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ORIGINAL ARTICLE
Year : 2019  |  Volume : 26  |  Issue : 2  |  Page : 71-76  

Clinical profile and treatment outcomes of amblyopia across age groups


Department of Ophthalmology, American University of Beirut Medical Center, Beirut, Lebanon

Date of Web Publication26-Aug-2019

Correspondence Address:
Dr. Christiane Al-Haddad
American University of Beirut Medical Center, Post Box 110236, Beirut
Lebanon
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/meajo.MEAJO_182_17

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   Abstract 


PURPOSE: The purpose is to study the clinical profile of amblyopia by age at diagnosis.
SUBJECTS AND METHODS: A retrospective chart review of 327 amblyopic patients over 7 years (September 2009–December 2016) was performed, divided by age at diagnosis into four groups: <3, 3–7, 8–15, and >15 years. Demographics, eye conditions and eye examination parameters including visual acuity (VA), refractive errors, and motility measurements were collected.
RESULTS: Mean age at diagnosis and follow-up time was 6.2 ± 6.1 years standard deviation (SD) and 12.4 months ± 20.6 SD, respectively. The most common overall cause of amblyopia was strabismus (37%) followed by anisometropia (36%). The main causes by age at diagnosis were: strabismus at <3 years, anisometropia at 3–7 years, anisometropia at 8–15 years, and mixed at >15 years. Significant improvement in VA with treatment was noted with age between 3 and 15 years (3–7 years,P= 0.001 and 8–15 years,P= 0.03).
CONCLUSIONS: Strabismus was the main cause of amblyopia at <3 years of age; anisometropia was more prevalent in older children (3–15 years). The fact that more than a quarter of our amblyopic patients were detected late (after the age of 8 years) underscores the need for expanded vision screening measures in young children.

Keywords: Age groups, amblyopia, anisometropia, strabismus


How to cite this article:
Al-Haddad C, Ismail K, Jurdi KW, Keaik M. Clinical profile and treatment outcomes of amblyopia across age groups. Middle East Afr J Ophthalmol 2019;26:71-6

How to cite this URL:
Al-Haddad C, Ismail K, Jurdi KW, Keaik M. Clinical profile and treatment outcomes of amblyopia across age groups. Middle East Afr J Ophthalmol [serial online] 2019 [cited 2019 Sep 17];26:71-6. Available from: http://www.meajo.org/text.asp?2019/26/2/71/265365




   Introduction Top


Amblyopia is defined as a decrease in the best-corrected visual acuity (VA) with no identifiable ocular pathology.[1] Its prevalence is estimated to be 0.5%–3.5% in preschool and school-aged children.[2] The treatment should be initiated before the critical age of 8 years when response to treatment decreases with increasing maturity of the visual pathway.[1],[2],[3],[4] Amblyopia can be caused by strabismus, anisometropia, deprivation, or by a combination.

In one study, 45% of patients had strabismus, 35% had combined anisometropia and strabismus, 17% had anisometropia alone, and 3% had deprivational amblyopia.[5] Other studies worked on establishing clinical characteristics of amblyopia but did not delve into a specific age group stratification. The Pediatric Eye Disease Investigator Group studies showed equal distribution of anisometropia and strabismus among patients <7 years.[6] With age, anisometropia became the more prominent amblyogenic factor; half of the adult amblyopes were anisometropic in one report.[7]

The efficacy of treatment prior to visual maturation is well established,[3] with lower response rates in adults.[3],[8] In Lebanon, scarce literature exists on the clinical characteristics of amblyopia. A survey done in 1996 on children aged 5–12 years showed that 5% of subjects had refractive error, suggesting that amblyopia may be underestimated.[9] It was thus important to conduct this study aiming to describe the clinical profile of amblyopic patients at the American University of Beirut Medical Center (AUBMC) across different age groups.


   Subjects and Methods Top


This study was a retrospective chart review of all patients diagnosed with amblyopia at the pediatric ophthalmology service, AUBMC between September 2009 and December 2016. The study was approved by the Institutional Review Board, and informed consent was waived because of the retrospective nature of the study.

Patient selection

Patients of any age were included if they had a diagnosis of amblyopia at presentation or later during follow-up. Amblyopia was defined as a 2-line interocular difference (IOD) in the best-corrected VA (BCVA), or a vision <20/30 with no underlying ocular pathology. For those who could not perform the optotype vision examination, the assessment of amblyopia depended on fixation preference (FP). This mostly applied to children <3 years old, or those with poor cooperation or developmental/speech delays. Patients presented for examination after failing school screening or due to family history of refractive errors or amblyopia or were referred from pediatricians' clinics.

