Corneal thickness in congenital glaucoma

PURPOSE: To compare central corneal thickness between eyes with congenital glaucoma and normal controls and to correlate this parameter with corneal diameter and axial length. METHODS: Eyes of consecutive children with congenital glaucoma with previous glaucoma surgery and eyes of children with inadequacy of lacrimal drainage system with age less than 3 years old were examined under inhalatory general anesthesia. Complete ophthalmologic examination, central corneal thickness, axial length, and corneal diameter measurements were performed. All patients presented with intraocular pressure (IOP) less than 21 mm Hg and no clinical sign of corneal edema. RESULTS: Fifty-five eyes of 55 patients (30 congenital glaucoma and 25 controls) were examined (mean age = 16.6 +/- 10.6 months; 20 female/ 35 males). There was no significant difference in age and gender between glaucoma patients and normal subjects. Mean IOP was higher in glaucomatous eyes (P = 0.02). Corneal diameter and axial length between glaucomatous eyes and controls were significantly different (P < 0.0001 for both). Central corneal thickness was significantly thinner in glaucomatous eyes (P = 0.01). There was a significant correlation between corneal diameter and central corneal thickness and also between central corneal thickness and axial length (r2 = 0.32 and r2 = 0.18, respectively; P < 0.0001 for both). CONCLUSION: Central corneal thickness was significantly thinner in children with congenital glaucoma. This finding may be another confounding factor when measuring IOP in those patients. Pachymetry should be considered during their examination.     

Central corneal thickness and glaucoma in aphakic and pseudophakic children.

BACKGROUND: The risk of glaucoma among aphakic children is as high as 32%, based primarily on intraocular pressure (IOP) measurements. Although IOP may be falsely elevated by increased central corneal thickness, central corneal thickness (CCT) values have not been reported in this population. METHODS: Patients from the practices of 2 pediatric ophthalmologists and 2 glaucoma specialists had measurements of CCT, IOP, and optic nerve cupping, with visual field analysis when possible. Normal fellow eyes of unilateral aphakes and pseudophakes were included as controls. RESULTS: In 36 aphakic and 6 pseudophakic eyes CCT averaged 660 microns compared with 576 microns for phakic fellow eyes (P < 0.0001). Glaucoma, defined by IOP at least 35 mm Hg or by IOP at least 22 mm Hg associated with optic nerve changes, occurred in 21% of 28 aphakic patients but in no pseudophakic patient. CONCLUSIONS: CCT in aphakic/pseudophakic children is substantially increased compared with control patients. These values may be important in interpreting IOP measurements in these children.     

Cataract surgery for congenital cataract: endothelial cell characteristics, corneal thickness, and impact on intraocular pressure.

PURPOSE: To investigate whether central corneal thickness (CCT), endothelial cell characteristics, and intraocular pressure (IOP) are affected in patients with previous congenital cataract surgery and to focus on their clinical significance. METHODS: CCT and IOP measurements and specular microscopy were performed in 31 eyes of 17 cases of extracted congenital cataracts and 40 eyes of 20 age- and sex-matched participants as control group. The mean of three pachymetry measurements of the central cornea was taken as CCT. IOP was checked using an applanation tonometer. RESULTS: The mean corneal thickness of the eyes with extracted congenital cataract (632+/-45 microm) was significantly greater than that of the control eyes (546+/-33 microm; p<0.001). There was no significant difference in the corneal endothelial cell count, coefficient of variation (CV), and mean cell area (AVG) of endothelial cells between operated eyes and the control group. The mean measured IOP in the operated group (22.8+/-3.3 mm Hg) was significantly greater than IOP in controls (14.1+/-1.8 mm Hg, p<0.001). CONCLUSIONS: Although the corneas were clinically clear and there was no significant difference in endothelial characteristics of eyes with extracted congenital cataract and controls, central corneas of operated eyes were significantly thicker than those of controls. To differentiate the actual glaucoma from ocular hypertension in these patients, the central corneal thickness measurement should strongly be considered.     

