Pediatrics
Amblyopia
Suzanne M. Wickum
ICD-9: 368.01—AMBLYOPIA, STRABISMIC
ICD-9: 368.02—AMBLYOPIA, DEPRIVATION
ICD-9: 368.03—AMBLYOPIA, REFRACTIVE
THE DISEASE
Pathophysiology
Amblyopia is a unilateral or bilateral decrease in visual acuity, uncorrectable by optical means, without detectable anatomic damage in the eye or visual pathway. When form vision deprivation and abnormal binocular interaction occur during the critical or sensitive periods, amblyopia may develop.
Etiology
Amblyopia is a diagnosis of exclusion. In addition to ruling out ocular pathology, an amblyogenic factor must be present. There are four main etiologic categories of amblyopia.
Strabismic Amblyopia
Abnormal binocular interaction secondary to constant or intermittent strabismus.
Moderate to deep amblyopia is associated with constant, unilateral strabismus.
Shallow amblyopia is possible with frequent intermittent, unilateral strabismus.
Refractive Amblyopia
Isoametropic
Bilateral visual disruption because of significant uncorrected ametropia.
Bilateral hyperopia greater than 2 to 4 D, myopia greater than 6 to 8 D, and astigmatism greater than 1.50 to 2.50 D can cause isoametropic amblyopia.
Anisometropic
Unilateral visual disruption because of significant uncorrected anisometropia.
The greater the amount of anisometropia, the deeper the amblyopia.
Uncorrected hyperopic anisometropia greater than 3.50 D and myopic anisometropia greater than 6.50 D lead to a 100% incidence of amblyopia.
Uncorrected hyperopic anisometropia of 2.00 to 3.50 D and myopic anisometropia of 5.00 to 6.50 D lead to a 50% incidence of amblyopia.
Meridional
Uncorrected astigmatism leads to meridional visual deprivation.
Uncorrected astigmatism of 1.50 to 2.00 D or more can be amblyogenic.
Combined Anisometropic-Strabismic Amblyopia
Both anisometropia and strabismus are present.
The strabismic eye is generally the more ametropic eye.
Deprivation Amblyopia
Unilateral or bilateral visual deprivation because of the obstruction of the visual axis by ptosis, corneal opacity, cataracts, or other media opacities. May also be iatrogenic.
Often causes very deep amblyopia.
The Patient
Clinical Symptoms
Decreased vision in one or both eyes.
Clinical Signs
Reduced best-corrected visual acuity in one or both eyes in the absence of ocular disease and in the presence of an amblyogenic factor.
Abnormal contour interaction (crowding phenomenon) in the amblyopic eye.
Eccentric fixation (usually associated with strabismic amblyopia).
Decreased contrast sensitivity in the amblyopic eye.
Binocular suppression of the amblyopic eye.
Reduced accommodative response in the amblyopic eye.
Mild afferent pupillary defects have also been reported in some severely amblyopic eyes.
Demographics
Amblyopia occurs in 2% to 4% of the general population. Amblyopia is the most common visual disability in children, with approximately 120,000 children diagnosed per year in the United States. Amblyopia is the leading cause of monocular vision loss in the 20- to 70-year age group.
Significant History
A history of “lazy eye,” misaligned eyes, uncorrected ametropia, extraocular muscle surgery, occlusion therapy, or other vision therapy may be elicited.
Ancillary Tests
A thorough eye examination is indicated with particular attention to best-corrected visual acuity, binocularity, cycloplegic retinoscopy/refraction, and ocular health. Visuoscopy is a useful ancillary test to determine the presence or absence of eccentric fixation.
The Treatment
Strabismic Amblyopia
Optical correction of ametropia based on cycloplegic retinoscopy/refraction.
Part-time, direct, full occlusion for 2 to 6 h/d for mild to moderate amblyopia, with the possible need for increased hours for deep amblyopia.
