Age at onset predicts risk of rapid myopic progression

Columbus, OH-In children with juvenile myopia, younger age at onset appears to be associated with an increased risk for rapid progression of refractive error, said Karla Zadnik, OD, PhD.

To identify characteristics that predict rapid myopia progression in school-aged children, Dr. Zadnik and colleagues analyzed data collected in the Orinda Longitudinal Study of Myopia (OLSM). Candidate factors investigated included age at myopia onset, amount of myopia at the first myopic visit, maternal and paternal refractive error status, number of myopic parents, years of follow-up, and diopter-hours of near work at myopia onset.

With rapid progression defined as an average change of at least -0.75 D per year, age at myopia onset was the only independent predictor. For every year older at the time of myopia development, there was a 33% decrease in the risk of rapid progression.

"Furthermore, this information can be helpful in selecting appropriate subjects for juvenile myopia intervention studies, and if effective treatment is found, might be used to identify which children are the best candidates," she continued.

A 12-year community trial The OLSM was a 12-year, community-based trial launched in 1989. It enrolled children in the Orinda Union School District as they entered the first grade and followed them annually through the eighth grade. The primary objectives of the OLSM were to study normal eye growth and factors predicting the onset of myopia in school-age children. However, the investigators recognized that the data also lend themselves to analysis for identification of risk factors of rapid myopia progression.

To investigate that latter issue, Dr. Zadnik and colleagues identified 219 study participants who presented with myopia between -0.75 and -4.00 D in both meridians with astigmatism ≤1.00 D as measured with cycloplegic autorefraction and who had not been myopic at previous study visits. Of that subgroup, 54 children were excluded who either had <1 year of data collection or no subsequent follow-up visits.

The children were categorized as having rapid or slow progression, and features of those subsets were compared. In univariate analyses, the children with rapid and slow progression differed significantly only in their mean age at onset and mean duration of follow-up (p < 0.0001 for both comparisons). Relative to those with slow progression, children whose myopia increased rapidly were significantly younger at onset (9.7 ± 1.7 years versus 11.4 ± 1.2 years) and had a significantly longer length of follow-up (3.4 ± 1.7 versus 1.7 ± 0.9 years).

However, in the multivariate analysis controlling for years of follow-up, age at onset was the only significant factor that predicted rapid myopia progression (odds ratio = 0.67, p = 0.03).

"The shorter length of follow-up in the children with slow progression is most likely related to the older age at which the myopia presented in slow progression and the continuation of the study only through the eighth grade," noted Dr. Zadnik.

In the univariate analysis, the groups with rapid and slow progression did not differ significantly in mean refractive error at first myopic visit (-1.64 ± 0.7 D versus 1.47 ± 0.7 D), proportion with myopic mothers (77.0% versus 69.1%), proportion with myopic fathers (61.1% versus 67.7%), or mean diopter-hours of near work (50.9 ± 21.8 versus 55.9 ± 25.6).

Proportions of children with no, one, or two myopic parents were also similar in the two groups.

"That is not to say that some of these factors are not associated with a risk for juvenile myopia, because many absolutely are. However, these analyses only were designed to tease out features associated with a myopic child being at risk for rapid progression," Dr. Zadnik said.