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OPTOMETRIC STUDY CENTER How to Roll Out the Welcome Mat For the Youngest Patients Young children can pose a daunting diagnostic challenge.
Here are the problems you need to look for in these patients, and the protocols you can use to find them. by Eric Borsting, O.D., M.S. and Carmen Barnhardt, O. D., Fullerton, Calif. The importance of
identifying eye and vision disorders in young children is clearly a priority within the eye-care community.1,2,3 Children younger than 6 years are not receiving adequate eye care.1,2
For example, amblyopia affects approximately 2.5 percent of children and is the leading cause of vision loss in people age 20-70.2,4,5
Early diagnosis and treatment result in good to excellent outcomes, but diagnosis in refractive amblyopia and some cases of strabismic amblyopia is often delayed until the child fails a screening at elementary school. This is one reason why the AOA recommends routine eye care for all children starting at 6 months of age.
3 We predict that optometry will have an increasing role in primary eye care for the pediatric patient under age 6. So, you need to develop a strategy for diagnosing common conditions in young
children. Working with younger children requires that you shift from relying on subjective responses (refractive sequence and phorometry) to objective testing (retinoscopy and cover test). In fact, gathering accurate and reliable
clinical data is a key factor in differential diagnosis for young children. This Optometric Study Center will focus on the various components of the pediatric exam, and differential diagnoses of amblyopia, esotropia, exotropia and
refractive errors in children ages 3-5. These are probably the most common conditions you'll see in this age group.
Diagnostic Strategy
• Ocular alignment. We typically start this part of the exam by evaluating the alignment with the unilateral and alternating cover test. Many children have sufficient fixation ability to provide accurate information on such a test. Use an age-appropriate target and assess the laterality, magnitude, frequency and comitancy of any strabismic deviation. You can evaluate comitancy objectively, with versions/duction
If the child cannot maintain fixation, then we utilize angle kappa and the Hirschberg test by assessing corneal reflections with a transilluminator attached to a puppet figure (figure 2). Angle kappa is the monocular corneal reflection, and this information is then compared with the binocular reflexes observed in the Hirschberg test. To increase the sensitivity of assessing ocular alignment, you can add the Brückner test which evaluates the consistency of the retinal reflex in each eye (figure 3). Suspect anisometropia or strabismus if either eye appears to be whiter or brighter than the other.7• Sensory testing. We typically begin this phase of testing by evaluating the child's ability to detect random dot stereopsis targets. This is important because patients with constant strabismus usually do not pass a random-dot stereopsis test.8 Several tests are available for preschool children (figure 4). You can do the Lang and Lang II without polarized glasses, and they are easy for the preschooler to perform. The Randot Preschool Stereoacuity Test (PST) and Random Dot E (RDE) are other examples of frequently used stereopsis tests, but
• Visual acuity. Several pediatric visual acuity tests are available for the preschooler (figure 5). For example, the Broken Wheel Test uses Landolt C's for wheels; one card has complete "wheels" and the other has the Landolt C's, representing the broken wheels. The Lea symbols and HOTV acuity tests are also appropriate for these patients.
• Ocular health. For assessing the anterior segment, a condensing lens and a penlight give you a magnified view of the structures if the child cannot fit into the slit lamp. For the posterior segment, we recommend dilation of all first-time patients and the use of binocular indirect ophthalmoscopy. When examining darkly pigmented children, you may need to add tropicamide to the cycloplegic agent to fully dilate the pupil.13 You can assess color vision with the Color Vision Testing Made Easy test. Of course the ocular health assessment would not be complete without assessing the pupils and intraocular pressure prior to dilation.
