Brief daily periods of unrestricted vision can prevent form-deprivation amblyopia.
OBJECTIVE
To characterize how the mechanisms that produce unilateral form-deprivation amblyopia integrate the effects of normal and abnormal vision over time, the effects of brief daily periods of unrestricted vision on the spatial vision losses produced by monocular form deprivation were investigated in infant monkeys.


METHODS
Beginning at 3 weeks of age, unilateral form deprivation was initiated in 18 infant monkeys by securing a diffuser spectacle lens in front of one eye and a clear plano lens in front of the fellow eye. During the treatment period (18 weeks), three infants wore the diffusers continuously. For the other experimental infants, the diffusers were removed daily and replaced with clear, zero-powered lenses for 1 (n=5), 2 (n=6), or 4 (n=4) hours. Four infants reared with binocular zero-powered lenses and four normally reared monkeys provided control data.


RESULTS
The degree of amblyopia varied significantly with the daily duration of unrestricted vision. Continuous form deprivation caused severe amblyopia. However, 1 hour of unrestricted vision reduced the degree of amblyopia by 65%, 2 hours reduced the deficits by 90%, and 4 hours preserved near-normal spatial contrast sensitivity.


CONCLUSIONS
The severely amblyogenic effects of form deprivation in infant primates are substantially reduced by relatively short daily periods of unrestricted vision. The manner in which the mechanisms responsible for amblyopia integrate the effects of normal and abnormal vision over time promotes normal visual development and has important implications for the management of human infants with conditions that potentially cause amblyopia.
Wensveen
Janice M
JM
College of Optometry, University of Houston, Houston, Texas 77204-2020, USA. jwensveen@uh.edu
Harwerth
Ronald S
RS
Hung
Li-Fang
LF
Ramamirtham
Ramkumar
R
Kee
Chea-su
CS
Smith
Earl L
EL
D000550:Amblyopia / Q000209:etiology / Q000517:prevention & control*; D000818:Animals; D000831:Animals, Newborn; D015350:Contrast Sensitivity / Q000502:physiology; D004195:Disease Models, Animal; D008253:Macaca mulatta; D012160:Retina / Q000502:physiology; D012683:Sensory Deprivation; D013997:Time Factors; D014785:Vision, Ocular / Q000502:physiology*