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 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.     

Pulsatile ocular blood flow in primary open-angle glaucoma and ocular hypertension

PURPOSE: To compare pulsatile ocular blood flow measurements in untreated ocular hypertensive (OHT) subjects and primary open-angle glaucoma (POAG) patients. DESIGN: A prospective observational study in an institutional setting. METHODS: A total of 97 subjects were recruited to the study (50 ocular hypertensives, 24 glaucoma patients, and 23 normal subjects). "High-risk" OHT had intraocular pressure (IOP) > 25 mm Hg; "low-risk" OHT had IOP 相似文献   

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.     

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.     

Effects of central corneal thickness on the efficacy of topical ocular hypotensive medications

PURPOSE: To determine the effect of central corneal thickness (CCT) on the efficacy of intraocular pressure (IOP)-reducing drugs in patients with ocular hypertension (OHT). METHODS: This retrospective study analyzed research records of 115 OHT patients and 97 ocular normotensive (ONT) volunteers. CCT was measured by slit-lamp pachymetry and IOP by pneumatonometry. The OHT patients were divided into Thick (>540 microm, n=52) and Thin (相似文献   

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.     

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.     

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)     

Diurnal variation of intraocular pressure in suspected glaucoma patients and their outcome

Background A case-controlled prospective study was conducted to evaluate the diurnal variation of intraocular pressure (IOP); the mean, the amplitude of variation and the peak and trough times of pressure readings in the suspected open-angle glaucoma patients as compared with a control group. We also looked at the outcome of these suspects after diurnal variation of IOP measurements. Methods Diurnal variation of intraocular pressure was measured in 202 eyes of suspected open-angle glaucoma patients and 100 control eyes, at 4-hourly intervals for 24 hours (phasing). Based on the phasing results, optic disc changes and visual field defects, the patients were diagnosed as primary open angle glaucoma (POAG), normal tension glaucoma (NTG), ocular hypertension (OHT), or physiologic cup (PC), or still remained as glaucoma suspects due to inconclusive diagnosis. The last group (glaucoma suspects) was then followed up 6-monthly for their eventual outcome. Results The highest percentage of suspected glaucoma patients had peak (maximum) readings in the mid-morning (10–11 a.m.) and trough (minimum) readings after midnight (2–3 a.m.); the highest percentage of control group had peak readings in the late evening (6–7 p.m.) and trough readings after midnight (2–3 a.m.). The mean amplitude of variance was 6 mm Hg in suspected glaucoma group and 4 mm Hg in the control group. After ‘phasing’, 18.8% of the suspected glaucoma patients were diagnosed as POAG, 16.8% as NTG, 5% as OHT, and 28.7% as physiologic cup; 30.9% remained as glaucoma suspects. After 4 years follow-up, 70% of the glaucoma suspects still remained as glaucoma suspects, 6.7% developed NTG and another 6.7% POAG; 16.6% were normal. Conclusions Serial measurement of IOP ( phasing) in a 24-hour period is still needed, in order not to miss the peak and the trough IOP readings in suspected open-angle glaucoma patients, which helps in better management of glaucoma. Among 30.9% of patients who remained as glaucoma suspects after the initial phasing, 13.4% developed NTG/POAG over a period of 4 years. This paper was presented in part at the 19th Congress of Asia Pacific Academy of Ophthalmology (APAO), Bangkok, Thailand, 28 November-3 December 2003. The authors have no financial support in the writing of this paper.     

Diurnal intraocular pressure variations: an analysis of 690 diurnal curves.

Out of a total of 2272 diurnal curves (DC) of intraocular pressure (IOP) obtained from 1178 patients 690 first curves of the right eye of all patients were analysed. For each DC there were 4-6 IOP readings taken between 8 am and 6.30 pm of the same day. The patients' diagnosis, age, sex, type of IOP lowering medication, diabetes, and the calendar month of the year were recorded. In 40% of cases the highest IOP was found at the earliest morning measurement with some 65% of peaks occurring before noon. The lowest IOP measurement showed no specific predilection for any particular time of the day. These findings were true for all diagnosis groups. The mean range of IOP fluctuation during the DC was 5.0 mm Hg in normals, 5.8 mm Hg in patients with open angle glaucoma (OAG), and 6.8 mm Hg in patients with ocular hypertension (OHT). Patients treated with timolol had a lower mean IOP fluctuation range than those on other types of IOP lowering treatment. No association was found between all other parameters examined and the diurnal IOP distribution.     

