GDxVCC和SWAP及SAP在开角型青光眼早期诊断中的敏感性及特异性

目的:评价并比较青光眼早期诊断仪GDxVCC、短波视野计(SWAP)、标准自动视野计(SAP)各参数诊断早期开角型青光眼的敏感性和特异性。方法:采用GDxVCC和SWAP及SAP对正常人42例42眼和早期开角型青光眼患者84例84眼进行检查,绘制GDxVCC各参数(TSNIT,SA,IA,IES,NFI)ROC(receive operating characteristic curve)曲线,比较GDxVCC,SAP,SWAP的敏感性和特异性。结果:TSNIT,SA,IA,IES,NFI的ROC面积分别为0.77,0.76,0.80,0.85,0.87。GDxVCC,SWAP,SAP的敏感性分别为80.6%,74.2%,67.8%;特异性分别为95.2%,85.7%,76.2%。结论:GDxVCC参数中,NFI和IES是区分正常人和青光眼最有效指标。GDxVCC诊断能力优于SWAP,SWAP优于SAP。     

应用GDx VCC检测原发性开角型青光眼视网膜神经纤维层

目的 采用GDx VCC检测青光眼和正常人视网膜神经纤维层厚度(retinal nerve fiber layer,RNFL),并进行对比分析.方法 选择正常人44人44眼,原发性开角型青光眼患者45例45眼行GDx VCC检查.将获取的参数(椭圆平均值、上方平均值、下方平均值、TSNIT标准差、眼间对称性、视神经纤维指征)进行分析.结果 所有参数在正常人组与青光眼组比较中均有统计学意义(P＜0.01).GDxVCC不同参数检测青光眼RNFL缺损敏感性为68.9%～82.2%,特异性84.1%～100.0%.其中下方平均值、视神经纤维指征ROC曲线下面积为0.959、0.964.结论 GDx VCC在RNFL检查中有较高的敏感性和特异性,可客观反应受检者的RNFL情况,对于青光眼的早期诊断有一定的临床价值.     

GDxVCC系统检测视网膜神经纤维层在青光眼早期诊断中的价值

目的 比较正常人和不同程度青光眼患者GDxVCC系统检测RNFL参数的不同,评价GDx各参数的敏感性、特异性,探讨GDxVCC系统检测视网膜神经纤维层在青光眼早期诊断中的价值.方法 对35例(35只眼)原发性开角型青光眼、33例(33只眼)慢性闭角型青光眼、27例(27只眼)急性闭角型青光眼以及年龄相匹配的36人(36只眼)正常人进行GDxVCC系统和静态视野检查.GDxVCC系统检查,视盘周围视网膜神经纤维层(retinal nerve fiber layer,RNFL)任一参数与系统内所附中国正常人数据库对比概率＜5%或NFI＞30或视网膜神经纤维标准偏差图上连续有10个超级像素概率＜5%定义为具有青光眼性视网膜神经纤维层结构损害,并判断为青光眼.结果 22只正常眼被判断为非青光眼(61.1%),82只青光眼被判断为青光眼(86.3%),RNFL参数椭圆平均值、上方平均值、下方平均值、TSNIT标准偏差、神经纤维指数,标准偏差图诊断青光眼的敏感性分别为48.4%、56.8%、48.4%、50.5%、62.1%,特异性分别为97.2%、100%、97.2%、94.4%、97.2%、61.1%.GDxVCC系统诊断早期、中期、晚期青光眼的敏感性分别为77.36%、95.83%、100%.结论 GDxVCC系统诊断早期青光眼的敏感性和特异性均高,而且RNFL参数中神经纤维指数的敏感性最高.

