Efficacy of Amblyopia Treatments in Children Up to Seven Years Old: A Systematic Review

Amblyopia is a neurodevelopmental disorder of the visual system that impairs the vision of millions of children worldwide. Amblyopia is best treated within the sensitive period of visual development when a child is up to seven years of age. Currently, the gold standard for early treatment of childhood amblyopia is patching, with new treatments emerging in recent years. We aim to evaluate the effectiveness of these newly developed treatments for amblyopia in children aged seven years and younger while comparing them to the current industry standard of patching. We searched online databases including PubMed, Google Scholar, and Cochrane Library for randomized controlled trials (RCTs), systematic reviews, meta-analyses, and narrative reviews relating to amblyopia treatment in children aged seven and younger. We only included articles and studies completed within the last five years and those written in the English language. After compiling a list of 297 articles, we removed duplicates, articles without an available full text, and those not relevant to our topic. Of the remaining 51 articles, we were left with 22 after reading abstracts and removing further irrelevant articles. We did a quality assessment on the remaining 22 articles and were left with 14 articles for our systematic review after removing eight low-quality articles. Of the 14 articles, we had eight RCTs, two systematic reviews, one comparative interventional study, and three narrative reviews. Seven of the articles contained data reinforcing the effectiveness of patching while comparing it to other treatment modalities. Three of the articles had data supporting spectacle correction, including a novel form called alternative flicker glass which delivers occlusion therapy via a spectacle frame with unique lenses, and ultimately deemed it at least as effective or more than patching. Data from three articles supported the use of surgery to successfully correct the angle of strabismus. Findings from five articles backed the use of pharmacologic therapy, specifically atropine when used alongside patching as a more effective alternative to patching solely. However, levodopa plus patching had no advantage over patching alone. Additionally, seven articles addressed the use of virtual reality (VR) and dichoptic therapy as prospective treatments for childhood amblyopia. VR therapy proved beneficial when used within one week after strabismus surgery. Dichoptic training was also effective in improving amblyopic-eye visual acuity when used on its own or in conjunction with spectacles. Furthermore, dichoptic movie therapy was found to be more effective than patching. Thus, we found multiple highly effective treatments for childhood amblyopia that are as effective or more than patching. Future studies should consider prescribing these treatments to larger cohorts while also performing a cost-benefit analysis for each treatment. In addition, more needs to be learned about the potential adverse side effects of these treatments, especially for pharmaceutical therapy.

Prevalence of residual amblyopia in adulthood and its association on educational outcome and quality of life in the Northern Finland Birth Cohort

PURPOSE

The purpose of the current study was to evaluate the prevalence of residual amblyopia in adults in a population screened and treated in childhood. We also wanted to evaluate the association of amblyopia on school success, level of education, and quality of life.

METHODS

This is a follow-up study of 2708 subjects of the Northern Finland Birth Cohort. At the age of 46, the subjects took part in ophthalmic examinations, including the measurement of best-corrected visual acuity (BCVA) and refraction. Residual amblyopia was defined as BCVA 20/30 or less (logMAR ≥0.2) in one or both eyes or a two-line interocular visual acuity difference and absence of any pathological ocular factors. The quality of life was assessed with a 15D questionnaire, and educational outcome, school success, and episodic memory with a CANTAB-PAL (paired associates learning) test were evaluated.

RESULTS

The prevalence of amblyopia in the current adult population aged 46 years was 1.3% (n = 36). At 14 years, the amblyopia subjects had had significant differences in mean spherical equivalent between the amblyopic and fellow eye and strabismus more often than controls. No significant differences were observed in the CANTAB-PAL test or in educational outcome. However, amblyopia subjects had significant difficulties in the 15D questionnaire in terms of vision (54% vs. 34%, p = 0.01).

CONCLUSION

Due to screening and treatment in childhood, the number of adults with residual amblyopia was low. Despite minor visual impairment and discomfort, they cope very well in life in terms of educational outcome and quality of life.

The Need for a Unified Protocol for Termination of Amblyopia Treatment

Introduction:

Many authors have investigated the methodology and outcomes of amblyopia treatment. However, the evidence on termination of treatment, specifically referring to the stability of visual outcome and timing of reviewing patients after treatment ends, has received less interest with no agreement on risk factors of visual regression.

Purpose:

To study the final part of amblyopia service with particular emphasis to stability of visual outcome; efficacy and timing of follow up after treatment ends.

