Efficacy of amblyopia therapy initiated after 9 years of age

Effects of virtual reality on the treatment of amblyopia in children: A systematic review and meta-analysis

PROBLEM

Virtual reality technology has been used to treat amblyopia in children. However, it is unclear how virtual reality technology differs from conventional patching therapy in terms of effectiveness.

ELIGIBILITY CRITERIA

Eligible randomized controlled studies were retrieved from PubMed, Embase, Scopus, the Cochrane Library, and Web of Science through February 2023.

SAMPLE

Eight studies included 10 trials with 459 participants were included in the current meta-analysis. Two studies (Herbison et al., 2016; Huang et al., 2022) included two trials each. Thus, a total of ten trials were included in the current meta-analysis.

RESULTS

Overall, virtual reality technology treatment significantly improved visual acuity by 0.07 log MAR (95% confidence interval [CI], -0.11 to -0.02; P < 0.001; I2 = 94.4%) compared with traditional patching therapy. In addition, subgroup analyses also revealed that treatment with virtual reality technology was more effective when the child was younger than seven years old, or when the duration of the intervention was no more than twenty hours.

CONCLUSIONS

Virtual reality technology treatment showed significant effects in improving visual acuity in children who were seven years of age or younger with amblyopia.

IMPLICATIONS

Virtual reality technology treatment is effective in treating amblyopia in children. Virtual reality therapy is also entertaining and popular among children and can be applied to the treatment of amblyopia in children in the future.

Comparison of novel clinic-based approach (amblyopia school) Vs. home-based occlusion for amblyopia therapy - A retrospective study

Purpose

To compare visual outcomes of standard occlusion therapy at home versus clinic in amblyopic children.

Methods

A retrospective study of case records of children aged <15 years with diagnosis of strabismic or anisometropic amblyopia or both was conducted at a tertiary eye hospital located in rural North India between Jan 2017-Jan 2020. Those with at least 1 follow-up visit were included. Children with ocular co-morbidities were excluded. Treatment in clinic by admission or at home was based on the parents' discretion. Children in clinic group underwent part time occlusion & near work exercises for minimum 1 month, in classroom format which we called amblyopia school. Those in home group underwent part time occlusion as per PEDIG recommendations. Primary outcome measure was improvement in number of Snellen's lines at the end of 1 month & at final follow-up.

Results

We included 219 children with mean age of 8.8±3.23 years, out of which clinic group had 122 (56%) children. At one-month, visual improvement in clinic group (2.1±1.1 lines) was significantly greater than home group (mean=1.1±0.8 lines) (P < 0.001). Both groups continued to improve vision on follow-up, however the vision in the clinic group (2.9±1.2 lines improvement at mean follow-up of 4.1±1.6 months), continued to be better than home group (2.3±1.1 lines improvement at mean follow-up 5.1±0.9 months) (P = 0.05).

Conclusion

Clinic based amblyopia therapy in the form of an amblyopia school can help expedite visual rehabilitation. Thus, it may be a better option for rural settings where patients in general tend to be poorly compliant.

Awareness and Knowledge of Amblyopia: A Cross-Sectional Study Among the Population of Hail City, Saudi Arabia

Introduction Amblyopia, also known as the lazy eye, is the reduction of the best-corrected visual acuity of one or both eyes that cannot be attributed exclusively to a structural abnormality of the eye. This study investigated the Hail population's awareness of amblyopia. Methods A cross-sectional study was conducted in Hail, Kingdom of Saudi Arabia (KSA), from May to October 2022. Data entry and analysis were done using RStudio (R version 4.1.1). Results This study included 496 of the general population (23.8% males and 76.2% females), and the majority of them had a university degree (65.7%). Of the population, 52.4% knew the definition of amblyopia, 43.4% knew the treatment of amblyopia, and 85.1% knew the importance of checking the child's vision before school to ensure normal development. In 35.7% of the population, the main source of information was the internet and social media. The median knowledge score of participants was 4 (interquartile range (IQR): 3-5) with a minimum of 0 and a maximum of 9. Based on the univariate analysis, participants aged 41 years or older had significantly lower knowledge scores (β = -0.40, 95% confidence interval (CI): -0.81 to -0.99, p = 0.049), whereas respondents with a positive family history of amblyopia had a significantly higher knowledge score (β = 0.32, 95%CI: 0.02 to 0.61, p = 0.034). Conclusions This study assessed the awareness and knowledge of amblyopia among the population in Hail city. According to our data, we found a significantly poor awareness and knowledge compared to other big cities in the same country such as Riyadh and Jeddah. This indicates that knowledge in smaller cities is deficient in enough and accurate sources of knowledge of eye conditions.

Efficacy of vision therapy for unilateral refractive amblyopia in children aged 7-10 years

Background

There is a critical period for visual development, conventionally considered to be the first 6 years of life. Children aged 7 years and older are significantly less responsive to amblyopia treatment. This study investigated the efficacy of binocular vision therapy in amblyopic children aged 7–10 years.

Methods

This retrospective study enrolled 36 children with unilateral amblyopia who were divided into a case group (receiving vision therapy, optical correction, and part-time patching of the weaker eye) and a control group (receiving optical correction and part-time patching of the weaker eye). Visual acuity (VA) was measured at baseline, at the 3-month, 6-month, and 9-month visits, and 3 months after cessation of treatment.

Results

There were 19 subjects in the case group and 17 subjects in the control group. Mean VA in the case group improved from 0.39 ± 0.24 logMAR at baseline to 0.10 ± 0.23 logMAR at the endpoint of treatment (p < 0.001, paired t-test). Mean VA in the control group improved from 0.64 ± 0.30 logMAR at baseline to 0.52 ± 0.27 logMAR at the endpoint of treatment (p = 0.015, paired t-test). The improvement was significantly greater in the case group than in the control group (p = 0.006, two-samples independent t-test). All subjects underwent follow-up examinations within 6 to 12 months. There was no regression of VA in the case group 3 months after cessation of vision therapy. The patients in the case group who received visual therapy were with better VA improvement then patients with only optic correction and patching.

