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)     

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.     

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.     

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.     

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.     

Assessment of the diurnal variation in central corneal thickness and intraocular pressure for patients with suspected glaucoma

OBJECTIVE: To assess whether a single daily measurement using ultrasonic pachymetry gives a representative assessment of mean central corneal thickness (CCT) in patients with suspected glaucoma and whether diurnal changes in CCT are related to diurnal variations in intraocular pressure (IOP). DESIGN: Cross-sectional study. METHOD: Central CCT and IOP were measured by a single observer in 56 eyes of 28 patients with suspected glaucoma using an ultrasonic pachymeter and a Goldmann tonometer. Four measurements were made over a 24-hour period: at 8:00 AM, 12:00 PM, 4:00 PM, and 8:00 PM. MAIN OUTCOME MEASURES: Intraocular pressure and pachymetry. RESULTS: Mean IOP was 19.80 mmHg at 8:00 AM (95% confidence interval [CI], 18.95-20.66 mmHg), 20.38 mmHg at 12:00 PM (95% CI, 19.49-21.26 mmHg), 19.91 mmHg at 4:00 PM (95% CI, 19.99-21.83 mmHg), and 19.23 mmHg at 8:00 PM (95% CI, 18.35-20.11 mmHg). Mean CCT was 569.4 microm (95% CI, 560.2-578.7 microm), 567.6 microm (95% CI, 558.4-576.7 microm), 569.1 microm (95% CI, 559.5-578.6 microm), and 567.2 microm (95% CI, 557.9-576.4 microm) at the four respective time points. There was no significant correlation between IOP and CCT in any patient (Pearson rank correlation coefficient); nor was there any significant correlation between the mean diurnal variations of IOP and CCT. CONCLUSIONS: In this group of patients with suspected glaucoma, there was no significant variation in CCT. Therefore, a single measurement of CCT is sufficient when assessing patients with suspected glaucoma. There was no correlation between change of IOP and change of CCT.     

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.     

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.     

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.     

Five-year risk of progression of ocular hypertension to primary open angle glaucoma. A population-based study

PURPOSE: To report the progression of ocular hypertension (OHT) to primary open angle glaucoma (POAG) during a 5-year follow up of a population-based sample. METHODS: Twenty-nine patients diagnosed to have OHT and 110 randomly selected normals from a population-based study in 1995 were invited for ocular examination in 2000. All patients underwent a complete ophthalmic examination; including the daytime diurnal variation of intraocular pressure (IOP) and measurement of central corneal thickness (CCT). The "corrected" IOP was used for analysis. Progression to POAG was based on typical optic disc changes with corresponding field defects on automated perimetry. RESULTS: Twenty-five of the 29 persons with OHT who could be contacted were examined. After correcting for CCT, two persons were reclassified as normal. Four of 23 (17.4%; 95% CI: 1.95-32.75) had progressed to POAG. One person amongst the 110 normals progressed to normal tension glaucoma (NTG). The relative risk of progression amongst OHT was 19.1 (95% CI: 2.2-163.4). All those who progressed had bilateral OHT. The mean and peak IOP in those who progressed was 25.4 mm Hg and 29.3 mm Hg compared to 23.9 mm Hg and 25.7 mm Hg in those who did not. Those who progressed had more than 8 mm Hg diurnal variation. The diurnal variation was less than 6 mm Hg in those who did not progress. No patient developed blindness due to glaucoma. CONCLUSION: The 5-year incidence of POAG amongst OHT in this population was 17.4% (3.5% per year). Bilateral OHT, higher peak IOP and large diurnal variation may be the risk factors for progression.     

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.     

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.     

