Vision Science Research Group, University of Ulster, Coleraine, Northern Ireland, United Kingdom.
Invest Ophthalmol Vis Sci. 2013 Jan 9;54(1):251-7. doi: 10.1167/iovs.12-10506.
Children with Down syndrome (DS) and cerebral palsy (CP) often have reduced visual acuity (VA). This study assessed VA and low-contrast acuity (LCA) with Lea symbols in DS and CP populations to explore whether LCA measures provide useful additional information about visual performance. VA and LCA were also measured in a large group of typically developing young people.
High-contrast VA and LCA performance was measured monocularly using crowded Lea symbols with 45 young people with CP (mean age 11.8 ± 4 years), 44 with DS (mean age 10.5 ± 3 years), and 211 controls (mean age 11.4 ± 3 years). Refractive status was confirmed with cycloplegic retinoscopy.
DS AND CP GROUPS HAD SIGNIFICANTLY LOWER ACUITIES THAN CONTROLS AT ALL CONTRASTS (P 0.001). MEAN (SD) HIGH-CONTRAST VA WAS AS FOLLOWS: DS = +0.39 ± 0.2 logMAR; CP = +0.18 ± 0.2 logMAR; controls = -0.04 ± 0.1 logMAR. Mean 2.5% LCA was as follows: DS = +0.73 ± 0.2 logMAR; CP = +0.50 ± 0.2 logMAR; controls = +0.37 ± 0.1 logMAR. For controls, the mean difference between VA and 2.5% LCA was 0.40 logMAR (95% limits of agreement, ± 0.22 logMAR). While there was a positive relation between VA and 2.5% LCA scores (linear regressions, P < 0.0001), considerable variation existed, with VA explaining only 36% of the variance in LCA performance for control data.
VA and LCA performance was significantly poorer in DS and CP groups than in controls, and high-contrast VA did not reliably predict low-contrast performance. Therefore both high- and low-contrast acuity assessment are valuable to fully describe an individual's visual function, and this may be particularly relevant in DS and CP in cases in which patients are unable to articulate visual difficulties. Age-specific reference data from a large sample of typically developing young people across a broad age range are presented for clinicians using high- and low-contrast Lea symbols.
唐氏综合征（DS）和脑瘫（CP）患儿常伴有视力（VA）降低。本研究采用 Lea 符号评估 DS 和 CP 人群的 VA 和低对比度视力（LCA），以探讨 LCA 测量值是否能为视觉表现提供有用的补充信息。此外，还在一大组发育正常的年轻人中测量了 VA 和 LCA。
使用 45 名 CP 患者（平均年龄 11.8 ± 4 岁）、44 名 DS 患者（平均年龄 10.5 ± 3 岁）和 211 名对照组（平均年龄 11.4 ± 3 岁）的单眼拥挤 Lea 符号分别测量高对比度 VA 和 LCA。通过睫状肌麻痹检影验光确认屈光状态。
与对照组相比，DS 和 CP 组在所有对比度下的视力均显著降低（P < 0.001）。高对比度 VA 的平均（标准差）值如下：DS = +0.39 ± 0.2 logMAR；CP = +0.18 ± 0.2 logMAR；对照组 = -0.04 ± 0.1 logMAR。2.5% LCA 的平均结果如下：DS = +0.73 ± 0.2 logMAR；CP = +0.50 ± 0.2 logMAR；对照组 = +0.37 ± 0.1 logMAR。对于对照组，VA 和 2.5% LCA 之间的平均差异为 0.40 logMAR（95%一致性界限，± 0.22 logMAR）。虽然 VA 和 2.5% LCA 评分之间存在正相关（线性回归，P < 0.0001），但存在很大差异，VA 仅能解释对照组 LCA 表现的 36%的变异性。
DS 和 CP 组的 VA 和 LCA 表现明显低于对照组，高对比度 VA 并不能可靠地预测低对比度表现。因此，高对比度和低对比度视力评估对于全面描述个体的视觉功能都很有价值，在 CP 和 DS 患者无法表达视觉困难的情况下，这可能尤为相关。本研究为使用高对比度和低对比度 Lea 符号的临床医生提供了来自大样本发育正常的年轻人在广泛年龄范围内的年龄特异性参考数据。
