Early-onset myopia model and axial length elongation

[caption id="attachment_6144" align="alignnone" width="350"] Willem Tideman  MD[/caption] A model incorporating factors associated with axial length elongation performs well for predicting early-onset myopia and also shows the importance of lifestyle factors in myopia development, said Willem Tideman MD at the 2016 annual meeting of the Association for Research in Vision and Ophthalmology (ARVO) in Seattle, USA. The model was developed recognising that high myopia is characterised by a disproportional elongation of axial length during childhood. First, factors independently predicting axial length elongation during childhood between the ages of six and nine were determined using data from 4,734 children participating in Generation R, a multi-ethnic, birth-cohort study under way in Rotterdam, 
The Netherlands. Then, a risk score was created using betas from linear regression models of the associated variables. Finally, its accuracy for discriminating between children who had become myopes by age nine and those remaining non-myopic was estimated, based on the area under the receiver operation characteristic (ROC) curve. The variables found to be independently associated with axial length elongation were parental myopia, books read per week, time spent reading, reading distance, time spent outdoors, sports, ethnicity, and axial length/corneal radius curvature. The risk score for all children ranged from zero to 30. Children at age six whose score was less than or equal to five were at almost no risk for developing myopia at age nine whereas the risk was 54% for those with a risk score of 13 or higher. The area under the ROC curve was 0.77, indicating good accuracy for discriminating between the children who did and did not develop myopia. “Our model using non-invasive ophthalmic measurements and easy-to-obtain data performs well for identifying children at risk for developing high myopia as adults,” said Dr Tideman, Department of Ophthalmology and Epidemiology, Erasmus Medical Centre, Rotterdam, The Netherlands. LIFESTYLE FACTORS “In addition, it shows that interventions aimed at lifestyle factors may help to mitigate the risk. According to our model, lifestyle adjustments may reduce axial length elongation by about 20%,” he added. Of the 2,136 children who underwent cycloplegic refractive error measurement and were non-myopic at age six, by age nine, 215 (10%) had developed myopia. For all eyes, mean axial length increased from 22.34mm at age six to 23.10mm at age nine, and the mean rate of elongation was 0.21mm/year. However, the annual axial length elongation rate was significantly greater in eyes that developed myopia at age nine compared with the non-myopes, 0.34 versus 0.19mm/year. Willem Tideman: j.tideman@erasmusmc.nl