Averbuch-Heller L, Dell'Osso L F, Jacobs J B, Remler B F
Veterans Affairs Medical Center, Department of Neurology, Case Western Reserve University, Cleveland, Ohio 44106, USA.
J Neuroophthalmol. 1999 Sep;19(3):166-72.
Although nystagmus has been reported in Down syndrome (DS), it has been poorly characterized, because most investigators have relied on clinical observations rather than on eye movement recordings. This study was conducted to investigate nystagmus in DS, using quantitative measurements of eye movements.
Ocular motility and visual functions were examined in 26 unselected adults with DS and compared with those in an age-matched group of 35 subjects with other causes of mental retardation. The eye movements of those with clinically evident nystagmus were recorded with the infrared technique. We also recorded the eye movements of a child with DS and nystagmus.
Nystagmus was identified in six (23%) adults with DS and in none in the control group. All six patients showed latent/manifest latent nystagmus (LMLN), prominent with the covering of one eye, and esodeviations of 10 to 30 prism diopters. Eye movement recordings confirmed LMLN with its exponentially decaying waveform. Frequencies ranged from 2 to 5 Hz and amplitudes from 5 degrees to 20 degrees. While attempting to fixate straight ahead in the absence of visual cues, three subjects exhibited shifts in the mean eye position. In contrast with the findings in adults, the only child with DS examined had both congenital nystagmus and LMLN waveforms.
The predominant type of nystagmus in the study subjects with DS is LMLN. The high prevalence of LMLN may reflect abnormal integration of visuospatial information that is typical of DS. The concurrent presence of congenital nystagmus in a child but only LMLN in the adults with DS raises the possibility of age-related waveform changes or could reflect sample variation.
尽管已有唐氏综合征（DS）患者出现眼球震颤的报道，但由于大多数研究者依赖临床观察而非眼动记录，其特征描述尚不充分。本研究旨在通过眼动的定量测量来研究DS患者的眼球震颤。
对26例未经挑选的成年DS患者进行眼动和视觉功能检查，并与35例年龄匹配的其他智力发育迟缓病因患者进行比较。对有临床明显眼球震颤的患者采用红外技术记录眼动。我们还记录了1例患有DS和眼球震颤的儿童的眼动。
6例（23%）成年DS患者被发现有眼球震颤，而对照组无1例。所有6例患者均表现为潜伏性/显性潜伏性眼球震颤（LMLN），遮盖一眼时明显，内斜度为10至30棱镜度。眼动记录证实为LMLN，其波形呈指数衰减。频率范围为2至5Hz，振幅为5度至20度。在无视觉线索时试图直视前方时，3例受试者平均眼位发生偏移。与成人的结果相反，所检查的唯一1例DS儿童既有先天性眼球震颤又有LMLN波形。
本研究中DS受试者的主要眼球震颤类型为LMLN。LMLN的高患病率可能反映了DS典型的视觉空间信息整合异常。DS儿童同时存在先天性眼球震颤而成年患者仅存在LMLN，这增加了与年龄相关的波形变化的可能性，或者可能反映了样本差异。