Amblyopia • Strabismic. This type of amblyopia typically occurs in unilateral strabismus and is thought to be caused by active inhibition or suppression over time.15 It is associated with an early onset of strabismus prior to 6-8 years of age, and is more common in esotropia than exotropia.16 In cases of strabismic amblyopia, fixation may be poor and result in variable findings on the cover test. In those cases you can use the Hirschberg test to confirm the diagnosis. Strabismic amblyopes are also more likely to have eccentric fixation. You should document the location, magnitude and steadiness using visuoscopy. Although amblyopia can occur in intermittent or alternating strabismus, it is uncommon. When it does occur, it is most often shallow (20/60 or better). • Refractive. This form of amblyopia usually results from uncorrected anisometropia. In hyperopes, anisometropic differences as small as 1.00D can cause amblyopia. If the amount exceeds 3.50D, then the risk is 100 percent.17,18 In myopes a 3.00D to 4.00D asymmetry is needed before amblyopia will potentially develop.18 This is because in myopic anisometropia the patient can use the less myopic eye for far viewing and the more myopic eye for near viewing. In contrast, the hyperope will usually fixate with the less hyperopic eye for both distance and near. • Isoametropic. A relatively equal but high refractive error in each eye characterizes this form of amblyopia. The bilateral uncorrected refractive error creates a blurred image in each eye, and this subtle form of visual deprivation usually creates a shallow amblyopia. Hyperopia greater than 5.00D, astigmatism greater than 2.50D and myopia greater than 8.00D in each eye can
The best method for evaluating acuity in amblyopia is with psychometric testing. This allows for a more stable visual acuity measurement because there is an equal number of presentations at each acuity level, the degree of difficulty between each presentation is equal, and the contour interaction between each presentation is constant. It also provides a psychophysical method for determining visual acuity (i.e., a 50 percent threshold, corrected for guessing). We recommend using the HOTV, Lea Symbols or the Broken Wheel cards with four presentations around threshold acuity (figure 6). The acuity level is where the child would get three out of four correct in the amblyopic eye.
Treatment of amblyopia typically involves providing the best optical correction and occlusion of the fixating eye. Spectacle lenses or contact lenses may be
appropriate. Preschool children typically respond well to occlusion if the parent and child comply with the patching schedule. Specific treatment regimens can be found in other sources.
22,23 Esotropia
• Infantile esotropia. This form has an onset within the first six months of life and is characterized by a large angle constant eye turn of 30pd or more.16,23 Most of
these cases are farsighted, and approximately half have hyperopia greater than +2.00D.16 However, hyperopic correction typically does not improve the magnitude
of the esotropia significantly. Common clinical characteristics include the presence of latent nystagmus, overaction of inferior oblique muscles and a dissociated vertical deviation.
16,23 Due to the cosmetic concerns, parents often pursue early
treatment. You may see a preschooler with infantile esotropia following surgical intervention. • Accommodative esotropia. This type of esotropia typically has an onset between 2 and 3 years of age.
16 The onset of the eye turn is usually gradual and intermittent,
and may be more frequent when the child is tired, sick or performing near work. The deviation is usually variable and is often larger during near vs. distance fixation.
Accommodative esotropia can be one of two basic types based on the amount of hyperopia and the AC/A ratio:24 1)
hyperopia greater than +2.00D with a normal AC/A ratio and variable deviation on distance and near fixation; 2) low or no
hyperopia and a high AC/A ratio. In the latter cases, the esotropia is larger at near fixation. The type of accommodative esotropia often indicates whether you initially
correct the patient with single vision lenses (normal AC/A) or a bifocal (high AC/A). When managing accommodative esotropia, a residual deviation can occur
following optical correction. When you suspect partially accommodative esotropia, perform another cycloplegic refraction and determine if the full amount of hyperopia
was initially corrected. If not, then you should correct the full amount of hyperopia if the patient continues to manifest an esotropia. • Non-accommodative acquired esotropia. You will also encounter esotropia
cases that are non-accommodative and have an onset after 6 months of age. Non-accommodative acquired esotropia can be divided into three basic categories, according to the Duane-White classification scheme: basic eso,
divergence insufficiency and convergence excess.23,25 This classification scheme
is based on the relationship between the far and near-point deviations. In basic esotropia the deviation at distance and near fixation are approximately
equal. In divergence insufficiency the deviation is greater at distance than at near fixation. In any case of acquired esotropia, you must rule out an underlying
pathology, especially in the patient with divergence insufficiency.26 For example, divergence paralysis originating from a midbrain lesion often presents with a
greater esodeviation at distance than at near fixation. An evaluation of onset, diplopia symptoms, comitancy, optic nerve head (papilledema or optic atrophy) and
other neurological signs can help determine if the patient has a tumor or other disorder causing the eye turn.26
• Microtropia. You may encounter a microtropia or comitant small angle esotropia
(less than 10pd). Often the unilateral cover test will show a small or intermittent flick out, and the alternate cover test may show a larger angle of deviation. Other clinical
characteristics may include central suppression of the strabismic eye, no random dot stereopsis, amblyopia and possibly eccentric fixation.16 Small angle esotropia
has been defined as microtropia, monofixation syndrome and subnormal binocular vision.23 The condition is often seen secondary to strabismus surgery or vision
therapy for a larger angle esotropia. This makes your history-taking all the more important. • Sensory strabismus. In this type of esotropia the primary cause of the strabismus is a unilateral loss in vision.
