This issue of eMedRef provides information to clinicians on the pathophysiology, diagnosis, and therapeutics of amblyopia

Hutchinson, Elizabeth

Sands, Jarret

English

University of Missouri: MOspace

Amblyopia Page 1 of 4    3.11.12 AMBLYOPIA  Definition & General Information 1. Abnormal vision (generally affecting one eye) not corrected by refraction, without abnormality in visual pathway 2. Condition reversible during “critical period” of vision maturation (age 1-7)1  Pathophysiology    1. May occur early in the first weeks of life with abnormal maturity of visual pathways to brain 2. Conditions that prevent development of visual perception may lead to amblyopia: strabismus, refractive errors, cataracts2   Incidence, Prevalence 1. 2-5% of children depending on population and diagnostic criteria1  Risk Factors 1. Family history of amblyopia or strabismus, childhood cataract or glaucoma, and delayed visual or neurologic maturation of unclear etiology3 2. Prematurity  - Modest degrees of low birth weight and prematurity may be associated with increased ophthalmic morbidity at age 6 years4  Morbidity / Mortality 1. Treatment outcomes dependent on compliance 2. Possible untoward outcomes - Permanent vision loss; loss of stereoscopic vision; damage to healthy eye 2   Diagnostics  1. Screening:  o Appropriate for children age 3 to late school age o No standardized protocol or personnel to carry out testing (MD/DO/PA/NP, optometrist, RN or school based) o Programs rely on reduced, condition-associated visual acuity as marker for disease. (high sensitivity, low specificity) o Components of screening tests:   monocular visual acuity with an age-appropriate testing   assessment of extra-ocular muscle function   binocular status   color vision assessment o Protocols vary with regard to vision and binocular function test used, threshold for referral and age at which children screened o USPSTF   Recommends vision screening for all children at least once between ages of 3 and 5 years, to detect presence of amblyopia or its risk factors. Grade B recommendation  Amblyopia Page 2 of 4    3.11.12  Insufficient to assess balance of benefits and harms of vision screening for children <3 years of age. I statement (Insufficient evidence for or against)5  No optimal screening interval 2. Benefits of screening:  o Prevention or reversal of vision impairment o improvement of visual acuity o correction of strabismus o maintaining alignment of eyes  o reducing need for repeat surgery3 3. Potential Harms of screening o Risk of developing strabismus or occlusion amblyopia in the better eye o Risks of wearing patch: skin irritation, accidents, psychological effects5 o Risks of atropine use: systemic side effects, possibility of blur-induced amblyopia, development of strabismus3 o Risk of false-positive screening: unnecessary use of corrective lenses o USPSTF found inadequate evidence for harms from screening and treatment for children <3 years of age5 4. History  o Patients (or caregivers) may complain of vision loss or show signs of strabismus or ptosis o Commonly no presenting symptoms or signs  o Often goes unnoticed by parents or caregivers6  o Prematurity, perinatal history (e.g., alcohol, tobacco, and drug use during pregnancy); past hospitalizations and operations; and general health and development3 5. Physical examination  o Four main steps in   diagnosis of amblyopia:3   Monocular visual acuity assessment using an age-appropriate vision test;  Refraction: retinoscopy recommended  In young children, cyclopentolate hydrochloride or similar topical (cycloplegic) agent required to paralyze accommodation, as most young children unable to maintain distance fixation during testing;  Fundus and media examination to exclude pathology;  Rechecking visual acuity with corrective lenses in place  During critical period, some improvement in visual acuity expected after wearing appropriate corrective lenses (approximately