into the eyes also should make the
baby blink. In the newborn, the vestibulo-ocular reflex i.e. Doll’s eye
maneuver should also exert conjugate eye movement in the opposite direction
of turning the head thus testing CN 3,4.6. Nystagmus, or involuntary rhythmic
eye movements regardless of direction, should always be referred to an ophthalmologist.
Most infants begin tracking and following in the first
few weeks and by 3 months of age most babies will be able to fix well and
easily follow an object past midline. By 4 months accommodate, and by 6
months, babies should have well-developed conjugate gaze, and be able to
track though the horizontal and vertical planes.
The retina, optic nerve and visual cortex begin to develop
in the first weeks of life in response to visual stimuli but the ability
to start focusing an image on the retina does not occur until about 2-3
months of age. If functioning correctly, each eye focuses the image on the
macula (full macular development does not occur until 4yo) and the visual
cortex translates this into binocular vision. If one eye does not receive
an equal stimulus the cortex suppresses the image from the non-functioning
eye in order to facilitate clear vision. This will lead to amblyopia.
Newborns have a visual acuity of about 20/400 (20/200 is
legally blind in adults!), by 3yo 20/40, 4yo 20/30 and 5yo 20/20.
By 4 months babies have color vision almost similar to
adults. They are able to discriminate between longer wavelengths (red, orange,
yellow) in the first few months and later the shorter wavelengths (green,
blue, violet). This is due to the development of the different subclasses
of cones. There are three different pigment cones: red, green and blue.
Color blindness results from a mutation in these cones. Since the red and
green genes are next to each other on the X chromosome, more men than women
suffer from red-green color blindness (just FYI the gene for blue cones
is on chromosome 7).
Case 3: You are
seeing a 2 month old for a well child visit. The father shows you the family
holiday picture and you notice that only the right eye has red eye in the
picture and the left eye looks white. Are you concerned? An 18mo seems to
be cross-eyed, how do you evaluate this?
Answer: The first child
has leukocoria. Of children with retinoblastoma, 60% present with leukocoria
and 20% with strabismus. Other presentations are glaucoma, hyphema and preseptal
cellulitis. Cataracts and glaucoma as well as any other corneal opacities
may present this way. The red reflex test should pick up leukocoria. This
child needs immediate evaluation by an ophthalmologist, if it is retinoblastoma
there is a >95% cure if confined to the eye.
RED REFLEX TEST—At every visit. This test evaluates
for abnormalities in the back of the eye as well as for entities physically
blocking the visual pathway.
The ophthalmoscope is held up to the examiner’s eye and
the patient’s pupils are first viewed separately at a distance of about
18-24 inches with the ophthalmoscope on the "0" diopter, preferably in a
dark room. The red reflex is then examined in both eyes simultaneously at
2-3 ft away (Bruckner Test). The examiner is looking for symmetry in clarity,
intensity and color of the reflection from the pupil. The reflex is a bright
reddish-yellow color but can be light gray in darkly pigmented brown-eyed
patients.
A normal or negative red reflex exam is symmetrical with
equal red reflexes in both eyes. An abnormal or positive red reflex includes
asymmetry of intensity (one side dull other bright), dark spots, white reflex
or leukocoria, or no reflex and require speedy referral to the ophthalmologist.
An abnormal red reflex most commonly can be seen with cataracts, glaucoma,
retinoblastoma, abnormalities of the retina, strabismus or refractive errors.
CORNEAL LIGHT REFLEX TEST- 2mo-8yo WCC (AAP), 3y-5y
(USPSTF).
This test is used to screen for strabismus. (Figure 2)
Strabismus affects approximately 4% of children under 6
years of age. Medial deviations are the most common occurring in more than
half of strabismus cases.
The examiner shines a light into the child’s eyes. When
the child fixes on the light, the position of the reflected dot of light
is compared between the two eyes, and differentiates strabismus from pseudostrabismus.
Pseudostrabismus (Figure 3) is the appearance of misalignment
due to epicanthal folds or a wide nasal bridge. With pseudostrabismus the
corneal light reflex test is normal with the reflected dot of light in a
central symmetrical position on both eyes. Of children with strabismus 30-50%
develop amblyopia. The corneal light reflex does not detect this loss of
vision.
COVER/UNCOVER and ALTERNATING COVER/UNCOVER TESTS—
4mo to 8yo WCC (AAP) 3y-5y (USPSTF).
These tests are used to screen for strabismus AND detect amblyopia.
The cover/uncover test screens for strabismus as well as
for fixation preference suggesting amblyopia in a child with a "tropia".