Full-time occlusion may be necessary when trying to break down and/or prevent binocular sensory anomalies (suppression, anomalous correspondence); however, care must be taken to prevent occlusion amblyopia. For patients 5 years and under, occlude the preferred eye the number of days equal to the child’s age, and then occlude the amblyopic eye for 1 day.
Penalization with 1% atropine may be used instead of traditional occlusion for mild to moderate amblyopia.
Active monocular visual activities for 30 to 60 min/d while occluded.
Follow up every 4 to 6 weeks.
Manage the strabismus once the amblyopia treatment is completed or abandoned.
Isoametropic Amblyopia
Optical correction of ametropia based on cycloplegic retinoscopy/refraction.
Follow up in approximately 4 weeks.
If necessary, make any changes to the prescription.
Follow every 4 to 6 months to monitor acuity improvement.
Patching or penalization is necessary only in cases of asymmetric aided acuity.
Anisometropic Amblyopia
Optical correction of ametropia based on cycloplegic retinoscopy/refraction.
Part-time, direct, full occlusion for 2 to 6 h/d for mild to moderate amblyopia, with the possible need for increased hours for deep amblyopia.
Penalization with 1% atropine may be used instead of traditional occlusion for mild to moderate amblyopia.
Active monocular visual activities for 30 to 60 min/d while occluded. Once visual acuity in the amblyopic eye reaches 20/40-50, consider the addition of binocular vision therapy to break down remaining suppression.
Follow up every 4 to 6 weeks.
Deprivation Amblyopia
Remove the obstruction of the visual axis promptly, ideally within 2 months of onset.
Correct any significant ametropia or aphakia.
Part-time, direct, full occlusion for 2 to 6 h/d for mild to moderate amblyopia, with the possible need for increased hours for deep amblyopia.
Penalization with 1% atropine may be used instead of traditional occlusion for mild to moderate amblyopia.
Active monocular visual activities for 30 to 60 min/d while occluded.
Follow up every 4 to 6 weeks.
Esodeviations
Suzanne M. Wickum
ICD-9: 378.00—ESOTROPIA, UNSPECIFIED
ICD-9: 378.01—ESOTROPIA, MONOCULAR
ICD-9: 378.02—ESOTROPIA, MONOCULAR WITH “A” PATTERN
ICD-9: 378.03—ESOTROPIA, MONOCULAR WITH “V” PATTERN
ICD-9: 378.04—ESOTROPIA, MONOCULAR WITH OTHER NONCOMITANCY
ICD-9: 378.05—ESOTROPIA, ALTERNATING
ICD-9: 378.06—ESOTROPIA, ALTERNATING WITH “A” PATTERN
ICD-9: 378.07—ESOTROPIA, ALTERNATING WITH “V” PATTERN
ICD-9: 378.08—ESOTROPIA, ALTERNATING WITH OTHER NONCOMITANCY
ICD-9: 378.21—ESOTROPIA, INTERMITTENT, UNILATERAL
ICD-9: 378.22—ESOTROPIA, INTERMITTENT, ALTERNATING
ICD-9: 378.35—ESOTROPIA, WITH ACCOMMODATIVE COMPONENT
THE DISEASE
Pathophysiology
Esodeviations present with an intermittent or constant inward eye turn resulting in convergent visual axes.
Etiology
Innervational, accommodative, genetic, and environmental factors play a role in the development of esotropia.
The Patient
Clinical Symptoms
Patients may report diplopia, asthenopia, and/or blurred vision.
Esotropia Classification and Characteristics
Infantile Esotropia
Clinical characteristics: Onset occurs between birth and 6 months of age. Esotropia is constant, comitant (A or V patterns may be present), moderate to large magnitude (30 to 70 prism diopters), and cross-fixation is common. The accommodative- convergence accommodation (AC/A) ratio is usually normal. Ametropia is skewed toward low hyperopia. Sensory adaptations are present in 35% to 72% of cases. Dissociated vertical deviation is present in 50% to 75% of cases. Overaction of the inferior oblique muscle is present in 68% of cases. Latent or manifest-latent nystagmus is found in 25% to 52% of cases.
