HJO  >> Vol. 7 No. 4 (December 2018)

    小梁切除术对青光眼患者眼部生物学参数的影响
    The Influence of Trabeculectomy on Biological Parameters of Glaucoma

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作者:  

李洪垒:青岛大学附属医院眼科,山东 青岛

关键词:
小梁切除术前房深度角膜曲率Trabeculectomy Anterior Chamber Depth Keratometry Intraocular Lens

摘要:

目的:总结有关小梁切除术后眼部生物学参数变化的证据,为青光眼联合白内障手术或抗青光眼术后再行白内障手术前人工晶体度数的选择提供临床指导。结论:小梁切除术可导致眼轴长度(AL),前房深度(ACD),晶状体厚度,脉络膜厚度和角膜曲率的短期波动和长期变化。AL,ACD和角膜曲率测量的变化对于影响白内障手术后屈光结果的预测具有重要意义。为了获得最佳屈光状态,建议延迟白内障手术,直到AL,ACD和角膜曲率在手术后约6个月达到稳定状态。

Purpose: To summarize the evidences of the changes of ocular biological parameters after tra-beculectomy, and to provide clinical guidance for the selection of intraocular lens power before combined glaucoma cataract surgery or anti-glaucoma surgery. Conclusion: With the decrease of intraocular pressure after trabeculectomy, axial length (AL) and anterior chamber depth (ACD) decrease, while lens thickness, choroidal thickness and with-the-rule astigmatism usually increase. These changes in biological parameters may affect the calculation of intraocular lens power. In order to obtain the best refractive state, it is recommended that cataract surgery be delayed until AL, ACD and corneal curvature reach a stable state about 6 months after surgery.

1. 引言

全球青光眼的发病率大约为3.5%,据预测至2020年,全世界范围内将会有近8000万青光眼患者 [1] [2] 。小梁切除术是目前青光眼最常用的长期降低眼压的治疗方法。其人为地建立房水流出途径,增加房水外流而达到降眼压的目的。有效降低眼压的同时,在小梁切除术后眼部生物学参数会发生一些变化。随着眼压的降低,眼轴长度(AL)和前房深度(ACD)减小,晶状体厚度、脉络膜厚度和顺规散光通常增加。对于青光眼小梁切除术后再行白内障超声乳化吸除联合人工晶体植入术或青光眼联合白内障手术患者,这些生物学参数的改变可能会对人工晶体度数的测算产生影响。

2. 角膜曲率的变化

大多数研究发现,小梁切除术后角膜曲率的变化引起顺规散光,术后三个月散光值平均为0.81 ± 1.08D,在一年内趋于消退 [3] [4] [5] [6] [7] 。这些角膜曲率变化对于行5 × 5 mm巩膜瓣小梁切除术后早期角膜曲率变化特别显著 [8] 。

角膜地形图可以更详细地揭示术后角膜曲率的变化 [9] 。小梁切除术后角膜地形图显示大多数角膜参数变化发生于上半部分 [5] [9] 。角膜地形图的变化有两种较为广泛的形式;大多数患者发展为明显的角膜陡峭化,而一些患者则变为明显的角膜扁平化。尽管在地形图变化方面存在这些差异,但两组都表现出顺规散光的增加。上方角膜扁平化和下方角膜陡峭的共存导致垂直角膜曲率值和顺规散光的整体增加 [9] 。

尽管术后早期顺规散光的幅度很大,但在手术后一年内它往往会消退并达到术前值 [3] [10] 。Cunliffe等 [10] 观察到,术后2个月的顺规散光在第10个月恢复至术前。同样,Kook等 [11] 证实小梁切除术后12个月与术前一周相比,散光值无显著差异。

为了进一步分析引起角膜曲率变化的可能原因,一些研究者评估了小切口小梁切除术诱导的顺规散光的程度,2 mm × 2 mm巩膜瓣,导致散光较少,散光恢复更快 [6] 。相反,在手术时使用抗代谢物是手术诱导的顺规散光持续时间长的危险因素 [3] [12] 。解释诱发散光的其他可能原因包括:巩膜瓣缝合较松,巩膜内口靠后以及术中广泛的烧灼术 [4] [8] [10] ;然而,最可能的解释是眼压的降低,因此,眼睑压力的影响更明显。Delbek等 [13] 报道,一个月后,散光变化与眼压降低之间存在显著相关性;眼压越低,顺规散光越大;然而,这种相关性在六个月后消失。

