Schmid Katrina L, Hilmer Katherine S, Lawrence Rebecca A, Loh Shook-Yee, Morrish Linda J, Brown Brian
Centre for Health Research, School of Optometry, Queensland University of Technology, Brisbane, Australia.
Optom Vis Sci. 2005 Jul;82(7):602-11. doi: 10.1097/01.opx.0000171337.02376.60.
Accommodation errors during reading and the subsequent near work-induced transient myopia (NITM) that occurs have been implicated in the development and progression of myopia. This study investigated the effects of two letter variables, size and contrast, on accommodation accuracy during the near task and on NITM and its subsequent decay. These were varied so as to mimic what might occur when students photocopy and reduce reading materials.
Based on their refractive errors, young adult subjects (18-25 years) were classified into three groups: emmetropes (n = 19), stable myopes (n = 17), and progressing myopes (n = 17). Three print sizes (N4, N6, and N8) and two print contrasts (90% and 60%) were used to give six different reading targets. Targets were presented in random order at 25 cm (4 D demand) and the text read for comprehension for 3 minutes. For each target, accommodation accuracy and NITM and its decay were measured using the free space Shin-Nippon SRW-5000 autorefractor.
When data for all subjects were pooled, there was a significant effect of letter size (p = 0.030) but not contrast (p = 0.898) on accommodation accuracy; however, differences were small and unlikely to be clinically relevant. NITM (p = 0.033) and its decay (p = 0.012) also varied with letter size. NITM was greater and decay longer for larger letters. We found no effect of refractive error group on accommodation accuracy. In contrast, there was a significant difference in the magnitude of NITM and its decay for emmetropic and myopic subjects (although no effect of progression status); myopes had larger NITM values and longer decay times to baseline than emmetropes (NITM myopes: 0.37 +/- 0.14D vs. emmetropes: 0.19 +/- 0.17 D, p = 0.005; decay time myopes: 15.12 +/- 6.58 seconds vs. emmetropes 7.10 +/- 4.82 seconds, p = 0.0045). The differences in NITM and its decay between the two refractive groups were of similar magnitude for all six combinations of letter size and contrast.
Our data do not support the suggestion that common reductions in letter size or contrast of reading material (as might occur for photocopied reading materials) cause greater accommodation inaccuracy and greater near work-induced adaptation effects that would exacerbate myopia development in young adults.
阅读时的调节误差以及随后出现的由近距工作诱发的短暂性近视（NITM）被认为与近视的发生和发展有关。本研究调查了两个字母变量，即大小和对比度，对近距任务期间的调节准确性、NITM及其随后的消退的影响。这些变量的变化是为了模拟学生复印和缩小阅读材料时可能发生的情况。
根据屈光不正情况，将年轻成年受试者（18 - 25岁）分为三组：正视眼组（n = 19）、稳定近视眼组（n = 17）和进行性近视眼组（n = 17）。使用三种字号（N4、N6和N8）和两种印刷对比度（90%和60%）来给出六个不同的阅读目标。目标以随机顺序呈现在25 cm处（4 D需求），让受试者阅读文本以理解内容，持续3分钟。对于每个目标，使用自由空间日本新日本SRW - 5000自动验光仪测量调节准确性、NITM及其消退情况。
当汇总所有受试者的数据时，字母大小对调节准确性有显著影响（p = 0.030），而对比度无显著影响（p = 0.898）；然而，差异很小，不太可能具有临床相关性。NITM（p = 0.033）及其消退（p = 0.012）也随字母大小而变化。字母越大，NITM越大，消退时间越长。我们发现屈光不正组对调节准确性没有影响。相比之下，正视眼和近视眼受试者在NITM的大小及其消退方面存在显著差异（尽管进展状态没有影响）；近视眼的NITM值更大，恢复到基线的时间比正视眼更长（近视眼的NITM：0.37 +/- 0.14D，正视眼：0.19 +/- 0.17 D，p = 0.005；近视眼的消退时间：15.12 +/- 6.58秒，正视眼：7.10 +/- 4.82秒，p = 0.0045）。对于字母大小和对比度的所有六种组合，两个屈光组之间NITM及其消退的差异幅度相似。
我们的数据不支持这样的观点，即阅读材料常见的字母大小减小或对比度降低（如复印阅读材料时可能发生的情况）会导致更大程度的调节不准确以及更大的由近距工作诱发适应效应，从而加剧年轻人近视的发展。
