Abstract
Purpose:
To report data on the response of previously untreated strabismic amblyopia to spectacle correction.
Design:
Prospective, interventional case series
Methods:
12 patients with previously untreated strabismic amblyopia were prescribed spectacles and examined at 5-week intervals until visual acuity was not improved from the prior visit.
Results:
Amblyopic eye acuity improved by ≥ 2 lines from spectacle-corrected baseline acuity in 9 of the 12 patients (75%), resolving in 3 (IOD ≤ 1 line). Mean change from baseline to maximum improvement was 2.2 ± 1.8 lines. Improvement continued for up to 25 weeks.
Conclusion:
These results support the suggestion from a prior study that strabismic amblyopia can improve and even resolve with spectacle correction alone. Larger studies with concurrent controls are needed to confirm or refute these findings.
Keywords: amblyopia, strabismus, visual acuity, refractive correction
Brief Report
Stewart et. al. reported that refractive correction alone can be effective in treating young children with previously untreated strabismic amblyopia, even in the absence of anisometropia.1 In 16 patients with strabismic amblyopia treated with spectacles alone, they found amblyopic eye acuity improved a mean of 3.0 lines over an 18-week period. This was somewhat surprising because, in such cases, the amblyopia is presumably due to the ocular misalignment, which most often would not be fully corrected with spectacles alone. We reviewed data from our recent prospective study2 to determine if our results were consistent with those of Stewart and coworkers.
This study was registered at ClinicalTrials.gov (Identifier NCT00091923).3 The full study protocol is available online.4 The protocol and HIPAA-compliant informed consent forms were approved by the respective institutional review boards and the parent or guardian of each study patient gave written informed consent.
As a run-in phase to a randomized trial of patching treatment for amblyopia,5 spectacles were prescribed to correct refractive error, no other amblyopia treatment was prescribed, and patients were followed until visual acuity appeared stable. Results in patients with previously untreated anisometropic amblyopia have been reported2. Data were available for 12 patients (75% female, 83% white, mean age 5.0±0.9 years) with previously untreated strabismic amblyopia who had a constant strabismus at distance and near and anisometropia of ≤0.75 D in spherical equivalent or ≤1.25 D in astigmatism (Table 1). Spectacle-corrected monocular distance visual acuity was measured using the electronic Amblyopia Treatment Study HOTV protocol6, 7 at baseline and every 5 (±1) weeks provided amblyopic eye acuity had improved at least 1 line (0.1 logMAR) from the prior visit and remained at least 1 line worse than sound eye acuity. Patients whose acuity did not improve at least 1 line from the prior visit but still had ≥2 lines of interocular difference (IOD) entered a randomized trial.5 Those randomized to the control group continued spectacles if needed but did not start other therapy, and provide additional data on the course of the amblyopia treated with spectacles alone.
Table 1.
Baseline Clinical Characteristics and Change in Amblyopic Eye Visual Acuity
| Patient | Age (Years) |
Strabismus Type and Magnitude at Distance (Δ)* |
Strabismus Type and Magnitude at Near (Δ)* |
Cycloplegic Refractive Error in Amblyopic Eye |
Baseline Amblyopic Eye Visual Acuity |
Cycloplegic Refractive Error in Sound Eye |
Baseline Sound Eye Visual Acuity |
Change in Amblyopic Eye to Visit of Best Acuity (Lines) |
|---|---|---|---|---|---|---|---|---|
| 1 | 4.5 | ET 6Δ | ET 10Δ | +5.75 | 20/50 | +5.25 | 20/20 | 0 |
| 2 | 5.7 | ET 15Δ | ET 18Δ | +2.50 | 20/63 | +1.75 | 20/20 | 0 |
| 3 | 6.2 | ET 12Δ | ET 12Δ | +2.00+0.25×075 | 20/63 | +1.25+0.50×105 | 20/20 | 0 |
| 4 | 3.7 | ET 4Δ | ET 12Δ | +3.00+1.50×090 | 20/80 | +3.00+1.50×090 | 20/32 | +2 |
| 5 | 4.2 | ET 40Δ | ET 40Δ | +5.00+1.00×080 | 20/100 | +4.75+0.50×100 | 20/40 | +2 |
| 6 | 5.3 | ET 20Δ | ET 25Δ | +5.00+0.25×080 | 20/50 | +5.00+0.25×100 | 20/25 | +2 |
| 7 | 5.9 | ET 2Δ | ET 4Δ | +1.50 | 20/40 | +1.50 | 20/16 | +2 |
| 8 | 6.3 | ET 4Δ | ET 4Δ | +4.75+1.00×090 | 20/50 | +4.25+0.75×090 | 20/20 | +2 |
| 9 | 4.0 | ET 14Δ | ET 14Δ | +2.00+0.75×090 | 20/80 | +2.00+0.50×090 | 20/25 | +3 |
| 10 | 5.3 | XT 10Δ† | XT 20Δ† | +0.00+1.50×165 | 20/250 | +0.00+1.00×090 | 20/20 | +3 |
| 11 | 4.6 | ET 20Δ‡ | ET 20Δ‡ | +3.50+0.50×090 | 20/100 | +3.00+0.50×090 | 20/40 | +4 |
| 12 | 4.1 | ET 25Δ | ET 25Δ | +5.00+1.00×090 | 20/100 | +5.00+1.00×100 | 20/32 | +6 |
Patients are sorted by lines change in amblyopic eye to visit of best acuity in amblyopic eye
Strabismus was measured at baseline and may not have been present after prolonged spectacle treatment
Patient also had a left hypertropia of 25Δ at distance and 30Δ at near
Strabismus measured with Krimsky test
Among the 12 strabismic patients, during the spectacles-only phase of follow up, amblyopic eye acuity improved by ≥ 2 lines from spectacle-corrected baseline acuity in 9 (75%) resolving in 3 (IOD ≤ 1 line), Table 2. Mean change from baseline to maximum improvement was 2.2 ± 1.8 lines. Improvement continued for up to 25 weeks. Additional amblyopia improvement ≥1 line occurred, though amblyopia did not resolve, in 3 of the 5 patients with residual amblyopia who entered the subsequent randomized trial as controls.
