中央角膜厚度对压平眼压计测量值的影响

目的采用非接触式角膜内皮镜测量高眼压症与临床常见类型青光眼患者的中央角膜厚度central corneal thickness(CCT),并与正常人CCT平均值比较,探讨CCT对青光眼诊断、分类与治疗的指导意义.方法采用KONAN非接触式角膜内皮镜测量中央角膜厚度,Goldmann压平眼压计测量眼内压(IOP).将39例52眼原发性开角型青光眼(POAG),32例45眼慢性闭角型青光眼(CACG),18例29眼高眼压症眼(OHT),15例24眼正常眼压性青光眼(NTG),34例66眼可疑开角型青光眼(GS)的CCT和IOP值与173例322眼正常眼进行比较研究.所有资料输入计算机后在Windows操作环境下使用SPSS10.0统计软件进行统计分析.结果平均CCT值比较高眼压症(OHT)眼(600.21±24.20μm)＞POAG眼(574.37±31.92μm)＞正常对照眼(554.78±32.61μm)＞NTG眼(528.43±36.40μm).OHT、NTG、POAG眼与正常眼的CCT值有差异(F=9.629,P=0.000),CACG眼与POAG及正常眼CCT值均无差异(P=0.119).GS眼CCT值(564.72±31.96μm)较正常眼厚.CCT与IOP成直线正相关,眼压测量值的校正公式为眼压校正值(mmHg)=-(测得的角膜厚度μm-555μm)×(1/24).IOP经CCT校正后,OHT眼平均高估1.89mHg,NTG眼平均低估1.1mmHg,POAG眼平均高估0.80mmHg.根据经CCT校正后的IOP值,13.5%POAG眼重新诊断为NTG眼,34.5%OHT眼重新诊断为正常眼,16.7%NTG眼重新诊断为POAG眼.结论非接触式角膜内皮镜能准确地测量中央角膜厚度.OHT眼CCT较厚,而NTG眼CCT较薄.CCT测量对青光眼的分类与治疗有重要的指导意义,应作为OHT、NTG及GS的常规检查项目.     

中央角膜厚度及屈光度对压平眼压计测量值的影响

目的 探讨中央角膜厚度(CCT)以及屈光状态对Goldmann压平眼压计(GAT)测量值的影响.方法 应用OCT3测量正常人121例(199只眼)与近视患者81例(159只眼)的CCT,用Goldmann压平眼压计测量眼压,比较两组之间CCT和眼压测量值的差异,分析CCT与眼压测量值的关系.结果 正视组平均CCT值为(525.05±32.83)μm,眼压的均值为(12.91±2.26)mmHg;近视组平均CCT值为(524.85±29.76)μm,眼压的均值为(14.23±2.54)mmHg;两组的CCT值比较差异无显著性(t=-0.600,P=0.952),两组的眼压值比较差异有显著性(t=-5.139,P＜0.001).高度近视眼CCT偏薄,眼压随屈光度数较少而增加,近视组眼压与屈光度相关(r=-0.296,P＜0.001),屈光度数每增加-4.05D,眼内压升高1 mmHg.正视组(r=0.317,P＜0.001)和近视组(r=0.341,P＜0.001)的眼压与CCT相关,眼压校正公式分别为1 mmHg/45.45 μm、1 mmHg/34.48 μm.结论 CCT可以影响Goldmann压平眼压计测量值,屈光状态也可以影响眼压值,高度近视眼的眼压建议用从近视人群中获得的眼压校正公式校正.     

