What is the association between axial length, refractive error, and risk of visual impairment?
In this cross-sectional study of data from several population-based studies and a case-control study in the Netherlands, axial lengths of 26 mm and greater and refractive errors of −6 diopters and less were significantly associated with an increased lifetime risk of visual impairment.
Extrapolating these results to regions that have recently experienced a strong rise in myopia indicates that myopia will become the most important cause of blindness.
Myopia (ie, nearsightedness) is becoming the most common eye disorder to cause blindness in younger persons in many parts of the world. Visual impairment due to myopia is associated with structural changes of the retina and the globe because of elongation of the eye axis. How axial length—a sum of the anterior chamber depth, lens thickness, and vitreous chamber depth—and myopia relate to the development of visual impairment over time is unknown.
To evaluate the association between axial length, spherical equivalent, and the risk of visual impairment and to make projections of visual impairment for regions with high prevalence rates.
Design, Setting, and Participants
This cross-sectional study uses population-based data from the Rotterdam Study I (1990 to 1993), II (2000 to 2002), and III (2006 to 2008) and the Erasmus Rucphen Family Study (2002 to 2005) as well as case-control data from the Myopia Study (2010 to 2012) from the Netherlands. In total, 15 404 individuals with data on spherical equivalent and 9074 individuals with data on axial length were included in the study; right eyes were used for analyses. Data were analyzed from September 2014 to May 2016.
Main Outcomes and Measures
Visual impairment and blindness (defined according to the World Health Organization criteria as a visual acuity less than 0.3) and predicted rates of visual impairment specifically for persons with myopia.
Of the 15 693 individuals included in this study, the mean (SD) age was 61.3 (11.4) years, and 8961 (57.1%) were female. Axial length ranged from 15.3 to 37.8 mm; 819 individuals had an axial length of 26 mm or greater. Spherical equivalent ranged from −25 to +14 diopters; 796 persons had high myopia (ie, a spherical equivalent of −6 diopters or less). The prevalence of visual impairment varied from 1.0% to 4.1% in the population-based studies, was 5.4% in the Myopia Study, and was 0.3% in controls. The prevalence of visual impairment rose with increasing axial length and spherical equivalent, with a cumulative incidence (SE) of visual impairment of 3.8% (1.3) for participants aged 75 years with an axial length of 24 to less than 26 mm and greater than 90% (8.1) with an axial length of 30 mm or greater. The cumulative risk (SE) of visual impairment was 5.7% (1.3) for participants aged 60 years and 39% (4.9) for those aged 75 years with a spherical equivalent of −6 diopters or less. Projections of these data suggest that visual impairment will increase 7- to 13-fold by 2055 in high-risk areas.
Conclusions and Relevance
This study demonstrated that visual impairment is associated with axial length and spherical equivalent and may be unavoidable at the most extreme values in this population. Developing strategies to prevent the development of myopia and its complications could help to avoid an increase of visual impairment in the working-age population.
Tideman JWL, Snabel MCC, Tedja MS, van Rijn GA, Wong KT, Kuijpers RWAM, Vingerling JR, Hofman A, Buitendijk GHS, Keunen JEE, Boon CJF, Geerards AJM, Luyten GPM, Verhoeven VJM, Klaver CCW. Association of Axial Length With Risk of Uncorrectable Visual Impairment for Europeans With Myopia. JAMA Ophthalmol. 2016;134(12):1355-1363. doi:10.1001/jamaophthalmol.2016.4009