Attention is first focused on the uncovered eye for movement and then the
covered eye. The alternating cover/uncover test screens for "phorias", latent
deviations but does not detect amblyopia. Attention is focused only on the
covered eye.
See Figures 4 and 5 for diagrams and explanation on how
to do the test.
Amblyopia must be addressed as soon as possible. If not
treated before 6-8 years of age, blindness may occur in the affected eye.
Treatment requires removal of any obstruction (cataract, hemangioma etc.)
and treating refractive errors e.g. in accommodative esotropia. For other
reasons, patching the unaffected eye intermittently promotes visual development
in the affected eye and stereopsis (depth perception). Surgical realignment
is used when non-surgical treatment fails or for cosmetic reasons.
The USPSTF issued new recommendations regarding vision screening in 2011
updating their 2004 recommendation for vision screening for all children
under the age of 5. The new recommendations state that vision screening
for the presence of amblyopia and its risk factors should be performed at
least once in between the ages of 3y and 5y, and that there is insufficient
evidence to assess the harm or benefit of vision screening in children under
the age of 3. Vision screening was defined as visual acuity test, stereoacuity
test, cover-uncover test, Hirschberg light reflex test, autorefraction and
photoscreening. Red reflex testing was not assessed as part of the recommendations.
The AAP has not changed their recommendations based on this report. There
was also a 2012 policy statement on automated vision screening technology
which supported its use as an alternative to standard vision screening.
The AAP did not recommend mass photoscreening.
Case 4: A post-doctoral
fellow brings his 2month old for a well child visit and asks what developmental
milestones should he look out for in order to know his daughter’s vision
is developing correctly?
Answer: By 3 months of
age most babies will be able to fix well and follow an object past midline
as well. By 4 months accommodate, and by 6 months, babies should have well-developed
conjugate gaze and be able to track though the horizontal and vertical planes.
Some milestones that require eyesight include fixing, following, developing
a social smile, later on searching for objects, fine pincer grasp, crawling/walking.
He should also be told to look out for eye movements that appear abnormal.
Some "phorias" are first picked up at home when the child is ill or tired.
Case 5: What other
conditions or family history that may affect visual development should prompt
an ophthalmology referral?
Answer:
- Prematurity— 31 weeks GA or less, BW <1250gms
- Family history of congenital cataracts, retinoblastoma,
congenital retinal dysplasia, aniridia.
- Developmental delay/neurological problems—Cerebral Palsy
- Systemic/genetic disease associated with eye abnormalities
e.g. Neurofibromatosis 1, JRA, Galactosemia, Diabetes, Marfan Syndrome,
Down Syndrome, Crouzon Syndrome, Graves Disease.
- Fetal alcohol syndrome
- TORCH infection
- Torticollis
- Ptosis
- Eyelid hemangioma
References:
- American Academy of Pediatrics, Committee
on Practice and Ambulatory Medicine and Section on Ophthalmology et. Al.
Policy Statement: Eye Examination in Infants, Children and Young Adults
by Pediatricians. Pediatrics. April 2003; 111; 902-7.
- American Academy of Pediatrics, Section
on Ophthalmology. Policy Statement: Red Reflex Examination in Infants.
Pediatrics. May 2002; 109; 980-1.
- Broderick, Peter, M.D. Pediatric Vision
Screening for the Family Physician. American Family Physician. Sept 1,
1998;58; 691-700. (All of the diagrams except for the Snellen and HOTV
charts are from here).
- American Academy of Pediatrics, Surgical
Advisory Panel. Guidelines for Referral to Pediatric Surgical Specialists.
Pediatrics. July 2002;110; 187-191
- http://www.psych.ucalgary.ca/PACE/VA-Lab/Marcela/Pages/index.html
(VISUAL DEVELOPMENT)
- Silbernagl, Stefan, et. Al. Color
Atlas of Pathophysiology. 2000. 324. (COLOR VISION)
- "Red-Green Color Vision Defects".
http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=rgcb
- http://www.health.state.mn.us/divs/fh/mch/webcourse/vision/toc.cfm
(GOOD TUTORIAL ON VISION SCREENING)
- Merck Manual. Sections on Strabismus
and Amblyopia. 2007.
- US Preventive Services Task Force. Vision screening
for children 1 to 5 years of age: US Preventive Services Task Force recommendation
statement. Pediatrics. 2011;127(2):340–346
- Another good vision screening tutorial with cases, (Good
cases with questions)
http://one.aao.org/Flash/VisionScreening/PediatricVisionScreening.html
- Instrument-Based Pediatric Vision Screening Policy Statement.
Pediatrics. 2012;130(5):983-986.