动态轮廓眼压计的临床应用

目的 探讨动态轮廓眼压计(OCT)在原发性开角型青光眼(POAG)、高眼压症(OHT)、正常眼压性青光眼(NTG)及正常对照人群眼压和眼压脉动振幅(OPA)测量中的临床应用价值及影响因素.方法 选取POAG、OHT、NTG及正常对照组各30例,分别采用Goldmann压平眼压计(GAT)测量眼压,DCT测量眼压及OPA,并测量中央角膜厚度(CCT)、中央角膜曲率(CCV)以及心率、收缩压、舒张压等指标,以了解这些指标对OPA的影响.各组统计量两两比较采用q检验.各统计量之间的相关分析采用Pearson相关分析,对于多个变量之间的线性关系采用多重线性回归分析.结果 DCT测量POAG、OHT、NTG及对照组的眼压值分别为(21.68±2.02)、(23.37±2.65)、(18.43±3.08)、(17.04±2.07)lnln Hg(1 mm Hg=0.133 kPa);GAT测最的眼压值分别为(21.18±2.95)、(23.28±5.95)、(16.39±3.60)、(14.66±2.27)mm Hg.两者测量结果的差异无统计学意义(t=1.338,1.445,1.682,1.803;P=0.197,0.151,0.136,0.081).POAG、OHT、NTG及对照组的OPA值分别为3.03±1.13,3.53±1.43,2.21±0.55,2.87±0.60,组间比较差异有统计学意义(F=21.311,P=0.000);OPA值与心率、收缩压、舒张压、GAT测量值、CCT均相关,与年龄无明显相关性.结论 DCT测量结果与GAT有良好的一致性,受干扰因素少,可信度高;POAG、NTG、OHT患者和正常人的OPA存在差异,其中NCT患者OPA值明显较低,提示各组间眼内血液动力学状况的差异,OPA可能对青光眼的诊断及治疗具有一定的潜在价值.     

动态轮廓眼压计在正常眼压性青光眼及原发性开角型青光眼的应用研究

目的:应用动态轮廓眼压计(dynamic contour tonometer,DCT)测量正常眼压性青光眼(normal tension glaucoma,NTG)及原发性开角型青光眼(primary open angle glaucoma,POAG)患者的眼压(intraocular pressure,IOP)及眼脉动幅度值(ocular pulse amplitude,OPA),并探讨影响OPA测量值的相关因素。方法:选取NTG患者20例,POAG患者21例及正常对照组各20例,应用Goldmann压平眼压(Goldmann applanation tonometer,GAT)及DCT测量IOP,同时测量了中央角膜厚度(central corneal thickness,CCT)、眼轴(axial length,AL)、心率(heart rate,HR)、收缩压(systolic blood pressure,SBP)、舒张压(diastolic blood pressure,DBP)等指标,并探讨GAT,DCT两种眼压计测量的相关性,进而分析OPA测量值的影响因素。结果:三组被检者的IOP,OPA,SBP及DBP差异均有统计学意义(P<0.05),而CCT,AL及HR差异无统计学意义(P>0.05)。其中OPA值NTG组为(1.7±0.9)mmHg,POAG组为(2.8±0.7)mmHg,正常对照组为(2.4±0.6)mmHg;NTG组与POAG组比较(P=0.001),与正常对照组比较(P=0.005)差异均有统计学意义,POAG组与正常对照组比较(P=0.502)差异无统计学意义;OPA值与IOP,HR及CCT无相关性(P>0.05),与AL,SBP及DBP具有一定的相关性(P<0.05)。结论:NTG患者与POAG患者及正常人的OPA值存在差异,同时OPA值受AL及SBP及DBP影响。     

不同角膜厚度下Pentacam系统对压平眼压计测量值的校正

目的 比较Goldmann压平眼压计(Goldmann applanation tonometry,GAT)和Pentacam眼压校正系统在中央角膜厚度(central corneal thickness,CCT)不同的正常眼测量值的差异,评价其校正准确性.方法 对69例(69只眼)按CCT不同,分为正常组(520～<580μm)42只眼、较薄组(450～<520μm)16眼、增厚组(580～640μm)11只眼.应用Pentacam前房分析仪检查和Goldmann压平眼压计测量眼压,并用Pentacam系统所提供的4种校正方法对眼压测量值进行校正.结果 角膜正常组和角膜增厚组中,平均GAT、各组眼压校正值之间差异均无统计学意义(P>0.05),GAT、各组眼压校正值与CCT之间无线性相关(P>0.05);角膜较薄组中,平均GAT、各组眼压校正值之间差异均有统计学意义(P<0.05),GAT值与CCT之间线性相关(IOP=0.067×CCT-16.582,r2=0.730,P<0.05),Shah组校正值与CCT之间亦存在线性相关(IOP=0.076×CCT-25.349,r2=0.328,P<0.05);其余各组与CCT之间无明显相关(P>0.05).结论 Pentacam三维眼前段分析仪根据角膜厚度校正眼压测量值,尤其对角膜较薄组使用Dresden校正公式,有助于对其诊断和治疗提供更加准确的依据.     

