Complications and Challenges of Therapy
Reverse amblyopia and new strabismus
Both occlusion therapy and pharmacologic treatment carry a risk of overtreatment, which can result in reverse amblyopia in the sound eye. Strabismus can also develop or worsen with amblyopia treatment (although strabismus can also improve with amblyopia treatment).
Full-time occlusion carries the greatest risk of reverse amblyopia and thus requires close monitoring. Consequently, most ophthalmologists do not use full-time occlusion in younger children. Children with binocular fusion, especially, may benefit from time spent viewing binocularly. The family of a strabismic child should be instructed to watch for a reversal of fixation preference with full-time occlusion and to report its occurrence promptly. Usually, iatrogenic reverse amblyopia can be treated successfully by judicious patching of the formerly worse-seeing, now better-seeing, eye. Sometimes, simply stopping treatment leads to equalization of vision.
During pharmacologic treatment, the risk of reverse amblyopia is greatest if daily treatment is coupled with undercorrection of hyperopic refractive error in the sound eye undergoing cycloplegia (see the section Refractive Correction, earlier in the chapter).
Lack of adherence to the therapeutic regimen is a common problem that can prolong the treatment period or lead to outright failure. If difficulties derive from a particular treatment method, the clinician should seek a suitable alternative. Adhesive and cloth patches may not be covered by medical insurance in the United States; if treatment cost is a burden, pharmacologic treatment may facilitate adherence. If the skin becomes irritated from patch adhesives, switching to a different brand or applying skin lotion after patching may help. A barrier application of tincture of benzoin can protect the skin from contact with adhesive and help when patches do not adhere because of perspiration; however, it can make patch removal more traumatic.
Families who seem to lack sufficient motivation should be counseled concerning the importance of the therapy and the need for consistency in carrying it out. They can be reassured that once an appropriate routine is established, the daily effort required is likely to diminish, especially if the amblyopia improves. For an older child, it can also be helpful for the physician to explain and emphasize the importance of treatment adherence directly to the child in an age-appropriate manner. Further, it is important for the family to understand that amblyopia treatment is performed primarily to improve vision rather than ocular alignment (even though ocular alignment may sometimes improve) and, conversely, that improving ocular alignment (with surgery or glasses) does not obviate the need for treatment of associated amblyopia.
Adherence to a patching regimen in older children can be improved by creating goals and offering rewards or by linking patching to play activities (eg, decorating the patch or patching while the child plays a video game). For infants and toddlers, adherence to a patching regimen depends greatly on parental engagement and commitment. Arm splints and mittens are sometimes used as a last resort.
Sometimes even conscientious application of an appropriate therapeutic program fails to improve vision at all or beyond a certain level. Complete or partial unresponsiveness to treatment occasionally affects younger children but more often occurs in patients older than 5 years. When there is a significant deviation from the expected treatment response despite good adherence, reexamination may reveal subtle optic nerve or retinal anomalies. Neuroimaging may be considered if an occult compressive optic neuropathy is suspected.
In a prognostically unfavorable situation, decisions about treatment should take into account the patient’s and parents’ wishes. Amblyopia is not always fully correctable, even in younger children. Primary therapy may reasonably be terminated if there is a lack of demonstrable progress over 3–6 months despite good treatment adherence. Progress or lack thereof may be harder to quantify in preverbal children, however, so longer treatment is appropriate in this setting.
When amblyopia treatment is discontinued after complete or partial improvement of vision, up to one-third of patients show some degree of recurrence. Reducing the occlusion regimen (to 1–2 hours per day) or the frequency of pharmacologic treatment for a few months before cessation is associated with a decreased incidence of recurrence, although no randomized trial has compared tapered and nontapered cessation. If recurrence occurs, vision can usually be improved again with resumption of therapy. In a study of children who were between 7 and 12 years of age when treated for amblyopia, the vision improvements that occurred seemed to be mostly sustained after cessation of treatment other than spectacles. Younger patients may require periodic monitoring until vision is stable with spectacle treatment alone (eg, until age 8–10 years). With stable vision, 12-month examination intervals are acceptable.
Hertle RW, Scheiman MM, Beck RW, et al; Pediatric Eye Disease Investigator Group. Stability of visual acuity improvement following discontinuation of amblyopia treatment in children aged 7 to 12 years. Arch Ophthalmol. 2007;125(5):655–659.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.