When we say someone is ‘nearsighted’, it means their vision is ‘near’, that is, they see better up close than far away. This is the reverse problem optically from farsightedness, and a much different problem physiologically, or in terms of how the body deals with it. Myopes are more likely to succeed in primary and post-secondary school because their vision is more tuned to near work than farsighted people who typically find reading a chore that takes effort and requires some discomfort.
Pseudomyopia is a condition where the eyes are farsighted but overcorrect themselves beyond neutral and become mildly nearsighted. If the wrong prescription is applied, the eyes’ focusing system can become even more stressed and things can worsen. Headaches, fatigue, and blurred vision in the distance and near are common concerns.
Nearsighted prescriptions will change with time depending upon many factors of health, environment, and genetics. It is not uncommon for a moderate myope to see an increase over the lifetime then finally levelling-off in the early twenties. There is some evidence to suggest that undercorrection and late correction can significantly slow progression of myopia, but this is more in clinical observations and not from formal studies.
Generally genetics is the primary determinant in myopia, like with other refractive errors, but environmental factors have been shown to contribute to increasing prescriptions. One factor is extended near work, especially when under duress. Here’s one recent study looking at the effect of near-point visual tasks on the axial length of the eye – which then determines the prescription in part.
Axial elongation following prolonged near work in myopes and emmetropes.
Br J Ophthalmol. 2011; 95(5):652-6 (ISSN: 1468-2079)
Woodman EC; Read SA; Collins MJ; Hegarty KJ; Priddle SB; Smith JM; Perro JV
Queensland University of Technology, Contact Lens and Visual Optics Laboratory, School of Optometry, Victoria Park Road, Kelvin Grove 4059, Australia. e.woodman@qut.edu.au
BACKGROUND/AIMS: To investigate the influence of a period of sustained near work upon axial length in groups of emmetropes (EMM) and myopes.
METHODS: Forty young adult subjects (20 myopes and 20 emmetropes) were recruited for the study. Myopes were further classified as early onset (EOM), late onset (LOM), stable (SM) or progressing (PM) subgroups. Axial length was measured with the IOLMaster instrument before, immediately after and then again 10 min after a continuous 30 min near task of 5 D accommodation demand. Measures of distance objective refraction were also collected.
RESULTS: Significant changes in axial length were observed immediately following the near task. EOM axial length elongated on average by 0.027±0.021 mm, LOM by 0.014±0.020 mm, EMM by 0.010±0.015 mm, PM by 0.031±0.022 mm and SM by 0.014±0.018 mm. At the conclusion of the 10 min regression period, axial length measures were not significantly different from baseline values.
CONCLUSION: Axial elongation was observed following a prolonged near task. Both EOM and PM groups showed increases in axial length that were significantly greater than emmetropes.