Abstract：

Objective To evaluate the usefulness of the scanning laser polarimeter with variable corneal compensation (GDxVCC) for glaucoma detection in a Chinese population,and to investigate the retinal nerve fiber layer (RNFL) thickness difference between normal subjects and glaucoma patients.Methods Thirty-six eyes of 36 normal subjects,33 eyes of 33 primary chronic angle-closure glaucoma patients,27 eyes of 27 primary acute angle-closure glaucoma and 35 eyes of 35 primary open-angle glaucoma patients were studied.The glaucoma patients were age-matched with the normal.The thickness of retinal nerve fiber layer was measured with GDxVCC.An eye was diagnosed as glaucoma,ifone of the parameters showed P＜0.05 on the results of the examination reports including four TSNIT parameters (the average of TSNIT,superior,inferior,and TSNIT Std.Dev.),nerve fiber indicator (NFI) ＞ 30,and at least 10 consecutive defects of superpels showed in deviation map (P ＜0.05).Results Of 22 normal eyes (61.1%) were diagnosed as non-glaucoma and 82 glaucomatous eyes (86.3%) were diagnosed as glaucoma by GDxVCC.Sensitivity of the average of TSNIT,superior,inferior,TSNIT Std.Dev.,NFI and the deviation map were 48.4%,56.8%,48.4%,50.5%,62.1% respectively and specificity were 97.2%,100%,97.2%,94.4%,97.2% and 61.1% respectively.Sensitivity of detection early,moderate and progression glaucoma by GDxVCC were 77.36%,95.83%,100% respectively.Conclusions GDxVCC is a valuable technology to detect retinal nerve fiber layer defect in early glaucoma.It is shown that the NFI has highest sensitivity.     

神经节细胞-视网膜内丛状层复合体厚度在早期青光眼的诊断价值

目的评估神经节细胞层-视网膜内丛状层厚度(GCIPL)及GCIPL联合神经纤维层厚度(RNFL)参数在诊断青光眼中的作用。方法选择青光眼患者48例(62只眼)及健康志愿者39例(62只眼),分别测试患者每只眼视乳头周边RNFL厚度及黄斑区GCIPL分布图。评估GCIPL、RNFL及GCIPL和RNFL联合参数的敏感性、特异性,阳性似然比(PLR)和阴性似然比(NLR),并判断各参数的诊断效能。结果 GCIPL参数中,下半区域GCIPL厚度有最好的诊断效能,(敏感度88.7%,特异度为98.4%;PLR,55.4;和NLR,0.169)。下四分之一扇区,是RNFL诊断效能最好的参数(灵敏度,90.3%;特异性98.4%;PLR,56.4;和NLR,0.10)。下方区域GCIPL厚度和下四分之一扇区RNFL层厚度的或逻辑的组合具有最佳诊断性能(敏感度96.8%,特异度为98.4%;PRL,60.5;和NLR,0.033),而第6或第7点钟方位RNFL层厚度与下半区域GCIPL层厚度的或逻辑组合拥有最佳的敏感度(敏感度100%,特异度为93.5%;PRL,15.4;和NLR,0)。结论下方区域GCIPL厚度与下四分之一扇区RNFL层厚度的或逻辑的组合具有最佳诊断性能,比单独的GCIPL,RNFL参数拥有更好的诊断性能,该联合参数的使用可以减少一部分早期青光眼的漏诊。     

