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T. Langaas, P.M. Riddell, E. Svarverud, A.E. Ystenæs, I. Langeggen, M.H. Fjerdingstad, J. Lid, J. Bruenech; Stability of Accommodation in Early Onset Myopia . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3679.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal defocus (blur) has been demonstrated to be a causal factor in the development of myopia. One possible cause of blur is poor ability to control accommodation. Previous studies have demonstrated poor accommodation in adults with late onset myopia. This study looked at the accommodative abilities of children with early onset myopia.
42 children with informed consent participated. 23 children with a non–cycloplegic refraction of at least –0.5 DS and otherwise healthy eyes were included in the myopia index group. 19 age matched control children with emmetropia or low hyperopia were also tested. Measures of accommodation were made using an eccentric infrared autorefractor (PowerRefractor). The refractive status of the eyes was recorded dynamically at a frequency of 0.25Hz. The children were instructed to focus on highly accommodative targets set at three different distances (accommodative demands of 0.25, 2 and 4 D). Targets were viewed in a pseudo–random sequence with all distances tested twice.
A repeated measures ANOVA showed a main effect of group (F 1,38 = 7.08, p < 0.0001), a main effect of distance (F 1,36 = 105.53, p < 0.0001) and an interaction between group and distance (F 1,36 = 3.25, p < 0.05). Both groups accommodated accurately for the near and distance targets, but showed about 1 D of lag for the mid target (2 D: F 1,1 = 6.61, p < 0.05). In support of our hypothesis, the accommodative response of the myopes was more variable than the control group (F 1,1 = 5.82, p < 0.05). T–tests showed that this difference was significant for the 4 D target (t(40) = –4.8, p < 0.001) and the 0.25 D target (t(40) = 3.71, p < 0.001).
The results suggest that children with early onset myopia show variable accommodation when viewing near and far targets. This could produce higher stress in the accommodative system in myopic children resulting in an increase in retinal blur.
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