Conclusions

Vision therapy combined with conventional treatment (optical correction and part-time patching) is more effective than conventional treatment alone in children aged 7–10 years with unilateral refractive amblyopia. The treatment results not only in greater vision gain, but also in shorter duration of treatment.

A systematic review of Amblyopia prevalence among the children of the world

Objective: to assess the prevalence of Amblyopia disease in the children of the world. Methods: In order to perform this systematic review, PICO was considered as the research question. Then, the preferred keywords were searched in Medline (via PubMed), Embase, Scopus, Web of Science, and ProQuest databases. The retrieved citations were reviewed by two independent inspectors in a three-step process in terms of the title, abstract, and full-text, based on the inclusion criteria. The studies included in the review were critically evaluated and then were extracted by two dependent expert reviewers. Finally, the prevalence of Amblyopia disease in the children of the world was pooled by meta-analysis CMA v.2 software. The heterogeneity of the selected studies was evaluated using I2 and chi-square. Also, subgroup-analysis was performed using designs and continents. Results: Out of 952 retrieved citations, 131 studies were included. The total prevalence of Amblyopia in the children of the world was calculated to be 4.3% [Pooled Prevalence: 4.3%, 95% CI: 2.6%-7.00%, P-value 0.0001]. In addition, the heterogeneity of the studies was reported to be high (Q: 48281.18, df: 56, p-value 0.001, I-square: 99.88). The subgroup analysis showed that America had the highest (5.57%, 95% CI: 2.23%-13.94%, P-value 0.0001) prevalence, and the lowest prevalence of Amblyopia in the children of the world was seen in Africa (7.1%, 95% CI: 0.003%-172.53%, P-value 0.05). Conclusion: It can be concluded that the total prevalence of Amblyopia is 3.4%, but this estimate varies in all continents, especially in Africa. The major reason for this variation was reported to be the heterogeneity of studies. These assessments have investigated different populations in terms of severity of illness, age, and gender. Therefore, further worldwide high-quality and valid studies should be carried out to allow the calculation of the real prevalence of Amblyopia among children of the world. Abbreviations: VA = visual acuity, ALSPAC = Avon Longitudinal Study of Parents and Children, JBI = Joanna Briggs Institute, PRISMA = Systematic Review and Meta-analysis, CMA = Comprehensive Meta-analysis Software.

Clinical Profile and Treatment Outcomes of Amblyopia Across Age Groups

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.

Oral fluoxetine in the management of amblyopic patients aged between 10 and 40 years old: a randomized clinical trial

OBJECTIVE

The objective of this study is to assess the efficacy of oral fluoxetine therapy in improving the visual function of amblyopic patients aged between 10 and 40 years old.

METHODS

In this double-blinded, randomized, controlled trial (IRCT2016052428046N1; registered retrospectively), 40 eligible participants with anisometropic or mixed amblyopia were randomly assigned to either fluoxetine or placebo groups. Participants with anisometropia and logMAR best spectacle-corrected visual acuity (BSCVA) worse than 0.2 logMAR in the amblyopic eye or at least a two-line of difference in the BSCVA between the fellow eyes were included. Participants with significant ocular or systemic diseases were excluded. In both groups, the better eye of each patient was patched for 4-6 h a day during the study period. Participants in the treatment group were treated with oral fluoxetine for 3 months. Change in the Snellen BSCVA (after 3 months) was regarded as the primary outcome measure.

RESULTS

Data from 20 participants in the fluoxetine group and 15 participants from the placebo group were analyzed (aged 11-37 years). The magnitude of improvement in visual acuity (from baseline to 3 months after treatment) was significantly higher in the fluoxetine group (0.240 ± 0.068 logMAR; 2.4 line-gain) compared with the control group (0.120 ± 0.086 logMAR; 1.2 line-gain).

CONCLUSIONS

This study suggests beneficial effects of fluoxetine in the management of adult and adolescent amblyopia.

Fluoxetine does not enhance the effect of perceptual learning on visual function in adults with amblyopia

Amblyopia is a common visual disorder that is treatable in childhood. However, therapies have limited efficacy in adult patients with amblyopia. Fluoxetine can reinstate early-life critical period-like neuronal plasticity and has been used to recover functional vision in adult rats with amblyopia. We conducted a Phase 2, randomized (fluoxetine vs. placebo), double-blind, multicenter clinical trial examined whether or not fluoxetine can improve visual acuity in amblyopic adults. This interventional trial included 42 participants diagnosed with moderate to severe amblyopia. Subjects were randomized to receive either 20 mg fluoxetine (n = 22) or placebo (n = 20). During the 10-week treatment period, all subjects performed daily computerized perceptual training and eye patching. At the primary endpoint, the mean treatment group difference in visual acuity improvement was only 0.027 logMAR units (95% CI: −0.057 to 0.110; p = 0.524). However, visual acuity had significantly improved from baseline to 10 weeks in both fluoxetine (−0.167 logMAR; 95% CI: −0.226 to −0.108; p < 0.001) and placebo (−0.194 logMAR; 95% CI: −0.254 to −0.133; p < 0.001) groups. While this study failed to provide evidence that fluoxetine enhances neuroplasticity, our data support other recent clinical studies suggesting that improvement of vision can be accomplished in adults with amblyopia.

Effectiveness of the addition of citicoline to patching in the treatment of amblyopia around visual maturity: a randomized controlled trial

Aim:

To study the effectiveness of the addition of citicoline to patching in the treatment of amblyopia in the age group of 4-13 years.

