When amblyopia treatment fails, adherence is likely an issue

With patching, for example, parent-kept diaries tend to overestimate the actual patching time.¹ According to Dr. Kowal, this phenomenon may explain why PEDIG demonstrates no difference between prescriptions of 2 hours versus 6 hours per day, or of 6 hours versus full-time occlusion when parent self-reporting is used to measure adherence.

"The first thing to suspect when patching therapy isn't having the desired results is poor compliance," he said. "Don't forget that we are often placed in the situation of prescribing a treatment and waiting to see how effective our treatment instruction is, not how effective the treatment is."

"Parents don't like parading an obviously defective child," Dr. Kowal said. "They also don't like to inflict discomfort on their children. So it's a tough situation for everyone involved."

Patient adherence is a must if amblyopia therapy is to be successful, however, he added.

Dr. Kowal cited one study in which 14 children who received a diagnosis of newly identified amblyopia were measured for adherence with a patch that contained an electronic sensor (occlusion dose monitor).² The study took place over the course of 1 week, 6 months after the start of occlusion therapy.

The mean age of the patients was 4 years. Five of the patients had anisometropia, four had strabismus, and five had anisometropia and strabismus. Adherence was measured as the percentage of electronically registered occlusion time compared with the amount of prescribed time.

Satisfactory acuity increase following 6 months of occlusion therapy was defined as reaching any of the following criteria: acuity increase, expressed as a ratio between acuity of the amblyopic eye and acuity of the good eye, of more than 0.75; acuity of the amblyopic eye exceeding 0.5 as measured on a standard E-chart or Landolt-C chart; or a three-line increase in logMAR acuity.

In the eight patients in whom acuity increase was deemed satisfactory, the occlusion adherence rate during the study week was 80%. In the six in whom the acuity increase was unsatisfactory, the occlusion adherence rate was 34% (p = 0.04).

Treatment options

For ophthalmologists who are assured they are getting adequate patient adherence with their patching regimen but still are not achieving satisfactory results, Dr. Kowal suggested several other treatment options:

1. What he calls "Type A" parents are going to try to be perfect parents with a perfect adherence score. These parents are the type to say, "We did the patching exactly as you asked, but on Thursday, we only patched for 5 hours, so we made up for it with 7 hours on Friday."

2. "Type B" parents try to comply with your regimen but are busy and simply forget sometimes.

3. "Type C" parents are excuse-makers.

"These parents don't want to deal with it," Dr. Kowal said. "These are the types who will say, 'My child hates it,' 'We didn't do it for the past week because the child was sick,' 'We didn't do it because we were on vacation,' or 'We only do it on school days.'"

In these cases, it may take a little extra effort to achieve adherence, he said.

"Sometimes we find that the best way to get your therapy to work is to find a way to help the parents maintain enthusiasm for a task that everyone finds difficult," he said. "You have to keep the therapeutic environment alive for them, even if it means your office has to call them daily," Dr. Kowal said.

"Refractive surgery may work in a significant minority of anisometropic amblyopes," he said. "It's safe in the short term and probably safe in the medium term, but my personal experience with it is zero. And drug therapies, such as L-dopa [Atamet, Laradopa, Sinemet] or citicoline [Cognizin, Kyowa Hakko], are only anecdotally helpful in some cases of resistant amblyopia."

References

1. Awan M, Proudlock FA, Gottlob I. The effect and compliance of strabismic amblyopia monitored with the occlusion dose monitor. Invest Ophthalmol Vis Sci. 2003;44 E-abstract 4797.

2. Loudon SE, Polling JR, Simonsz HJ. Electronically measured compliance with occlusion therapy for amblyopia is related to visual acuity increase. Graefes Arch Clin Exp Ophthalmol. 2003;241:176-180.