How Much Amblyopia Treatment Is Enough?

Amblyopia treatment is accepted by consensus as a valuable medical intervention.^{1 - 2} If amblyopia is not treated in children and adolescents, it results in a lifetime of unilateral or bilateral visual loss. Recent clinical trials have clarified many aspects of proper treatment. The Pediatric Eye Disease Investigator Group has demonstrated visual acuity improvement in most eyes with moderate amblyopia associated with strabismus or hypermetropic anisometropia. This outcome has been accomplished with eye patch occlusion or atropine penalization of the fellow eye.^{3 - 6} In many cases, minimally disruptive treatment protocols, such as patching for 2 hours per day or administering atropine eye drops twice weekly, have been effective. Indeed, investigators have found that an initial period of glasses correction alone before adding occlusion or other therapy can cure amblyopia in as many as one-third of affected children and improve it in many others.^{7 - 8} It might be noted that, despite occlusion therapy's long history of clinical application, it was not until 2006 that this therapy was shown to be more effective than no treatment in controls given glasses.⁹

Although these treatment results are encouraging, they should not obscure that current treatments are not completely effective. Even with reasonable patient compliance in the setting of a clinical trial, residual visual acuity deficit is common. In 1 study of conventional treatment with patching or atropine eye drops, mean visual acuity improved from 20/60 to 20/32, leaving the amblyopic eye on average 1.8 lines poorer than the fellow eye.¹⁰ About 1 in 4 children had acuities worse than 20/30 two years after treatment was initiated. For children with more severe amblyopia at the outset, residual amblyopia is even more common.

Compounding the incomplete treatment effect is that not all preschool- and elementary school–aged children and their parents are compliant with therapy. This is especially true for patients with deprivation forms of amblyopia, for example, from unilateral aphakia.

The problem of inadequate amblyopia treatment because of poor compliance has led to the suggestion of numerous treatments, including arm splints and/or casts, combined patching, atropine penalization,^{11 - 12} and oral levodopa, with the intention of improving parents' ability to deliver treatment.¹³ In 1 definitive study, children who were previously noncompliant with occlusion were admitted to a hospital for constant supervision of their occlusion.¹⁴ Both their patching compliance and acuity improved. Compliance may also be improved by teaching parents about the importance of therapy to developing life-long good vision in an affected eye, especially the need to complete therapy when their child is young.¹⁵

In the Archives, 2 research groups have presented 1-month pilot studies of novel approaches to enforce compliance with occlusion therapy among previously noncompliant children. They each rely on the use of eye occlusion among children with severe amblyopia. The authors include strabismic, anisometropic, and deprivation forms of amblyopia. In their study, Rubab and colleagues¹⁶ glued a conventional patch to the faces of 5 patients using a commercially available medical skin adhesive. They applied the monomeric 2-octyl cyanoacrylate formulation to the adhesive portion of the patch. Before the adhesive set-up, the patch was positioned over the eye, taking care to avoid getting the adhesive in the eye. Other than mild redness of the skin, the treatment was apparently well accepted by the families and improved the duration of daily occlusion therapy. Each patch was intended to stay in place for 1 week, with removal and reapplication performed in the office. In most cases, the patch did stay on for at least 4 days each week and there was said to be increased acceptance over the course of the month. However, the sample provides insufficient data to assess acceptance or effectiveness of the increased duration of patching on visual acuity. Although patch removal was noted to be easy, the complications associated with parents inadvertently applying the adhesive to the ocular surface during placement, perhaps when the child suddenly jerked out of the way, are concerning with widespread adoption of this technique. For clinicians and parents interested in adopting this technique, the high-viscosity adhesive formulation could be considered, as it may be less likely to spread into the eye during patch placement.

Arnold and colleagues¹⁷ took an even more aggressive approach in 10 children who had not been compliant with amblyopia treatment by suturing a polycarbonate occluder to the skin of the children's faces for 1 month. The compliance measures attempted before the sutured occluder were not described. The sutured occluder was fabricated from shower-stall window plastic and molded to fit each child's face. Facial scarring on the brow and cheeks was described as “acceptable,” but the details of that assessment are not reported. As in the case of the hospital-admitted patients noted previously, these 10 children exhibited a substantial improvement on average: 3 lines of visual acuity during a 1-month treatment period. However, since there were neither controls nor long-term follow-up, it is uncertain whether this approach was more successful than standard treatment alternatives. There was also no assessment of the impact of this treatment on quality of life.

Although conventional treatments have been reasonably well tolerated in the short term,¹⁸ many clinicians will recall patients of all ages who described the unpleasantness, frustration, and social stigma associated with wearing a patch as a child or parents who can no longer treat their children owing to weariness from constant negotiating. I am concerned that the escalation of treatment intensity as described in these 2 articles may increase the risk of psychological adverse effects on the children and their caregivers. Future studies should be designed to evaluate this issue.

These 2 studies raise another important issue. Before we adopt increasingly aggressive treatments to manage treatment noncompliance or reduce the amount of residual amblyopia in the population, we need to examine the goals for amblyopia therapy and consider just what methods are justified in their achievement. Amblyopia treatment is considered cost-effective compared with other health care interventions.^{2 ,19} However, there remains substantial uncertainty in these studies as to the effect of treatment on quality of life. For instance, these economic modeling studies do not account for the impact of adaptation to the visual impairment. A large cohort study of adults in the United Kingdom was unable to find functionally or clinically significant differences in educational, social, or employment attainment between amblyopic and control patients.²⁰ On the other hand, a questionnaire-based study of adults with amblyopia and strabismus on their quality of life found life-long benefits.²¹ In summary, as we continue to refine our treatments of amblyopia, we need long-term studies documenting improved treatment effectiveness and an associated improvement of quality of life measured by educational, social, and employment outcomes.

Correspondence: Dr Repka, Wilmer Ophthalmological Institute, Johns Hopkins Hospital, 600 N Wolfe St, Room Wilmer 233, Baltimore, MD 21287-9028 (mrepka@jhmi.edu).

Financial Disclosure: None reported.

Funding/Support: This work was supported by grant EY11571 from the National Eye Institute.