Clinical definitions

Anisometropic amblyopia was defined as >1D spherical equivalent (SE) difference between the two eyes, or >1.5D cylindrical difference between the two eyes. Bilateral amblyopia was defined as a VA of <20/30 in both eyes in the presence of high refractive error (>3D SE). Strabismic amblyopia was defined as evidence of IOD in BCVA in patients with strabismus with no anisometropia or any underlying ocular pathology. Combined amblyopia was defined as amblyopia present in the setting of both strabismus and anisometropia. Deprivational amblyopia was defined in the setting of media opacities (cataract, corneal disease, or any known pathology) leading to sensory deprivation in the absence of anisometropia or strabismus. Treatment parameters were: occlusion therapy, response to therapy, and atropine penalization therapy which were reserved for patients with very poor compliance with occlusion therapy. Occlusion therapy varied with age of the patient and level of VA: for infants below 1 year of age, 2 up to 5 h of patch therapy was prescribed daily (half waking hours), for older children occlusion of 6–8 h daily was started and tapered after resolution of amblyopia. The resolution of amblyopia was defined as equal VA between fellow eyes or VA better than 20/30 in the amblyopic eye. For preverbal children, amblyopia was deemed resolved when the child showed equal fixation between the fellow eyes.

Data collection

Data collected included: age at diagnosis in years, gender, past medical history, past ocular history, initial and final VA (converted to Log Mar), ocular motility, stereoacuity (Titmus fly test), dilated fundoscopy, cycloplegic retinoscopy, slit lamp examinations, follow-up time, and duration and type of treatment. IOD in VA of the amblyopic and better-seeing eye was calculated by counting the difference in lines on ETDRS scale when recorded. Patching treatment was considered a failure if mean final VA in the amblyopic eye was worse than 20/30 (log Mar = 0.2).

Outcome

The study's main outcome was to describe the clinical profile of amblyopia in the Lebanese population presenting to AUBMC, and to compare the characteristics of amblyopia (etiology, visual function, refraction, treatment, and outcome) across four different age groups: <3 years (young and preverbal), 3–7 years (sensitive age of visual development), 8–15 years (those that could still be in the sensitive period but who may have slower response to treatment), and >15 years (older patients who were least likely to respond to any treatment).

Statistical analysis

Data were entered into SPSS v23 (IBM SPSS Statistics for Windows, Version 23.0. Armonk, NY: IBM Corp., USA). Means were computed and analysis was performed using Chi-square test for categorical variables and t- test for continuous variables; ANOVA was used for multivariate comparison. Statistical significance was set at P < 0.05.


   Results Top


Patient characteristics

A total of 403 charts were reviewed; 76 were excluded due to missing information. The study thus included 327 amblyopic patients; mean age at diagnosis was 6.2 ± 6.1 years standard deviation (SD). Age range was from 1 to 63 years. Female to male ratio was 0.9 and was similar across the age groups. Right to left eye ratio was 1.1. Amblyopia was previously diagnosed in 124/327 (38%) of patients prior to presentation. Mean follow-up time among all amblyopic patients was 12.4 m ± 20.6 SD. Follow-up time differed significantly by age: 10.3 m ± 17.3 SD for <3 years, 16.0 m ± 24.1 SD for 3–7 years, 7.9 m ± 15.5 SD for 8–15 years, and 8.3 m ± 15.9 SD for >15 years, (P = 0.027).

Most patients examined were Lebanese (317/327, 97%); others included: Syrian, Palestinian, American, Brazilian, Danish, Iraqi, and Jordanian. Deprivational amblyopia included microphthalmos, cataract, and glaucoma. Systemic conditions included asthma, microcephaly, allergies, hypertension, dyslipidemia, and cerebral palsy.

Causes of amblyopia

Strabismus and anisometropia were the main causes of amblyopia in the whole cohort. Strabismus was observed in 37%: 74/121 (61%) had esotropia, 18/121 (15%) had exotropia, 2/121 (2%) had hypertropia, and 27/121 (22%) had mixed forms of horizontal and vertical strabismus. Anisometropia was found in 36% of our cohort: 63/117 (54%) had hyperopia; 27/117 (23%) had myopia; and 27/117 (23%) had astigmatism. Strabismus was the most common underlying cause of amblyopia in patients <3 years (54/94, 57%). Strabismus and anisometropia were equally distributed among patients >15 years. When analyzing results within each age group, strabismus was more prevalent than anisometropia in patients younger than 3 years (P< 0.001). Anisometropia, on the other hand, was more prevalent than strabismus in the age groups of 3–7 years (P = 0.03) and 8–15 years (P = 0.006) [Table 1].
Table 1: Causes of amblyopia stratified by age groups