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     

Optic disc size in ocular hypertension

PURPOSE: To study the optic disc size in eyes with ocular hypertension (OHT) in comparison to primary open-angle glaucoma (POAG) and normals. METHODS: Optic disc photographs obtained with the Nidek 3dx NM camera were digitized (Nikon coolscan) and disc area calculated using Littmann correction in a randomly chosen eye of 28 OHT, 42 POAG and 30 normal subjects. OHT was defined as increased intraocular pressure with no disc or field changes suggestive of glaucoma with open angles. RESULTS: The optic disc area in OHT was 9.47 +/- 1.09 mm2; 12.27 +/- 2.87 mm2 in POAG; and 12.11 +/- 2.83 mm2 in normal individuals. CONCLUSION: Using magnification corrected morphometry and the criteria for OHT diagnosis, the optic disc area in OHT was significantly smaller (p < 0.0001) in POAG and normals.     

高眼压症及原发性开角型青光眼患者的24 h眼压波动规律

目的 通过24 h眼压测量来深入分析对比高眼压症与原发性开角型青光眼(POAG)患者的眼压曲线特征。方法 收集2016年1月~2019年3月在我科门诊诊断为高眼压症的患者52例(104眼)及POAG尚未接受降眼压治疗的患者38例(76眼)。入院后行24 h眼压检查,用非接触性眼压计从早9时起每隔2 h测量眼压1次,至次日7时结束。分析2组患者的平均眼压,峰值眼压及时间点,谷值眼压及时间点,昼夜眼压波动及双眼眼压压差值及其分布情况,比较2组眼压波动的异同点。结果 104眼高眼压症患者的平均眼压为(18.73±1.71)mmHg(1 mmHg=0.133 kPa),平均峰值眼压为(22.36±2.40) mmHg,平均谷值眼压为(15.63±2.09) mmHg,平均昼夜眼压波动为(6.72±2.24) mmHg。76眼POAG患者的平均眼压为(20.65±2.53) mmHg,平均峰值眼压为(25.78±2.81) mmHg,平均谷值眼压为(17.45±2.54) mmHg,平均昼夜眼压波动为(8.34±2.37) mmHg。2组的峰值及谷值眼压值分布最多的时间点均为凌晨3时及夜晚21时,大部分患者的峰值眼压时间点在门诊时间之外。高眼压症组中昼夜眼压波动位于5~8 mmHg的占比最大,为54.81%(57/104),POAG组中昼夜眼压波动>8 mmHg的占比最大,为53.95%(41/76)。高眼压症组中,16例患者经24 h眼压检查后监测到眼压波动异常,占比为30.77%(16/52);POAG组中经24 h眼压检查后有29例患者可以监测到眼压波动异常,占比为76.32%(29/38)。结论 24 h眼压监测中,POAG患者较高眼压症患者的平均眼压、峰值眼压、谷值眼压、昼夜眼压波动及双眼压差均有增加。对于24 h眼压发现眼压波动较大的高眼压症患者应在后续加强密切随访,而对于POAG患者24 h眼压监测可在治疗前提供眼压的基线水平,为后续治疗提供参考及评估依据,因此建议将24 h眼压作为高眼压症及POAG的常规检查手段。     

Corneal thickness in glaucoma: an important parameter?

Central corneal thickness was measured by pachometry in 49 patients with primary open-angle glaucoma (POAG), 41 with ocular hypertension (OHT), 14 with normal tension glaucoma (NTG) and 48 normal subjects. The mean corneal thickness of the OHT patients was significantly greater than that of the normal control group. The NTG patients, on the other hand, had a cornea on average thinner than the normals. These differences may cause misclassification of normals with a thick cornea as ocular hypertensive eyes or, contrarywise, cause those normals whose IOP is underestimated because of a thin cornea to be classed as NTG patients.     

