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.     

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 and visual field damage in glaucoma patients

PURPOSE: To verify whether there was a significant correlation between central corneal thickness (CCT) and visual field damage in patients with primary open angle glaucoma (POAG). METHODS: A total of 99 eyes with POAG were consecutively recruited. Patients were classified as glaucomatous based on visual field and optic nerve head damage. All underwent applanation tonometry, Humphrey perimetry, and measurement of CCT with ultrasonic pachymetry. Based on CCT value, the sample was split at the mode in two groups (group 1<535 microm, n=49; group 2>or=535 microm, n=50). RESULTS: Entire cohort: mean CCT 554 microm+/-45.03; mean deviation (MD) -6.68 dB+/-7.32; pattern standard deviation (PSD) 5.33+/-3.75; intraocular pressure (IOP) 17.91+/-4.16 mmHg with treatment. Group 1: CCT was 504.8 microm+/-30.8; MD -9.01 dB+/-8.72; PSD 6.38+/-3.99; IOP 18.02 mmHg+/-4.66. Group 2: mean CCT 574.6 microm+/-35.03; MD -4.39 dB+/-4.70; PSD 4.25+/-3.19; IOP 17.79 mmHg+/-3.57. A significant difference was found between the two groups for both MD and PSD. Linear regression analysis showed a significant correlation between CCT and PSD (P<0.001). CONCLUSIONS: Our data show that patients with a thinner cornea had a worse MD and PSD. As a thinner CCT causes an underestimation of the true IOP, there may be a delay in the diagnosis of POAG or an inadequate estimate of the clinical course despite apparently desirable IOP applanation readings.     

Comparison of Pentacam Scheimpflug camera with ultrasound pachymetry and noncontact specular microscopy in measuring central corneal thickness

PURPOSE: Although central corneal thickness (CCT) can be measured by several methods, interchangeability of different modalities has not been fully investigated. CCT is known to correlate with intraocular pressure (IOP). The aim of this study was to evaluate the agreement of Pentacam Scheimpflug system with noncontact specular microscopy (NCSM) and ultrasound (US) pachymetry in measuring CCT and the relation between IOP taken with Goldmann applanation tonometer (GAT) and the CCT measured with these three methods. METHODS: The right eyes of 135 enrolled persons without antiglaucoma drug use (100 females and 35 males), who comprised 32 patients with primary open-angle glaucoma, 14 with ocular hypertension, 45 with primary angle-closure glaucoma, and 44 controls, were studied. Intermethod comparison of CCT was made by the 95% limits of agreement analysis according to Bland and Altman. Linear regression analysis was used to assess the relationship between IOP and CCT taken with each modality. RESULTS: The mean CCT (+/-SD) taken with Scheimpflug, US, and NCSM was 559.49 +/- 38.44 microm, 553.01 +/- 39.33 microm, and 552.04 +/- 42.95 microm, respectively. The average values of CCT taken with the three instruments were not significantly different (one-factor ANOVA; p = 0.26), although the marginal mean difference between Scheimpflug and US or NCSM was statistically significant (paired t test; p = 0.0009 and 0.005, respectively). The 95% limits of agreement were 6.47 +/- 43.21 microm between Scheimpflug and US, 7.45 +/- 58.86 microm between Scheimpflug and NCSM, and 0.98 +/- 51.69 microm between US and NCSM. There was a positive association between IOP and CCT measured with US or NCSM, whereas there was no correlation between IOP and CCT measured with Scheimpflug. CONCLUSIONS: Although CCT values measured with Scheimpflug, US, and NCSM are closely similar, clinicians should keep in mind that these methods are not simply interchangeable.     

Central corneal thickness: congenital cataracts and aphakia

PURPOSE: To evaluate central corneal thickness (CCT) in normal children (controls) and in those with cataracts, pseudophakia, and aphakia. DESIGN: Prospective, observational case series. METHODS: CCT was measured in 369 eyes of 223 children. Subjects with glaucoma, anterior segment abnormalities, or intraocular pressure of more than 30 mm Hg were excluded. Group means were compared for controls and for eyes with pediatric cataracts, pseudophakia, and aphakia. RESULTS: The mean CCT of eyes with cataracts was more than that of controls (574 +/- 54 microm [n = 46] and 552 +/- 38 microm [n = 230], respectively; P = .001). After excluding from the cataract group those eyes with aniridia, Down syndrome, Marfan syndrome, or glaucoma surgery, the mean CCT (564 +/- 34 microm [n = 36]) was no longer greater than that of controls (P = .07). The mean CCT of pseudophakic eyes (598 +/- 56 microm [n = 29]) was greater than the mean CCT of controls (P < .001) and was similar to the mean CCT of eyes with cataracts (P = .06). The mean CCT of aphakic eyes (642 +/- 88 microm [n = 64]) was greater than the mean CCT of controls (P < .001), eyes with cataracts (P < .001), and eyes with pseudophakia (P = .003). CONCLUSIONS: In the absence of factors known to affect CCT (Down syndrome, Marfan syndrome, and aniridia), CCT is similar in eyes with pediatric cataracts and normal controls and increases after cataract surgery.     