Corneal biomechanical properties in primary open angle glaucoma and normal tension glaucoma

PURPOSE: To determine and compare the corneal biomechanical properties between eyes with primary open angle glaucoma (POAG) and eyes with normal tension glaucoma (NTG). PATIENTS AND METHODS: Prospective cross-sectional study. Consecutive eligible POAG and NTG patients attending the Glaucoma Clinic had assessment of their corneal biomechanical properties-corneal hysteresis (CH) and corneal resistance factor (CRF)-using the Ocular Response Analyzer by an observer masked to the diagnosis. Exclusion criteria included previous intraocular surgery, corneal pathology, inflammatory connective tissue disease, and refraction of 5-dimensional or over. If both eyes were eligible, then the right eye was used for analysis. The main outcome measures were corneal hysteresis and CRF measurements. Data analysis was performed using the t test and general linear model. RESULTS: Eighty-one patients (80 whites) were analyzed. Forty had NTG, whereas 41 had POAG. Thirty-five were females. There was a statistically significant difference in mean CH (NTG 9.6+/-1.3 mm Hg; POAG 9.0+/-1.4 mm Hg; P=0.01), but not in mean CRF (NTG 9.9+/-1.4; POAG 10.8+/-1.7; P=0.06). The highest recorded Goldmann applanation intraocular pressure (IOP) was statistically significantly associated with lower CH (P=0.01) and higher CRF (P=0.02). CONCLUSIONS: There was a small but statistically significant difference in the mean CH between POAG and NTG (CH was higher in NTG). The highest recorded Goldmann applanation IOP was also statistically significantly correlated with lower CH and higher CRF, suggesting that alterations to the corneal biomechanical properties may occur as a result of chronic raised IOP in POAG.     

Sequential office pressure measurements in the management of glaucoma

PURPOSE: To evaluate the usefulness of day-long sequential office measurements of intraocular pressure (IOP) to make therapeutic decisions in patients with progressive glaucomatous damage despite apparently 'controlled' IOP. METHODS: We reviewed the records of 93 consecutive glaucoma patients (185 eyes) who underwent sequential office IOP measurements (every hour from 7 AM to 5 PM on a single day). These included 53 patients with normal-tension glaucoma (NTG), 12 glaucoma suspects (GS), and 28 patients with primary open-angle glaucoma (POAG) whose visual field deteriorated despite apparently 'controlled' IOP. Only one eye per patient was included in the study. RESULTS: The pattern of the day-long IOP curve was similar in the 3 groups of patients. IOPs were highest in the early morning hours in all groups. The mean +/- SD of the IOP range was 5 +/- 2 mm Hg. An IOP > 21 mm Hg was found in 3 eyes (3%), whereas a range of IOPs > 5 mm Hg was detected in 33 eyes (35%). In the NTG group, there was a significant correlation between visual field deterioration and the peak and range of IOP (P = 0.0002 and P = 0.05, respectively). CONCLUSIONS: Day-long sequential office IOP measurements are useful in selected patients who demonstrate progressive glaucomatous damage. Early morning measurements are most frequently highest. The range of IOP may be as important, or more important than, the peak IOP level.     

Central corneal thickness in congenital glaucoma

PURPOSE: The aim of this study was to compare central corneal thickness between eyes with congenital glaucoma and normal fellow eyes in unilateral glaucoma or less affected fellow eyes in bilateral glaucoma. METHODS: Eyes of consecutive phakic children with congenital glaucoma and previous glaucoma surgery were examined under chloral hydrate. Complete ophthalmologic examination, central corneal thickness (CCT), axial length, and corneal diameter measurements were performed. Patients were included in the study if presented with intraocular pressure (IOP) less than 21 mm Hg and no biomicroscopic signs of corneal edema. RESULTS: Nine patients were included in the study. The mean CCT in the more affected eye/glaucomatous eye was 522.3 +/- 65.2 microm and in the less affected eye/healthy eye was 579.7 +/- 44.5 microm. This difference was statistically significant (P = 0.0013). CONCLUSION: CCT was significantly thinner in glaucomatous eyes than in normal fellow eyes in phakic children with congenital glaucoma. This finding may be another confounding factor when measuring IOP in these patients.     