Materials and Methods:

A randomized controlled trial, which included patients who were randomly divided into two groups. Both the groups received patching therapy till plateau was achieved in phase 1 of the study. Then in phase 2, group I received citicoline plus patching and group II continued to receive only patching.

Outcome Measures:

Outcome was measured by the visual acuity in logMAR every month in phase 1 till plateau was achieved and then for 12 months in phase 2.

Results:

No significant difference was found in the mean visual acuities in these two groups in phase 1 till plateau was reached. In phase 2, for the initial four months, there was no significant difference in the visual acuities in these two groups, at the respective intervals. However, five months onward, up to 12 months, there was a significant difference in the visual acuities in these groups. The result was the same in younger patients (< seven years of age) as well as in older patients (> seven years of age). In phase 2, the mean proportional improvement in group I was significantly more than that in group II, at two months and onward, at the respective intervals.

Conclusion:

The improvement in visual acuity with citicoline plus patching was significantly more than that with patching alone, in one year of treatment.

Prevalence of Amblyopia in School-Aged Children and Variations by Age, Gender, and Ethnicity in a Multi-Country Refractive Error Study

PURPOSE

To estimate the age-, gender-, and ethnicity-specific prevalence of amblyopia in children aged 5 to 15 years using data from the multi-country Refractive Error Study in Children (RESC).

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

Among 46 260 children aged 5 to 15 years who were enumerated from 8 sites in the RESC study, 39 551 had a detailed ocular examination and a reliable visual acuity (VA) measurement in 1 or both eyes. Information on ethnicity was available for 39 321 of these participants. This study focused on findings from the 39 321 children.

METHODS

The examination included VA measurements, evaluation of ocular alignment and refractive error under cycloplegia, and examination of the external eye, anterior segment, media, and fundus.

MAIN OUTCOME MEASURES

The proportion of children aged 5 to 15 years with amblyopia in different ethnic cohorts. Amblyopia was defined as best-corrected visual acuity (BCVA) of ≤20/40 in either eye, with tropia, anisometropia (≥2 spherical equivalent diopters [D]), or hyperopia (≥+6 spherical equivalent D), after excluding children with fundus or anterior segment abnormalities.

RESULTS

The overall prevalence of amblyopia was 0.74% (95% confidence interval, 0.64-0.83) with significant (P < 0.001) variation across ethnic groups: 1.43% in Hispanic, 0.93% in Chinese, 0.62% in Indian, 0.52% in Malay, 0.35% in Nepali, and 0.28% in African children. Amblyopia was not associated with age or gender. The most common cause of amblyopia was anisometropia.

CONCLUSIONS

In this study, the prevalence of amblyopia varied with ethnicity and was highest in Hispanic children and lowest in African children. Most cases were unilateral and developed before the age of 5 years. The impact of changes of definitions on prevalence estimates is discussed.

A morphological study of amblyopic eyes in children failing to achieve normal visual acuity after electronically monitored long-term occlusion treatment

PURPOSE

To search for morphological abnormalities in compliant unilaterally amblyopic children with poor occlusion treatment outcomes, for the first time with electronically recorded patching dosage. We included school children with remaining interocular logMAR (logarithm of the minimum angle of resolution) difference ≥ 0.3 after patching time of more than 22 months and 1300 h total in a previous prospective study.

METHODS

Six patients with a mean age of 11.19 years were included. Four patients had anisometropic amblyopia and two patients had a mixed strabismic and anisometropic amblyopia. Best-corrected visual acuity, cycloplegic refraction, dilated fundus examination, optic disc morphology and macular thickness using optical coherence tomography (OCT), retinal visual acuity, color perception, and the presence of a relative afferent pupillary defect (RAPD) were assessed. Paired t tests were performed to compare optic disc values and macular thickness of the amblyopic eyes to those of the fellow eyes.

RESULTS

Average (± SD) logMAR VA in the amblyopic eyes was 0.42 (±0.23) with a remaining average interocular difference (IOD) of 0.51 (± 0.23), despite electronically monitored occlusion treatment of more than 1300 h. All patients presented with hyperopia and a significantly different mean spherical equivalent of + 4.73 (± 2.73) D in the amblyopic eye compared with the fellow eye (p = 0.02). A statistically significant difference in macular thickness was found between amblyopic and fellow eyes, with amblyopic eyes having an increased average thickness (p = 0.0062) and total volume (p = 0.0091) of the macula. One patient had familial hereditary primary macrodisc in both eyes.

CONCLUSIONS

Our results provide evidence that average macular thickness and total macular volume tended to be increased among these compliant amblyopic children with unsatisfactory occlusion treatment outcomes. Further studies are warranted to evaluate whether morphological changes may have an impact on the effectiveness of amblyopia treatment. Moreover, our findings suggest that greater magnitude of hyperopia and anisometropia as well as older age may be risk factors associated with a poor visual acuity outcome among compliant amblyopic children.

Interventions for strabismic amblyopia

BACKGROUND

Amblyopia is reduced visual acuity in one or both eyes in the absence of any demonstrable abnormality of the visual pathway. It is not immediately resolved by the correction of refractive error. Strabismus develops in approximately 5% to 8% of the general population. The aim of treatment for amblyopia is to obtain the best possible level of vision in the amblyopic eye. Different treatment options were examined within the review.

OBJECTIVES

By reviewing the available evidence we wanted to establish the most effective treatment for strabismic amblyopia. In particular this review aimed to examine the impact of conventional occlusion therapy for strabismic amblyopia and to analyse the role of partial occlusion and optical penalisation for strabismic amblyopia.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2013, Issue 12), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to January 2014), EMBASE (January 1980 to January 2014), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to January 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 30 January 2014.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) for the treatment of strabismic amblyopia including participants of any age.

DATA COLLECTION AND ANALYSIS

Two authors working independently extracted and entered data into Review Manager 5 and then independently checked the data for errors.

