中央角膜偏厚的高眼压症患者临床观察

目的预测中央角膜厚度在高眼压症转归中的作用。方法将门诊用非接触眼压计检测的高眼压症患者做超声角膜厚度测量,中央角膜厚度大于及等于575μm的患者60例(120只眼)纳入本研究,不予降眼压治疗,追踪观察眼压、视乳头、视野变化。结果随访36～76个月,平均48个月。其中1例1只眼出现视野改变,发生率为0.83%(1/120)。结论角膜厚度是判断高眼压症是否发展为青光眼的最有力的预测因素.常规中央角膜厚度测量对高眼压症患者的合理处理是非常重要的。中央角膜偏厚且眼压低于28mmHg的高眼压症患者不需要抗青光眼治疗,仅需定期观察。     

角膜中央厚度对高眼压症和开角型青光眼眼内压测量值的影响

目的研究角膜中央厚度对高眼压症和原发性开角型青光眼病人的眼内压测量值的影响.方法对44例(88眼)临床诊断为高眼压症的患者,31例(61眼)原发性开角型青光眼患者及52例(104眼)与高眼压症患者屈光状态相近的正常人的角膜中央厚度及眼内压进行检测,用统计学方法比较3组的角膜中央厚度的差异及高眼压症患者的眼内压值与角膜中央厚度的相关关系.结果①高眼压症组的角膜中央厚度的平均值585.6±35.7μm明显高于原发性开角型青光眼(54.1±38.7μm)(P＜0.01)及正常对照组(535.5±29.4μm)(P＜0.01),而原发性开角型青光眼的角膜中央厚度与正常对照组相比无显著性差异(P＜0.05).②将高眼压症患者的角膜中央厚度与眼内压测量值进行简单线性相关分析,可见角膜中央厚度与眼内压测量值呈明显正相关,相关系数为0.636(P＜0.01).角膜中央厚度每增加50μm可使眼内压测量值升高约2mmHg.结论①高眼压症患者的角膜中央厚度明显大于原发性开角型青光眼和正常眼,高眼压症患者的角膜中央厚度与眼内压呈明显的正相关,提示高眼压症患者是由于角膜中央厚度高于正常范围而造成眼内压测量值的升高.②角膜中央厚度值可作为高眼压症及原发性开角型青光眼的诊断与鉴别诊断的重要依据.提示临床工作中,可将角膜中央厚度检测作为排除青光眼的常规检查手段.③当角膜中央厚度在520±50μm的范围内,眼压读数相对准确,如果角膜中央厚度超过570μm,眼压读数相应增高,这可能是高眼压症患者眼压测量值高于正常范围的重要原因之一.     

非接触眼压计及Schiotz眼压计测量的高眼压症与角膜厚度

目的　探讨高眼压症患者与正常人角膜厚度的差异 ,分析角膜厚度与眼压之间的关系。方法　用超声角膜测厚仪检测 3组人的中央角膜厚度 :(1组 )用 Schiotz眼压计测得之高眼压者 35例 (70只眼 ) ;(2组 )用非接触眼压计测得之高眼压者 30例 (6 0只眼 ) ;(3组 )正常人 4 7例 (94只眼 ) ,并将测量结果进行比较。结果　用 Schiotz眼压计的高眼压组中央角膜厚度为 5 5 1.71± 2 .85μm(范围 4 90～ 6 38) ;用非接触眼压计的高眼压组中央角膜厚度为 5 6 0 .0 2± 3.4 2μm (范围 4 86～ 6 4 0 ) ;正常对照组中央角膜厚度为 5 2 5 .6 5± 2 .2 4μm (范围 4 12～ 6 2 0 ) ;(1组 )与 (3组 )比较 (t=2 .5 80 ,P <0 .0 1) ;(2组 )与 (3)比较 (t=2 .5 78,P <0 .0 1)。差异有显著性。结论　高眼压症者 ,中央角膜厚度高于正常人 ,提示其眼压高可能与角膜厚度偏高有关 ,这类患者有可能减轻青光眼的发展危险     

