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第四节、集合功能不足 【症状】 阅读或近距离工作时眼部不适或视物模糊。最常见于年轻人，也可见于老年患者。 【主要体征】 视近时眼球外转，外隐斜或外斜视，表现为近融合性集合(辐辏)幅度过小；调节性集合/调节(AC/A)比值低；集合的近点较远。参见检查部分。 【其他体征】 视近较视远时外隐斜更为明显。 【鉴别诊断】 1.屈光不正未矫正 远视或近视过矫。 2.调节功能不足(AI) 通常见于老视前期，未矫正的低度远视或近视过矫。阅读时戴4△基底向内的棱镜，调节功能不足患者视物模糊，但集合功能不足患者视物变清晰。偶有青少年患者出现一过性集合轻瘫，需要戴用阅读眼镜或双焦点眼镜。这种特发性病变可在数年后痊愈。调节功能不足患者的阅读眼镜加用基底向内的棱镜可改善症状。 3.集合功能麻痹 外斜视急性起病，仅在视近时出现复视；内收和调节正常。通常是由于四叠体或第Ⅲ颅神经核病变引起，并且可能与Parinaud综合征相关。 【病因学】 1.疲劳或疾病。 2.药物(副交感神经阻滞剂)。 3.葡萄膜炎。 4.Adie强直瞳孔。 5.产生基底向外的棱镜效应的眼镜。 6.疹后脑炎。 7.外伤。 8.通常为特发性。 【检查】 1.显然验光 不使用睫状肌麻痹。 2.测定集合近点 让患者注视一可调节目标(如铅笔擦)，将该视标移向患者，让其报告何时出现复视。正常的集合近点为小于6~8cm。 3.遮盖试验 检查患者视远和视近有无外斜或内斜，参见附录3，遮盖/去遮盖和交替遮盖试验；或马氏杆试验。 4.检查患者视近时的融合功能 让患者注视置于其阅读即离的一可调节目标，将棱镜串基底向外置于眼前，缓慢增加度数，直到患者报告眼前出现复视，是为融合破坏点；然后渐减度数，直到恢复为单像，是为融合恢复点。融合破坏点低，如10△~15△；或恢复点低或二者均有，表明集合功能不足。 5.患者阅读时 在其眼前放置4△基底向内的棱镜，观察字迹变清晰还是更模糊，以排除调节功能不足。 6.睫状肌麻痹后验光 在以上检查完成后进行。 注：如果患者需用近用眼镜，上述检查应要求患者戴镜进行。 【治疗】 1.矫正屈光不正 远视应轻度低矫，而近视应全部矫正。 2.近点训练 嘱患者注视面前一臂远的铅笔擦，缓慢向面部移近，患者需集中精力维持铅笔擦的单像；出现复视，则重新操作。嘱患者每次训练时在维持单视的状态下尽量拿近铅笔。重复训练15次，每天5次。 3.戴基底向外的棱镜做近点训练 适用于集合近点尚可或无需配戴棱镜即可进行铅笔尖训练者。患者一眼戴6△基底向外的棱镜，铅笔的操作如前所述。 4.近距离工作的间歇期 应有充足的照明和休息放松时间。 5.对老年人或虽经近点训练但症状无改善者 阅读眼镜加用基底向内的棱镜可有所帮助。 【随访】 非急症，1个月后复查。 13.4 Convergence Insufficiency Symptoms Eye discomfort or blurred vision from reading or near work. Most common in young adults, but may be seen in older people. Signs Critical. An exodeviation (either a phoria or tropia) at near in the presence of poor near-fusional convergence amplitudes, a low accommodative convergence/accommodation (AC/A) ratio, and a remote near point of convergence (see Work-up). Other. An exophoria greater at near than at distance. Differential Diagnosis Uncorrected Refractive Error: Hyperopia or over-minused myopia. Accommodative insufficiency (AI): Often in prepresbyopia age range from uncorrected low hyperopia or over-minused myopia. While reading, a 4-diopter base-in prism placed in front of the eye blurs the print in AI, but improves clarity in CI. Rarely, adolescents may acquire transient paresis of accommodation, requiring reading glasses or bifocals. This idiopathic condition resolves in several years. Patients with AI may benefit from reading glasses with base-in prism. Convergence paralysis: Acute onset of exotropia and diplopia on near fixation only; normal adduction and accommodation. Usually results from a lesion in the corpora quadrigemina or the third cranial nerve nucleus, and may be associated with Parinaud syndrome. Etiology Fatigue or illness. Drugs (parasympatholytics). Uveitis. Adie tonic pupil. Glasses inducing a base-out prism effect. Postexanthematous encephalitis. Traumatic injury. Often idiopathic. Work-Up Manifest (without cycloplegia) refraction. Determine the near point of convergence: Ask patient to focus on an accommodative target (e.g., a pencil eraser) and to state when double vision develops as you bring the target toward them; a normal near point of convergence is <6 to 8 cm. Check for exodeviations or esodeviations at distance and near by using the cover tests (see Appendix 3, Cover/Uncover and Alternate Cover Tests) or the Maddox rod test. Measure the patient's fusional ability at near. Have patient focus on an accommodative target at their reading distance. With a prism bar, slowly increase the amount of base-out prism in front of one eye until patient notes double vision (the break point), and then slowly reduce the amount of base-out prism until a single image is again noted (the recovery point). A low break point (e.g., 10 to 15 prism diopters) or a low recovery point, or both, are consistent with CI. Place a 4-diopter base-in prism in front of one eye while patient is reading. Determine whether the print becomes clearer or more blurred to rule out AI. Perform cycloplegic refraction after the previous tests. Note These tests are performed with the patient's spectacle correction in place (if glasses are worn for near work). Treatment Correct any refractive error. Slightly undercorrect hyperopia, and fully correct myopia. Near-point exercises (e.g., pencil push-ups): The patient focuses on a pencil eraser while slowly moving it from arm's length toward the face. Concentrate on maintaining one image of the eraser, repeating the maneuver when diplopia manifests. Try to bring the pencil in closer each time while maintaining single vision. Repeat the exercise 15 times, five times per day. Near-point exercises with base-out prisms (for patients whose near point of convergence is satisfactory or for those who have mastered pencil push-ups without a prism): The patient performs pencil push-ups as described previously, while holding a 6-diopter base-out prism in front of one eye. Encourage good lighting and relaxation time between periods of close work. For older patients, or those whose condition shows no improvement despite near-point exercises, reading glasses with base-in prism can be useful. Follow-Up Nonurgent. Patients are reexamined in 1 month.
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