MAIN RESULTS

We included three RCTs in this review. The studies reported mean logMAR visual acuity achieved. Mean difference in visual acuity was calculated. When comparing conventional part-time occlusion (with any necessary glasses), PEDIG 2006 reported that this treatment was more beneficial than glasses alone for strabismic amblyopia; the mean difference between groups was -0.18 LogMAR (statistically significant 95% confidence interval (CI) -0.32 to -0.04). Supplementing occlusion therapy with near activities may produce a better visual outcome compared to non-near activities after four weeks of treatment (PEDIG 2005). The results of the pilot study showed mean difference between groups was -0.17 LogMAR (95% CI -0.53 to 0.19). Results from a larger RCT (PEDIG 2008) are now available, showing that supplementing occlusion therapy with near activities may produce a better visual outcome after eight weeks of treatment; the mean difference between groups was -0.02 LogMAR (95% CI -0.10 to 0.06). One further article ia awaiting assessment as in its current format there is insufficient information to include (Alotaibi 2012).

AUTHORS' CONCLUSIONS

Occlusion, whilst wearing necessary refractive correction, appears to be more effective than refractive correction alone in the treatment of strabismic amblyopia. The benefit of combining near activities with occlusion is unproven. No RCTs were found that assessed the role of either partial occlusion or optical penalisation to refractive correction for strabismic amblyopia.

Ocular disorders in children with spastic subtype of cerebral palsy

AIM

To document common ocular abnormalities in children with spastic subtype of cerebral palsy (CP) and to find out whether any correlation exists between their occurance and etiologic factors.

METHODS

Totally 194 patients with the diagnosis of spastic type CP were enrolled in this retrospective study. Detailed ophthalmic examinations were performed. Demographic data and neuroradiological findings were documented. Kruskal-Wallis, Mann Whitney U, Pearson Chi-square tests and Student's t tests were used in the statistical analysis.

RESULTS

The mean age was 64.7±44.2 months on the first ophthalmic examination. Prevalences of diplegia (47.4%) and tetraplegia (36.1%) were found to be higher than the frequency of hemiplegia (16.5%) in our study population. Etiologic factor was asphyxia in 60.8% of the patients. Abnormal ocular findings were present in 78.9% of the patients. Statistically significant poor vision was detected in tetraplegia group among all the spastic ubtypes of CP (P=0.000). Anisometropia and significant refractive error were found in 14.4% and 70.1% of the patients, respectively. Thirty-six children (18.6%) had nystagmus and 107 children (55.2%) had strabismus. Lower gestational age and birth weight were statistically higher in patients with esotropia than exotropia (P=0.009 and P=0.024, respectively). Abnormal morphology of the optic disc was present in 152 eyes (39.2%). Severe periventricular leukomalacia (PVL) was found in 48 patients and statistically significant poor vision was detected in the presence of PVL (P=0.000).

CONCLUSION

Spastic diplegic or tetraplegic CP patients with positive neuroradiological symptoms, younger gestational age and lower birth weight ought to have detailed ophthalmic examinations as early as possible to provide best visual rehabilitation.

Can perceptual learning be used to treat amblyopia beyond the critical period of visual development?

BACKGROUND

Amblyopia presents early in childhood and affects approximately 3% of western populations. The monocular visual acuity loss is conventionally treated during the 'critical periods' of visual development by occluding or penalising the fellow eye to encourage use of the amblyopic eye. Despite the measurable success of this approach in many children, substantial numbers of people still suffer with amblyopia later in life because either they were never diagnosed in childhood, did not respond to the original treatment, the amblyopia was only partially remediated, or their acuity loss returned after cessation of treatment.

PURPOSE

In this review, we consider whether the visual deficits of this largely overlooked amblyopic group are amenable to conventional and innovative therapeutic interventions later in life, well beyond the age at which treatment is thought to be effective.

RECENT FINDINGS

There is a considerable body of evidence that residual plasticity is present in the adult visual brain and this can be harnessed to improve function in adults with amblyopia. Perceptual training protocols have been developed to optimise visual gains in this clinical population. Results thus far are extremely encouraging; marked visual improvements have been demonstrated, the perceptual benefits transfer to new visual tasks and appear to be relatively enduring. The essential ingredients of perceptual training protocols are being incorporated into video game formats, facilitating home-based interventions.

SUMMARY

Many studies support perceptual training as a tool for improving vision in amblyopes beyond the critical period. Should this novel form of treatment stand up to the scrutiny of a randomised controlled trial, clinicians may need to re-evaluate their therapeutic approach to adults with amblyopia.

Can human amblyopia be treated in adulthood?

Amblyopia is a common visual disorder that results in a spatial acuity deficit in the affected eye. Orthodox treatment is to occlude the unaffected eye for lengthy periods, largely determined by the severity of the visual deficit at diagnosis. Although this treatment is not without its problems (poor compliance, potential to reduce binocular function, etc) it is effective in many children with moderate to severe amblyopia. Diagnosis and initiation of treatment early in life are thought to be critical to the success of this form of therapy. Occlusion is rarely undertaken in older children (more than 10 years old) as the visual benefits are considered to be marginal. Therefore, in subjects where occlusion is not effective or those missed by mass screening programs, there is no alternative therapy available later in life. More recently, burgeoning evidence has begun to reveal previously unrecognized levels of residual neural plasticity in the adult brain and scientists have developed new genetic, pharmacological, and behavioral interventions to activate these latent mechanisms in order to harness their potential for visual recovery. Prominent amongst these is the concept of perceptual learning--the fact that repeatedly practicing a challenging visual task leads to substantial and enduring improvements in visual performance over time. In the normal visual system the improvements are highly specific to the attributes of the trained stimulus. However, in the amblyopic visual system, learned improvements have been shown to generalize to novel tasks. In this paper we ask whether amblyopic deficits can be reduced in adulthood and explore the pattern of transfer of learned improvements. We also show that developing training protocols that target the deficit in stereo acuity allows the recovery of normal stereo function even in adulthood. This information will help guide further development of learning-based interventions in this clinical group.