糖尿病患者视网膜神经纤维层厚度的测定及相关因素分析

目的用GDx神经纤维分析仪（GDxVCC）测定眼底表现正常的2型糖尿病患者双眼视网膜神经纤维层（RNFL）,了解有无早期RNFL变薄,分析危险因素与RNFL厚度的相关性。方法收集42例2型糖尿病患者相关病例资料。眼科常规检查后,用GDxVCC仪强化角膜补偿（ECC）和可变角膜补偿（VCC）测定双眼颞侧、上方、鼻侧、下方、颞侧曲线平均（TSNIT平均）、上方平均、下方平均、TSNIT标准差和神经纤维指数（NFI）5项值。分析糖尿病组的ECC、VCC5项检测值在诊断能力上的差异,即受试工作者曲线下面积（ROC）;糖尿病组5项检测值的最大值、最小值和均数;血糖水平与糖尿病组检测值的相关性;糖尿病组中ECC与VCC5项检测值的差异比较;糖尿病组与对照组5个检测指标的差异;建立年龄与NFI值的线性回归方程。结果NFI值的ROC最大;ECC和VCC的NFI值均约为20;血糖与RNFL延迟量间无明显相关性。糖尿病组ECC与VCC5项指标的NFI值的差异无统计学意义（t=1．787,P=0．072）;年龄对糖尿病患者NFI值的影响远远大于其对正常人NFI值的影响。结论NFI值为反映RNFL厚度的主要参考指标,年龄对糖尿病患者RNFL厚度存在较大影响;眼底表现正常的糖尿病患者存在早期RNFL变薄;ECC和VCC模式检测的NFI值无明显差异。糖尿病组2个测量模式间TSNIT标准差差异有统计学意义。     

光学相干断层成像术测量视网膜神经纤维层厚度在青光眼早期诊断中的意义

目的:探讨光学相干断层成像术(optical coherence tomography,OCT)测量视网膜神经纤维层厚度(retinal nerve fiber layer,RNFL)在青光眼早期诊断中的意义.方法:应用OCT测量正常人62例101眼和青光眼患者41例64眼的RNFL厚度,将正常人和青光眼患者的各象限和平均RNFL厚度进行比较;并比较各期青光眼的RNFL厚度;计算平均RNFL厚度和视野平均缺损的相关性,计算OCT测量平均RNFL厚度的敏感性和特异性.结果:青光眼患者和早期青光眼患者的各象限和平均RNFL厚度均比正常人减少,差异有统计学意义(P＜0.05).随着青光眼病程的发展,RNFL厚度逐渐下降.平均RNFL厚度和视野平均缺损呈高度正相关(r=0.722,P=0.000),OCT测量平均RNFL厚度的敏感性为85.9%,特异性为97.0%.结论:OCT测量RNFL厚度为青光眼早期诊断提供了一种新的手段.     

HD-OCT测量黄斑区神经节细胞层-内丛状层厚度对开角型青光眼诊断的意义

目的：评估利用高分辨率相干光断层扫描( Cirrus-HD OCT)测量黄斑区神经节细胞层-内丛状层( GCIPL)厚度参数对早期和中晚期青光眼的诊断意义。
　　方法：本研究共纳入20例健康个体,26例早期青光眼患者,29例中晚期青光眼患者。对所有纳入个体均测量黄斑区GCIPL厚度参数,视盘( ONH )区参数以及视盘周围神经纤维层( RNFL )厚度参数。最后将所有数据利用SPSS 17.0统计学软件进行分析,分别计算各参数诊断早期和中晚期青光眼的AUC值,以比较和评价各参数的诊断意义。
　　结果：对于早期青光眼组, AUC值最高的为RNFL平均值(0.871)和7：00位值(0.896),GCIPL各参数也表现出较高的AUC值,其中GCIPL平均值和最小值相应的AUC值分别为0.847和0.812。对于中晚期青光眼组,AUC值最高为盘沿面积(0.992),其次为RNFL平均值(0.991),而GCIPL各参数中平均值与最小值的AUC值分别为0.967和0.983。对于早期青光眼诊断,灵敏度最高的指标为RNFL平均值(76.9%),而特异度最高的指标为GCIPL平均值(93.5%)。
　　结论：GCIPL作为诊断青光眼的新指标在诊断早期和中晚期青光眼时,具有与RNFL相似的诊断意义。对于早期青光眼,诊断时应重点观察RNFL平均值,而在筛查时应重点观察GCIPL的平均值。     

