Transactions 29th European Strabismological Association Meeting – de Faber (ed) © 2005 European Strabismological Association, ISBN 04 1537 211 9

Combined optical and atropine penalization in the treatment of amblyopia

S. Zıylan, Ö. Yabas & D. Serin

Sisli Etfal Education and Research Hospital, Istanbul, Turkey

ABSTRACT: We aimed to evaluate the effectiveness of combined optical and atropine therapy in the treatment of anisometropic or strabismic amblyopia. Patients in the penalization group were instructed to instill 1 drop of 1% atropine sulphate in the fellow eye daily and their spectacle prescription for the fellow eye was replaced with a plano lens. A control group was treated with full time patching. The treatment continued until the visual acuity of the amblyopic eye became 1.0 or stayed the same after 3 consecutive visits. The mean follow-up was 6 months. At the end of the therapy, improvement of visual acuity did not show significant difference between the two groups. Combined optical and atropine therapy is effective as an alternative or supportive therapy for anisometropic or strabismic amblyopia.

1INTRODUCTION

Amblyopia is defined as a decrease of visual acuity in one eye caused by abnormal binocular interaction or occurring in one or both eyes as a result of pattern vision deprivation during visual immaturity for which no cause can be detected during the physical examination of the eye(s) and which in appropriate cases is reversible by therapeutic measures (von Noorden 1977). Amblyopia occurs in approximately 2% of the population and it is the most common cause of decreased vision in childhood.

The basic strategy for treating amblyopia is to provide a clear retinal image first and then correct ocular dominance. Correction of ocular dominance is accomplished by forcing fixation to the amblyopic eye by patching or blurring the vision of the sound eye (penalization) (Wright 1995). Patching by patching has been the mainstay of amblyopia treatment (von Noorden 2002). However, there are some disadvantages of patching treatment such as its high cost, allergic skin reactions and social stigmatization. These factors lead to noncompliance and failure of therapy (Simons 1996, Woodroff 1994). Optical and atropine penalization have been found to be effective as alternatives to patching in suitable cases and these two methods might have an additive effect when combined (Foley-Nolan et al. 1997, Repka & Ray 1993, France & France 1999). This study aimed to evaluate the effectiveness of combined optical and atropine penalization as an alternative to patching in the treatment of anisometropic or strabismic amblyopia.

2METHODS

In this study, we reviewed two groups of patients with anisometropic or strabismic amblyopia. The first group consisted of patients receiving combined optical and atropine therapy (COAT group). The second group, identified as the patch group, included patients receiving full time patching therapy. The following data were recorded for each patient at the initial visit: age, gender, cycloplegic refraction, best corrected visual acuity, type of amblyopia and type and amount of strabismus if present. Follow up visits were made every 3 to 4 weeks. The treatment continued at least for

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3 months unless the visual acuity (VA) of both eyes became equal earlier. The treatment was discontinued if the VA of the amblyopic eye stayed the same after 3 consecutive visits. Long term follow up visits were made at 2 to 6 month intervals.

Refraction was documented at the initial visit by cycloplegic retinoscopy 30 minutes after one drop of 1% cyclopentolate in each eye. Spherical equivalent was calculated as the algebraic sum of the sphere power and half of the cylinder power. VA of each eye was measured with Snellen linear optotypes or the tumbling E chart at each visit and converted to logMAR units for statistical analysis. In the evaluation of the data unpaired and paired Student’s t tests and chi-square analysis were used. In strabismic patients, the amount of strabismus was measured with simultaneous prism cover test at distance and near.

2.1COAT group

This group of patients either was noncompliant to patching therapy or failed to show any improvement despite apparent compliance. Before starting COAT patients had stopped patching for at least 3 months. At the initial visit the full cycloplegic refraction was prescribed to the amblyopic eye, while the prescription for the sound eye was replaced with a plano lens. Also patients were instructed to instill one drop of 1% atropine sulphate in the sound eye daily. The near vision of the sound eye was blurred by the iatrogenic accommodation paralysis that atropine provided and its distance VA was decreased with the plano lens. By penalizing the sound with these methods the amblyopic eye was forced to take up fixation. At follow up visits, VA of both eyes was recorded. Compliance was confirmed with dynamic retinoscopy. It was ensured at each follow up visit that the corrected VA of the amblyopic eye was higher than the uncorrected VA of the atropinized sound eye at distance and near. After the discontinuation of therapy, patients resumed full spectacle prescription. At long term follow up visits part time patching was started as maintenance therapy if necessary. The VA of the amblyopic eye at the last visit was recorded as the long term follow up VA.

2.2Patch group

At the initial visit the full cycloplegic refraction was prescribed to both eyes. Patients were instructed to occlude the sound eye with adhesive skin patches during waking hours. At follow up visits VA of both eyes was recorded. For patients who responded well to the treatment the amount of patching could be reduced. Compliance was determined by questioning the parents. At long term follow up visits maintenance therapy with part time patching was offered if necessary. The VA of the amblyopic eye at the last visit was recorded as the long term follow up VA.

3RESULTS

30 patients were treated with combined optical and atropine penalization and 20 patients were treated with full time patching.