27 A severe vision loss in one eye disrupts sensory
fusion and leads to the eye turn. The resulting eye turn may be eso or exo if the onset is before age 5.27
Causes depend on the etiology of the vision loss. They include ocular trauma, optic atrophy, congenital cataract and high, uncorrected anisometropia. The ocular health evaluation is critical to diagnosing this form of strabismus.
• Incomitant esotropia. There are special, less common forms of esodeviation. One such form is Duane's Retraction Syndrome. This syndrome is characterized by a
marked limitation or absence of abduction and globe retraction with narrowing of the palpebral fissure on adduction.16,23 Globe retraction helps to differentiate this disorder from a sixth nerve paresis.
Management of esotropia is complex and depends on the type of deviations. Correction of significant refractive errors and treatment of amblyopia are often the
first steps in treatment. Refer to other sources for a discussion of the management options.22,23 Exotropia
It's important that you identify the onset and frequency of the turn during the case history. Due to the variability of exodeviations, you need to get the parents' input on the frequency of the turn.
Exotropia has typically been divided into these three basic categories: • Basic exotropia. In this form of exotropia, the magnitude of the deviation is approximately the same at distance and near fixation. • Divergence excess. In divergence excess the amount of deviation is greater at distance than at near fixation, which implies that the AC/A ratio is high. There are
two types of divergence excess: simulated and true.16,23 In the former the smaller
near deviation will increase when the patient is occluded for an extended period of time (more than 30 minutes). In true divergence excess, the AC/A ratio is high and
the angle of deviation will not change significantly after extended occlusion. • Convergence insufficiency. This type of exotropia occurs when the amount of
deviation is greater at near than at distance fixation. Few preschoolers manifest this type of strabismus.28
However, we do encounter preschoolers with high exophoria at near. In these cases we evaluate sensory fusion, near point of convergence and base-out ranges.
Management of exotropia depends on the extent of the deviation as well as the sensory and motor status of the patient. For preschoolers management strategies have centered on passive approaches, which are supplemented with simple
convergence exercises.29 Refer to other sources for a more detailed discussion of treatment approaches.
22,23 Refractive Errors • Hyperopia. In hyperopia without concurrent esotropia, consider prescribing when
the refractive error is greater than +2.50D. Significant amounts of hyperopia may put the child at risk for strabismus or amblyopia, and can also cause binocular dysfunction or poor visual perceptual development.
29,30 Definitely prescribe when the hyperopia is +5.00D or more because of amblyogenic factors we've discussed previously.
Cases of high hyperopia may not manifest strabismus because the patient chooses to see blur instead of accommodating appropriately. You need to be aggressive
when prescribing. In high hyperopes, correct the full cycloplegic refractive error minus 1.00D. A partial correction may allow the patient to accommodate comfortably for clear vision, but create an accommodative esotropia. These
children adjust rapidly to the spectacle lens prescription. In our experience compliance is excellent. For hyperopic refractive errors closer to +2.50D, we will evaluate for significant
esophoria and accommodative dysfunction. If all signs are normal, we may monitor the patient at six-month intervals. We also ask the parents about performance in
school. If the child is struggling we are more likely to consider the spectacle lens prescription. If you decide not prescribe spectacle lenses, inform the parent that the child may
need glasses in the future when his or her child's school work leads to an increased demand for sustained near fixation. • Anisometropia. This may lead to amblyopia, or cause asthenopia and binocular
dysfunctions. In preschoolers 4 years and older, consider prescribing if the hyperopic anisometropia is greater than 1.00D and when the myopic anisometropia is greater than -2.00D. The likelihood of amblyopia increases with
the amount of anisometropia. We recommend correcting the full amount of anisometropia and reducing the full cycloplegic refraction in the hyperopic patient by 1.00D. For example, a
non-strabismic child has a manifest refraction of +1.00DS and +2.00DS and cycloplegic retinoscopy reveals +2.00 and +3.50. The ideal prescription would be
+1.00 and +2.50. This decreases the chance that the full cycloplegic findings would cause distance blur and allows each eye to have a clear image. Also, since the
patient is non-strabismic, it is not necessary to prescribe the full cycloplegic findings. For children under 4, consider follow-up visits at three and six months to
measure the stability in the anisometropia and refractive error before prescribing. • Astigmatism. Age 3 is considered to be a major milestone for astigmatism.