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Visual acuity measures

VA differed by cause of amblyopia (P = 0.04) with worse baseline VA found among anisometropic (0.5 ± 0.4) compared to strabismic (0.4 ± 0.4) patients. Baseline VA was similar across age groups. Among amblyopes, significant difference was found between baseline and final visual acuities (P = 0.001 for the age group 3-7 years and P = 0.03 for the age group 8-15 years), with children 3–7 years showing persistently significant results. Compared to initial IOD (4.7 ± 4.1), final IOD (3.1 ± 3.4) was significantly decreased among all amblyopic eyes. Statistical significance was seen in the age groups of 3–7 years and 8–15 years, but not in the younger or older groups. Patients with mixed amblyopia had greater IOD (5.9 ± 4.7) than those with deprivational (5.8 ± 4.6), strabismic (3.8 ± 3.9), or anisometropic amblyopia (4.6 ± 3.7), P = 0.005. Vision in the better-seeing eyes of patients was similar across age groups and when comparing baseline to final [Table 2]. In preverbal children <3 years with no numerical VA, mean time to resolution of amblyopia was 0.3 ± 0.4 years SD.
Table 2: Vision outcomes among the four age groups

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One hundred and sixty-nine subjects completed stereoacuity testing; the rest either had very poor vision or were too young/uncooperative. Differences among age groups were statistically significant (P< 0.001) with better stereoacuity noted among children diagnosed and treated earlier and worst among older patients [Table 2].

Treatment outcomes

Sixty-seven percent of patients (216/327) with amblyopia were patched. The mean duration of patching was 3.2 m ± 6.6 SD and varied significantly with age (P = 0), with a mean of 3.4 m ± 5.5 SD for patients aged <3 years, 4.1 m ± 7.5 SD for patients aged 3–7 years, 1.5 m ± 6.0 SD for patients aged 8–15 years, and 0.1 m ± 0.3 SD for patients aged >15 years. Atropine was used among 11/327, 3% of amblyopes. Thirty-five percent of those who patched were deemed successfully treated, with a mean final logMAR of 0.35 ± 0.36 (n = 162). No correlation was found between hours of patching and final vision in the group who received patch therapy. Among those who did not patch, no difference in amblyopic eye vision was noted in any age group.

Mean follow-up for patients <3 years whose vision was measured using FP was 10.3 m ± 17.2 SD. Since no objective VA (or IOD) could be recorded in this group, preverbal children (n = 41) were stratified by months to resolution of amblyopia: 9 (17%) showed improvement at <3 months, while 7 (14%) improved by 3–5 months and 9 (17%) by 6–12 months; 8 (15%) had a slow improvement after >1 years of follow-up; 19 (37%) had no improvement, but many were lost to follow-up with median follow-up of 3 months (mean 1.7 m ± 4.2 SD). Treatment success differed by cause of amblyopia (P = 0.03), with patients who had successful treatment being more likely strabismic or mixed amblyopes [Table 3].
Table 3: Comparison of treatment success versus treatment failure among amblyopic patients

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   Discussion Top


Strabismus and anisometropia were the main causes of amblyopia in the whole cohort. Strabismus was observed in 37%, being most common among patients younger than 3 years. Anisometropia was found in 36% of the cohort. Strabismus and anisometropia were equally common as causes of amblyopia among patients aged >15 years. This was an interesting finding and may be due to old cultural beliefs that strabismus was not treatable, contributing to a late presentation. Anisometropia as a cause was most common among patients aged 3–15 years.

A hospital-based study in India showed that strabismus was the most common cause of amblyopia (37%).[10] Two earlier studies similarly identified strabismus as the most common cause, with a younger mean age in strabismic compared to anisometropic groups.[5],[10] Discrepancies in etiology across studies could be attributed to differences in study population (hospital- vs. community-based and ethnicity).[9],[11] Another study conducted in Germany on adult amblyopes found that anisometropia was the predominant cause (49%), followed by strabismus (23%) and deprivation (17%).[12] Anisometropia was also the major cause of amblyopia among Saudi Arabian children (77%) in a school-based study.[13] This most likely reflects the failure of referral of anisometropic amblyopes and unreliable preschool screening.[5] We similarly found anisometropia to be the most prominent cause in our cohort after 3 years of age.

Among patients aged 3–15 years, a significant difference was found between baseline and final VA. However, no differences were found in children aged <3 years and more than 15 years. This may be due to poor compliance with patching, the small number of verbal children with numerical VA or the short follow-up in the age group of 3–15 years in our cohort. As expected no change in vision was noted in the group >15 years. These children are expected to be less responsive to treatment,[9],[11],[12],[13],[14] although improvement with patching has been reported in older patients.[6],[8],[9],[15] Stereo acuity outcomes paralleled VA scores.