Interventions for strabismic amblyopia

BACKGROUND

Amblyopia is reduced visual acuity in one or both eyes in the absence of any demonstrable abnormality of the visual pathway. It is not immediately resolved by the correction of refractive error. Strabismus develops in approximately 5% to 8% of the general population. The aim of treatment for amblyopia is to obtain the best possible level of vision in the amblyopic eye. Different treatment options were examined within the review.

OBJECTIVES

By reviewing the available evidence we wanted to establish the most effective treatment for strabismic amblyopia. In particular this review aimed to examine the impact of conventional occlusion therapy for strabismic amblyopia and to analyse the role of partial occlusion and optical penalisation for strabismic amblyopia.

SEARCH STRATEGY

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2011, Issue 6), MEDLINE (January 1950 to June 2011), EMBASE (January 1980 to June 2011), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to June 2011), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) and ClinicalTrials.gov (www.clinicaltrials.gov). There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 1 June 2011.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) for the treatment of strabismic amblyopia including participants of any age.

DATA COLLECTION AND ANALYSIS

Two authors working independently extracted and entered data into Review Manager 5 and then independently checked the data for errors.

MAIN RESULTS

We included three RCTs in this review. The studies reported mean logMAR visual acuity achieved. Mean difference in visual acuity was calculated. When comparing conventional part-time occlusion (with any necessary glasses), PEDIG 2006 reported that this treatment was more beneficial than glasses alone for strabismic amblyopia; the mean difference between groups was -0.18 LogMAR (statistically significant 95% confidence interval (CI) -0.32 to -0.04). Supplementing occlusion therapy with near activities may produce a better visual outcome compared to non-near activities after four weeks of treatment (PEDIG 2005). The results of the pilot study showed mean difference between groups was -0.17 LogMAR (95% CI -0.53 to 0.19). Results from a larger RCT (PEDIG 2008) are now available, showing that supplementing occlusion therapy with near activities may produce a better visual outcome after eight weeks of treatment; the mean difference between groups was -0.02 LogMAR (95% CI -0.10 to 0.06).

AUTHORS' CONCLUSIONS

Occlusion, whilst wearing necessary refractive correction, appears to be more effective than refractive correction alone in the treatment of strabismic amblyopia. The benefit of combining near activities with occlusion is unproven. No RCTs were found that assessed the role of either partial occlusion or optical penalisation to refractive correction for strabismic amblyopia.

Eye patching as a treatment for amblyopia in children aged 10-16 years

PURPOSE

To investigate the effects of full-time patching regimen on the treatment of amblyopia in children aged 10-16 years.

METHODS

Forty-seven patients with a mean age of 12.09 ± 1.65 years were included in this study. All of the patients received eye patching for the entire day, 6 days a week, during the first 3 months. The patients who achieved visual acuity of 0.00 logMAR at the third month were provided with additional patching treatment (4-6 h/day). On the other hand, the patients who showed no change in their visual acuity or an increase of less than 0.00 logMAR at the third month had 3 more months of eye patching for the entire day, 6 days a week.

RESULTS

Prior to treatment, the best mean visual acuity of the amblyopic eyes was 0.48 ± 0.25 (range 1.00-0.15) logMAR. After follow-up, the visual acuity of the amblyopic eyes was 0.20 ± 0.22 (range 1.00-0.00) logMAR. Thus, visual acuity in the amblyopic eyes improved by 0.2 log unit or more in 38 of 47 patients (81%).

CONCLUSIONS

The present results show that patching in older children with amblyopia improves visual acuity with no serious complications. The use of patching in children to improve amblyopia seems promising.

Part-time occlusion therapy for amblyopia in older children

Aim:

To compare the efficacy of part-time versus full-time occlusion for treatment of amblyopia in children aged 7-12 years.

Materials and Methods:

Prospective interventional case series. One hundred children between 7-12 years of age with anisometropic (57), strabismic (25) and mixed (18) unilateral amblyopia were randomized (simple randomization) into four groups (25 each) to receive two hours, four hours, six hours or full-time occlusion therapy. Children were regularly followed up at six-weekly intervals for a minimum of three visits.

Statistical Analysis:

Intragroup visual improvement was analyzed using paired t-test while intergroup comparisons were done using ANOVA and unpaired t-test.

Results:

All four groups showed significant visual improvement after 18 weeks of occlusion therapy (P<0.001). Seventy-three (73%) of the total 100 eyes responded to amblyopia therapy with 11 eyes (44%), 17 eyes (68%), 22 eyes (88%) and 23 eyes (92%) being amblyopia responders in the four groups respectively, with the least number of responders in the two hours group. In mild to moderate amblyopia (vision 20/30 to 20/80), there was no significant difference in visual outcome among the four groups (P=0.083). However, in severe amblyopia (vision 20/100 or worse), six hours (P=0.048) and full-time occlusion (P=0.027) treatment were significantly more effective than two hours occlusion.

Conclusion:

All grades of part-time occlusion are comparable to full-time occlusion in effectiveness of treatment for mild to moderate amblyopia in children between 7-12 years of age unlike in severe amblyopia, where six hours and full-time occlusion were more effective than two hours occlusion therapy.