原发性青光眼及高眼压症患者中央角膜厚度的比较研究

目的 探讨用超声角膜测厚仪测量的急性原发性闭角型青光眼、慢性原发性闭角型青光眼、原发性开角型青光眼、高眼压症及正常人中央角膜厚度(central corneal thickness,CCT)的差异.方法 临床病例对照研究.对2010年2月至2011年11月在承德医学院附属医院眼科应用超声角膜测厚仪测量62例(107只眼)的CCT值.急性原发性闭角型青光眼16例(18只眼)、慢性原发性闭角型青光眼14例(26只眼)、原发性开角型青光眼10例(19只眼)、高眼压症6例(12只眼)及正常人16例(32只眼).采用单因素方差分析及SNK-q检验行统计分析.结果 各组CCT值:急性原发性闭角型青光眼(548.44±30.46)μm、慢性原发性闭角型青光眼(522.70±50.39)μm、原发性开角型青光眼(546.32±22.85) μm、高眼压症(585.67±21.22) μm、正常人(536.38±26.53)μm.组间比较差异有统计学意义(F=7.661,P＜0.01).两两比较显示:高眼压症与原发性青光眼组及正常人比较,差异有统计学意义;原发性青光眼各组及正常人两两比较,差异无统计学意义.结论 与正常人及原发性青光眼相比,高眼压症CCT较厚;原发性青光眼CCT与正常人相比差异无统计学意义;CCT与原发性青光眼类型无相关性.     

角膜厚度对眼压测量的影响及其意义

眼压是诊治青光眼的一个重要参数。压平眼压计测量眼压受角膜中央厚度的影响 ,正常人群中角膜中央厚度个体差异较大 ,带来眼压测量值也存在差异 ,这种差异会引起一些临床意义 ,对高眼压症和正常眼压性青光眼的诊治造成影响。本文就正常人的角膜中央厚度、每日角膜厚度变化曲线、与眼压测量之间的关系以及高眼压和青光眼的角膜厚度方面进行综述。     

角膜厚度对眼压测量的影响及其意义

眼压是诊治青光眼的一个重要参数。压平眼压计测量眼压受角膜中央厚度的影响,正常人群中角膜中央厚度个体差异较大,带来眼压测量值也存在差异,这种差异会引起一些临床意义,对高眼压症和正常眼压性青光眼的诊治造成影响。本文就正常人的角膜中央厚度、每日角膜厚度变化曲线、与眼压测量之间的关系以及高眼压和青光眼的角膜厚度方面进行综述。     

高眼压症中央角膜厚度与眼压关系的临床观察

目的 评价高眼压症患者中央角膜厚度(CCT)与眼压(IOP)的关系,并探讨CCT在判断高眼压症患者是否给予降眼压药物干预治疗中的临床意义.方法 对54例(108只眼)高眼压症患者进行非接触眼压计检测和超声角膜厚度测量,并对校正眼压＜21 mmHg的患者31例62只眼(占57.4%)不予降眼压治疗,追踪观察其眼压、视野、视乳头以及视网膜神经纤维层的情况.结果 IOP随CCT增加而增高,并呈正相关(CCT每增加100μm,IOP将随之增加2.1mmHg).对校正眼压＜21mmHg的患者不予降眼压治疗,随访24～36个月,平均30个月,其中1例2只眼出现视野改变,发生率为1.85%.结论 中央角膜厚度测量可以作为高眼压症与青光眼进行鉴别诊断,以及判断高眼压症能否发展为青光眼的重要依据,常规测量高眼压症患者的CCT并校正其眼压,对高眼压症患者的合理处置非常重要,对校正眼压＜21mmHg的患者可以不需降压药物干预治疗,仅需密切随访.     

青光眼角膜水肿与眼压关系的临床研究

角膜水肿是青光眼急性发病时主要临床体征之一,眼压越高角膜水肿越明显。裂隙灯检查水肿的角膜呈雾状混浊,角膜厚度增加,眼压高到什么程度角膜即发生水肿,角膜增厚到什么程度即代表角膜水肿。眼压、角膜水肿和角膜厚度三者的关系为本文重点研究的问题。材料和方法一、检查对象:原发性闭角型青光眼74例148眼,急性期30眼、慢性期56眼,缓解期30眼、临床前期32眼;开角型青光眼15例30眼;继发性青光眼29例30眼;绝对期青光眼41例42眼;共159例250眼。另外测量106例212眼20～55岁正常人角膜厚度。二、检查方法:用裂隙灯检查角膜有无     

原发性虹膜睫状体囊肿与眼压相关性研究

目的探讨原发性虹膜睫状体囊肿与眼压是否存在相关性。方法于2013年就诊于我院屈光矫正激光中心共60例患者,这些患者除了激光矫正近视常规检查外另行超声生物显微镜（UBM）检查,共119只眼,通过Pentacam角膜地形图系统矫正眼压公式Ehlers：IOP-修正=0.071×（545μm-测量角膜厚度）,排除中央角膜厚度对眼压的影响,并通过UBM检查确定是否存在原发性虹膜睫状体囊肿：其中高度近视62只眼,中低度近视57只眼;发现单发囊肿27只眼,多发囊肿20只眼,无囊肿72只眼;眼压正常72只眼,高眼压47只眼;其中高眼压患者排除青光眼可能;所得数据通过SPSS19.0行Spearman相关性分析。结果原发性虹膜睫状体囊肿与眼压之间相关系数为0.235,P=0.01〈0.05。结论通过该相关研究发现原发性虹膜睫状体囊肿与眼压高低具有很强的相关性。     

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。     

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.     