频域OCT检测视乳头形态及视网膜神经纤维层厚度在青光眼诊断中的作用

目的 探讨频域相干光断层扫描(OCT)检测视乳头形态及视网膜神经纤维层(RNFL)厚度在青光眼诊断中的作用.方法 为非干预性、观察性研究.应用RTVue OCT检测60例正常人和97例青光眼患者的视乳头各参数,以及平均和各个区域的RNFL厚度.采用单因素方差分析对以上各参数组间进行比较.用受试者工作特性曲线下面积(AUC)和特异性≥80%的敏感性来评价每一个检测参数区分正常与各期青光眼的能力大小.结果 除视乳头面积外,正常人和各期青光眼患者各参数测量值之间差异均有统计学意义(F=1.024,P=0.596;F=36.519,54.464,27.659,36.176,20.562,63.833,30.031, 54.652,98.146,78.705,99.839,43.728,75.720,45.709,39.380, 33.590,66.887,78.335,45.485;P=0.000).其中,平均RNFL厚度正常人为109.950μm,早期青光眼患者为93.313 μm,中期青光眼患者为80.374μm,晚期青光眼患者为65.570 μm.在视乳头周围8个RNFL区域中,正常人最厚的为颞下150.066μm和颞上146.285μm.各期青光眼患者最厚的均为颞上,分别为早期108.569 μm,中期103.420μm,晚期88.708μm,其次为颞下,分别为早期108.201μm,中期102.830 μm,晚期86.369 μm.而鼻侧(NU+NL)和颞侧(TU+TL)无论在正常人还是青光眼患者中均较薄.在视乳头形态各参数中,各期青光眼诊断效能最高的均为垂直杯盘比,其AUC值在早、中、晚期青光眼患者中分别为0.762,0.946和0.988,它们特异性在80%时的敏感性分别为62.2%,76.5%和99.2%.在RNFL厚度参数中,早期青光眼诊断效能最高的是颞上区域RNFL厚度,其AUC值为0.915,特异性在80%时的敏感性为89.5%;中期青光眼诊断效能最高的是下方平均RNFL厚度,其AUC值为0.967,特异性在80%时的敏感性为94.1%;晚期青光眼诊断效能最高的是平均RNFL厚度,其AUC值为0.985,特异性在80%时的敏感性为99.2%.在视乳头周围8个RNFL区域中,诊断效能最高的是颞上区域(ST),其AUC值在早、中、晚期青光眼患者中分别为0.915,0.926和0.966,它们特异性在80%时的敏感性分别为89.5%,88.2%和92.9%.诊断效能较低的是颞侧(TU+TL)和鼻侧(NU+NL).结论 RTVue OCT具有较好的区别正常人和各期青光眼患者的能力,在青光眼诊断方面是一个有用的工具.     

倍频视野检测在40岁以上人群中筛查青光眼的价值

目的探讨倍频视野检测(FDP)程序在40岁以上自然人群中筛查青光眼的敏感性和特异性.方法 2001年5至10月对北京市大兴区榆垡乡3个自然村及市区北部4个社区40岁以上居民4439人进行青光眼筛查.所有受试者均用倍频视野计的C-20-1筛查程序检测视野.对可疑青光眼者在非筛查日进行Octopus阈值视野、前房角镜及视乳头立体照相检查.根据Octopus视野检测的平均缺损(MD)值,将筛查出的青光眼分为轻、中、重三级.FDP的分析指标包括FDP检测时间、异常位点数、FDP计分、4个象限FDP计分等.正常人随机选一只眼的数据用于分析;双眼青光眼患者选择视神经或Octopus视野损害较轻的眼用于分析.结果 4330例(97.5%)用于FDP分析.以FDP结果≥1个点异常为临界点,将人群分为正常人与青光眼两组,则FDP检查青光眼的敏感性为50.7%(72/142),特异性为96.6%(2260/2340),受试者工作特征曲线下面积(AUC)为0.7,阳性预测值47.7%,阴性预测值96.9%,阳性似然比14.8,阴性似然比0.5.若除外无青光眼性视神经与Octopus视野损害的青光眼,则FDP检测青光眼的敏感性为76.4%,AUC为0.9, 阳性预测值为40.7%,阴性预测值99.2%,阳性似然比22.3,阴性似然比0.2.检测轻、中、重度青光眼的敏感性分别为54.2%、76.0%、100.0%.FDP视野的4个象限计分与Octopus视野4个相应象限的MS呈显著负相关(Rs分别为-0.732、-0.628、-0.639、-0.679,均P＜0.01).结论 C-20-1 FDP筛查程序适用于在大规模人群中筛查青光眼,具有较高的特异性;对中、重度青光眼性视野缺损患者具有良好的敏感性.     

