Table 3.

Quality assessment of observational studies.

Article	Inclusion criteria	Comparability	Outcome •Objective •Lost to follow-up •Treatment duration
PEDIG (2003b)34	•Sufficient maturity to complete the study's visual acuity testing protocol •Visual acuity in the amblyopic eye between 20/40 and 20/100 inclusive •Inter-eye acuity difference 0.3 LogMAR •The presence or a history of an amblyogenic factor meeting study-specified criteria for strabismus or anisometropia, •the wearing of optimal spectacle correction for a minimum of 4 weeks at the time of enrollment, •No more than 2 months of amblyopia treatment in the previous 2 years	NA	•Yes •NA •6 months
Arikan et al (2005)15	•Patients with strabismic, anisometropic and mixed amblyopia •No previous occlusion therapy •Complete follow up for at least 6 month •Patients with esotropia deviation	The mean age at start of treatment was significantly higher for anisometropic amblyopia	•Yes •51/128 •Mean:3 years and 2 months
Hug (2004)13	•Patients with diagnosis of amblyopia •Patients with age range of 3–7 years •No organic amblyopia •Completing the follow up	NA	•Yes •NA •For the full-time occlusion group was 6 weeks (range: 1–9 weeks). •For the part-time group was 26 weeks (range: 8–58 weeks).

NA: Not Available.

PEDIG: Pediatric Eye Disease Investigator Group.