Cirrus HD-OCT与HRT2测量近视眼视盘参数的一致性评估

背景 近视是常见的眼病且是原发性开角型青光眼的风险因素.近视眼视盘参数的准确测量在临床工作中具有重要意义. 目的 比较频域光学相干断层扫描仪(Cirrus HD-OCT)和海德堡激光共焦断层扫描仪(HRT2)测量近视眼视盘参数的一致性,并探讨近视患者眼轴长度(AL)与2种仪器测量差值的关系.方法 采用横断面研究设计,纳入2010年9-12月在汕头大学·香港中文大学联合汕头国际眼科中心就诊的单纯近视患者150例,每例患者任意选择一眼纳入分析.受检眼均接受眼部检查,包括裸眼视力(UCVA)、最佳矫正视力(BCVA)、裂隙灯显微镜、视野检查和眼底检查.根据等效球镜度(SE)将受检眼分为低度近视组(SE≤-3.00 D)、中度近视组(-3.00 D＜SE＜-6.00 D)和高度近视组(SE≥-6.00D),分别为35、60和55眼.分别采用IOLMaster、Cirrus HD-OCT和HRT2测量受检眼AL和视盘参数,后者包括视盘面积、盘沿面积、视杯容积、杯盘面积比(ACDR)和垂直杯盘比(VCDR),对Cirrus HD-OCT测量的视盘参数进行光学放大效应校正,比较HRT2和校正后的Cirrus HD-OCT视盘参数测量值的一致性;分析AL与2种仪器视盘参数测量差值之间的关系.结果 受检者平均屈光度为(-5.22±2.34)D,平均AL为(25.62±1.10)mm.经光学放大效应矫正后的Cirrus HD-OCT视盘参数值均大于校正前的测量值,差异均有统计学意义(均P＜0.001).高度近视组受检眼经Cirrus HD-OCT测量的视盘面积值明显大于HRT2的测量值(P＜0.001),中度近视组HRT2测量的盘沿面积大于Cirrus HD-OCT的测量值(P=0.040),低、中、高度近视组Cirrus HD-OCT测量的ACDR、VCDR和视杯容积值均明显大于HRT2的测量值,差异均有统计学意义(均P＜0.001).Cirrus HD-OCT和HRT2测量的视盘面积的95％一致性范围(LoA)为-0.64～ 0.74 mm2,盘沿面积的95％ LoA为-0.74 ～0.62 mm2,均大于0.5;2种仪器测量的视盘面积、盘沿面积、视杯容积的差值与AL均呈微弱正相关(r=0.158、0.148、0.156,均P＜0.05);2种仪器测量的ACDR和VCDR差值与AL间均无明显相关性(r=0.012、0.093,均P＞0.05).结论 Cirrus HD-OCT测量近视眼视盘参数受光学放大效应的影响,眼轴越长,光学放大效应越明显.Cirrus HD-OCT与HRT2测量的视盘参数一致性较差,临床上2种检测结果不能相互替代,2种仪器测量的差异随着眼轴的增长而变大.

Agreement in optic disc measurements between Cirrus HD-OCT and Heidelberg retinal tomograph Ⅱ in myopic eyes

Background As myopia is a common ocular condition which has been reported as the risk factor of primary open angle glaucoma,it is of great importance to evaluate the optic disc morphology in myopic eyes.Objective This study was to evaluate the agreement of optic disc measurements between Cirrus high-density optical coherence tomography (HD-OCT) and Heidelberg retina tomograph (HRT) in myopic eyes;and to investigate the relationships between axial length (AL) and differences of optic disc parameters measured with the two devices.Methods One hundred and fifty myopic subjects were included in this prospective cross-sectional study.One eye from each subject was randomly selected for optic disc imaging by Cirrus HD-OCT and HRT2 in Joint Shantou International Eye Center of Shantou University and The Chinese University of Hong Kong from September to December in 2010 under the approval of Ethic Committee of this hospital and informed consent of each patient was received.Each subject received complete ophthalmic examinations including intraocular pressure (IOP) measurement,visual acuity,refraction,slit lamp,dilated fundus examination and perimetry.The subjects were divided into low (≤-3.00 D,35 eyes),moderate (-3.00 D＜SE＜-6.00 D,60 eyes) and high myopia (SE ≥-6.00 D,55 eyes) groups according to the refractive status.Measurement of axial length was performed with IOL master.Optic disc parameters including disc area,rim area,cup volume,vertical cup-to-disc ratio (VCDR) and average cup-to-disc area ratio (ACDR) were measured by Cirrus HD-OCT and HRT2,respectively.The OCT measurements were corrected for ocular magnification using the Littman's formula,and the results were compared between the instruments.The measurement agreement was evaluated using Bland-Altman plots.Pearson correlation analysis was used to evaluate the associations between AL and the measurement differences of the two instruments.Results The mean axial length and refraction were (25.62±1.10) mm and (-5.22±2.34) D,respectively.The corrected optic disc parameters were significantly larger than those without adjustment by using Cirrus HD-OCT (all at P＜ 0.001).In the high myopic group,the disc area measured by Cirrus HD-OCT was significantly larger than that by HRT2 (P＜0.001).In the moderate myopic group,the rim area measured by HRT2 was significantly larger than that by the Cirrus HD-OCT (P =0.040).The measurements of ACDR,VCDR and cup volume by Cirrus HD-OCT were all larger than those by HRT2 in the three myopic groups (all at P＜0.001).The 95％ limits of agreement (LoA) of disc area and rim area with the two devices were-0.64 to 0.74 and-0.74 mm to 0.62 mm2,respectively.The differences of disc area,rim area and cup volume measurements from the two devices were significantly and positively associated with axial length (r=0.158,0.148,0.156,all at P＜0.05).No significant correlation was detected between AL and the differences of ACDR and VCDR (r =0.012,0.093,both at P ＞ 0.05).Conclusions Optic disc parameters measured by Cirrus HD-OCT are affected by optical magnification in myopic eyes.Poor agreement is found across all of the disc measurements with Cirrus HD-OCT and HRT2.The two devices should not be used interchangeably for measurements of optic disc.Moreover,the differences between measurements of the two devices are significantly associated with AL.