Hayes G J, Cohen B E, Rouse M W, De Land P N
Southern California College of Optometry, Fullerton 92831-1699, USA.
Optom Vis Sci. 1998 Jul;75(7):506-12. doi: 10.1097/00006324-199807000-00019.
Nearpoint of convergence (NPC) values of 8 to 10 cm are widely used to diagnose binocular dysfunctions such as convergence insufficiency. However, there are no published age-related normative values in the literature to substantiate these values.
Subjects were 297 schoolchildren in kindergarten, third grade, and sixth grade who had passed a school-based Modified Clinical Technique vision screening. Each child had the NPC break and recovery taken three times using a standardized protocol developed by the Convergence Insufficiency and Reading Study group. The examiners used an Astron International (ACR/21) Accommodative Rule with a movable column of 20/30 letters as the target.
For each grade, the distribution of NPC break was right skewed, with a concentration of values between 1 and 6 cm. At least 85% of the subjects in each grade had an NPC break < or = 6 cm. NPC break values (mean +/- SD) were 3.3 +/- 2.6 cm for kindergartners, 4.1 +/- 2.4 cm for third graders, and 4.3 +/- 3.4 cm for sixth graders, and the means were found to be statistically different (analysis of variance, p = 0.031). NPC recoveries (mean +/- SD) for the three groups were 7.3 +/- 4.8 cm, 8.7 +/- 4.2 cm, and 7.2 +/- 3.9 cm, respectively, which were also significantly different (analysis of variance, p = 0.027). The recovery distributions were more symmetric and less skewed than those for break. For each grade level, there was a strong positive relationship between NPC recovery and NPC break, but the difference between NPC recovery and break had a low correlation with the NPC break.
Kindergartners had somewhat better NPC breaks than third or sixth graders, whereas no clear age trend was present for NPC recovery. A supporting study using a random sample of clinic patients (aged 10-12 years) suggests that patients with NPC breaks > 6 cm are more than twice as likely to be symptomatic than patients with NPC breaks < or = 6 cm. Based on these results and the NPC break distributions in this study, a clinical cutoff value of 6 cm is suggested for patients of elementary school age. A cutoff value in the 6- to 10-cm range is recommended for children of elementary school age in a screening context. The exact value within this range depends on the level of concern with identifying patients who have visual signs and symptoms associated with a receded NPC.
8至10厘米的集合近点（NPC）值被广泛用于诊断诸如集合不足等双眼功能障碍。然而，文献中尚无已发表的与年龄相关的标准值来证实这些数值。
研究对象为297名幼儿园、三年级和六年级的在校儿童，他们均通过了基于学校的改良临床技术视力筛查。使用集合不足与阅读研究组制定的标准化方案，对每个孩子的NPC破裂和恢复情况进行三次测量。检查人员使用Astron International（ACR/21）调节尺，以一列可移动的20/30字母作为目标。
对于每个年级，NPC破裂值的分布呈右偏态，数值集中在1至6厘米之间。每个年级至少85%的受试者NPC破裂值≤6厘米。幼儿园儿童的NPC破裂值（均值±标准差）为3.3±2.6厘米，三年级学生为4.1±2.4厘米，六年级学生为4.3±3.4厘米，经方差分析，这些均值存在统计学差异（p = 0.031）。三组的NPC恢复值（均值±标准差）分别为7.3±4.8厘米、8.7±4.2厘米和7.2±3.9厘米，也存在显著差异（方差分析，p = 0.027）。恢复值的分布比破裂值的分布更对称，偏态更小。对于每个年级水平，NPC恢复与NPC破裂之间存在很强的正相关关系，但NPC恢复与破裂之间的差异与NPC破裂的相关性较低。
幼儿园儿童的NPC破裂情况比三年级或六年级学生略好，而NPC恢复情况没有明显的年龄趋势。一项对临床患者（10至12岁）随机样本的支持性研究表明，NPC破裂值>6厘米的患者出现症状的可能性是NPC破裂值≤6厘米患者的两倍多。基于这些结果以及本研究中的NPC破裂值分布，建议小学年龄段患者的临床临界值为6厘米。在筛查情况下，建议小学年龄段儿童的临界值在6至10厘米范围内。该范围内的确切值取决于对识别有与NPC后移相关视觉体征和症状患者的关注程度。