Table 2.
Improvement in Amblyopic Eye Visual Acuity and Resolution of Amblyopia Stratified by Degree of Refractive Error in Amblyopic Eye
| Lines Improvement In Amblyopic eye |
Interocular Acuity Difference* |
Resolution of Amblyopia† |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| N | 0 | 1 | 2 | 3 | 4 | 5 | 6 | Mean | Mean | N (%) | |
| Overall | 12 | 3 | 0 | 5 | 2 | 1 | 0 | 1 | 2.2 | 3.2 | 3 (25%) |
| By Degree of Refractive Error in Amblyopic Eye | |||||||||||
| ≤+3.00 D spherical equivalent | 5 | 2 | 0 | 1 | 2 | 0 | 0 | 0 | 1.6 | 4.4 | 0 |
| <1.50 D astigmatism | 4 | 2 | 0 | 1 | 1 | 0 | 0 | 0 | 1.3 | 3.5 | 0 |
| ≥1.50 D astigmatism | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 3.0 | 8.0 | 0 |
| >+3.00 D spherical equivalent | 7 | 1 | 0 | 4 | 0 | 1 | 0 | 1 | 2.6 | 2.3 | 3 (43%) |
| <1.50 D astigmatism | 6 | 1 | 0 | 3 | 0 | 1 | 0 | 1 | 2.7 | 2.0 | 3 (50%) |
| ≥1.50 D astigmatism | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 2.0 | 4.0 | 0 |
Interocular acuity difference evaluated using better of sound eye acuity at baseline or sound eye acuity at visit of best measured amblyopic eye acuity.
Interocular acuity difference within 1 line.
Our results support the suggestion of Stewart et al.1 that strabismic amblyopia can improve and even resolve with spectacle correction alone. Although the results are consistent, they are not conclusive, because neither study had a concurrent control group and both had small numbers of patients. It is not possible to rule out the possibility that change in strabismus angle, learning effect, age effect, regression to the mean, or chance could account for some of the observed improvement. Larger studies with concurrent controls are needed to confirm or refute these findings.
Acknowledgements
Writing Committee for the Pediatric Eye Disease Investigator Group*: Lead authors: Susan A. Cotter, O.D.; Allison R. Edwards, M.S.; Additional writing committee members (alphabetical): Robert W. Arnold, M.D.; William F. Astle, M.D.; Carmen N. Barnhardt, O.D.; Roy W. Beck, M.D., Ph.D.; Eileen E. Birch, Ph.D.; Sean P. Donahue, M.D., Ph.D.; Donald F. Everett, M.A.; Joost Felius, Ph.D.; Jonathan M. Holmes, B.M., B.Ch; Raymond T. Kraker, M.S.P.H.; B. Michele Melia, Sc.M.; Michael X. Repka, M.D.; David K. Wallace, M.D.; Katherine K. Weise, O.D., M.B.A.
1)FUNDING/SUPPORT - This study was supported by a cooperative agreement from the National Eye Institute, EY11751.
2)FINANCIAL DISCLOSURES - None
3) CONTRIBUTION OF AUTHORS Design of the study (SC, RA, WA, CB, RB, EB, SD, DE, JF, JH, RK, MR, DW, KW); all authors were involved in the collection, management, analysis, and interpretation of the data and the preparation, review, and final approval of the manuscript.
4)OTHER ACKNOWLEDGMENTS - None
Footnotes
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A list of Pediatric Eye Disease Investigator Group sites participating in this study appears in Ophthalmology 2006;113:895-903.
REFERENCES
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