3. 前房深度(ACD)变化

使用接触式生物测量仪器测量,术后不久ACD变浅,术后2至3天达到术后最小深度 [14] [15] 。此后,ACD开始逐渐增加,到第14天达到术前值的83%至91% [10] [14] [15] ;然而,ACD仍比术前缩短近0.11~0.22 mm,即使术后数年亦如此 [16] 。相反,一些使用非接触性仪器测量的研究表明至少在小梁切除术后3周,ACD不受手术影响 [17] [18] 。在最近的一项研究中,评估了MMC小梁切除术后接触和非接触生物测量的ACD变化,发现这两种方法之间没有显著差异。手术后6个月,接触式和非接触式生物测量ACD分别减少0.10~0.12和0.07~0.10 mm [19] 。

小梁切除术后ACD变化与眼压减少水平相关,特别是原发性开角型青光眼患者 [16] 。原发性开角型青光眼患者巩膜较薄且具有韧性,术后ACD波动较原发性闭角型青光眼患者大 [16] 。

4. 晶状体厚度变化

尽管晶状体厚度在最新一代人工晶体度数计算公式中很重要,但很少有关于小梁切除术后晶状体厚度变化的研究。Cunliffe等 [10] 将手术后近视移位和浅前房部分归因于晶状体的可能变化。他们认为可能由于术后浅前房导致睫状体向前移动,与睫状肌痉挛相结合,会释放悬韧带上的张力,导致晶状体增厚和前移;然而,在他们的研究中没有测量晶状体厚度和晶状体位置的变化。最近有研究发现,在用MMC进行小梁切除术后6个月,晶状体厚度显著增加 [19] 。这些微小的变化可能表明早期白内障的形成或进展,这是小梁切除术后常见的并发症 [3] [20] [21] [22] [23] 。晶状体厚度的增加可能是小梁切除术后报告的ACD减少的部分原因。将来需要更多的研究来评估小梁切除术对晶状体厚度的影响及其与ACD的关系。

5. 脉络膜厚度变化

有研究评估小梁切除术后的脉络膜厚度变化 [24] [25] [26] 。由于这些研究大多数只调查了一次术后脉络膜厚度的变化,小梁切除术后这种变化的持续过程仍然未知;然而,所有这些研究一致表明,随着眼压和AL的减少,小梁切除术后脉络膜厚度明显增加。这些变化在小梁切除术后的第一天迅速发生,并且可以持续至术后至少六个月 [24] [25] [26] 。尽管在短期研究中眼压和脉络膜厚度的变化之间没有关联,但是较长时期的研究表明脉络膜厚度和眼压变化之间存在高度相关性; 每减少1.0 mmHg的眼压,脉络膜厚度增加3.4 μm [24] [25] [26] 。同样,脉络膜厚度的变化与眼灌注压的变化之间存在显著正相关性,小梁切除术后其显著增加(31.4%) [24] 。脉络膜含有丰富的非血管平滑肌,因此,当这些肌肉收缩引起脉络膜变薄,平滑肌一旦松弛就会扩张,脉络膜变厚。因此,大幅降低眼压可能会导致脉络膜扩张。需要进一步的研究来确定脉络膜变化的确切机制及其对视功能的影响。脉络膜厚度的变化可能是所观察到的AL变化的基础,因为IOL Master,Lenstar和A-scan等仪器对AL测量是从前角膜到内界膜或视网膜色素上皮的距离。

6. 眼轴长度的变化

Nemeth等 [27] 首次报道了小梁切除术后AL的变化,并观察到术后第4天AL减少。进一步的研究表明,在60个月的随访过程中,小梁切除术后AL持续较少 [3] [11] [16] [24] [25] [27] [28] [29] 。使用非接触式生物学测量,AL在术后3个月趋于稳定,此过程中AL减少了0.10至0.18 mm [24] [25] [28] [29] 。

术中使用抗代谢药物可最大限度地减少瘢痕组织形成和滤过泡失败率,从而会降低术后眼压和AL [11] 。使用压平式眼部超声检查的研究也表明小梁切除术后AL的减少会更多 [3] [11] [16] 。Kook等 [3] 报道,术中使用抗代谢物丝裂霉素-C (MMC)在术后3个月显著降低AL (0.83~1.00 mm),而最近的研究使用非接触式测量方法(IOL Master和Lenstar),AL减少(0.10至0.18 mm)的程度明显低于接触式的测量方法 [24] [25] [28] [29] 。然而,术后低眼压(IOP为0到4 mmHg)的患者AL减少几乎是没有低眼压的患者的三倍,这进一步强调了术后较低的眼压引起AL降低幅度较大 [28] 。