Central corneal thickness and corneal diameter in patients with childhood glaucoma

PURPOSE: To determine and compare the central corneal thickness (CCT) and corneal diameter among groups of patients with childhood glaucomas and assess the relationship between CCT and corneal diameter in these patients. DESIGN: A multicenter observational case series using prospective and retrospective data. METHODS: Patients from the Scheie Eye Institute, Children's Hospital of Philadelphia, and Emory and Vanderbilt Medical Centers with childhood glaucomas were eligible to participate. Retrospective data on CCT and corneal diameter of these patients were collected when available; otherwise, patients were asked to return to the ophthalmology clinics for measurements. Patients with corneal edema or central corneal scarring were excluded. One hundred eighty four glaucomatous eyes from 109 patients (median age = 9.0 y; age range = 0 to 60 y) were included. RESULTS: The mean CCT (+/-SE) was 651.1+/-63.5 microm for aphakic, 528.7+/-38.5 microm for Axenfeld-Rieger, and 563.4+/-67.9 microm for 1 degrees infantile eyes. The mean corneal diameter in aphakic, Axenfeld-Rieger, and 1 degrees infantile glaucoma eyes were 11.2+/-1.0, 12.5+/-0.9, and 13.2+/-1.2 mm, respectively. There was a significant difference in CCT and in corneal diameter between aphakic and 1 degrees infantile glaucoma eyes, and between aphakic and Axenfeld-Rieger eyes (P < 0.0001). There was a negative correlation between CCT and corneal diameter in all eyes (r = -0.41, P < 0.0001). CONCLUSIONS: Patients with aphakic glaucoma are different from those with congenital glaucoma or Axenfeld-Rieger in CCT and corneal diameter. A patient with pediatric glaucoma and a larger corneal diameter was more likely to have a thinner CCT. Attention should be paid to the CCT of patients with childhood glaucomas for interpretation of intraocular pressure.     

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 children: Racial differences (black vs. white) and correlation with measured intraocular pressure

PURPOSE: To test the hypotheses that the mean central corneal thickness (CCT) of healthy black children is thinner than that of healthy white children and to confirm the relationship between increased CCT and measured intraocular pressure (IOP) in children. METHODS: This prospective observational case series included 178 eyes of 92 children aged 9 months to 17 years without anterior segment abnormalities or a clinical diagnosis of glaucoma. CCT was measured by ultrasonic pachymetry and IOP was measured by Goldmann or Tono-pen technique. RESULTS: The mean CCT for the 102 eyes of 52 white children was 562+/-35 microm versus 543+/-37 microm for the 66 eyes of 35 black children (P = 0.02). There was a positive relationship between CCT and IOP (P = 0.0002). For every 100 mum increase in CCT, the IOP increased by 2.2+/-0.6 mm Hg. CONCLUSIONS: The mean CCT of black children is thinner than that of white children. There is a positive relationship between increasing measured IOP and CCT among children with normal corneas and anterior segments. The interpretation of elevated IOP in eyes with abnormal anterior segment anatomy and thickened corneas awaits further study.     

Corneal hysteresis measured with the Ocular Response Analyzer® in normal and glaucomatous eyes

Purpose: To identify differences in corneal hysteresis (CH) and central corneal thickness (CCT) between healthy and glaucomatous patients. Methods: Retrospective observational study. One hundred and thirty‐three eyes of 75 healthy and 58 glaucomatous patients were included. CH was measured in each patient using Ocular Response Analyzer. CCT was determined by ultrasonic pachymetry. For each patient, one eye was randomly selected. We used a Student t‐test to search for significant differences between the different groups (p<0.05). Results: In healthy and glaucomatous eyes, mean CH values were 10.46 ± 1.6 and 8.77 ± 1.4 mm Hg, respectively. Mean CCT values were 560.2 ± 36.3 and 535.3 ± 42.7 μm, respectively. CH and CCT were significantly lower in glaucomatous eyes than in normal eyes, (p<0.05). Discussion: In our series, CH was lower in glaucomatous than in normal eyes. The relationship between glaucoma, IOP, and ocular structures may not be confined to the consideration of CCT. A low CH value could be responsible for under‐estimation of IOP. CH could also be a risk factor for glaucoma, independent of IOP. Further studies are needed to support these hypotheses. Conclusion: In our investigation, CCT and CH were significantly lower in glaucomatous eyes than in healthy eyes.     

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.     