相干光断层扫描仪检测正常人及青光眼患者中央角膜厚度

目的探讨相干光断层扫描仪(OCT)测量正常人、原发性开角型青光眼(POAG)、正常眼压性青光眼(NTG)、高眼压症(OHT)患者的中央角膜厚度(CCT)。方法采用OCT3测量正常人143例(143只眼)、POAG患者36例(36只眼)、NTG患者39例(39只眼)及OHT患者40例(40只眼)的CCT,并进行单因素4水平设计定量资料的方差分析;用线性回归方法分析正常人CCT与Goldmann压平眼压测量值的相关关系;对OCT测量CCT观察者间和观察者内的一致性进行类内相关系数(ICC)分析。结果正常组、POAG组、NTG组及OHT组的平均CCT值分别为(523.66±32.13)μm、(530.92±27.32)μm、(506.92±21.49)μm及(573.13±27.39)μm。POAG组与正常人组的平均CCT值差异无统计学意义(P=0.099);OHT组的平均CCT值大于其他各组,均P<0.01;NTG组的平均CCT值小于其他各组,均P<0.01。正常组CCT与眼压值呈正相关(r=0.318,R2=0.101,P<0.01)。OCT测量CCT的测量者间和测量者内的ICC值分别为0.995和0.996。结论OCT可以准确地测量CCT;NTG患者平均CCT比正常人薄,而OHT患者比正常人厚;CCT可以影响Goldmann压平眼压计的测量值,但贡献率较小。(中华眼科杂志,2006,42:199-203)     

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.     

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.     

Central corneal thickness determined with optical coherence tomography in various types of glaucoma

AIMS: To evaluate central corneal thickness determined by optical coherence tomography (OCT) in various types of glaucoma, and its influence on intraocular pressure (IOP) measurement. METHODS: Central corneal thickness (CCT) was determined by using OCT in 167 subjects (167 eyes). 20 had primary open angle glaucoma (POAG), 42 had low tension glaucoma (LTG), 22 had ocular hypertension (OHT), 10 had primary angle closure glaucoma (AC), 24 had pseudoexfoliation glaucoma (PEX), 13 had pigmentary glaucoma (PIG), and 36 were normal. RESULTS: CCT was significantly higher in ocular hypertensive subjects (593 (SD 35) microm, p <0.0001) than in the controls (530 (32) microm), whereas patients with LTG (482 (28) microm, p < 0. 0001), PEX (493 (33) microm, p <0.0001), and POAG (512 (30) microm, p <0.05) showed significantly lower readings. There was no statistically significant difference between the controls and patients with PIG (510 (39) microm) and AC (539 (37) microm). CONCLUSIONS: Because of thinner CCT in patients with LTG, PEX, and POAG this may result in underestimation of IOP, whereas thicker corneas may lead to an overestimation of IOP in subjects with OH. By determining CCT with OCT, a new and precise technique to measure CCT, this study emphasises the need for a combined measurement of IOP and CCT in order to obtain exact IOP readings.     

The relationship between central corneal thickness-adjusted intraocular pressure and glaucomatous visual-field loss.

BACKGROUND: Although measurement of central corneal thickness (CCT) is increasingly becoming an important component of glaucoma risk analysis, significant controversy exists regarding the benefit of calculating a corrected intraocular pressure (IOP) value from measured IOP and CCT data. METHODS: Three hundred forty-four male subjects were identified from a VA eye clinic with one of the following clinical diagnoses: ocular hypertension (OHT), primary open-angle glaucoma (POAG), normal tension glaucoma (NTG), and normal tension glaucoma suspect (NTGS). Using one eye per subject, multivariate logistic regression and correlational analyses were performed to determine relationships between glaucomatous visual-field loss and several glaucoma risk factors, including adjusted IOP values. RESULTS: Multivariate logistic regression analysis did not identify CCT-adjusted IOP values as independent risk factors for development of either NTG or POAG-related glaucomatous visual-field loss. CCT, however, was found to be strongly associated with both NTG and POAG-related visual-field loss. Correlational analysis revealed a weak correlation between Ehlers-adjusted pre-treatment IOP and severity of POAG-related visual-field loss, but no other adjusted IOP values significantly correlated with severity of visual-field loss in either POAG or NTG. CONCLUSIONS: Our results suggest that adjusted IOP, as calculated using current algorithms, is not useful within glaucoma risk analysis, since adjusted IOP was unable to predict either presence or severity of glaucomatous visual-field loss in this study. CCT, conversely, was found to be a robust and independent predictor of glaucomatous visual-field loss. These findings, while supporting routine CCT measurements for all glaucoma suspects, do not support routine clinical computation of adjusted IOP values using current algorithms.     