Neural mechanisms of recovery following early visual deprivation

Natural patterned early visual input is essential for the normal development of the central visual pathways and the visual capacities they sustain. Without visual input, the functional development of the visual system stalls not far from the state at birth, and if input is distorted or biased the visual system develops in an abnormal fashion resulting in specific visual deficits. Monocular deprivation, an extreme form of biased exposure, results in large anatomical and physiological changes in terms of territory innervated by the two eyes in primary visual cortex (V1) and to a loss of vision in the deprived eye reminiscent of that in human deprivation amblyopia. We review work that points to a special role for binocular visual input in the development of V1 and vision. Our unique approach has been to provide animals with mixed visual input each day, which consists of episodes of normal and biased (monocular) exposures. Short periods of concordant binocular input, if continuous, can offset much longer episodes of monocular deprivation to allow normal development of V1 and prevent amblyopia. Studies of animal models of patching therapy for amblyopia reveal that the benefits are both heightened and prolonged by daily episodes of binocular exposure.

Interventions for strabismic amblyopia

BACKGROUND

Amblyopia is reduced visual acuity in one or both eyes in the absence of any demonstrable abnormality of the visual pathway. It is not immediately resolved by the correction of refractive error. Strabismus develops in approximately 5% to 8% of the general population. The aim of treatment for amblyopia is to obtain the best possible level of vision in the amblyopic eye. Different treatment options were examined within the review.

OBJECTIVES

By reviewing available evidence we wanted to establish the most effective treatment for strabismic amblyopia. In particular this review aimed to examine the impact of conventional occlusion therapy for strabismic amblyopia and analyse the role of partial occlusion and optical penalisation for strabismic amblyopia.

SEARCH STRATEGY

We searched CENTRAL, MEDLINE, EMBASE and LILACS in October 2007. There were no language or date restrictions in the electronic searches for trials.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) for the treatment of strabismic amblyopia including participants of any age.

DATA COLLECTION AND ANALYSIS

Two authors working independently extracted and entered data into Review Manager 4.2 using the double data entry facility to check for errors.

MAIN RESULTS

We included two RCTs. The studies reported mean logMAR visual acuity achieved. Mean difference in visual acuity was calculated. When comparing conventional part-time occlusion (with any necessary glasses), PEDIG 2006 reported this treatment was more beneficial than glasses alone for strabismic amblyopia. Mean difference between groups was -0.18 (statistically significant 95% CI -0.32 to -0.04). Supplementing occlusion therapy with near activities may produce a better visual outcome compared to non-near activities after four weeks of treatment (PEDIG 2005). Mean difference between groups was -0.17 (95% CI -0.53 to 0.19). However, this data is from a pilot study and the full data set will be added to updates of the review when available.

AUTHORS' CONCLUSIONS

Occlusion, whilst wearing necessary refractive correction, appears to be more effective than refractive correction alone in the treatment of strabismic amblyopia. Combining occlusion and refractive correction with near activities may be more effective than occlusion and refractive correction alone. Further study of the role of near activities is necessary before a more definitive conclusion can be made. Results of a full trial are expected within the coming year. No RCTs were found that assessed the role of either partial occlusion or optical penalisation to refractive correction for strabismic amblyopia.

Outcomes of 6 hour part-time occlusion treatment combined with near activities for unilateral amblyopia

PURPOSE

To evaluate the outcome of the part-time occlusion therapy with near activities in monocular amblyopic patients according to gender, age, severity of amblyopia, and the cause of amblyopia.

METHODS

Fifty eight patients who were prescribed part-time occlusion therapy with near activity from July 1998 to October 2004, were included in this retrospective study. All patients were divided into groups by gender, age, severity of amblyopia, and the cause of amblyopia. Main outcome measures were best corrected visual acuity, line improvement, and success rate.

RESULTS

At the end of patch therapy, visual acuity improved from baseline by an average of 3.2+/-2.5 lines (0.33+/-0.26 log MAR), and follow-up period was 19.71+/-14.61 months (1.62+/-1.20 years). At the last follow-up, visual acuity improved from baseline by an average of 3.7+/-2.4 lines (0.38+/-0.26 log MAR), and follow-up period was 37.41+/-25.83 months (3.08+/-2.12 years). The success rate was 86% (50 patients) at the end of patch therapy. In 44 patients out of 50 patients (88%), the visual acuity was maintained. While 43 patients out of 47 patients who were less than 7 years old (91%) achieved success, 7 patients out of 11 patients 7 years or older (64%) achieved success (p=0.035).

CONCLUSIONS

Six-hour part-time occlusion treatment combined with near activities appears to be favorable in treating 58 children during follow-up of mean 3.08 years. The significant factor was the age at initial treatment.

Assessment of a computer-based treatment for older amblyopes: the Glasgow Pilot Study

PURPOSE

There have been few viable alternatives to patching the better eye as a treatment of amblyopia for more than two centuries. The success of patching depends on compliance, which is problematic for up to 59% of children and their families.

METHODS

This pilot study trialled the interactive binocular treatment (I-BiT) system as an alternative amblyopia treatment in 12 older amblyopes (6.1-11.4 years, median 8.2), who had not complied with or responded to occlusion. Virtual reality images were projected to each eye simultaneously via a headset during eight treatment sessions of 25-min duration. Outcome measures were changes in high- (HCVA) and low-contrast log MAR acuity (LCVA) at 1 week, 4 weeks and a final follow-up (3-18 months) after the final treatment.

RESULTS

Sustained improvements in HCVA were observed in seven children (58%) and in LCVA in eight children (67%), including two for whom amblyopia was eliminated. Five children had visual acuities equivalent to 6/12 or better at least 6 months after stopping treatment, compared with one child prior to treatment. Significant improvements in HCVA occurred up to the fourth treatment; in LCVA to the seventh treatment.

CONCLUSION

Sustained improvements in visual acuity were observed for 58% of this small group of children using the I-BiT system, despite prior failure with conventional treatment. This offers hope for a potential time-saving alternative to patching, in which compliance can easily be monitored, but the results need to be validated by means of a randomised controlled trial.