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.     

Role of argon laser trabeculoplasty as primary and secondary therapy in open angle glaucoma in Indian patients

AIMS: To study the efficacy of argon laser trabeculoplasty (ALT) as a primary and secondary therapy in Indian patients with primary open angle glaucoma (POAG). METHODS: ALT was performed as a primary therapy in 40 eyes of 21 patients newly diagnosed with POAG (group I) and as a secondary therapy in 39 eyes of 21 patients who had been taking topical antiglaucoma medications for more than 1 year. The best corrected visual acuity, baseline intraocular pressure (IOP), diurnal variation of IOP, anterior chamber angles, and visual fields were the various parameters evaluated before and after performing ALT. Follow up visits were scheduled at 24 hours, 1 week, 1 month, 3 months, 6 months, and 1 year after the surgery. The patients were recalled at the end of 5 years for the final follow up examination. Success of ALT was defined as IOP 相似文献   

Additive effect of unoprostone and latanoprost in patients with elevated intraocular pressure.

AIMS: To assess the additive effect of unoprostone and latanoprost in patients with primary open angle glaucoma (POAG) or ocular hypertension (OHT) METHODS: 32 patients with POAG or OHT were randomised to receive either latanoprost once daily or unoprostone twice daily for 4 weeks. After 4 weeks, all patients received both latanoprost and unoprostone for another 4 weeks. The IOP was measured at 9 am and 5 pm on the baseline, day 28, and day 56 visits, and at 9 am on day 14 and day 42 visits. The medications were given to the patients in an open label fashion. The observer was masked to the treatment given. The mean of the measurements was calculated. Safety parameters were also recorded. The additive effect of the medications was assessed by the reduction in intraocular pressure (IOP) when both medications were used, compared with when one medication was used. RESULTS: 28 patients completed both treatment periods and had IOP data available for evaluation. After 1 month of treatment, latanoprost significantly reduced IOP (mean by 6.1 (SEM 0.8) mm Hg (p<0.001) and unoprostone by 4.9 (1.0) mm Hg (p<0.001) from the baseline of 24.4 (0.6) mm Hg and 24.4 (1.1) mm Hg respectively (p = 0.18). When latanoprost once daily was given to patients treated with unoprostone, there was additional IOP lowering of 1.9 (0.6) mm Hg (p = 0.012). However, adding unoprostone to those being treated with latanoprost produced an IOP change of +0.4 (0.5) mm Hg (p = 0.42). Ocular symptoms and findings were mild and equally distributed between treatment groups, and after combined therapy. Hyperaemia and ocular irritation were the most frequently reported events. Over a third of patients experienced ocular irritation with the combination of medications. CONCLUSIONS: Latanoprost once daily causes additional IOP lowering in eyes which were being treated with unoprostone twice a day. However, there was no additional IOP lowering when unoprostone was added to eyes which were being treated with latanoprost. Both drugs were well tolerated together with few ocular adverse events.     

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.     

The role of central corneal thickness in the diagnosis of glaucoma

PURPOSE: To determine the effect of central corneal thickness (CCT) on applanation tonometry and any resultant misclassification of normals as ocular hypertension. METHOD: The central corneal thickness was measured using the ultrasound pachometer in 50 normals, 25 glaucoma and 23 ocular hypertensive patients. The student's "t" test was used to determine any significant difference in CCT between the three groups. RESULTS: There was a statistically significant difference in the mean CCT of the ocular hypertensives (0.574 +/- 0.033 mm) as compared to the glaucomas (0.534 +/- 0.030 mm) and normals (0.537 +/- 0.034 mm). Applying the described correction factor for corneal thickness, 39% of eyes with ocular hypertension were found to have a corrected IOP of 21 mmHg or less. CONCLUSIONS: Increased corneal thickness in ocular hypertension may lead to an overestimation of IOP in 39% of cases. Measurement of central corneal thickness is advisable when the clinical findings do not correlate with the applanation IOP.