Inter-instrument agreement and influence of central corneal thickness on measurements with Goldmann, pneumotonometer and noncontact tonometer in glaucomatous eyes

PURPOSE: This study was conducted to compare the intraocular pressure (IOP) measurements by the Goldman applanation tonometer (GAT), non contact tonometer (NCT) and the ocular blood flow (OBF) pneumotonometer in different IOP ranges in glaucomatous eyes. The effect of central corneal thickness (CCT) on IOP measurement in chronic glaucomatous eyes using the three different tonometers was also evaluated. MATERIALS AND METHODS: IOP measurements of 130 eyes of primary glaucoma patients were performed using GAT by an ophthalmologist while NCT and OBF-pneumotonometer measurements were performed by an experienced optometrist. The IOP values were compared amongst the three instruments in the three different IOP ranges (0-18 mmHg, > 18 to 25 mmHg, > 25 mmHg). CCT was also measured in all patients. RESULTS: The mean of paired difference between GAT and NCT was 0.9 +/- 3.1 mmHg while that between GAT and OBF-pneumotonometer was 0.3 +/- 3.4 mmHg. The OBF-pneumotonometer and NCT were more affected by corneal thickness (0.41 mmHg and 0.4 mmHg / 10 micro corneal thickness respectively) while GAT was the least affected by corneal thickness (0.3 mmHg / 10 micro corneal thickness) though the difference was not statistically significant ( P =0.42). CONCLUSION: With appropriate correction for corneal thickness the NCT and OBF-pneumotonometer can be used as reliably as GAT in following up glaucomatous patients.     

Central corneal thickness in children with congenital glaucoma

PURPOSE: To evaluate central corneal thickness in children with congenital glaucoma. MATERIAL AND METHODS: Central corneal thickness was measured with the use of ultrasound pachymeter in 49 eyes of 30 children, with congenital glaucoma aged 0-12 years. RESULTS: Mean central corneal thickness was 462 microm. Very wide differences between minimum and maximum recorded values were observed (380-780 microm). Three groups of patients could be distinguished: with very thin cornea of 380-450 microm (73% children), with normal corneal thickness of about 550 microm (15%) and with very thick cornea of 680-780 microm (12% patients). CONCLUSIONS: 1. Mean central corneal thickness in children with congenital glaucoma is significantly thinner than in healthy children in the same age and in adult patients with glaucoma. A very wide differences between minimum and maximum recorded values, are observed in these patients. 2. The results of applanation tonometric measurements are underestimated in most cases or less frequently overestimated. 3. The measurements of central corneal thickness should be performed in every patient with congenital glaucoma to correct the IOP values.     

Central corneal thickness measurement in clinical practice

OBJECTIVE: To determine if a single measurement of central corneal thickness (CCT) is an adequate sample to aid in glaucoma risk assessment in clinical practice. METHODS: Central corneal thickness was measured by ultrasound pachymetry (mean of 15 measurements for each eye) on two separate occasions at least one month apart (range, 33 to 610 days). Eyes with a history of prior incisional surgery or corneal pathology were excluded. RESULTS: Ninety-eight eyes of 98 patients (43 male, 55 female) were enrolled. Mean age was 61.2 +/- 15.5 years. Mean inter-test period was 276 +/- 124 days. No significant difference in mean CCT was observed between the two visits (549 +/- 41 microm versus 548 +/- 42 microm, P = 0.4, two-tailed, paired t test). Measured CCT values differed by more than 20 microm in 20 eyes (20.4%), whereas CCT difference of at least 40 microm was seen in 5 eyes (5.1%). There was no correlation between the measured or absolute difference in CCT and IOP (r = -0.016, P > 0.43), inter-test time period (r = 0.072, P > 0.23), and glaucoma diagnosis. CONCLUSION: Central corneal thickness measurements in this study differed by at least 20 microm in 20% of eyes. This has important implications for risk assessment, management, and follow-up of patients with glaucoma and related disorders. Factors affecting CCT measurement, such as examiner error or true alterations in corneal thickness, require continued investigation.     

Der Einfluss von kornealer Hysterese und kornealem Resistenzfaktor auf die Messung des intraokularen Drucks