Our study compared amblyopia characteristics across different age groups in a Middle Eastern population and correlated treatment outcomes, showing significant differences by age group and etiology. In any study on amblyopia, segregation into age groups is essential for meaningful interpretation of results. Only one study has previously similarly looked into amblyopia across age groups in India.[5] Results revealed that strabismus was the predominant cause of amblyopia among all age groups, in contrast to our differential distribution by age. Anisometropia, although not the major cause of amblyopia in their study, was predominantly seen after the age of 4 years. Two papers studied amblyopia among patients aged <3 years,[9],[16] which agreed with our results. Two studies investigated amblyopia among patients aged 3–7 years,[5],[8],[10],[16],[17] with strabismus being the main cause, as we found in our study. As shown in [Table 4], all studies were similarly hospital based, except for one study which was community based.[12] Our results emphasized the importance of vision screening at school age where amblyopia is most amenable to treatment, and where anisometropia could otherwise be missed. Anisometropia accounted for a large proportion of amblyopes in our series (who were diagnosed and treated late) and was significantly associated with treatment success.
Table 4: Comparative table of five amblyopia studies

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Limitations of our study include small sample size and arbitrary age group stratification. A difference in the stratification of age groups, with 3–7 years being the dominant age group in our study may have caused discrepancy from others, especially that this group may include nonverbal children. Our study also came from a hospital referral practice and may not reflect demographics of the general Lebanese population. The assessment of vision in preverbal children using FP and recording improvement/resolution of amblyopia was inherently subjective as expected in this very young population.


   Conclusions Top


Causes of amblyopia differed by age group with strabismus accounting for the majority of children aged <3 years and anisometropia for the majority of children aged between 3 and 15 years. Older age at diagnosis led to poorer visual outcomes and stereoacuity due to low compliance and decreased treatment effectiveness. Early and standardized amblyopia screening is thus needed as anisometropia can be asymptomatic; urgent referral is of paramount importance to prevent irreversible and lifelong visual morbidity.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Cotter SA, Tarczy-Hornoch K, Song E, Lin J, Borchert M, Azen SP, et al. Fixation preference and visual acuity testing in a population-based cohort of preschool children with amblyopia risk factors. Ophthalmology 2009;116:145-53.  Back to cited text no. 1
    
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McKean-Cowdin R, Cotter SA, Tarczy-Hornoch K, Wen G, Kim J, Borchert M, et al. Prevalence of amblyopia or strabismus in Asian and non-Hispanic white preschool children: Multi-ethnic pediatric eye disease study. Ophthalmology 2013;120:2117-24.  Back to cited text no. 2
    
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Holmes JM, Lazar EL, Melia BM, Astle WF, Dagi LR, Donahue SP, et al. Effect of age on response to amblyopia treatment in children. Arch Ophthalmol 2011;129:1451-7.  Back to cited text no. 6
    
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Scheiman MM, Hertle RW, Beck RW, Edwards AR, Birch E, Cotter SA, et al. Randomized trial of treatment of amblyopia in children aged 7 to 17 years. Arch Ophthalmol 2005;123:437-47.  Back to cited text no. 8
    
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Repka MX, Kraker RT, Holmes JM, Summers AI, Glaser SR, Barnhardt CN, et al. Atropine vs. patching for treatment of moderate amblyopia: Follow-up at 15 years of age of a randomized clinical trial. JAMA Ophthalmol 2014;132:799-805.  Back to cited text no. 11
    
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Elflein HM, Fresenius S, Lamparter J, Pitz S, Pfeiffer N, Binder H, et al. The prevalence of amblyopia in Germany: Data from the prospective, population-based Gutenberg health study. Dtsch Arztebl Int 2015;112:338-44.  Back to cited text no. 12
    
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Xiao O, Morgan IG, Ellwein LB, He M. Refractive Error Study in Children Study Group. Prevalence of amblyopia in school-aged children and variations by age, gender, and ethnicity in a multi-country refractive error study. Ophthalmology 2015;122:1924-31.  Back to cited text no. 13
    
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Aldebasi YH. Prevalence of amblyopia in primary school children in Qassim province, Kingdom of Saudi Arabia. Middle East Afr J Ophthalmol 2015;22:86-91.  Back to cited text no. 14
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Cabi C, Sayman Muslubas IB, Aydin Oral AY, Dastan M. Comparison of the efficacies of patching and penalization therapies for the treatment of amblyopia patients. Int J Ophthalmol 2014;7:480-5.  Back to cited text no. 15
    
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Park KH, Hwang JM, Ahn JK. Efficacy of amblyopia therapy initiated after 9 years of age. Eye (Lond) 2004;18:571-4.  Back to cited text no. 16
    
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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