GDx神经纤维厚度分析仪在正常中老年国人中的应用评价

目的 评价GDx神经纤维厚度分析仪在正常中老年国人中的检测意义。方法 采用GDx神经纤维厚度分析仪两种检测模式检测正常中老年国人的视网膜神经纤维层（RNFL）厚度。测量参数：TSNIT平均延迟、上方平均延迟、下方平均延迟、TSNIT标准差、神经纤维指数（NFI）。结果 VCC模式：5项参数分别为56.17±5.25,68.35±7.20,67.31±8.06,23.46±4.31,17.15±10.09。ECC模式：5项参数分别为54.15±5.12,67.28±8.33,67.91±8.70,25.80±3.72,18.88±10.51。两种模式参数检测结果均在正常范围,除下方平均延迟差异有统计学意义外其余4项参数之间的差异无统计学意义,所有检测参数指标与年龄均无统计学意义的相关性。结论 GDx神经纤维厚度分析仪对正常中老年国人RNFL厚度分布的测定结果符合生理解剖特点。VCC和ECC两种模式对检测正常中老年国人的RNFL厚度差异无统计学意义。     

Intersession reproducibility of retinal nerve fiber layer thickness measurements by GDx-VCC in healthy and glaucomatous eyes

BACKGROUND: To assess intersession reproducibility of retinal nerve fiber layer (RNFL) thickness measurements on scanning laser polarimetry with variable corneal compensation (GDx-VCC) in a sample of healthy subjects and glaucoma patients. METHODS: One eye each from 29 healthy and 29 glaucomatous subjects was selected and underwent RNFL scanning by the same operator at baseline and 1 week later. Glaucoma diagnosis relied on the presence of a reproducible defect on automated perimetry. GDx-VCC parameters considered were those available on page 1 of the printout [TSNIT average and standard deviation (SD), superior and inferior average (SA, IA), Nerve Fiber Indicator]. Reproducibility was assessed by calculating coefficient of variation and intraclass correlation coefficient separately for the two groups and for each parameter. The percentage of eyes with an intersession difference in thickness parameters of more than 5% was also calculated. RESULTS: Coefficient of variation was <6% for TSNIT average, SA and IA in both groups. Corresponding values for TSNIT SD in healthy subjects and in glaucoma patients were 13.7 and 11.4%, respectively, whereas for Nerve Fiber Indicator they were 82.9 and 13.3%. Intraclass correlation coefficient ranged from 0.794 to 0.907 in healthy subjects and from 0.924 to 0.972 in glaucoma patients. In healthy subjects, TSNIT average, SA and IA intersession difference was 5% or less in 55-69% of eyes, whereas the value for TSNIT SD was 34.5%. Corresponding values in glaucomatous eyes ranged from 69 to 79.3% for TSNIT average, SA and IA and was 37.9% for TSNIT SD. CONCLUSIONS: Intersession reproducibility of RNFL thickness measurements on GDx-VCC is high, both in healthy and in glaucomatous eyes. In a few cases, however, intersession variation may be larger than 10%. Caution is necessary while interpreting these changes during follow-up, in order to separate physiological variability from real RNFL thickness variations.     

Effect of cataract surgery on retinal nerve fiber layer thickness parameters using scanning laser polarimetry (GDxVCC)

Purpose:

To study the effect of cataract extraction on the retinal nerve fiber layer (RNFL) thickness, and assessment by scanning laser polarimetry (SLP), with variable corneal compensation (GDx VCC), at the glaucoma service of a tertiary care center in North India.