Accommodative Esotropia
Refractive Accommodative Esotropia
Clinical characteristics: Onset is usually between 1 and 8 years of age with an average of 2.5 years. Deviation is typically comitant (A or V patterns may be present), moderate (20 to 40 prism diopters), variable, and intermittent with a gradual increase in frequency and duration over time.
If the deviation becomes constant, sensory adaptations may develop. The AC/A ratio is normal. The etiology is uncorrected hyperopia and insufficient fusional divergence. Ametropia is usually between +2 and +6 D with an average of +4.75 D.
Nonrefractive Accommodative Esotropia
Clinical characteristics: The characteristics are the same as refractive accommodative esotropia with a few exceptions. The AC/A ratio in this case is high, and thus the near angle is larger than distance. The average ametropia is +2.25 D, but any refractive error can be found. The etiology in this case is the high AC/A ratio; therefore, esotropia typically responds to plus lenses at near.
Partially Accommodative Esotropia
Clinical characteristics: The characteristics are the same as refractive accommodative esotropia with a few exceptions. Esotropia is constant; therefore, sensory adaptations are likely. The AC/A ratio is normal or high. Typically, there is moderate to high hyperopia present. Esotropia magnitude decreases, but is not eliminated, with the hyperopic correction.
Nonaccommodative Acquired Esotropia
Clinical characteristics: Onset occurs after 6 months of age. Esotropia is typically constant, comitant (A or V patterns may be present), and of moderate to large magnitude (20 to 70 prism diopters), and sensory adaptations may occur. Often, some amount of hyperopia is present. Causes include idiopathic, decompensated esophoria; disruption of fusion by occlusion; physical/emotional stress; and rarely CNS pathology.
Basic Esotropia
This is the most common subcategory. The AC/A ratio is normal. The refractive error is usually insignificant.
Divergence Insufficiency Esotropia
The AC/A ratio is low, and thus the distance magnitude is greater than near. Divergence paralysis, which originates from a midbrain lesion, must be ruled out. Divergence paralysis initially presents as a noncomitant esotropia that shows spread of comitancy.
Acute Esotropia
Diplopia is likely. Some patients may close or wink one eye to alleviate the diplopia.
Sensory Esotropia
Onset may occur at any age. Deviation is constant, comitant, and unilateral, and the magnitude is often variable. The strabismus is secondary to significantly reduced visual acuity, resulting in a sensory obstacle to fusion. Visually depriving factors may include uncorrected anisometropia, ptosis, corneal opacities, cataracts, optic nerve lesions, or retinal lesions. Sensory esotropia is as frequent as sensory exotropia in children under 6 years of age; however, sensory exotropia predominates in older children and adults.
Microtropia
Clinical Characteristics
Primary microtropia is likely present since birth, with no history of a larger angle of strabismus. Secondary microtropia is often the result of vision therapy or surgery for a larger deviation. Other causes may include aniseikonia, anisometropia, uncorrected vertical deviation, and foveal lesions. Deviation is usually constant and comitant, and the magnitude is between 1 and 10 prism diopters. Sensory adaptations are common and include anomalous correspondence, mild amblyopia, central suppression, and eccentric fixation. These patients often have some peripheral fusion with anomalous vergence
ranges and some local stereopsis but no global stereopsis.
Incomitant Esotropia
Abducens Nerve Palsy (Sixth Cranial Nerve Palsy)
A noncomitant esotropia with greatest magnitude in the affected muscle action field. The distance magnitude may be larger than near. An abduction deficit is present, with no restriction on forced duction testing. Patients typically report diplopia and may adopt a face turn toward the paretic eye to obtain fusion. (See Chapter 19, “Neuro-ophthalmic Disease.”)