不同类型青光眼患者前部巩膜厚度与中央角膜厚度和眼轴长度的相关性分析

背景 巩膜厚度与青光眼关系密切,不同类型青光眼的临床特点不同,其巩膜厚度可能存在一定差异,但目前的相关研究结果有一定争议. 目的 研究各种类型的青光眼患者前部巩膜厚度(AST)、中央角膜厚度(CCT)和眼轴长度间的关系.方法 采用回顾性描述性研究设计.纳入2009年3月至2010年11月就诊于北京大学第一医院眼科门诊的连续患者160例,其中原发性开角型青光眼(POAG) 34例34眼、正常眼压性青光眼(NTG) 37例37眼、原发性闭角型青光眼(PACG) 35例35眼及高眼压症(OHT) 17例17眼,对照组为早期白内障患者37例37眼.分别采用超声角膜测厚仪、眼部A型超声测量仪测量各组患者的CCT、AST及眼轴长度,采用超声生物显微镜(UBM)测量系统测量颞侧巩膜突后2 mm处的巩膜厚度.采用协方差分析法和SNK-q检验对各组的测量参数进行比较,用Pearson积矩相关分析和线性回归法对上述各组患者AST、CCT及眼轴长度间的关系进行分析. 结果 PACG组、POAG组、NTG组及OHT组的CCT值分别为(535.54±5.20)、(550.47±5.28)、(521.61±5.07)和(575.75±7.76) μm,对照组为(535.06±5.06) μm,5个组间的总体差异有统计学意义(F=9.560,P=0.000),其中OHT组的CCT值较其他各组均增加,差异均有统计学意义(均P=0.000),POAG组的CCT值较PACG、NTG及对照组均增加(P=0.046、0.000、0.040),NTG组及PACG组与对照组间CCT值的差异均无统计学意义(P=0.950、0.060).PACG组、POAG组、NTG组及OHT组AST值分别为(0.593±0.050)、(0.600±0.050)、(0.592士0.060)、(0.610±0.060) mm,对照组为(0.604±0.060) mm,5个组间AST的差异无统计学意义(F=0.700,P=0.590).PACG组的眼轴长度短于其他各组,差异均有统计学意义(均P=0.000).POAG组和NTG组患者的CCT与AST呈正相关(POAG:r=0.445,P=0.008;NTG:r=0.400,P=0.014). 结论 不同类型青光眼患者的CCT不同,AST无明显不同;POAG患者及NTG患者的CCT与AST变化间可能存在一定的正相关.     

正常眼压性青光眼、原发性开角型青光眼患者及正常人DCT眼压及OPA的比较性研究

目的探讨在原发性开角型青光眼(PrimaryOpenAngleGlaucoma,POAG)及正常眼压性青光眼(NormalTensionGlaucoma,NTG)患者使用动态轮廓眼压计(DynamicContourTonometer,DCT)测量时的影响因素。方法POAG、NTG及正常对照组各31例,测量了Goldmann压平眼压(GoldmannApplanationTonometer,GAT)、DCT眼压、眼脉动幅度值(OcularPulseAmplitude,OPA)、以及心率(HeartRate,HR)、收缩压(SystolicBloodPressure,SBP)、舒张压(DiastolicBloodPressure,DBP)等指标,评估GAT、DCT两种眼压计测量的一致性,分析测量中的影响因素,并比较三组被检者OPA的差异;结果除HR以外(P=0.130),三组被检者的DCT眼压、OPA、GAT眼压、HR、SBP及DBP均存在显著性差异(P<0.05)。其中,正常对照组OPA为(2.85±1.15)mmHg,NTG组为(1.99±1.04)mmHg,POAG组为(3.00±1.07)mmHg,POAG组与正常对照组比较差异(P=0.568)无显著性意义,与NTG组比较差异有显著性意义(P<0.001),NTG组与正常对照组(P=0.003)比较有显著性意义;结论DCT眼压和GAT眼压表现出良好的一致性,DCT的测量结果可信;POAG、NTG患者和正常人的OPA存在差异。     

