The influence of first near-spectacle reading correction on accommodation and its interaction with convergence.
OBJECTIVE
Accommodation and convergence can adapt to blur and disparity stimuli and to age-related changes in accommodative amplitude. Does this ability decline with age? The authors investigated short-term adaptation to first near-spectacle reading correction on the accommodative-stimulus response (ASR) function, accommodative amplitude (AA), AC/A, and CA/C ratios in a pre-presbyopic and an incipient presbyopic population and determined whether changes in these functions recovered after discontinuation of the use of near spectacles.


METHODS
Thirty subjects with normal vision participated; their ages ranged from 21 to 30 years (n = 15) and 38 to 44 years (n = 15). Oculomotor functions were measured before and after single-vision reading spectacles were worn for near tasks over a 2-month period and then 2 months after the use of near spectacles was discontinued.


RESULTS
The slope of the ASR function and the AC/A and CA/C ratios did not change significantly after near spectacles were worn. There was a hyperopic shift of the ASR function that significantly reduced the near point of accommodation (NPA) and lowered the far-point refraction. These changes were age invariant and did not recover after 2 months of discontinuation of near spectacle wear.


CONCLUSIONS
These results imply that the NPA may be enhanced normally by tonic bias of accommodation that elevates the entire ASR function and produces myopic refraction bias. When this bias relaxes after reading spectacles are worn, there is a hyperopic shift of the refractive state and a reduction of the NPA, specified from optical infinity.
Vedamurthy
Indu
I
School of Optometry, University of California at Berkeley, Berkeley, California 94720, USA.
Harrison
Wendy W
WW
Liu
Yue
Y
Cox
Ian
I
Schor
Clifton M
CM
D000065:Accommodation, Ocular / Q000502:physiology*; D000221:Adaptation, Ocular / Q000502:physiology*; D000328:Adult; D003290:Convergence, Ocular / Q000502:physiology*; D005139:Eyeglasses; D006801:Humans; D011305:Presbyopia / Q000503:physiopathology / Q000628:therapy*; D011932:Reading; D012029:Refraction, Ocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult