Nearwork - a risk factor for overcorrectingpatients?

Introduction: Research has shown that people become more myopic when performing nearwork. This phenomenon is called nearwork-induced transient myopia (NITM). Although this nearsightedness is temporary it is possible that it has an effect on individuals over time, causing permanent myopia, but from a more short-term and clinical point of view; can NITM have implications on the ordinary visual examination? Aim: The purpose of this study was to investigate if prolonged nearwork can produce a change in the distance refraction significant enough to be measured with commonly occurring instrumentation used in clinics and if patients can be overcorrected because of this. Methods: 23 emmetropic and myopic subjects with a mean age of 24 years were examined at two occasions; prior to and after approximately 2 hours of nearwork. The refraction was determined using a Topcon VT-10 manual phoropter and the end-point of refraction was defined using the duo-chrome test. Results: When the data was averaged across all test subjects it revealed a statistically significant myopic refractive shift of 0.16 D. A subgroup analysis revealed an average myopic shift of 0.28 D in the myopic subjects (Student’s paired t-test; P < 0.05) and an average myopic shift of 0.05 D in the emmetropic subjects (Student’s paired t-test; P > 0.05). Conclusion: Based on the data and results presented in this study and the results from earlier studies it is reasonable to say that there is a small risk that some patients could be overcorrected due to prolonged nearwork being performed prior to a visual examination