中央角膜厚度与视网膜神经纤维层厚度关系在正常眼和高眼压患者之间的比较研究

目的通过角膜中央厚度分组,观察正常眼和高眼压患者的角膜厚度和视网膜神经纤维层（RNFL）厚度之间的关系,并通过相干光断层扫描成像（OCT）和偏振激光扫描仪联合个体化角膜补偿技术（GDx-VCC）检查高眼压患者是否存在RNFL的异常,并分析OCT和GDx-VCC测得的RNFL厚度之间的相关性。方法对眼压高于21 mm Hg（1 mm Hg=0.133 kPa）的患者测量其中央角膜厚度（CCT）,根据CCT值对眼压进行校正。OCTOPUS-101自动视野仪检查及视盘观察入选高眼压组患者180只眼,均予OCT、GDx-VCC测量视盘一周视网膜神经纤维层厚度,另设正常人180只眼作为对照,获得数据进行统计学分析。结果高眼压患者的平均CCT为（536.14±35.99）（433～609）μm,正常组患者的平均CCT为（516.68±38.27）（368～598）μm。根据平均中央角膜厚度555μm分组,组间平均视网膜神经纤维层厚度（Average RNFL）、上方（S）、下方（I）的RNFL厚度以及其它参数有显著性差异,高眼压组CCT≤555μm的患者平均视网膜神经纤维层厚度要低于CCT〉555μm的患者。结论高眼压患者RNFL厚度GDx-VCC与OCT的检测值低于正常人。高眼压组CCT与平均视网膜神经纤维层厚度正相关。GDx-VCC与OCT有着较好的一致性。     

新型非接触式眼压分析仪ORA与Goldmann压平眼压计的比较

目的比较新型非接触式眼压分析仪ORA与Goldmann压平式眼压计测量眼压的差异,以评价ORA眼压测量仪在临床眼压测量中的应用价值。方法本院门诊127例237眼分别由专人进行非接触眼压测量仪ORA与Goldmann压平式眼压计测量,并同时用超声角膜测厚仪测量角膜厚度。结果127例病人237眼,Goldmann压平眼压值和ORA直接测量结果（IOPG）分别为（17.94±6.50）mmHg和（18.88±7.93）mmHg,两者比较差异有显著统计学意义（P=0.000）;正常人群平均角膜厚度为（546.19±36.34）μm,经角膜厚度-眼压公式校正IOPG平均值为17.42±3.92mmHg,ORA经自带软件处理后的眼压值（IOPcc）平均为（17.50±4.38）mmHg,两者比较差异无统计学意义（P=0.681）,IOPG校正前两者比较差异有统计学意义（P=0.024）。结论新型非接触式眼压分析仪ORA的直接测量值与Goldmann压平眼压计的测量值相近略高,ORA的测量分析值IOPcc是排除角膜因素影响更接近真实的眼压结果。     

不同角膜厚度下动态轮廓眼压计和Goldmann压平眼压计在不同角膜厚度的测量值比较

目的比较动态轮廓眼压计（dynamic contour to-nometry,DCT）和Goldmann压平眼压计（Goldmann applanation tonometry,GAT）在中央角膜厚度（central corneal thickness,CCT）不同的正常眼测量值的差异。方法患者69例（69眼）按CCT不同分为正常组（520～580μm）42眼、变薄组（450～520μm）16眼、增厚组（580～640μm）11眼。各组分别用DCT和GAT测量眼压。结果正常组平均CCT为（574.55±16.40）μm,平均GAT值为（16.62±3.15）mmHg（1kPa=7.5mmHg）,平均DCT值为（16.78±2.86）mmHg,DCT与GAP差异无统计学意义（P〉0.05）,平均GAT-DCT值为（-0.16±0.96）mmHg;变薄组平均CCT为（499.44±16.70）μm,平均GAT值为（14.03±2.72）mmHg,平均DCT值为（17.06±2.72）mmHg,2者差异有统计学意义（P〈0.01）,平均GAT-DCT值为（-3.03±1.32）mmHg;增厚组平均CCT为（605.18±17.90）μm,平均GAT值为（16.91±3.94）mmHg,平均DCT值为（16.80±4.25）mmHg,2者差异无统计学意义（P〉0.05）,平均GAT-DCT值为（0.05±2.47）mmHg。结论在角膜厚度正常眼,DCT值和GAT值较一致;在角膜厚度变薄眼,前者较后者准确;在角膜厚度变厚眼未体现DCT的优越性。     