Demographics
The prevalence of strabismus in the general population is between 2% and 6%. Esotropia occurs three times as often as exotropia. While most cases of esotropia have an accommodative component, 28% to 54% of esotropias are infantile.
Significant History
Age and nature of onset
Frequency of deviation
Changes in the size or frequency of the deviation
Associated symptoms (including diplopia)
History of injury or illness
History of neurologic, systemic, or developmental disorders
History of ocular disease or reduced visual acuity
History and outcome of prior treatment (occlusion, vision therapy, prism, surgery)
Positive family history of strabismus
Ancillary Tests
A thorough ocular examination is indicated in all strabismic patients. Careful refractive error and visual acuity measurements should be performed to evaluate for amblyopia. Visuoscopy can be utilized to detect eccentric fixation. Measurement of the esotropia including frequency, laterality, magnitude, and comitancy is essential. Evaluation of ocular motility is necessary to rule out abducens palsy. In cases of intermittent esotropia, base-in (compensating) vergence ranges should be measured and sensory-motor fusion should be assessed (Worth-dot/stereopsis). Subjective assessment of the deviation is performed with tests such as Maddox rod and Bagolini lenses. The subjective angle of deviation is compared to the objective angle of deviation to determine the presence/absence of anomalous correspondence. Cycloplegic retinoscopy/refraction is recommended. Lastly, a thorough ocular health examination is necessary to rule out causes for sensory deprivation.
The Treatment
Treatment of infantile esotropia starts with correction of any significant refractive error. When amblyopia is present, it should be treated prior to surgical intervention. Once the patient can freely alternate fixation, strabismus surgery should be offered. Ideally, surgery should be performed by 6 to 12 months of age for the best chance of establishing some form of binocularity.
Treatment of refractive/accommodative acquired esotropia includes prescribing the full hyperopic correction. Consider giving an add for cases with a high AC/A ratio. Treat amblyopia and sensory-motor fusion as needed. If the esotropia is only partially accommodative, consider adding base-out prism when the residual esotropia is less than 15 to 20 prism diopters and surgical intervention if greater than 15 to 20 prism diopters.
Once the etiology of nonaccommodative acquired esotropia has been determined, treatment can begin. If amblyopia is present, it should be treated. For esotropia less than 15 to 20 prism diopters, base-out prism and/or vision therapy should be utilized. For deviations greater than 15 to 20 prism diopters, surgery should be considered.
Microtropia treatment is often confined to best optical correction and treatment of amblyopia. When anomalous correspondence is present, binocular therapy is rarely undertaken; however, when normal correspondence is present, base-out prism and/or vision therapy can be utilized to obtain sensory-motor fusion.
In the case of sensory esotropia, the underlying cause must be addressed first. Any significant ametropia should be corrected, and all patients should wear protective glasses full-time. If superimposed amblyopia is suspected, treatment should be implemented. If improved ocular alignment is desired, strabismus surgery may be performed.
Exodeviations
Suzanne M. Wickum
ICD-9: 378.10—EXOTROPIA, UNSPECIFIED
ICD-9: 378.11—EXOTROPIA, MONOCULAR
ICD-9: 378.12—EXOTROPIA, MONOCULAR WITH ‘A’ PATTERN
ICD-9: 378.13—EXOTROPIA, MONOCULAR WITH ‘V’ PATTERN
ICD-9: 378.14—EXOTROPIA, MONOCULAR WITH OTHER NONCOMITANCY
ICD-9: 378.15—EXOTROPIA, ALTERNATING
ICD-9: 378.16—EXOTROPIA, ALTERNATING WITH ‘A’ PATTERN
ICD-9: 378.17—EXOTROPIA, ALTERNATING WITH ‘V’ PATTERN
ICD-9: 378.18—EXOTROPIA, ALTERNATING WITH OTHER NONCOMITANCY
ICD-9: 378.23—EXOTROPIA, INTERMITTENT, UNILATERAL
ICD-9: 378.24—EXOTROPIA, INTERMITTENT, ALTERNATING
THE DISEASE
Pathophysiology
Exodeviations present as an intermittent or constant outward eye turn resulting in divergent visual axes. Deviation often begins as an exophoria and over time becomes an intermittent exotropia. When left untreated, an intermittent exotropia may progress to a constant exotropia.
