Downward deviation of progressive addition lenses in a myopia control trial.
OBJECTIVE
To clarify how the downward deviation of progressive addition lenses (PALs) reduces their near-addition effect in schoolchildren participating in a myopia control trial.


METHODS
Among 95 schoolchildren wearing PALs for 6 months (age range: 6-12 years; refractive error range: -6.00 to -1.25 D), facial images were captured with a digital still camera placed 60 cm in front of the eyes while he or she was looking ahead with natural head posture. The vertical deviations of PALs from their ideal position (mm) were evaluated by analysing these images.


RESULTS
The mean (+/-SD) downward deviations of PALs for the right and left eyes were 3.7 +/- 2.3 and 3.7 +/- 2.0 mm, respectively, and the largest downward deviation was 10.2 mm. For simulations using the average downward deviation, the near-addition effect of PALs was reduced to 30 and 63% of the expected value at the 10 degrees and 20 degrees downward eye positions, respectively.


CONCLUSIONS
The downward deviation of PALs is a significant factor in reducing their therapeutic effect for near-addition. To ensure the proper alignment of PALs in children, the conventional spectacle-frame-fitting procedure is not sufficient, and repeated confirmation using a testing method similar to that used in this study is required.
Hasebe
Satoshi
S
Department of Ophthalmology, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama 700-8558, Japan. shasebe@md.okayama-u.ac.jp
Nakatsuka
Chiaki
C
Hamasaki
Ichiro
I
Ohtsuki
Hiroshi
H
D000065:Accommodation, Ocular / Q000502:physiology; D002648:Child; D004867:Equipment Design; D005139:Eyeglasses; D006801:Humans; D009216:Myopia / Q000503:physiopathology / Q000517:prevention & control*; D015203:Reproducibility of Results; D016896:Treatment Outcome