six - twelve weeks common)  Diagnosis made if visual acuity deficit persists after refractive error corrected for appropriate period1 6. Diagnostic “Criteria” for Amblyopia (If indicated) o Classification by cause:   Strabismic (caused by misalignment of eyes);  Stimulus deprivation (reduced vision occurring secondary to obstacle in anterior visual pathway);  Refractive:  Amblyopia Page 3 of 4    3.11.12  Anisometropic (difference in refractive (focusing) error of both eyes);  Ametropic (significant refractive error of both eyes);  Meridional (astigmatism of both eyes)3 o Classification based on severity:  Mild (worse than 20/25, but <20/200)   Severe (legal blindness, 20/200 or worse.)2  Key Differential Diagnoses 1. Refractive error  2. Anisometropia  Extensive Differential Diagnoses 1. Organic diseases,  2. Congenital cataracts,  3. Retinoblastoma  Therapeutics  Acute Treatment: 1. Refractive amblyopia:  o Optical correction (glasses) first line (SOR:A)1 o No evidence to support adding occlusion therapy for this sub-type of amblyopia 2. Strabismic amblyopia:  o Glasses plus occlusion (SOR:A)1  Two types of occlusions include:  Patching: 2-6 hrs/day (SOR:A)1 o Severe amblyopia: patching for 6 hrs/day equal to full time occlusion o Moderate amblyopia: patching for 2 hrs/day equal to 6 hrs/day  Penalization (vision blurring) with topical ophthalmic atropine equal to patching o Consider atropine in children who cannot comply with patching  o Atropine sulfate 1%. 1 drop in unaffected eye daily, 2-7 days/week (SOR:A)2, 6 3. Visual deprivation amblyopia (cataracts, vitreous hemorrhage, corneal scar/opacity) o surgical repair can be considered in these cases (SOR:B)3  Further Management:  1. Referral to ophthalmology recommended 2. Treatment and follow-up until maximal visual acuity obtained and/or until age 9-10 3. Long term treatment includes patient/parent education on use of eye protection during activities  Follow-Up   1. Depends on type, severity and age of patient 2. Generally, younger patients require closer follow-up (Amblyopia CPG)3 Amblyopia Page 4 of 4    3.11.12 Prognosis  1. 75% of amblyopic children younger than 7 years have significant improvement in amblyopic eye (to 20/30 or better) after treatment. (SOR:A)3  Prevention  1. Periodic eye and vision screening to detect pediatric eye disorders.  2. Reduction or prevention of risk factors: o premature birth and detrimental prenatal environmental,  o influences such as substance abuse and smoking   Patient Education 1. http://www.aafp.org/afp/2007/0201/p368.html 2. http://familydoctor.org/460.xml 3. http://www.aapos.org   References: 1. Shotton K, Powell C, Voros G, Hatt SR. Interventions for unilateral refractive amblyopia. Cochrane Database of Systematic Reviews, 2008, OCT 8, article No.: CD005137.  2. Doshi NR, Rodriguez ML. Amblyopia. American Family Physician. 2007 Feb 1; 75(3):361-367. 3. American Academy of Ophthalmology Pediatric Ophthalmology/Strabismus Panel. Amblyopia. San Francisco (CA): American Academy of Ophthalmology; 2007. 28 p. Available online at: http://www.guidelines.gov/content.aspx?id=11751 4. Robaei D, Kifley A, Gole GA, Mitchell P. The impact of modest prematurity on visual function at age 6 years: findings from a population-based study. Archives of Ophthalmology. 2006 Jun; 124(6):871-7. 5. Taylor K, Elliott S. Interventions for strabismic amblyopia. Cochrane Database of Systematic Reviews, 2011 Aug 10, article No.: CD006461 6. Powell C, Hatt SR. Vision screening for amblyopia in childhood. Cochrane Database of Systematic Reviews, 2009 Jul, article No.: CD005020     Authors:  Elizabeth Hutchinson, MD, Swedish FMRP – First Hill, WA  & Jarret Sands, DO, Madigan Army Medical Center, Tacoma, WA  Editor:  Robert Marshall, MD, MPH, MISM, CMIO,  Madigan Army Medical Center, Tacoma, WA  

Amblyopia

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Amblyopia

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