Nearwork-induced transient myopia in preadolescent Hong Kong Chinese.
OBJECTIVE
To compare the magnitude and time course of nearwork-induced transient myopia (NITM) in preadolescent Hong Kong Chinese myopes and emmetropes.


METHODS
Forty-five Hong Kong Chinese children, 35 myopes and 10 emmetropes aged 6 to 12 years (median, 7.5), monocularly viewed a letter target through a Badal lens for 5 minutes at either 5.00- or 2.50-D accommodative demand, followed by 3 minutes of viewing the equivalent target at optical infinity. Accommodative responses were measured continuously with a modified, infrared, objective open-field autorefractor. Accommodative responses were also measured for a countercondition: viewing of a letter target for 5 minutes at optical infinity, followed by 3 minutes of viewing the target at a 5.00-D accommodative demand. The results were compared with tonic accommodation and both subject and family history of refractive error.


RESULTS
Retinal-blur-driven NITM was significantly greater in Hong Kong Chinese children with myopic vision than in the emmetropes after both near tasks, but showed no significant dose effect. The NITM was still evident 3 minutes after viewing the 5.00-D near task for 5 minutes. The magnitude of NITM correlated with the accommodative drift after viewing a distant target for more than 4 minutes, but was unrelated to the subjects' or family history of refractive error.


CONCLUSIONS
In a preadolescent ethnic population with known predisposition to myopia, there is a significant posttask blur-driven accommodative NITM, which is sustained for longer than has previously been found in white adults.
Wolffsohn
James Stuart
JS
Neurosciences Research Institute, School of Life and Health Sciences, Aston University, Birmingham, United Kingdom. j.s.w.wolffsohn@aston.ac.uk
Gilmartin
Bernard
B
Li
Roger Wing-hong
RW
Edwards
Marion Hastings
MH
Chat
Sandy Wing-shan
SW
Lew
John Kwok-fai
JK
Yu
Bibianna Sin-ying
BS
D000065:Accommodation, Ocular; D044466:Asian People; D002648:Child; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D008297:Male; D009216:Myopia / Q000208:ethnology* / Q000209:etiology / Q000503:physiopathology; D013997:Time Factors; D014937:Work