Relationship between corneal thickness and measured intraocular pressure in a general ophthalmology clinic

OBJECTIVE: To assess whether central corneal thickness (CCT) is a confounding factor in the classification of patients attending for glaucoma assessment in a district general hospital. DESIGN: Cross-sectional study by a single observer. PARTICIPANTS: Patients attending a general ophthalmic clinic: 235 clinically normal eyes, 52 eyes with normal-tension glaucoma (NTG), 335 eyes with primary open-angle glaucoma (POAG), 12 eyes with pseudoexfoliative glaucoma (PXE), 42 eyes with chronic angle closure glaucoma (CACG), and 232 glaucoma suspect (GS) eyes. INTERVENTION: Central corneal thickness was measured using ultrasonic pachymetry. MAIN OUTCOME MEASURE: Correlation of CCT and diagnosis. RESULTS: Mean CCT was 553.9 microm (95% confidence intervals [CI] for the mean, 549.0-558.8 microm) in the clinically normal eyes, 550.1 microm (95% CI, 546.6-553.7 microm) in the POAG eyes, 514.0 microm (95% CI, 504.8-523.3 microm) in the NTG eyes, 530.7 microm (95% CI, 511.2-550.1 microm) in the PXE eyes, 559.9 microm (95% CI, 546.8-573.0 microm) in the CACG eyes, and 579.5 microm (95% CI, 574.8-584.1 microm) in the GS eyes. The differences of mean CCT between the groups were highly significant (P< 0.001 analysis of variance). Eighty-five percent of eyes with NTG and only 36% of eyes with POAG had a mean CCT of 540 microm or less. Thirteen percent of eyes with POAG and 42% of GS eyes had a mean CCT greater than 585 microm. CONCLUSIONS: The CCT measurement is desirable in patients attending for glaucoma assessment in a district general hospital to avoid misclassification resulting from the relationship between CCT and tonometric pressure. Central corneal thickness alone is not an accurate predictor for the clinical diagnosis in this group of eyes. However, many eyes diagnosed as having NTG have thin corneas, which would tend to lower the tonometrically recorded intraocular pressure (IOP), so the finding of a less-than-normal thickness cornea introduces some doubt as to the diagnosis of NTG. For the GS eyes, most eyes had thick corneas, which would tend to increase the tonometrically recorded IOP. Thus, GS eyes with modest elevation of IOP and a thick cornea may be at low risk of progressing to POAG. Thus, many patients with "high IOPs" and a thick CCT do not necessarily have high IOPs and may not need to be followed as GS eyes.     

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.     

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.     

Central corneal thickness and vascular risk factors in normal tension glaucoma

BACKGROUND: Normal tension glaucoma (NTG) has been shown to be associated with reduced central corneal thickness (CCT). The association of NTG with vascular risk factors is well documented. It has been postulated that a subset of NTG patients are misclassified due to incorrect intraocular pressure measurements on thin corneas. The aim of this study was to establish whether corneal thickness in NTG differs between patients with vascular risk factors specific to NTG and those without. METHODS: The study comprised a retrospective analysis of 108 eyes of 54 patients with NTG and 54 patients with primary open-angle glaucoma (POAG). Corneal thickness was measured in all patients. Vascular risk factors were recorded. Patients with NTG were divided into two groups depending on the presence (group A) or absence (group B) of vascular risk factors. RESULTS: The mean CCT was 549 +/- 34 microm in patients with POAG and 528 +/- 31 microm in patients with NTG (p = 0.001). Mean CCT was 512 +/- 31 microm in group A (n = 13) and 533 +/- 31 microm in group B (n = 41) (p = 0.034). A total of 40.9% of those with thin corneas (n = 22) had vascular risk factors versus only 12.5% of those with CCT within the normal range (n = 32) (p < 0.05). CONCLUSION: Central corneal thickness in NTG was significantly lower than in POAG and corneas were thinner in NTG patients with vascular risk factors than in those without. Vascular risk factors were significantly more common in patients with thin corneas. The finding of reduced corneal thickness in NTG does not obviate the need to consider vascular risk factors in the pathophysiology of the disease.