Central corneal thickness in primary open angle glaucoma, pseudoexfoliative glaucoma, ocular hypertension, and normal population

PURPOSE: This study was designed to determine the relationship between central corneal thickness (CCT) and intraocular pressure (IOP) measured by applanation tonometer in glaucomatous, ocular hypertensive, and normal eyes. METHODS: A total of 125 subjects were included in the study. Twenty-six had primary open angle glaucoma (POAG), 25 had pseudoexfoliative glaucoma (PXG), 24 had ocular hypertension (OHT), and 50 of them were normal. IOP values were measured by Goldmann applanation tonometer whereas CCT values were measured by ultrasonic pachymeter. RESULTS: CCT values in the OHT group (595.75+/-22.52 microm) were greater than the CCT values of the POAG group (539.92+/-21.50 microm), the PXG group (526.28+/-31.73 microm), and the normal group (533.96+/-29.25 microm) (p<0.05). Eight patients who were diagnosed with OHT showed IOP values of 21 mm Hg or lower with corrected IOP values according to CCT. CONCLUSIONS: Increased CCT may lead to falsely high values of IOP measured with Goldmann applanation tonometer. In this study, when IOP values of the OHT group were redefined according to the formulae regarding the CCT, the authors noted that one third of them were normal. Determination of the CCT in OHT cases is crucial since it has great impact on IOP values, measured with applanation tonometer, which is the main parameter in the diagnosis and follow-up of glaucoma.     

Ocular response analyser to assess hysteresis and corneal resistance factor in low tension, open angle glaucoma and ocular hypertension

Purpose: The aim of this study is to compare the hysteresis and corneal resistance factor (CRF) in normal tension glaucoma (NTG), primary open angle glaucoma (POAG) and ocular hypertension (OHT) eyes measured by the ocular response analyser (ORA). Methods: This is a prospective, cross‐sectional and comparative clinical trial. The setting was a teaching hospital in Birmingham, England. Patients: 216 eyes with POAG, 68 eyes with NTG and 199 eyes with OHT. Observational procedures: Goldmann applanation tonometry and intraocular pressure (IOP), hysteresis and CRF measured by ORA and central corneal thickness (CCT) by ultrasonic pachymetery. The main outcome measures were IOP, CCT, hysteresis and CRF. Results: The hysteresis in NTG, POAG and OHT eyes was 9.0 ± 1.9, 9.9 ± 2.1 and 10.2 ± 2.0 mmHg; CRF was 9.1 ± 2.2, 10.6 ± 2.0 and 12.0 ± 2.0 mmHg; IOP by Goldmann applanation tonometry and ORA was 14.7 ± 2.8 and 15.3 ± 4.2 mmHg, 16.7 ± 4.0 and 16.9 ± 4.6 mmHg and 20.5 ± 4.1 and 20.0 ± 4.5 mmHg; CCT was 526.5 ± 42.2, 537.0 ± 36.0 and 563.4 ± 35.9 µm, respectively. The difference for CRF, IOP and CCT for NTG, POAG and OHT eyes was statistically significant. Conclusion: Hysteresis and CRF were highest in OHT eyes. These factors may prove to be useful measurements of ocular rigidity and may help to understand role of the corneal rigidity in monitoring the progress of conditions such as NTG, POAG and OHT.     