Etiology
Innervational, mechanical/anatomic, and multifactorial genetic inheritance patterns have all been implicated in the development of exotropia.
The Patient
Clinical Symptoms
Patients may complain of asthenopia, squinting, photophobia, unilateral eye closure, diplopia, and/or blurred vision.
Exotropia Classification and Characteristics
Primary Comitant Exotropia
Clinical Characteristics
Onset is usually between 6 months and 8 years of age. Exotropia is typically intermittent (80%) and comitant, although A or V patterns are found with overaction of the superior or inferior oblique muscles. Deviation magnitude ranges from 20 to 70 prism diopters. Positive fusional vergence is insufficient. Sensory adaptations are minimal. Fatigue, illness, daydreaming, alcohol/sedatives, or going from dim to bright light (“dazzle effect”) may decrease control of the exotropia.
Subcategories of primary comitant exotropia are as follows (based on Duane’s categories):
Basic exotropia: Distance and near deviation magnitude are similar, yielding a normal AC/A ratio. Exotropia is manifest more often at distance than at near.
Convergence insufficiency exotropia: Near deviation magnitude is greater than distance, yielding a low AC/A ratio. Exotropia is typically at near and accompanied by a receded near point of convergence.
True divergence excess exotropia: Distance deviation magnitude is greater than near, yielding a high AC/A ratio. Exotropia is more frequent at distance.
Pseudo-divergence excess exotropia: Initial measurements look like divergence excess exotropia with the strabismus magnitude greatest at distance. These patients have increased tonic fusional convergence that is not broken down with a near cover test. With prolonged occlusion, or with +3.00 D overcorrection, the magnitude of the near deviation is found to be similar to the distance deviation, resulting in a basic exotropia. Pseudo- divergence excess is more common than true divergence excess.
Infantile Exotropia
Clinical Characteristics
A rare type of exotropia occurring in approximately 1/30,000 births. Onset occurs between birth and 6 months of age. Deviation is constant, moderate to large (30 to 90 prism diopters), and comitant with possible A or V patterns if superior or inferior oblique overactions are present. Sensory adaptations are likely. Infantile exotropia may occur in otherwise healthy infants but is typically associated with other ocular disorders, neurologic disease, craniofacial syndromes, and genetic syndromes.
Sensory Exotropia
Clinical Characteristics
Onset may occur at any age. Deviation is constant, unilateral, and comitant, and the magnitude is often variable. The strabismus is secondary to significantly reduced visual acuity, resulting in a sensory obstacle to fusion. Visually depriving factors may include uncorrected anisometropia, ptosis, corneal opacities, cataracts, optic nerve lesions, or retinal lesions. Sensory exotropia is as frequent as sensory esotropia in children under 6 years of age; however, sensory exotropia predominates in older children and adults.
Oculomotor Nerve Palsy (Third Cranial Nerve Palsy)
Clinical Characteristics
A large magnitude, noncomitant exotropia with hypotropia. Accompanied by limitation of elevation, depression, and adduction in the affected eye. A complete palsy also presents with ptosis, loss of accommodation, and a dilated pupil. These findings vary in the case of an incomplete palsy. (See Chapter 19, “Neuro-ophthalmic Disease.”)
Demographics
The prevalence of strabismus in the general population is between 2% and 6%. Exodeviations occur less often than esodeviations in a 1:3 ratio. In addition, exodeviations occur more often in females than males. Approximately one third of the exodeviations are evident by 2 years of age.
Significant History
Age and nature of onset
Frequency of deviation
Changes in the size or frequency of the deviation
Associated symptoms (including diplopia)
History of injury or illness
History of neurologic, systemic, or developmental disorders
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