During the first three years of life, astigmatism changes rapidly and may be a transient finding.31
Around age 3 astigmatic errors begin to stabilize and significant amounts are usually not transient.13,32
We recommend you consider prescribing when the astigmatism exceeds 1.25D, and definitely prescribe when it's 2.50D or more because of the amblyogenic factors we discussed previously.
For astigmatism closer to 1.25D we will evaluate for reduced visual acuity. If you do not prescribe for the refractive error, then monitor the patient at six-month intervals
for any significant astigmatic changes. Once you establish the need for correction, we recommend that you prescribe the full astigmatic amount in children older than 3
1/2 years. This will maximize visual acuity and decrease the chance of meridional amblyopia developing. Monitor children frequently to evaluate any residual meridional amblyopia and the stability of the astigmatic refractive error.
• Myopia. Significant amounts of myopia (more than -1.00D) are not as common in the preschool population as it is in other age groups. Most often significant myopia
will be associated with another condition (such as retinopathy of prematurity or Down syndrome). Consider prescribing when the myopia is greater than -1.00D
because of the child's reduced visual acuity. We typically prescribe the full correction and will follow the patient closely for any changes in refractive status.
Performing the differential diagnosis of common visual disorders in the preschooler is a two step-process. The first step involves gathering accurate and reliable
information by creating a child-friendly environment and using special testing procedures. The next step is to match the diagnostic data with diagnostic category.
It's important that we as primary-care doctors understand the signs and symptoms of common vision problems, and know how to treat them.
Dr. Borsting is associate professor at Southern California College of Optometry in Fullerton, Calif. Dr. Barnhardt is an assistant professor there.
1. Ciner EB, Dobson V, Schmidt PP, Allen D, et al. A survey of vision screening policy of preschool children in the United States. Surv Ophthalmol 1999;43:445-57. |
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How to Roll Out the Welcome Mat When working with the younger patient, it helps to understand some important developmental factors. The preschooler can name simple pictures (such as animals), but is often reticent during
the examination. Developmentally, it's easier for the child to match or choose the appropriate target. Fortunately, many of the subjective tests for visual acuity and stereopsis allow the child to either name the picture or use a
matching strategy. Preschool children are more likely to participate in activities that they perceive as relevant to them. For example, fixation is typically better when you use a relevant target—a Sesame Street character vs. a
pen tip or letter target. You can make tests into simple games for the child. This promotes patient cooperation and improves the reliability of your test results. Thus, it is important that you use developmentally appropriate tasks
and targets when evaluating the pre-school child. Creating a child-friendly environment can facilitate the examination sequence. Schedule the exam for a time when the child is well-rested and not ready for a nap. It's
helpful to have a children's area in the waiting room with books, toys and pediatric furniture. We also recommend not wearing a white coat for the examination, and introduce yourself with a simple name, such as Dr. Eric.
Approach the child at eye level and ask simple questions (How old are you? What TV shows do you watch?). We often tell children they're going to play some games. We try to make the first few tests fun and friendly. Using
age-appropriate targets for cover test and motility evaluation can help put the child at ease. We often use positive reinforcement to increase desired behaviors. Simple reinforcements, such as stickers, are quite effective for
promoting "good looking" during cover test or visual acuity testing. |
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Take the Optometric Study Center Quiz on Diagnosing Preschoolers
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