角膜厚度与高眼压症及青光眼的眼压

目的 探讨高眼压症、正常眼压性青光眼、原发性开角型青光眼患者及正常人的角膜厚度差异,分析角膜厚度与眼压间的关系,以及角膜厚度的测定对各型青光眼的诊断意见。方法 用超声波角膜测厚仪检测７３例（７３只眼）高眼压症、７９例（７９只眼）正常人的中央角膜厚度,并将其测定结果进行比较。回顾性分析每只青光眼治疗前的最高眼压（Ｇｏｌｄｍａｎｎ）,包括２４ｈ眼压曲线,用Ｅｈｌｅｒ法通过中央角膜厚度对眼压进行校正。结     

Central corneal thickness of normal tension glaucoma patients in Japan

PURPOSE: To compare central corneal thickness (CCT) of patients with normal tension glaucoma (NTG) with that of age-matched normal subjects, patients with open-angle glaucoma (POAG) and ocular hypertension (OH) subjects in Japan. METHODS: Central corneal thickness was measured in 79 NTG, 61 POAG, 73 OH, and 50 normal subjects with an ultrasonic pachymeter. One eye for 1 subject randomly selected in each group was used for inter-group comparison. The relationship between CCT and the maximum intraocular pressure (IOP) measured by Goldmann applanation tonometer with no ocular hypotensive medication (NTG, OH, and normal subjects) or under medication (POAG patients) was analyzed. RESULTS: The CCT of OH subjects (582 +/- 32 microm; mean +/- SD) was significantly greater than that of the other groups (P <.001), while no difference was seen in CCT among normal (552 +/- 36 microm), NTG (548 +/- 33 microm) and POAG (550 +/- 33 microm) subjects. In normal subjects, CCT and the maximum IOP were significantly correlated but the correlation coefficient was small (r = 0.420, P <.05). CONCLUSIONS: Central corneal thickness shows no significant difference among NTG, POAG, and normal subjects in Japan, while it is significantly greater in OH subjects. The CCT has little influence on the diagnosis of NTG in Japan.     

Should Orbscan pachometry be performed before or after Goldmann applanation tonometry?

PURPOSE: To compare the Orbscan central corneal thickness (CCT) values before and after intraocular pressure (IOP) measurement with Goldmann applanation tonometry in young normal adults. MATERIALS AND METHODS: Fifty-three eyes of 53 subjects who were free from any ocular problems were studied. The measurements included optical pachometry by the Orbscan II system, followed by Goldmann applanation tonometry, and finally Orbscan optical pachometry again. Standard Goldmann technique was adopted with the application of one drop of 0.4% benoxinate and fluorescein sodium prior to the measurement. The same operator was involved in the Orbscan pachometry before and after Goldmann tonometry. Another investigator was responsible for Goldmann tonometry. Three readings were obtained in each case, and the means were used for analysis. RESULTS: The mean IOP of the sample was 14.6 +/- 2.6 mmHg. There was no significant difference (paired t-test: p = 0.50) in the mean CCT values before and after the Goldmann tonometry (551 +/- 32 and 552 +/- 35 microm respectively). CONCLUSION: Standard Goldmann applanation tonometry does not affect the Orbscan CCT values. Measurement of CCT for the adjustment of true IOP can be carried out either before or after Goldmann tonometry.     

Intraocular pressure and ocular pulse amplitude comparisons in different types of glaucoma using dynamic contour tonometry

PURPOSE: To compare the intraocular pressures (IOP) and ocular pulse amplitudes (OPA) in patients with different types of glaucoma, ocular hypertension (OHT), and normal controls (NC) using dynamic contour tonometry (DCT) and the goldmann applanation tonometry (GAT). METHODS: 906 eyes of 501 adult patients in the following five groups were included in this cross-sectional study: primary open angle glaucoma (POAG), normal tension glaucoma (NTG), Pseudoexfoliative Glaucoma (PXG), OHT, and NC. The following tests were performed simultaneously during a single visit: IOP using DCT and GAT; OPA using DCT and central corneal thickness (CCT) using ultrasound pachymetry. Mixed effects regression models were used to compare the DCT and GAT IOP measurements in the five groups; the effect of CCT on IOP and the relationship between OPA and IOP within each group. RESULTS: DCT consistently had higher IOP values than GAT in POAG, PXG, NTG, and controls (p < 0.001) but not in OHT (p = 0.84). DCT IOP did not change while GAT IOP showed a non-significant increase (p = 0.09) with increased corneal thickness in each group. OPA was found to be highest in OHT (3.61 mmHg) and lowest in the control group (2.86 mmHg) and significantly increased with IOP in all groups. CONCLUSIONS: DCT measures an IOP that is significantly higher than GAT IOP in glaucoma and control subjects but not in ocular hypertensives. Furthermore, the DCT may measure an IOP that is independent of the CCT, which may not be true for the GAT, which increases with the CCT. OPA was highest in OHT and may be affected by the IOP.     