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.     

Influence of corneal structure, corneal responsiveness, and other ocular parameters on tonometric measurement of intraocular pressure

PURPOSE: To estimate the relationships between ocular parameters and tonometrically measured intraocular pressure (IOP), to determine the influence of ocular parameters on different instrument measurements of IOP, and to evaluate the association of ocular parameters with a parameter called hysteresis. METHODS: Patients presenting at a glaucoma clinic were recruited for this study. Subjects underwent IOP measurement with the Goldmann applanation tonometer (GAT), the TonoPen, and the Reichert Ocular Response Analyzer (ORA), and also measurements of central corneal thickness (CCT), axial length, corneal curvature, corneal astigmatism, central visual acuity, and refractive error. Chart information was reviewed to determine glaucoma treatment history. The ORA instrument provided a measurement called corneal hysteresis. The association between measured IOP and the other ocular characteristics was estimated using generalized estimating equations. RESULTS: Among 230 patients, IOP measurements from the TonoPen read lowest, and ORA read highest, and GAT measurements were closest to the mean IOP of the 3 instruments. In a multiple regression model adjusting for age, sex, race, and other ocular characteristics, a 10 microm increase in CCT was associated with an increase of 0.79 mm Hg measured IOP in untreated eyes (P<0.0001). Of the 3 tonometers, GAT was the least affected by CCT (0.66 mm Hg/10 mum, P<0.0001). Hysteresis was significantly correlated with CCT with a modest correlation coefficient (r=0.20, P<0.0007). CONCLUSIONS: Among parameters related to measured IOP, features in addition to CCT, such as hysteresis and corneal curvature, may also be important. Tonometric instruments seem to be affected differently by various physiologic characteristics.     

Comparison of central and peripheral corneal thicknesses between normal subjects and patients with primary open angle glaucoma, normal tension glaucoma and pseudoexfoliation glaucoma

BACKGROUND: While many comparative data are available about central corneal thickness in different types of open angle glaucoma, peripheral corneal thickness has been much less investigated up to now. Thus, the aim of this study was to compare the central and peripheral corneal thicknesses in patients with primary open angle glaucoma (POAG), normal tension glaucoma (NTG) and pseudoexfoliation glaucoma (PEXG) to values of normal subjects. PATIENTS: 104 patients with POAG, 20 patients with NTG, 23 patients with PEXG and 127 normal subjects were investigated with the Orbscan II. The central corneal thickness and the peripheral corneal thickness at 3 mm distance from the centre were determined in 4 quadrants. The acoustic equivalent factor of 0.92 was not used. Patients with eye diseases, patients who had undergone eye surgery or wearers of contact lenses were excluded. Differences were analysed with the Bonferroni-adjusted Mann-Whitney U Test for statistical significance. RESULTS: The median central corneal thickness in POAG was 600 +/- 35 microm, in NTG 577 +/- 31 microm, in PEXG 603 +/- 25 microm and in the control group 606 +/- 38 microm. The difference between NTG and the control group was statistically significant (p = 0.01). Superiorly the peripheral corneal thickness was lower in POAG (670 +/- 47 microm) and NTG (639 +/- 37 microm) compared to the control group (686 +/- 46 microm). Nasally the peripheral corneal thickness was lower in POAG (656 +/- 48 microm), NTG (658 +/- 55 microm) and PEXG (642 +/- 47 microm) compared to the control group (677 +/- 46 microm). Temporally and inferiorly there were only small differences compared to the control group. The differences in peripheral corneal thickness were not statistically significant. DISCUSSION: In accord with literature data the central corneal thickness was lower in patients with normal tension glaucoma compared to normal subjects. Superiorly and nasally the peripheral corneal thickness was lower in patients with open angle glaucoma than in normal subjects which was, however, not statistically significant. To what extent these characteristics of the corneal architecture are relevant for the pathogenesis of open angle glaucomas has to be clarified in further larger trials.