Thompson D A, Møller H, Russell-Eggitt I, Kriss A
Department of Ophthalmology, Great Ormond Street, Hospital for Children, NHS Trust, London.
Br J Ophthalmol. 1996 Sep;80(9):794-8. doi: 10.1136/bjo.80.9.794.
Patching the fellow eye in infancy is a well recognised therapy to encourage visual development in the lensectomised eye in cases of unilateral congenital cataract. The possibility of iatrogenic deficits of the fellow eye was investigated by comparing the vision of these patients with untreated unilateral patients and binocularly normal controls.
Sweep visual evoked potentials (VEPs) offer a rapid and objective method for estimating grating acuity. Sweep VEPs were used to estimate acuity in 12 children aged between 4 and 16 years who had had a congenital cataract removed in the first 13 weeks of life. The acuities of aphakic and fellow phakic eye were compared with the monocular acuities of similarly aged children who have good binocular vision, and with children with severe untreated uniocular visual impairment. Recognition linear acuities were measured with a linear Bailey-Lovie logMAR chart and compared with the sweep VEP estimates.
A significant difference was found between Bailey-Lovie acuity of the fellow eye of the patient group and the right eye of binocular controls, and the good eye of uniocular impaired patients (one way ANOVA, p < 0.01). However, this was not evident for a similar comparison with sweep VEP estimates. There was no significant difference between the right and left eye acuities in binocular controls measured by the two techniques (paired t test).
A loss of recognition acuity in the fellow phakic eye of patients treated for unilateral congenital cataract has been demonstrated with a logMAR chart. This loss was not apparent in children who have severe untreated uniocular visual impairment and may therefore be an iatrogenic effect of occlusion. An acuity loss was not apparent in the patient group using the sweep VEP method. Sweep VEP techniques have a place for objectively studying acuity in infants and in those whose communication difficulties preclude other forms of behavioural test. The mean sweep VEP acuity for the control groups is 20 cpd--that is, about 6/9. When acuities higher than this are under investigation--for example, in older children, slower transient VEP recording may be more appropriate, because higher spatial frequency patterns are not as visible at higher temporal rates (for example, 8 Hz used in sweep VEP recordings).
在单侧先天性白内障病例中，婴儿期遮盖对侧眼是一种公认的促进晶状体切除眼视觉发育的疗法。通过将这些患者的视力与未治疗的单侧患者以及双眼正常对照者的视力进行比较，研究了对侧眼医源性缺陷的可能性。
扫描视觉诱发电位（VEP）为估计光栅视力提供了一种快速且客观的方法。使用扫描VEP来估计12名年龄在4至16岁之间、在出生后13周内接受先天性白内障摘除术的儿童的视力。将无晶状体眼和对侧有晶状体眼的视力与年龄相仿、双眼视力良好的儿童以及严重未经治疗的单眼视力障碍儿童的单眼视力进行比较。使用线性贝利-洛维对数最小分辨角（logMAR）视力表测量识别线性视力，并与扫描VEP估计值进行比较。
患者组对侧眼的贝利-洛维视力与双眼对照者的右眼以及单眼视力受损患者的好眼之间存在显著差异（单因素方差分析，p < 0.01）。然而，与扫描VEP估计值进行类似比较时，这种差异并不明显。两种技术测量的双眼对照者的右眼和左眼视力之间没有显著差异（配对t检验）。
使用logMAR视力表已证明，接受单侧先天性白内障治疗的患者对侧有晶状体眼的识别视力有所下降。这种下降在严重未经治疗的单眼视力障碍儿童中并不明显，因此可能是遮盖的医源性效应。使用扫描VEP方法时，患者组中未出现视力下降。扫描VEP技术在客观研究婴儿以及那些因沟通困难而无法进行其他形式行为测试的人群的视力方面具有一席之地。对照组的平均扫描VEP视力为20周/度——即约6/9。当研究高于此的视力时——例如在年龄较大的儿童中，较慢的瞬态VEP记录可能更合适，因为在较高的时间频率（例如扫描VEP记录中使用的8赫兹）下，较高空间频率的图案不太明显。