Comparison of central corneal thickness in patients participating in a glaucoma screening programme and those who were examined in the glaucoma unit

BACKGROUND: The aim of this study was to compare central corneal thickness (CCT) and intraocular pressure in patients participating in a glaucoma screening programme and patients who were examined in the glaucoma unit. MATERIALS AND METHODS: 406 patients of a glaucoma screening programme (Salzburg-Moorfields collaborative glaucoma study) were included in this study. In addition a group of 406 patients who were admitted to the glaucoma clinic for a detailed glaucoma examination was included (outpatient clinic group). In all participants central corneal thickness (CCT) was measured and possible relations of CCT within the study groups were statistically analysed. RESULTS: In the population screening group the mean central corneal thickness in normal subjects was 536+/-4.3 microm, in patients with ocular hypertension (OHT) 552+/-5.7 microm, patients suffering from a normal tension glaucoma (NTG) showed a mean CCT of 534+/-14.2 microm and those with primary open angle glaucoma (POAG) had a value of 521+/-17.9 microm. In the 'outpatient clinic group' the OHT subgroup had a mean CCT of 553+/-6.8 microm, the NTG subgroup of 529+/-26.5 microm and the one with POAG had a mean of 527+/-19.8 microm. In addition, CCT was measured in all glaucoma patients whose "partner" eye was healthy (544+/-5 microm) and included in this study as part of the normal subgroup. In both groups (screening group and outpatient group), CCT was significantly higher in OHT patients than in normals. In contrast, no statistically significant difference between normals and NTG or POAG patients was detected. Intraocular pressure was significantly lower in the screening groups than in the other ones. CONCLUSIONS: Our data confirm the previously published results concerning OHT and healthy subjects. In this study no significant difference between NTG or POAG subjects and normal eyes was detected. The lower IOP in the screening population can be explained by the fact that patients contacting the screening program are self selected whereas patients of the glaucoma unit are admitted by practising ophthalmologists and are, therefore, rather advanced cases or carrying special risk factors.     

Attempted eyelid closure affects intraocular pressure measurement in open-angle glaucoma patients

PURPOSE: To evaluate the effect of attempted eyelid closure on intraocular pressure (IOP) measurements in normal-tension (NTG) and high-tension (HTG) open-angle glaucoma patients. DESIGN: Prospective clinical trial. METHODS: Forty randomly selected eyes of 40 patients underwent corneal pachymetry and IOP measurements using both Goldmann applanation tonometry and Tono-pen XL (Mentor, Inc., Norwell, Massachusetts, USA). Intraocular pressure was measured by the same examiner holding the eyelids open, both with and without the subject simultaneously attempting forced eyelid closure. Subjects were seated during all measurements and waited 5 minutes between measurements with each instrument; the order of measurement was randomized. RESULTS: Twenty NTG and 20 HTG eyes were enrolled. The mean age was 63.0 +/- 13.0 years (range, 31-80 years). The average corneal thickness was 540 +/- 32 microm (range, 480-608 microm) in NTG patients and 552 +/- 40 microm (range, 449-610 microm) in HTG patients (P =.07, analysis of variance [ANOVA]). Using Goldmann applanation tonometry, IOP measurement in eyes with NTG increased by 3.9 +/- 2.0 mm Hg with attempted eyelid closure (P <.0001, paired t test; range, 2-11 mm Hg). With the Tono-pen XL, IOP measurements increased 4.2 +/- 2.7 mm Hg (P <.0001, paired t test; range, 1-14 mm Hg). With attempted forced eyelid closure, the Goldmann applanation measurement in eyes with HTG increased 4.1 +/- 2.1 mm Hg (P <.0001, paired t test; range, 1-9 mm Hg). Using the Tono-pen XL, measurements increased 4.5 +/- 2.0 mm Hg (P <.0001, paired t test; range, 2-11 mm Hg). CONCLUSION: Attempted eyelid closure during tonometry is a significant and common source of error in eyes with glaucoma and may influence the clinical management and decision-making in the treatment of NTG and HTG.     

