Experts advocate atropine, 2-hour patching in certain amblyopia patients

Amblyopia affects approximately 3% of all children and causes more visual loss in the younger-than-40 age category than all other ocular diseases combined.

Treatment approaches for amblyopia differ depending on the age of the child. According to Jeffrey Cooper, MS, OD, clinical professor of optometry at SUNY, there are three sensitive age levels in amblyopia: 6 months to 2 years, 2 to 6 years and 6 years and up.

“The diagnosis and treatment of amblyopia during each of these periods is different,” Dr. Cooper told Primary Care Optometry News. “Because amblyopia treatment is the most effective between 9 months and 2 years, we tell all mothers that we want to see their children at 9 months of age.”

For years, patching the unaffected eye has been standard of care in amblyopia therapy. Patching forces the child to use the eye with amblyopia, stimulating vision improvement in that eye. An alternative to patching is the use of atropine drops for some candidates.

Atropine therapy

Dr. Cooper said atropine therapy is especially helpful for children who are resistant to wearing a patch. “Children who rip off the patch, won’t wear the glasses or have parents who are against patching can be treated with atropine 1% drops or ointment at nighttime,” he said. “I prefer the ointment, because it stings less and there is less systemic absorption. Parents should be advised that drops are as effective as patching.”

He cited a series of Amblyopia Treatment Studies (ATS) funded by the National Eye Institute. As a group, these studies suggest that in the 2- to 7-year-old age group, moderate amblyopes can be treated as effectively with atropine in the presence of emmetropia or hyperopia.

As a general rule, Dr. Cooper said, visual acuity may be expected to improve 1.2 lines in 5 weeks, 2.8 lines in 4 months and 3.1 lines in 6 months. More aggressive treatment was needed for amblyopes worse than 20/80 or 20/100.

“One may conclude that atropine has a strong role in the treatment of amblyopia,” Dr. Cooper said. “The recent ATS confirmed my clinical observations that atropine was almost as effective as patching in improving amblyopic eyes. Atropine is the way to go. It is easy for the parent, easy for the child and socially acceptable.”

Data recently released by the Pediatric Eye Disease Investigator Group (PEDIG) showed that while atropine may be comparable to patching for moderate amblyopia, patching reaches target visual acuity more quickly. In an article published in the Nov. 1 issue of Ophthalmology, PEDIG concluded that both patching and atropine benefit children ages 3 to 7 with a visual acuity range of 20/40 to 20/100.

However, the study stated that visual improvement is significantly faster for children with amblyopia who have visual acuities of 20/80 to 20/100 who were aggressively patched than those who were treated with atropine.

Susanna M. Tamkins, OD, a practitioner based in Coconut Grove, Fla., is a member of PEDIG and participates in the National Eye Institute-funded amblyopia studies.

“As a clinical investigator for the Amblyopia Treatment Studies, I prescribe atropine and occlusion for those study patients in whom its use is indicated by the protocols,” she said in an interview. “We have previously trialed atropine use in children 3 to 6 years of age and have found it to be an effective treatment for some patients. We are currently studying atropine use in conjunction with occlusion in older patients.”

Full-time vs. part-time patching

For cases in which patching is used, one issue confronting practitioners is the duration of patching each day.

In the PEDIG study, between May 2001 and March 2003, 175 children with severe ambylopia were enrolled at 32 clinical sites into a randomized trial comparing the response to prescribing full-time vs. part-time patching. Patients were randomized to either full-time patching of the sound eye (all waking hours or all but one waking hour) or to 6 hours of patching per day. Each patching regimen was combined with at least 1 hour per day of intense near activities.

Visual acuity was measured using a standardized protocol (isolated surrounded HOTV optotypes) at study entry, at 5 weeks and by a masked examiner at the 4-month study outcome.

Visual acuity in the amblyopic eye improved a similar amount in both groups at the 4-month study outcome. The improvement in the amblyopic eye acuity from baseline to 4 months averaged 4.8 lines in the 6-hour group and 4.7 lines in the full-time group (p=0.45).

There was no evidence of a different rate of improvement between groups. At the interim 5-week visit, visual acuity also had improved by a similar magnitude: 3.5 lines in the 6-hour group and 3.7 lines in the full-time group.

Michael J. Bartiss, OD, MD, a pediatric optomerist/ophthalmologist in private practice in Pinehurst, N.C., further discussed the PEDIG results with Primary Care Optometry News.

“In summary, the study showed that 6 hours of prescribed daily patching produces an improvement in visual acuity that is similar in magnitude to the improvement produced with full-time patching in patients with moderate amblyopia, when combined with at least 1 hour of intense near activities.”

Dr. Bartiss indicated that he was not entirely surprised by the PEDIG study results.