Materials and Methods:

Thirty-two eyes of 32 subjects were enrolled in the study. The subjects underwent RNFL analysis by SLP (GDx VCC) before undergoing phacoemulsification cataract extraction with intraocular lens (IOL) implantation (Acrysof SA 60 AT) four weeks following cataract surgery. The RNFL thickness parameters evaluated both before and after surgery included temporal, superior, nasal, inferior, temporal (TSNIT) average, superior average, inferior average, and nerve fiber index (NFI).

Results:

The mean age of subjects was 57.6 ± 11.7 years (18 males, 14 females). Mean TSNIT average thickness (μm) pre- and post-cataract surgery was 49.2 ± 14.1 and 56.5 ± 7.6 (P = 0.001). There was a statistically significant increase in RNFL thickness parameters (TSNIT average, superior average, and inferior average) and decrease in NFI post-cataract surgery as compared to the baseline values. Mean NFI pre- and post-cataract surgery was 41.3 ± 15.3 and 21.6 ± 11.8 (P = 0.001).

Conclusions:

Measurement of RNFL thickness parameters by scanning laser polarimetry is significantly altered following cataract surgery. Post the cataract surgery, a new baseline needs to be established for assessing the longitudinal follow-up of a glaucoma patient. The presence of cataract may lead to an underestimation of the RNFL thickness, and this should be taken into account when analyzing progression in a glaucoma patient.     

The relationship between optical coherence tomography and scanning laser polarimetry measurements in glaucoma

PURPOSE: To investigate the relationship between optical coherence tomography (OCT) and scanning laser polarimetry (SLP) in measuring peripapillary retinal nerve fiber layer (RNFL) thickness in glaucomatous eyes. METHODS: Fifty glaucomatous eyes were evaluated in this study. Evaluations were analyzed two ways. First, parameters of the Stratus OCT (average thickness, superior/inferior average) and GDx VCC (TSNIT average, nerve fiber indicator (NFI), superior/inferior average) were correlated using the Pearson's correlation coefficient (r). Secondly, comparison (r) of these parameters was completed using the mean deviation (MD) of visual field defect. RESULTS: The following parameters were found to be significantly correlated (P < 0.005). TSNIT average/average thickness (r = 0.673), NFI/average thickness (r = -0.742), superior average (r = 0.841), and inferior average (r = 0.736). In the correlation analysis using the severity of visual field defect, all these parameters had statistically meaningful correlations (P < 0.005). CONCLUSIONS: GDx VCC and Stratus OCT are highly correlated in glaucomatous eyes. Therefore, peripapillary RNFL thickness measured by Stratus OCT and GDx VCC may be equally helpful in the diagnosis of glaucoma.     

Scanning laser polarimetric analysis of retinal nerve fiber layer thickness in Turkish patients with glaucoma and ocular hypertension

PURPOSE: To assess the thickness of the retinal nerve fiber layer (RNFL) in patients with different stages of glaucoma, in comparison with ocular hypertensive (OHT) and healthy subjects in a Turkish population. METHODS: Scanning laser polarimetry was done with a GDx Nerve Fiber Analyzer (NFA, GDx version, 1.0.08) on 270 eyes with glaucoma, 52 OHT eyes, and 81 normal eyes. The eyes were classified as having early (146 eyes), moderate (66 eyes) and severe (58 eyes) glaucoma based on the Humphrey Visual Field indices. We compared 14 NFA parameters by analysis of variance (ANOVA) and Scheffe multiple comparison analysis. Receiver operator characteristic curves (ROC) and Fisher linear discriminant analysis (LDF) were used to measure the sensitivity and specificity of the NFA parameters. RESULTS: Except for symmetry, all NFA parameters showed significant differences between the groups (p<0.05). The eyes with glaucoma had significantly thinner RNFL than healthy eyes (p<0.01). The RNFL retardation measurements of OHT eyes were lower than controls, but higher than the early glaucoma group. The sensitivity and specificity of the GDx System were 87% and 72.8%, respectively. Applying LDF, the group with the highest sensitivity and specificity (85.9% and 74.1%) was determined as inferior ratio, superior/nasal ratio, superior maximum and the Number. CONCLUSIONS: Assessment of RNFL thickness with scanning laser polarimetry can distinguish glaucoma, OHT and normal subjects with relatively high sensitivity and specificity.     

