Abstract Read SA et al.

Axial Length Changes During Accommodation in Myopes and Emmetropes.

Read SA, Collins MJ, Woodman EC, Cheong SH.
Optom Vis Sci. 2010 Sep;87(9):656-62.

PURPOSE:
To investigate the influence of accommodation on axial length (AXL) anda comprehensive range of ocular biometric parameters) in populations of youngadult myopic and emmetropic subjects.

METHODS:
Forty young adult subjects had ocular biometry measured using a noncontact optical biometer (Lenstar LS 900) based on the principle of optical low coherence reflectometry under 3 different accommodation demands (0 D, 3 D, and 6 D). Subjects were classified as emmetropes (n = 19) or myopes (n = 21) based on their spherical equivalent refraction (mean emmetropic refraction -0.05 +/- 0.27 D sphere and mean myopic refraction -1.82 +/- 0.84 D sphere).

RESULTS:
AXL changed significantly with accommodation, with a mean increase of 11.9 +/- 12.3 mum and 24.1 +/- 22.7 mum for the 3 D and 6 Daccommodation stimuli, respectively. A significant axial elongation associatedwith accommodation was still evident even after correction of the AXL data forpotential error because of lens thickness change. The mean "corrected" increasein AXL was 5.2 +/- 11.2 mum and 7.4 +/- 18.9 mum for the 3 D and 6 D stimuli,respectively. There was no significant difference between the myopic andemmetropic populations in terms of the magnitude of change in AXL withaccommodation, regardless of whether the data were corrected or not. A number of other ocular biometric parameters, such as anterior chamber depth, lensthickness, and vitreous chamber depth also exhibited significant change withaccommodation. The myopic and emmetropic populations also exhibited nosignificant difference in the magnitude of change in these parameters withaccommodation.

CONCLUSIONS:
The eye undergoes a significant axial elongationassociated with a brief period of accommodation, and the magnitude of this changein eye length increases for larger accommodation demands, however, there is nosignificant difference in the magnitude of eye elongation in myopic andemmetropic subjects.