BACKGROUND: The influence of central corneal thickness (CCT) on the measurement of intraocular pressure (IOP) has been discussed extensively in recent years. The problem, however, has not been solved so far. In addition to CCT there are probably further biomechanical properties that play a role in IOP measurement. We wanted to find out whether these properties are related to Goldmann applanation tonometry (GAT), noncontact tonometry (NCT), or CCT. MATERIAL AND METHODS: Biomechanical properties of the cornea such as corneal hysteresis (CH) and corneal resistance factor (CRF) can be measured with the Ocular Response Analyzer (ORA, Reichert Ophthalmic Instruments, Depew, NY, USA). Furthermore, a corneal compensated IOP (IOPcc) is given. We examined 156 normal eyes of 80 patients who did not show corneal pathology nor glaucoma. In each eye GAT, NCT, and ORA data as well as CCT were measured. Data were statistically analyzed with respect to agreement and the influence of CH and CRF on IOP measurement. RESULTS: In our patients the following average values were calculated: GAT 14.8+/-3.0 mmHg, NCT 16.4+/-3.9 mmHg, IOPcc 16.2+/-4.1 mmHg, CH 10.6+/-2.3 mmHg, CRF 10.9+/-2.4 mmHg, and CCT 557+/-36 microm. IOPcc was not related to CCT in normal eyes and the only IOP value related to CH (p<0.01). CRF, however, was related to GAT and NCT values (p<0.01). DISCUSSION: In our group of normal eyes IOPcc, i.e., the value that is adjusted by measurement of viscoelastic properties of the cornea, in contrast to GAT and NCT does not depend on central corneal thickness. Corneal hysteresis and corneal resistance factor provide further information about biomechanical properties of the cornea beyond central corneal thickness.     

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     

New aspects of corneal pachymetry in congenital glaucoma and pediatric aphakic glaucoma

BACKGROUND: Knowledge of individual corneal thickness in individual eyes is proving to be more and more crucial for correcting Goldmann applanation tonometry, as well as to assess its predictive value regarding the possible progression of glaucomatous damage. It has become an important factor in determining appropriate glaucoma therapy. Only few pachymetric data exist about eyes with congenital or secondary pediatric aphakic glaucoma. METHODS: 12 eyes with congenital glaucoma (6 patients, mean age 3.3 years, mean 3.9 previous operations) and 7 eyes with secondary pediatric aphakic glaucoma (4 patients, mean age 14.8 years, mean 3 previous operations) without clinical signs of corneal decompensation were investigated by ultrasound pachymetry. RESULTS: Eyes with glaucoma due to aphakia had a mean corneal thickness of 708 +/- 77.3 microm. Mean corneal thickness of the eyes with congenital glaucoma was 688.1 +/- 115.9 microm, which is far above the values known from the literature. Two eyes, which had a central corneal thickness of 646 microm and 640 microm, presented with a localised paracentral corneal thickness of only 402 microm and 405 microm, respectively, correlating with microscopic descemet scars. CONCLUSIONS: Congenital glaucoma and the pediatric aphakic glaucoma present with very heterogeneous clinical pictures. Especially for congenital glaucoma, this is confirmed by the high interindividual, but also intraindividual, variability of corneal pachymetry.     

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.     

Clinical comparison of pascal dynamic contour tonometry and goldmann applanation tonometry in asymmetric open-angle glaucoma

PURPOSE: To investigate and compare the relationships between glaucomatous visual field loss and intraocular pressure (IOP) as measured by both Pascal dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT). PATIENTS AND METHODS: All primary open-angle glaucoma and normal tension glaucoma patients seen between July 2005 and June 2006 with at least 2 sets of good-quality, bilateral DCT and GAT measurements were retrospectively identified. Additional inclusion criteria required that all subjects had repeatable, asymmetric glaucomatous visual field loss that corresponded with asymmetric glaucomatous optic neuropathy. After mean IOP values were computed and visual fields were scored using Advanced Glaucoma Intervention Study (AGIS) criteria, paired-eye comparisons were conducted using right versus left eyes and higher versus lower AGIS-score eyes. RESULTS: Sixty-seven (42 primary open-angle glaucoma, 25 normal tension glaucoma) subjects met all criteria for study inclusion. Per paired t test, mean DCT-IOP was significantly higher in the higher AGIS-score eyes compared with the lower AGIS-score eyes (16.3 vs. 15.5 mm Hg, P=0.004), whereas GAT-IOP was not significantly different in these same eyes (14.5 vs. 14.4 mm Hg, P=0.56). Mean IOP difference between the 2 methods was significantly larger in higher versus lower AGIS-score eyes (P<0.001), and 72% of the subjects demonstrated larger intermethod IOP differences in their higher AGIS-score eye compared with their lower AGIS-score eye (P<0.001; 95% confidence interval: 0.59-0.82). Multivariate linear regression analysis revealed that AGIS-score differences between eyes were independently associated with both intermethod IOP differences between eyes (P=0.004) and central corneal thickness (CCT) differences between eyes (P=0.04). CCT, however, was not associated with intermethod IOP differences within or between eyes. CONCLUSIONS: These findings suggest that DCT-IOP is correlated with glaucomatous damage, and moreover, DCT-IOP is more closely related to extent of glaucoma damage than is GAT-IOP. The most likely explanation for these results is that GAT-IOP systematically underestimates IOP compared with DCT-IOP. Our findings also support the hypothesis that corneal biomechanical factors other than CCT are major confounders of applanation tonometry measurements.     

