International Strabismological Association ISA 2002

Jan-Tjeerd de Faber, Jan-Tjeerd de Faber

• Editore: CRC Press
• Anno: 2021
• ISBN:
  9781000446470
• Edizione: 1
• Argomento: Medizin
• Categoria: Neurologie

This volume contains the proceedings of the 9th Congress of the International Strabismological Association (ISA). The meeting took place in Sydney, Australia, from 17th to 20th April 2002. The text was written with the intention to provide the reader with information on developments in observations and therapies in strabismus and paediatric ophthalmology. The format of the work follows the meeting programme and is divided into sections of oral presentations, manuscripts of the posters, symposia and workshop. In order to assist the reader a list of keywords and authors have been added to the book.

Section 1 – Amblyopia/binocular vision

MODERATE AMBLYOPIA IN CHILDREN LESS THAN SEVEN YEARS OF AGE: EXPERIENCE OF THE AMBLYOPIA TREATMENT STUDY 1

Michael X. Repka^a, for the Pediatrie Eye Disease Investigator Group^b

Wilmer Ophthalmological Institute, Johns Hopkins University, Baltimore, MD, USA

Jaeb Center for Health Research, Tampa, FL, USA

Abstract

A cohort of 419 children with moderate amblyopia participated in Amblyopia Treatment Study 1. These children were less than seven years of age with strabismic, anisometropic or combined amblyopia and visual acuity in the amblyopic eye from 6/12 to 6/30. The average age was 5.3 years. The cause was strabismus in 38%, anisometropia in 37%, and combined in 24%. The mean acuity of the amblyopic eyes was 0.53 logMAR. For patients randomized to patching, 43% were treated initially with 6 hours per day of occlusion, while 17% were treated with full-time occlusion. A similar level of visual impairment was found irrespective of the cause of the amblyopia. The visual acuity of the sound eyes of strabismic patients was significantly worse than that of patients with anisometropia (P <0.001). There was considerable variation in patching treatment practices.

Keywords

Amblyopia, anisometropia, strabismus, atropine, occlusion

Introduction

Amblyopia is the most common cause of visual impairment in children.! Most cases are associated with strabismus, while less frequently they may be associated with anisometropia or a combination of amblyopia and strabismus.

The Amblyopia Treatment Study 1 (ATS1) is a randomized, controlled single-masked multi-center clinical trial comparing the visual acuity improvement achieved by occlusion therapy with adhesive patches to pharmacological penalization with topical atropine 1% drops. Children less than 7 years of age with moderate amblyopia were enrolled at both community-based and university-based practices throughout North America by the Pediatric Eye Disease Investigator Group. Visual acuity in the amblyopic eyes improved 3.16 lines in the patching group and 2.84 lines in the atropine groups when measured at 6 months.2 This difference was clinically inconsequential, about 2 letters. This report summarizes the key demographic and clinical characteristics of the enrolled patients, which have been reported in greater detail.³

Materials and Methods

Eligibility and exclusion criteria for this randomized clinical trial are listed in Table 1 and Reference 1. Prior to enrollment a cycloplegic refraction and ophthalmologic examination were performed. Any necessary glasses were worn for a minimum of 4 weeks. The visual acuity was measured with the ATS protocol, which uses random single surrounded HOTV optotypes at 3 to 6 m.⁴ The definitions used for classification of the type of amblyopia are listed in Table 2. The treatment protocols for occlusion and pharmacological therapy utilized in ATS1 have been described.²

Table 1. Eligibility and exclusion criteria for enrollment into ATS1.

Eligibility Criteria • Age < 7 years • Visual acuity measured using the ATS visual acuity testing protocol • Amblyopia associated with strabismus, refractive error/anisometropia, or both(see Table 2) • Visual acuity in the amblyopic eye ≤ 20/40 and ≥20/100 • Visual acuity in the sound eye ≥ 20/40 • Intereye acuity difference ≥3 logMAR lines • No more than 2 months of amblyopia therapy in the past 2 years • Refractive error corrected for at least four weeks

Exclusion Criteria • Presence of an ocular cause for reduced visual acuity • Prior intraocular surgery • Myopia (spherical equivalent of -0.50 D or more myopia) in either eye • Down Syndrome • Known skin reaction to patch or allergy to atropine or other cycloplegics

Table 2. Study Definitions of Amblyopia

Refractive/anisometropic amblyopia 1. anisometropia 0.50 D or more spherical equivalent, OR 2. 1.50 D or larger difference in astigmatism in any meridian 3. persisting after 4 or more weeks of continuous spectacle correction

Strabismic amblyopia 1. presence of a heterotropia at distance or near or history of strabismus surgery (or botulinum toxin injection) 2. refractive error criteria not meeting the definition of combined amblyopia

Combined amblyopia 1. presence of a heterotropia at distance or near or history of strabismus surgery (or botulinum toxin injection) 2. anisometropia 1.00 D or more spherical equivalent, OR 3. 1.50 D or larger difference in astigmatism in any meridian 4. persisting after 4 or more weeks of continuous spectacle correction

Results

The investigators at 47 sites enrolled 419 patients. Ten patients were ineligible based on the study definitions listed in Table 2 and excluded from this analysis. The average age was 5.3 ± 1.1 years, ranging from 2.6 to 6.9 years. Fifty-four percent were boys. Ethnic distribution was 83% white, 6% African-American, 6% Hispanic, 2% Asian, and 3% other. Only 27% had a history of prior amblyopia therapy.

The cause of amblyopia was anisometropia in 37%, strabismus in 38%, and combined in 24%. There was no significant difference in mean age between these sub-groupings based on cause of amblyopia. The mean visual acuities of the sound and amblyopic eyes are listed in Table 3. The visual acuity of the sound eyes of the strabismic patients was significantly poorer than the other groups (P < 0.001).

Table 3. Mean logMAR visual acuities at enrollment by cause of amblyopia

	Sound eye	Amblyopic eye
Refractive/anisometropia	0.05	0.52
Strabismic	0.13	0.52
Combined	0.09	0.55
Overall	0.09	0.53

The effect of the size of the anisometropia was analyzed in the combined and the refractive/anisometropic groups. Patients with anisometropia <3.00 D (N=87) had a mean acuity 0.48 logMAR, while those with 3.00 D or more (N=69) had a poorer mean acuity of 0.57 logMAR (P < 0.001).

If randomized to patching, investigators could choose to begin treatment with 6 or more hours per day. Six or 8 hours per day were prescribed for 73% of the 212 patients, whereas 10 or more hours were prescribed for 27%. The number of hours prescribed had no consistent relationship to age (P = 0.47), but was related to the amblyopic eye acuity (P=0.001).

Discussion

The 409 patients described in this report represent the cohort of children less than 7 years of age enrolled in the Amblyopia Treatment Study. These data must be interpreted cautiously as they represent those patients eligible for the study and do not generally describe all patients with moderate amblyopia in North America. Strabismus and anisometropia were nearly equal in prevalence as cause of amblyopia. Fewer patients with strabismic amblyopia were enrolled compared to previously reported studies^5,6, probably because deep amblyopia and extensive prior therapy were exclusions in our study. These criteria likely excluded patients with strabismic amblyopia.

The mean visual acuity ...