“The purpose of patching is really to establish central, steady foveal fixation in the amblyopic eye. Foveal fixation allows ‘proper stimulation’ of the visual system with resultant improved visual function at the cortical level,” he commented. “Patching alone is a very ‘passive’ therapeutic approach. Near activities that require foveal fixation to improve performance is much more ‘active’ therapy with better feedback to the patient.”

Part-time vs. minimal-time patching

Dr. Tamkins cited details from the ATS. The results, as reported on the NEI Web site, state that visual acuity improved a similar amount in groups of children assigned to either 2 hours of patching or 6 hours of patching. The improvement in the visual acuity of the amblyopic eye from baseline to 4 months averaged 2.40 lines in each group. (p=0.98).

The 4-month visual acuity was at least 20/32 and/or improved from baseline by three or more lines in 62% of patients in each group (p=0.99). When combined with prescribing 1-hour near visual activities, 2 hours of patching produces an improvement in visual acuity that is similar in magnitude to the improvement produced by 6 hours of daily patching in treating moderate amblyopia in children 3 to 7 years old.

“This was a valid prospective study and the product of years of collaborative work among a multitude of our nation’s most respected pediatric vision specialists,” Dr. Tamkins said. “While the results are surprising, they are scientifically sound. Two hours of patching with visual tasks was proven appropriate in lieu of 6 hours of patching for patients with moderate amblyopia.”

Adults and amblyopia

Although early treatment for amblyopia is considered the optimal approach, practitioners say the same amblyopia treatment method used in children can be successful in older patients.

“Success depends on the degree of amblyopia and the motivation of the patient, and adults are generally more motivated and more diligent,” Dr. Cooper said. “We have provided therapy to hundreds of older amblyopic patients. Remember, neurological plasticity ends at death.”

Dr. Tamkins emphasized the need to counsel adult amblyopia patients to give them an honest and realistic understanding of the success rates. “Anecdotal and case study information in the literature implies amblyopia treatment in adults may have limited success,” she said. “It is important to counsel adult patients prior to embarking on amblyopia treatment that the success rates are unknown and that this issue has not been extensively studied in a large randomized prospective study.”

Until data become available, Dr. Tamkins said she will keep an open mind as to whether amblyopia is treatable in adults. “However, I believe the key to therapeutic success is identifying which patient is most likely to benefit from this treatment,” she said.

Dr. Tamkins said adults likely to have improved vision are those who were treated as children with success, who present with inappropriate or no refractive error correction, have refractive (not strabismic) amblyopia and have improved vision function measures using interferometry or other potential acuity measures.

Case studies for adult amblyopia

Dr. Cooper said he has observed that motivated patients achieve a better outcome. “Studies show that one-third of patients who suffer loss of vision in one eye (secondary central retinal vein occlusion, macular degeneration, etc.) spontaneously improve their vision in the amblyopic eyes,” he said.

Dr. Cooper cited some examples of patients he has successfully treated, including an 8-year-old son of a physician who was told by two ophthalmologists that he was too old for amblyopia therapy. Initial visual acuity was 20/80 and final acuity was 20/25 with normal stereopsis. Therapy included glasses, patching, atropine therapy and office-based vision therapy.

Another patient was a 25-year-old who had juvenile diabetic retinopathy of the “good” eye that was worse than the amblyopic eye. Entering visual acuity of the amblyopic eye was 20/60; post-treated visual acuity was 20/30.

Dr. Cooper also discussed a 39-year-old patient who had subnormal stereopsis and amblyopia best corrected vision 20/70. Post-therapy visual acuity was 20/25, with stereopsis equal to 40 sec.

“These three cases represent the improvements you can get with older patients,” Dr. Cooper said. “It is more difficult to improve visual acuity in older patients. The prognosis is worse, but you never know. Both legally and morally, the OD has an obligation to discuss the risks and benefits of treatment to amblyopes of all ages.”

For Your Information:

• Jeffrey Cooper, MS, OD, is a clinical professor of optometry at State University of New York, College of Optometry and practices in New York. He can be reached at 539 Park Ave., New York, NY 10021-8167; (212) 758-0772; fax: (212) 758-3532; e-mail: cooperjsc1@aol.com.
• Susanna M. Tamkins, OD, is a PEDIG investigator and practices in Coconut Grove, Fla. She can be reached at 4141 Bonita Ave., Coconut Grove, FL 33133; (305) 519-6361; fax: (305) 326-6474.
• Michael J. Bartiss, OD, MD, is a Primary Care Optometry News Editorial Board member and medical director of ophthalmology at Family Eye Care of the Carolinas, Pinehurst, N.C. He can be reached at 5 Regional Circle, Ste. A, PO Box 2410, Pinehurst, NC 28370-2410; (910) 235-3700; fax: (910) 235-4447; e-mail: kidseyes@earthlink.net.