Scanning laser polarimetry with variable corneal compensation and detection of glaucomatous optic neuropathy

BACKGROUND: The aim of this study was to evaluate the ability of scanning laser polarimetry (SLP) parameters provided by commercially available GDx with variable corneal compensator (VCC) to discriminate between healthy and glaucomatous eyes. METHODS: Sixty-five healthy and 59 glaucomatous age-matched patients underwent a complete ophthalmological evaluation, an achromatic automated perimetry (AAP), and SLP with GDx-VCC. One randomly selected eye from each subject was considered. All glaucomatous eyes had reproducible visual field defects. Mean values (+/- SD) of all SLP-VCC parameters measured in the two groups were compared. Area under receiver operating characteristics (AUROC) curve and sensitivities at predetermined specificities of >or=80% and >or=95% for each single parameter were calculated. Moreover, the nerve fiber indicator (NFI) diagnostic accuracy was evaluated calculating positive, negative, and interval likelihood ratios (LRs) at different cutoff values. RESULTS: All SLP parameters were significantly different between the two groups (p<0.001). The NFI showed the best AUROC curve (0.938, SE 0.02) whereas temporal, superior, nasal, inferior, temporal (TSNIT) average was second best (0.897, SE 0.03), and normalized superior area was third (0.879, SE 0.04). At fixed specificity >or=95%, sensitivities ranged from 22% to 79.7% whereas for values >or=80%, sensitivities were in the 44.1-89.8% range. At a cutoff NFI value of 30, positive LR was 17.6 (95% CI: 5.8-53.6) and negative LR was 0.19 (95% CI: 0.11-0.33). Interval LRs for NFI showed that values 40 were associated with large effects on posttest probability. CONCLUSIONS: SLP-VCC allows good discrimination between healthy and glaucomatous eyes. New software-provided parameters NFI, TSNIT average, and normalized superior and inferior areas appear to be reliable in the evaluation of glaucomatous disease. In particular, after evaluation on interval LRs, the NFI showed a high diagnostic accuracy for values 40.     

The effect of ageing on retinal nerve fibre layer thickness: an evaluation by scanning laser polarimetry with variable corneal compensation

PURPOSE: To evaluate whether a significant age-related thinning of the retinal nerve fibre layer (RNFL) is measurable by means of scanning laser polarimetry with variable corneal compensation (GDx-VCC) in a sample of healthy eyes. METHODS: A sample of 324 eyes of 324 healthy subjects (mean age 56 +/- 14 years, range 21-85 years) underwent a complete ophthalmic evaluation, standard automated perimetry and RNFL scan with the GDx-VCC. Temporal-superior-nasal-inferior-temporal (TSNIT), superior and inferior average (SA and IA) values provided on the printout were collected and their mean value averaged from all eyes and also after separating the eyes by gender and by age decades. The values of the three parameters were plotted against age and linear regression was calculated. RESULTS: Ageing is associated with a significant RNFL thinning (0.08 micro, 0.16 micro and 0.12 micro per year for TSNIT, SA and IA, respectively; p < 0.001). Analysis showed a similar association with age decade (p < 0.001 on anova). For the TSNIT average, a 9.5% thinning from baseline values was estimated for a 65-year lifespan. Corresponding values for SA and IA were 16.2% and 11.7%, respectively. CONCLUSIONS: Analysis by GDx-VCC confirmed previous reports about significant age-related RNFL thinning. However, a lower rate per year was found, probably because GDx-VCC measurements are much more reliable than those obtained with the previous generation of polarimeters.     