The age range was 3 to 8 years. There was no difference between groups concerning years of age (p 0.05). Between the two groups there was a small but significant difference for initial VA (p 0.001). Patients in the patch group had lower initial VA than the ones in the COAT group. The mean duration of therapy was 3.73 (SD: 1.46) months in the COAT group and 3.95 (SD: 1.39) months in the patch group (p 0.05). The mean refractive errors of the amblyopic and fellow eyes in COAT were 5.09 1.84 and 4.08 1.97 respectively, while the mean refractive errors of the amblyopic and fellow eyes in patch group were 4.80 1.78 and 3.60 2.01 (p 0.05).

The improvement in VA in both treatment groups was significantly high (p 0.001). There was no significant difference between the groups regarding the efficacy of treatment (p 0.05). The improvement in VA was similar in strabismic and anisometropic amblyopic patients (p 0.05) in both groups.

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Table 1. Types of amblyopia among treatment groups.

Table 2. Mean visual acuities before and at the end of therapy.

Table 3. Improvement in visual acuity at the end of treatment.

When we stratified both treatment groups as initial VA 20/40 and initial VA 20/40, we did not find any significant difference in the amount of improvement (p 0.05).

Ten patients in the COAT group and ten in the patch group were evaluated for long term visual outcome. The mean long term follow up time was 24 months in the COAT group and 23 months in the patch group. There was no significant difference between the VA at the end of treatment and VA at the end of long term follow up (p 0.05).

4DISCUSSION

Amblyopia is one of the leading causes of monocular visual loss. Occlusion therapy, described 250 years ago, is still accepted as the gold standard. However, occlusion is beset with compliance problems, adhesive sensitivity, stigmatization and regression. Also, occlusion may not be an ideal solution in latent nystagmus and intermittent strabismus. In these situations, penalization therapy might be especially successful (Kaye et al. 2002). Pharmacological penalization has often been reserved for patients who are noncompliant with occlusion (Repka & Ray 1993). In a multicenter randomized trial comparing atropine with patching, the effect of atropine alone was comparable with full time occlusion (The Pediatric eye disease investigator group 2003). In another study of this group it was pointed out that although both atropine and patching were well tolerated, atropine was the favored choice of parents (The Pediatric eye disease investigator group 2002). In our study group the compliance rate for COAT was 97%.

According to Simons et al. occlusion or atropine treatment did not cause any different outcome on either VA or binocularity measures. They also claimed that penalization is an attractive alternative for parents’ and patients’ acceptability (Simons 1997).

In Repka & Ray’s study, it is stated that pharmacological penalization is best used by patients with high degrees of amblyopia ( 20/60), where as optical penalization is best reserved for

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patients with lesser amblyopia (20/25–20/60) (Repka & Ray 1993). In our study, when amblyopes were stratified as VA 20/40 and VA 20/40, difference in the magnitude of improvement was not significant in neither of the treatment groups (p 0.05). Our data suggest that COAT can be as successful as patching in mild and moderate amblyopia.

As Kaye et al suggest, COAT has a more rapid effect than a single modality penalization therapy but it produces a potentially higher risk of reverse amblyopia (Kaye et al. 2002). Reverse amblyopia in occlusion therapy was more common in a different study (Repka & Ray 1993). North & Kelly reported that 2 of their 189 patients suffered from permanent amblyopia after pharmacological penalization (North & Kelly 1991). In our study we also were faced with reverse amblyopia in two cases. One family is lost to follow up because of reverse patching. We think that close follow up is very important in penalization therapy.

5CONCLUSIONS

This study can not prove one treatment is superior over to the other. In our experience, combined optical and atropine therapy is as effective as patching and can be used as an alternative or supportive treatment to occlusion therapy in the management of amblyopia in chosen subjects, especially in school age children.

REFERENCES

Foley-Nolan A. et al. 1997. Atropine penalisation versus occlusion as primary treatment for amblyopia. Br J Ophthalmol 81: 5–7

Kaye et al. 2002. Combined optical and atropine penalization for the treatment of strabismic and anisometropic amblyopia. Journal of AAPOS 6: 289–93

Noorden G. K von 1997. Mechanisms of amblyopia. Doc Ophthalmol 34: 93 Noorden G. K von 2002. Binocular vision and ocular motility: 546. St Louis: Mosby

North R. V. & Kelly M. E. 1991. Atropine occlusion in the treatment of strabismic amblyopia and its effect upon the non-amblyopic eye. Ophthalmic Physiol Opt 11: 113–7

The pediatric eye disease investigator group 2002. A randomized trial of atropine vs patching for treatment of moderate amblyopia in children. Arch Ophthalmol 120: 268–78

The pediatric eye disease investigator group 2003. A comparison of atropine and patching treatments for moderate amblyopia by patient age, cause of amblyopia, depth of amblyopia, and other factors. Ophthalmology 110: 1632–8

Repka M. X. & Ray J. M. 1993. The efficacy of optical and pharmacological penalization. Ophthalmology 100: 769–74

Simons K. 1996. Preschool vision screening: rationale, methodology, outcome. Surv Ophthalmol 41: 3–30 Thomas D. F. & Leslie W. F. 1999. Optical penalization can improve vision after occlusion treatment. Journal

of AAPOS 3(4): 241–4

Woodroff G. 1994. Factors affecting the outcome of children treated for amblyopia. Eye 8(6): 623–6. Wright K. W. 1995. Pediatric ophthalmology and strabismus: 130 St.Louis: Mosby

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