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.     

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)     

Corneal thickness after overnight wear of an intraocular pressure fluctuation contact lens sensor

Purpose: To assess the effect of overnight wear of a contact lens‐based sensor (CLS) for monitoring of 24‐hr intraocular pressure (IOP) fluctuations on central corneal thickness (CCT). Materials and Methods: Changes in the CCT, mid‐peripheral corneal thickness and central corneal radius (CCR) during overnight CLS wear in 20 eligible patients with ocular hypertension or established glaucoma were prospectively studied using ultrasound pachymetry and topography. Corneal thickness and CCR changes were evaluated from pre‐to‐postsleep, with the fellow eye as control. Paired t‐test or Wilcoxon signed‐rank test was used as appropriate and with α = 0.05. Relationship between the IOP profile recorded by the CLS and the pre‐to‐postsleep corneal thickness differences was assessed using the Spearman correlation coefficient. Results: After CLS wear, mean CCT had changed from 523 to 537 μm (p = 0.015) in the study eye and from 518 to 522 (p = 0.206) in the fellow eye (n = 15). There was no difference in CCT change between eyes (p = 0.075). There were no statistically significant changes in horizontal or vertical CCR in either eye (p > 0.05 for all). No correlation was found between the pre‐to‐postsleep differences in the CLS signal and the pre‐to‐postsleep differences in ultrasound CCT measurements (p = 0.974). Conclusion: The continuous IOP monitoring does not appear to be affected by differences in corneal thickness that occur during overnight CLS wear, although the CLS did induce some corneal swelling. This effect was not statistically significantly different from the control eye and does not seem to influence the CLS IOP profile.     

Corneal thickness and endothelial cell density measured by non-contact specular microscopy and pachymetry in Rhesus macaques (Macaca mulatta) with laser-induced ocular hypertension

PURPOSE: Sustained increase in intraocular pressure (IOP) in humans results in a loss of corneal endothelial cells and an increase of corneal thickness. The effects of chronically elevated IOP on the corneal endothelium of monkeys with laser-induced ocular hypertension, a commonly used animal model of human glaucoma have not been documented. This study examined the central corneal thickness (CCT), the corneal endothelial cell density (ECD), and the corneal endothelial cell size (ACS) in Rhesus monkeys with experimental ocular hypertension.Materials and methods. Ten male monkeys with argon laser-induced ocular hypertension in one eye for an average duration of 2.4+/-0.7 years, were sedated with ketamine hydrochloride, and the CCT, ECD, and ACS measured at the center of the cornea of both eyes with a Topcon SP-2000P non-contact specular microscope (Topcon America Corporation((R)), Paramus, NJ, USA). CCT was also measured using a DHG-500 Pachette ultrasonic pachymeter (DHG Technology Inc., Exton, PA, USA). Mean and standard deviation (S.D.) of CCT, ECD and ACS for each eye was calculated and statistically compared.Results. Mean CCT in the hypertensive and normal eyes measured by specular microscopy was 0.477+/-0.023mm and 0.468+/-0.020 mm, respectively. Mean ECD in the hypertensive and normal eyes was 2601.7+/-631.8 and 3990.2+/-402.9 cells mm(-2), respectively. The mean size of the endothelial cells was 252.4+/-23.9 micro m(2) in the normal eye and 408.7+/-115.0 microm m(2) in the hypertensive eye. No significant difference in the measurement of CCT was observed between the specular microscope and the pachymeter (p=0.46).No significant difference in the mean CCT was observed between the two eyes (p=0.4820), whereas the mean ECD was significantly lower in the hypertensive eye than in the normal eye (p<0.001). The ECD was inversely related to the length of IOP elevation (p<0.001). CONCLUSIONS: No difference in the corneal thickness measurement was observed between the specular microscopy and the pachymetry techniques. Chronic ocular hypertension did not significantly affect the CCT, but caused a significant loss of endothelial cells in the center of the cornea of the laser treated eyes compared to the normotensive eyes. The duration of elevated IOP was the most important factor affecting the ECD.