Table 1.

Definitions of Vision Disorders in the Vision in Preschoolers Study.

Vision Disorder	Definitions
Hyperopia	Any hyperopia: >3.25 D in most positive meridian in either eye
	Hyperopia severity:
	Group 1: ≥5.0 D
	Group 2: >3.25D and <5.0D and interocular difference in SE of ≥0.5 D
	Group 3: >3.25D and <5.0D and interocular difference in SE of <0.5 D
Anisometropia	>1.00D interocular difference in hyperopia; >3.00D interocular difference in myopia; >1.50D interocular difference in astigmatism; antimetropic difference >1.00D and one eye >1.00D of hyperopia; antimetropic difference >3.00D and one eye >2.00D of myopia
Astigmatism	>1.50D between principal meridians
Unilateral Amblyopia	≥2-line interocular difference in VA and a unilateral amblyogenic factor†
Bilateral Amblyopia	3-year-olds : worse than 20/50 in one eye, worse than 20/40 in the contralateral eye, and a bilateral amblyogenic factor‡
	4- and 5-year olds: worse than 20/40 in one eye, worse than 20/30 in the contralateral eye, and a bilateral amblyogenic factor‡
Strabismus	Any heterotropia in primary gaze

D=diopters; VA=Visual Acuity

^†Strabismus, anisometropia and a difference in spherical equivalent of ≥0.50D when ≥1 eye had >3.50D of hyperopia were considered unilateral amblyogenic factors.

^‡Astigmatism of >2.50 D, hyperopia of >5.00 D, or myopia of >8.00 D in each eye were considered bilateral factors.