Methods:

A retrospective review of patients discharged following treatment for strabismic and anisometropic amblyopia. Exclusion criteria were ocular pathology, poor attendance or poor compliance. Collected data included: age at the start of treatment, type and duration of treatment, number of visits, visual acuity (at start and end). Additionally, we analysed the duration and number of visits after stopping treatment, final visual acuity at discharge and duration of treatment with minimal change in vision.

Results:

Thirty-nine patients were identified with a mean age 4.2 ± 1.7SD years. Patients had an average of 116.6 ± 13.9SD visits over 30.5 ± 21.5SD months. Of these, 71.8% had occlusion only and 28.2% in combination with atropine. All but three patients had improved vision, with mean letters gained 13.2 ± 8.7SD LogMAR. The improvement in vision was statistically significant p < 0.005 and patients were further followed without treatment for 10 ± 13.5SD months over 5.2 ± 6.6SD visits. The mean final vision at discharge was not significantly different from vision at termination (p = 0.68) and we found no significant recurrence.

Conclusion:

Amblyopia treatment is effective; however, there is inconsistency in many aspects of ending treatment. Further improvement is needed to standardise care from termination of treatment up to discharge from service.

Rebalancing binocular vision in amblyopia

PURPOSE

Humans with amblyopia have an asymmetry in binocular vision: neural signals from the amblyopic eye are suppressed in the cortex by the fellow eye. The purpose of this study was to develop new models and methods for rebalancing this asymmetric binocular vision by manipulating the contrast and luminance in the two eyes.

METHODS

We measured the perceived phase of a cyclopean sinewave by asking normal and amblyopic observers to indicate the apparent location (phase) of the dark trough in the horizontal cyclopean sine wave relative to a black horizontal reference line, and used the same stimuli to measure perceived contrast by matching the binocular combined contrast to a standard contrast presented to one eye. We varied both the relative contrast and luminance of the two eyes' inputs, in order to rebalance the asymmetric binocular vision.

RESULTS

Amblyopic binocular vision becomes more and more asymmetric the higher the stimulus contrast or spatial frequency. Reanalysing our previous data, we found that, at a given spatial frequency, the binocular asymmetry could be described by a log-linear formula with two parameters, one for the maximum asymmetry and one for the rate at which the binocular system becomes asymmetric as the contrast increases. Our new data demonstrates that reducing the dominant eye's mean luminance reduces its suppression of the non-dominant eye, and therefore rebalances the asymmetric binocular vision.

CONCLUSIONS

While the binocular asymmetry in amblyopic vision can be rebalanced by manipulating the relative contrast or luminance of the two eyes at a given spatial frequency and contrast, it is very difficult or even impossible to rebalance the asymmetry for all visual conditions. Nonetheless, wearing a neutral density filter before the dominant eye (or increasing the mean luminance in the non-dominant eye) may be more beneficial than the traditional method of patching the dominant eye for treating amblyopia.

Two-year follow-up of a randomized trial of spectacles plus alternate-day patching to treat strabismic amblyopia

PURPOSE

  To compare spectacles plus alternate-day patching for 8 hr or more with spectacles plus patching for 8 hr or more 6 days weekly to treat strabismic amblyopia 1 year after a 1-year randomized trial.

METHODS

Forty children (mean age, 4.3 years) participated. Refractive correction was provided. The children were assigned to alternate-day patching for 8 hr or more or patching for 8 hr or more daily 6 days weekly. VA, binocular function, and refractive errors were measured after 2 years. The main outcome measure was the median VA change in the amblyopic eye after 2 years.

RESULTS

The median VA change in the amblyopic eye at the 2-year visit was significantly (p = 0.0453) greater with alternate-day patching (0.8 log unit) versus patching daily 6 days weekly (0.6 log unit). The final median VA in the amblyopic eyes was 0.0 logMAR in the alternate-day patching group and 0.1 logMAR in the daily patching group. Binocular function improved with both treatments. The median spherical equivalent (SE) refractive error increased in the fellow eyes (alternate-day patching, p < 0.0001; patching daily 6 days weekly, p = 0.0033); no change was found in the amblyopic eyes in either group.

CONCLUSIONS

The magnitude of the VA change 2 years after treatment with spectacles plus alternate-day patching for 8 hr or more was significantly greater than with spectacles plus daily patching for 8 hr or more 6 days weekly for strabismic amblyopia. However, the final median VA did not differ significantly between the two treatments.