Preperimetric glaucoma assessment with scanning laser polarimetry (GDx VCC): analysis of retinal nerve fiber layer by sectors

PURPOSE: To evaluate the capability of the GDx VCC nerve fiber analyzer to detect preperimetric glaucoma across 12 retinal nerve fiber layer (RNFL) peripapillary sectors. METHODS: Data were obtained in a cross-sectional, hospital clinic-based study; 699 eyes from 699 glaucoma suspects were enrolled in this protocol. All subjects underwent ophthalmologic examination, static automated perimetry [Humphrey 24-2 Swedish interactive threshold algorithm (SITA) Standard], optic nerve stereoscopic photographs, red-free digital RNFL photographs and GDx VCC examination. Group S included 283 normal eyes and 39 preperimetric glaucoma eyes with RNFL superior or diffuse defects in the fiber layer photographs. Group I included 324 normal subjects and 24 with preperimetric glaucoma eyes with RNFL inferior or diffuse defects in fiber layer photographs. RESULTS: Mean values of the area under the curve (AUC) for receiver operating characteristic analysis for inferior average (Inf Avg), temporal-superior-nasal-inferior temporal average (TSNIT Avg), superior average (Sup Avg), and the nerve fiber indicator were significantly less in the eyes with RNFL defects than the control group compared with the AUC for thickness at hour 12 and at hour 6 calculated from the RNFL sector density. The AUC for receiver operating characteristic analysis of the new parameters improved by 12% with respect to the best GDx VCC standard values. CONCLUSIONS: Our results confirm that the 12 sector divisions of the GDx VCC have better diagnostic reliability in preperimetric glaucoma, and are able to improve the discrimination capability between normal and early damaged RNFLs.     

The effect of atypical birefringence patterns on glaucoma detection using scanning laser polarimetry with variable corneal compensation

PURPOSE: The purpose of this study was to investigate the effect of the presence of atypical birefringence patterns, as measured by the typical scan score (TSS), on the diagnostic accuracy of a scanning laser polarimeter (the GDx VCC; Carl Zeiss Meditec, Inc., Dublin, CA) assessed by receiver operating characteristic (ROC) curves for discriminating between glaucoma and healthy eyes. METHODS: Two hundred thirty-three glaucomatous eyes (repeatable abnormal visual fields by pattern standard deviation [PSD] and/or glaucoma hemifield test [GHT]) from 153 patients with glaucoma and 104 eyes from 71 healthy participants enrolled in the UCSD Diagnostic Innovations in Glaucoma Study (DIGS) were imaged using the GDx VCC. An ROC regression model was used to evaluate the influence of the covariates TSS; disease severity, defined as standard automated perimetry (SAP) mean deviation [MD]; and age in years on the diagnostic accuracy of the GDx parameters nerve fiber indicator [NFI], TSNIT (temporal, superior, nasal, inferior, temporal) average thickness, superior average thickness, inferior average thickness, and TSNIT standard deviation. Areas under the ROC curve were calculated for specific levels of the covariates according to the results provided by the model. RESULTS: TSS and SAP MD significantly affected the diagnostic accuracy of each investigated GDx VCC parameter. Low TSSs, indicating the presence of atypical scans, were associated with decreased accuracy. For NFI, ROC curve areas ranged from 0.749 (when TSS = 20) to 0.904 (when TSS = 100). A similar influence of TSS was found for other parameters. In addition, diagnostic accuracy increased with increasing disease severity. For instance, for NFI, ROC curve areas ranged from 0.853 (when SAP MD = -3) to 0.954 (when SAP MD = -15). CONCLUSIONS: The diagnostic accuracy of GDx VCC parameters is affected by disease severity and is adversely affected by the presence of atypical retardation patterns (i.e., decreasing TSS). GDx VCC scans with atypical scan patterns should be interpreted with caution when used in clinical practice.