Central corneal thickness and normal tension glaucoma: a cross-sectional study.

BACKGROUND: Recently published evidence has identified thinner central corneal thickness (CCT) as a strong predictive factor for the conversion from ocular hypertension (OHT) to primary open-angle glaucoma (POAG). The association between CCT and development of normal-tension glaucoma (NTG), however, is less clear. Accordingly, we designed this cross-sectional study to further explore the relationship between CCT and NTG. PATIENTS AND METHODS: All patients with a clinical diagnosis of NTG and NTG suspect (NTGS) who were seen from September 2002 through May 2003 at the Albuquerque VA Medical Center eye clinic were identified retrospectively. After eligible subjects were categorized into no, mild, moderate, and advanced visual field loss groups, analysis of variance (ANOVA) and regression analyses were used to determine group differences for several IOP variables, several systemic variables, and CCT. Additional analyses were completed after eligible subjects were recategorized into thin, intermediate, and thick CCT groups. RESULTS: Eighty-four eyes in 84 NTGS subjects and 56 eyes in 56 NTG subjects were studied. Mean CCT was significantly thicker in the no field loss group (NTGS) when compared with all 3 groups with glaucomatous visual field loss (NTG). In multivariate regression analysis, the association between CCT and the presence of NTG-related visual field loss was robust and independent. Conversely, no relationship was found between CCT and severity of NTG-related visual field loss. CONCLUSIONS: In eyes characterized by statistically normal intraocular pressure (IOP) measurements as measured by Goldmann applanation tonometry, we found a significant relationship between CCT and the presence, but not severity, of glaucomatous visual field loss. A prospective study is required to further explore and confirm these relationships.     

Novel pressure-to-cornea index in glaucoma

BACKGROUND: Several conversion tables and formulas have been suggested to correct applanation intraocular pressure (IOP) for central corneal thickness (CCT). CCT is also thought to represent an independent glaucoma risk factor. In an attempt to integrate IOP and CCT into a unified risk factor and avoid uncertain correction for tonometric inaccuracy, a new pressure-to-cornea index (PCI) is proposed. METHODS: PCI (IOP/CCT(3)) was defined as the ratio between untreated IOP and CCT(3) in mm (ultrasound pachymetry). PCI distribution in 220 normal controls, 53 patients with normal-tension glaucoma (NTG), 76 with ocular hypertension (OHT), and 89 with primary open-angle glaucoma (POAG) was investigated. PCI's ability to discriminate between glaucoma (NTG+POAG) and non-glaucoma (controls+OHT) was compared with that of three published formulae for correcting IOP for CCT. Receiver operating characteristic (ROC) curves were built. RESULTS: Mean PCI values were: Controls 92.0 (SD 24.8), NTG 129.1 (SD 25.8), OHT 134.0 (SD 26.5), POAG 173.6 (SD 40.9). To minimise IOP bias, eyes within the same 2 mm Hg range between 16 and 29 mm Hg (16-17, 18-19, etc) were separately compared: control and NTG eyes as well as OHT and POAG eyes differed significantly. PCI demonstrated a larger area under the ROC curve (AUC) and significantly higher sensitivity at fixed 80% and 90% specificities compared with each of the correction formulas; optimum PCI cut-off value 133.8. CONCLUSIONS: A PCI range of 120-140 is proposed as the upper limit of "normality", 120 being the cut-off value for eyes with untreated pressures or=22 mm Hg. PCI may reflect individual susceptibility to a given IOP level, and thus represent a glaucoma risk factor. Longitudinal studies are needed to prove its prognostic value.