不同的AL测量方法可以解释这些研究之间的差异。与非接触测量方法相比,一些研究中使用的超声生物测量法导致AL更明显的减少 [3] [11] [16] 。这种差异是因为采用非接触式方法避免了压迫眼球,不会导致眼球形态发生改变,这与接触式超声生物测量方法相反,后者在小梁切除术后的软眼中易于变形和低估AL。在这种情况下,由于巩膜塌陷或脉络膜水肿,AL可能被低估,尤其是接触式超声生物测量方法。

小梁切除术后AL显著降低的危险因素包括:术前高眼压,术后低眼压,年轻患者,术中使用抗代谢药物,近视以及手术并发症如脉络膜脱离 [3] [11] [28] 。低眼压是小梁切除术的常见并发症,其发生率大约为10%至37% [30] 。小梁切除术后AL减少的机制包括与IOP减少相关的脉络膜和眼球壁厚度增加。一些研究已经证实了IOP降低量与脉络膜厚度和AL降低之间的直接关系 [24] [26] 。在原发性开角型青光眼中,IOP每降低1.0 mmHg导致AL减小0.01 mm [16] 。与闭角型青光眼相比,开角型青光眼小梁切除术后AL的变化更敏感,并且AL的波动更大 [24] 。

7. 小梁切除术后患者再次行白内障摘除术后的屈光变化

青光眼和白内障通常是共存的眼部疾病 [31] [32] ,并且患者在小梁切除术后白内障形成或进展的风险也更高。因此,许多青光眼患者需要同时或不久进行白内障手术,由于IOP波动引起的生物识别变化,预测这些患者植入IOL后的屈光结果具有挑战性。白内障摘除术可能增加小梁切除术后眼压,可导致白内障摘除术后AL更长,引起近视移位。小梁切除术后眼行白内障手术后眼压升高的机制被认为是巩膜瓣和结膜滤过泡的炎症和纤维化 [33] [34] 。

一些研究 [35] [36] [37] [38] 研究了小梁切除术后眼再行白内障摘除术后的屈光结果。虽然有些人表现出近视转变,但有些人则表现出相当可预测的屈光结果。这种不一致可能与超声乳化和小梁切除术之间的时间间隔,青光眼的类型,白内障手术前的眼压和白内障手术后的眼压变化有关。Muallem等 [36] 发现,在小梁切除术后的前10个月,接受白内障手术的患者中超过1.00 D的近视移位更为普遍。此外,在主要为开角型青光眼的研究中,有明显的近视移位(0.36至0.66 D,p ≤ 0.01),这意味着这些眼睛可能对眼压变化更敏感 [37] [38] 。就AL变化而言,理论上可以预期在联合手术后的远视漂移;然而,使用非接触式生物测量法,青白联合手术的屈光结果与预测的屈光度没有显着差异 [39] 。在超声乳化摘除术后,AL和角膜曲率变化具有相反的屈光效应,使得生物特征变化可能相互抵消,使得原始计算的IOL度数预测的屈光结果是准确的 [29] 。此外,术后屈光的时间非常重要。如果在手术后三个月内测量,可能会观察到近视移位而不是远视移位,因为在术后早期,角膜变化比AL变化更明显 [38] 。

由于大多数关于小梁切除术患者的人工晶体屈光结果的研究主要是回顾性的。因而需要进行更长时间随访的前瞻性研究,以进一步评估小梁切除术或小梁切除术后再行白内障手术或青光眼联合白内障手术对眼部生物特征参数的影响。

8. 结论

小梁切除术可导致AL,ACD,晶状体厚度,脉络膜厚度和角膜曲率的短期波动和长期变化。小梁切除术后生物特征改变最重要的意义是它对青光眼联合白内障手术或随后的白内障手术的屈光结果的影响。AL,ACD和角膜曲率测量的变化对于影响白内障手术后屈光结果的预测具有重要意义。为了获得最佳屈光状态,建议延迟白内障手术,直到AL,ACD和角膜曲率在手术后约6个月达到稳定状态。另外,在这种情况下,优选使用非接触式光学生物测量仪器而不是接触式超声生物测量仪器来测量生物学参数以用于IOL度数计算。同样,一旦眼压稳定,验光配镜应延迟至手术后至少三个月。

文章引用:
李洪垒. 小梁切除术对青光眼患者眼部生物学参数的影响[J]. 眼科学, 2018, 7(4): 181-185. https://doi.org/10.12677/HJO.2018.74029

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