Adult visual experience promotes recovery of primary visual cortex from long-term monocular deprivation

Prolonged visual deprivation from early childhood to maturity is believed to cause permanent visual impairment. However, there have been case reports of substantial improvement of binocular vision in human adults following lifelong visual impairment or deprivation. These observations, together with recent findings of adult ocular dominance plasticity in rodents, led us to re-examine whether adult primary visual cortex (V1) is capable of any recovery following long-term monocular deprivation starting in development. Using mice as a model, we find that monocular deprivation from early development to mature ages (well past the critical period) severely impaired binocular vision by reducing the amplitude of responses elicited by stimulation of the deprived eye. Surprisingly, we find little effect on nondeprived eye responses. Restoration of binocular vision in mature adults yields modest but significant improvement of visual responses in V1. Remarkably, we find that when binocular vision is followed by occlusion of the nondeprived eye, visual responses in V1 recover almost fully, as measured by visual evoked potential amplitude, spatial frequency threshold, and single-unit activity. We conclude that adult V1 can recover from long-term deprivation when provided with an optimal regimen of visual experience.

Stability of visual acuity after the cessation of amblyopia treatment: review of the literature

INTRODUCTION AND PURPOSE

The treatment of amblyopia in children is frequently discussed in the literature. Less attention, however, has been given to the durability of the visual acuity results attained with therapy. The objective of this review is to conduct an in-depth analysis of the existing literature, on the stability of visual acuity following cessation of amblyopia treatment, and to identify any gaps in the literature, which could guide future investigations.

RESULTS

There did not appear to be any one consistent risk factor affecting the stability of vision after cessation of amblyopia treatment. Most of the reviewed studies varied with respect to lengths of follow-up visits, patient population, and method of visual acuity assessment. There was also a generalized lack of standardization of visual acuity measurements in these previous investigations. Only one of the studies analyzed was a prospective design.

CONCLUSION

The area of study in amblyopia is fraught with contradictions. It is obvious from this review that there exists uncertainty regarding the recurrence of amblyopia following treatment. Previous studies have failed to identify any common, predictive, influencing factors necessary for the maintenance of visual acuity after cessation of therapy. Also lacking is discussion on the potential role that therapy tapering plays in the recurrence of amblyopia following the cessation of treatment.

Legislative issues facing pediatric ophthalmology in 2006

PURPOSE OF REVIEW

There has been a surge in legislative activity concerning children's vision in recent years. This review will summarize and compare newly enacted state statutes and review legislation that has been introduced at both the state and federal level. Detailed reference sites are provided and may be a useful resource for those involved in legislative advocacy.

RECENT FINDINGS

The legislative arena has often mirrored the disparate views of ophthalmology and optometry regarding the most appropriate methods for identifying vision problems in young children. While state legislation mandating comprehensive eye examinations for all asymptomatic and risk free children was passed in Kentucky in 2000, no other state since has successfully enacted and implemented similar legislation. In contrast, numerous states, have enacted mandatory preschool vision screening legislation. Federal legislation, introduced separately by ophthalmology and optometry, would provide funds for uninsured children's eye exams, but the two bills have important differences in eligibility requirements. Issues such as eye safety and retinoblastoma detection have also been addressed through the legislative process.

SUMMARY

There has been a myriad of state and federal legislative activity in the area of children's vision. The momentum is likely to continue as additional states file new legislation.

Part-time occlusion therapy for anisometropic amblyopia detected in children eight years of age and older

Purpose

To determine the outcome of part-time occlusion therapy in children with anisometropic amblyopia detected after they were 8 years of age.

Methods

We analyzed 29 eyes with anisometropic amblyopia in children 8 years of age and older. The mean age was 8.79±0.98 (range 8~12) years old. The subjects whose best-corrected visual acuity (BCVA) did not improve by two lines or better within 2 weeks of wearing glasses full-time were prescribed occlusion therapy for 6 hours a day outside of school hours, along with the instruction to wear glasses full-time. Subjects who complied with occlusion for more than 3 hours a day were considered to comply well.

Results

The major component of the anisometropia was hyperopia in 51.7% of the subjects, and hyperopia plus astigmatism was found in 24.1%. The mean pretreatment BCVA score was 0.51±0.23 (LogMAR). Compliance was 89.66%. The mean posttreatment BCVA was 0.03±0.01 (LogMAR), and the success rate, based on a posttreatment BCVA of 0.1 (LogMAR) and better, was 96.43%. It took an average of 4.79±3.35 months to reach the desired posttreatment BCVA. The mean posttreatment stereopsis was 79.78±37.61 seconds of arc. The recurrence rate was 8%. The visual improvement was related to the degree of compliance (p=0.000). The time taken to reach the posttreatment BCVA was shorter in subjects with a better pretreatment BCVA (p=0.019), but it did not relate to the compliance (p=0.366).

Conclusions

The most common component of anisometropia detected after 8 years of age was hyperopia. The part-time occlusion therapy, which had been carried out after school hours, was successful in most cases.

Amblyopia

Results from recent randomised clinical trials in amblyopia should change our approach to screening for and treatment of amblyopia. Based on the current evidence, if one screening session is used, screening at school entry could be the most reasonable time. Clinicians should preferably use age-appropriate LogMAR acuity tests, and treatment should only be considered for children who are clearly not in the typical range for their age. Any substantial refractive error should be corrected before further treatment is considered and the child should be followed in spectacles until no further improvement is recorded, which can take up to 6 months. Parents and carers should then be offered an informed choice between patching and atropine drops. Successful patching regimens can last as little as 1 h or 2 h a day, and successful atropine regimens as little as one drop twice a week. Intense and extended regimens might not be needed in initial therapy.

Controversy in amblyopia management

BACKGROUND AND PURPOSE

Much has been written about amblyopia treatment. However, there is no consensus on the most efficacious therapeutic modality for amblyopia. The intensity of therapy needed to maximize visual acuity is also widely debated. The diversity of opinions emphasizes that the optimum treatment for amblyopia is unknown. Part of the uncertainty stems from the lack of standardization in the management of amblyopia. The objective of this paper is to conduct an in-depth review of the literature in an attempt to clarify the amblyopia treatment conundrum.

CONCLUSIONS

The treatment of amblyopia in children is frequently discussed in the literature. It is obvious from the literature that there is the need for prospective studies with consistent controls, clear definitions of what constitutes successful therapy endpoints, and standardization of testing procedures.

Amblyopia: diagnostic and therapeutic options

PURPOSE

To provide an overview of the current state of knowledge of amblyopia and highlight recent advances in diagnosis and treatment.

DESIGN

Review of literature and perspective.

METHODS

MEDLINE search for amblyopia, with a review of all recent literature adding authors' personal perspectives on the findings.

RESULTS

Increased awareness of amblyopia and better screening techniques are required to identify children who are at risk for amblyopia at a younger age. Randomized, controlled trials have established atropine penalization as a viable alternative to occlusion therapy, have suggested that less treatment may be better tolerated and as effective as more traditionally used dosages, and have found no compelling evidence that treatment is beneficial clinically for older (over age 10) children with amblyopia.

CONCLUSION

Early detection and treatment of amblyopia can improve the chances for a successful visual outcome. Considering that the conditions that place a patient at risk for amblyopia can be identified, that amblyopia responds to treatment, and that well-tolerated treatments for the condition are now recognized, it is not unreasonable to imagine that, in the near future, severe amblyopia could be eliminated as a public health problem.

Contemporary issues in amblyopia treatment

PURPOSE

The aim of this report is to review the contemporary research in amblyopia treatment and how it will affect clinical practice patterns.

METHODS

Topics addressed include prescribing the optimal refractive correction, the most effective treatment, duration and intensity of treatment, regression after treatment, the upper age for treatment, and the chance of the amblyope losing his or her sound eye.

RESULTS AND CONCLUSIONS

The optimal refractive correction is best determined with cycloplegic retinoscopy; pharmacologic penalization can be as effective as patching in children with moderate amblyopia; less-intense treatment regimens have been found to be as effective as more-intense treatment regimens; regression can occur in as many as 25% of all treated patients; some older amblyopes can be treated successfully; and the amblyope has a higher chance of becoming blind than the nonamblyope.

Voxel-based analysis of MRI detects abnormal visual cortex in children and adults with amblyopia

Amblyopia, sometimes called "lazy eye," is a relatively common developmental visual disorder well characterized behaviorally; however, the neural substrates associated with amblyopia in humans remain unclear. We hypothesized that abnormalities in the cerebral cortex of subjects with amblyopia exist, possibly as a result of experience-dependent neuronal plasticity. Anatomic magnetic resonance imaging (MRI) and psychophysical vision testing was carried out on 74 subjects divided into two age ranges, 7-12 years and 18-35 years, and three diagnoses, strabismic amblyopia, anisometropic amblyopia, and normal vision. We report a behavioral impairment in contrast sensitivity for subjects with amblyopia, consistent with previous reports. When the high-resolution MRI brain images were analyzed quantitatively with optimized voxel-based morphometry, results indicated that adults and children with amblyopia have decreased gray matter volume in visual cortical regions, including the calcarine sulcus, known to contain primary visual cortex. This finding was confirmed with a separate region-of-interest analysis. For the children with amblyopia, additional gray matter reductions in parietal-occipital areas and ventral temporal cortex were detected, consistent with recent reports that amblyopia can result in spatial location and object processing deficits. These data are the first to provide possible neuroanatomic bases for the loss of binocularity and visual sensitivity in children and adults with amblyopia.

Amblyopia characterization, treatment, and prophylaxis

Amblyopia has a 1.6-3.6% prevalence, higher in the medically underserved. It is more complex than simply visual acuity loss and the better eye has sub-clinical deficits. Functional limitations appear more extensive and loss of vision in the better eye of amblyopes more prevalent than previously thought. Amblyopia screening and treatment are efficacious, but cost-effectiveness concerns remain. Refractive correction alone may successfully treat anisometropic amblyopia and it, minimal occlusion, and/or catecholamine treatment can provide initial vision improvement that may improve compliance with subsequent long-duration treatment. Atropine penalization appears as effective as occlusion for moderate amblyopia, with limited-day penalization as effective as full-time. Cytidin-5'-diphosphocholine may hold promise as a medical treatment. Interpretation of much of the amblyopia literature is made difficult by: inaccurate visual acuity measurement at initial visit, lack of adequate refractive correction prior to and during treatment, and lack of long-term follow-up results. Successful treatment can be achieved in at most 63-83% of patients. Treatment outcome is a function of initial visual acuity and type of amblyopia, and a reciprocal product of treatment efficacy, duration, and compliance. Age at treatment onset is not predictive of outcome in many studies but detection under versus over 2-3 years of age may be. Multiple screenings prior to that age, and prompt treatment, reduce prevalence. Would a single early cycloplegic photoscreening be as, or more, successful at detection or prediction than the multiple screenings, and more cost-effective? Penalization and occlusion have minimal incidence of reverse amblyopia and/or side-effects, no significant influence on emmetropization, and no consistent effect on sign or size of post-treatment changes in strabismic deviation. There may be a physiologic basis for better age-indifferent outcome than tapped by current treatment methodologies. Infant refractive correction substantially reduces accommodative esotropia and amblyopia incidence without interference with emmetropization. Compensatory prism, alone or post-operatively, and/or minus lens treatment, and/or wide-field fusional amplitude training, may reduce risk of early onset esotropia. Multivariate screening using continuous-scale measurements may be more effective than traditional single-test dichotomous pass/fail measures. Pigmentation may be one parameter because Caucasians are at higher risk for esotropia than non-whites.