Corneal thickness determination and correlates in Singaporean schoolchildren

PURPOSE: To determine the central cornea thickness (CCT) in Singaporean children and to examine the possible relationship between intraocular pressure (IOP) and other biometric factors and CCT. METHODS: This was a cross-sectional study. The subjects (N=652) were obtained from the Singapore Cohort Study of the Risk Factors for Myopia (SCORM). The subjects' ages ranged from 9 to 11 years. There were 485 Chinese, 92 Malayan, and 75 Asian Indian children. Measurement procedures included air-puff tonometry, noncontact slit lamp optical pachymetry, cycloplegic autorefraction, and autokeratometry. RESULTS: The mean CCT was 543.6 +/- 32.0 microm. Chinese children had thicker corneas than Malayan or Indian children (P=0.002). The boys had thicker corneas than girls (P=0.011), but the mean difference was only 6.4 microm. There was high correlation of CCT (r=0.98) and IOP (r=0.88) between right and left eyes. IOP was correlated with CCT (r=0.45, P <0.001). In a multiple linear regression model, each millimeter of mercury of IOP was associated with a CCT difference of 5.90 microm (95% confidence interval [CI], 4.98-6.82). The radius of corneal curvature correlated with CCT (r=0.19, P <0.001). The following parameters were not significantly (P >0.05) associated with CCT: age, family income, father's education, axial length, and spherical equivalent. CONCLUSIONS: The mean CCT in Singaporean children aged 9 to 11 years was 543.6 microm and showed ethnic and gender variation. CCT affected measured IOP and correlated weakly with corneal curvature. Compared with data in adults, a change in CCT was associated with a greater difference in measured IOP.     

The influence of central corneal thickness and corneal curvature on intraocular pressure measured by tono-pen and rebound tonometer in children

PURPOSE: To find out the effect of central corneal thickness (CCT) and radius of the corneal curvature on intraocular pressure (IOP) measurements using rebound tonometer (RBT) and Tono-Pen in healthy schoolchildren. METHODS: IOP was measured with Tono-Pen and RBT, respectively, in 165 healthy schoolchildren with a mean age 9.8+/-3.1 (range: 7 to 12 y) years. Corneal radius of curvature (in mm) was determined using a keratometer before CCT and IOP measurements. CCT was measured using an ultrasonic pachymeter after all IOP determinations had been made. The effect of CCT, radius of the corneal curvature, and sex on measured IOP was evaluated by linear regression analysis. RESULTS: The mean IOP readings were 17.47+/-2.7 mm Hg using Tono-Pen, and 16.81+/-3.1 mm Hg using RBT. Tono-Pen measured IOP values slightly greater than that of RBT (P=0.006). Mean CCT was found to be 561.37+/-33 microm. A significant association between measured IOP and CCT was found with each device (r=0.220 for the Tono-Pen, r=0.373 for the RBT; P=0.006 for the Tono-Pen and P<0.0001 for the RBT). The IOP increased 2.2 and 3.7 mm Hg for every 100-microm increase in CCT for the Tono-Pen and the RBT, respectively. The relation between IOP and CCT was not different for boys and girls. Mean radius of the corneal curvature readings was 7.68+/-0.41 mm (42.75+/-1.37 D) for both sexes. There was no significant relationship between either the mean corneal curvature readings, or CCT and IOP (r=0.02; P=0.4 for CCT and r=0.01; P=0.5 for IOP). CONCLUSIONS: Both the Tono-Pen and RBT have a systematic error in IOP readings caused by its dependence on CCT. The CCT measurements should be considered to ensure proper interpretation of IOP measurements in children, like in adults. The corneal radius of curvature had no significant effect on measured IOP with each device.     

Diurnal variation of ocular hysteresis in normal subjects: relevance in clinical context

BACKGROUND: This study was conducted to assess the diurnal variation in ocular hysteresis, as measured by the Ocular Response Analyser to establish a relationship between diurnal hysteresis variation and diurnal intraocular pressure (IOP) variation. METHODS: Forty-two normal eyes of 21 colleagues and staff in a teaching hospital in Birmingham, UK, were recruited. The IOP and hysteresis were measured by the Ocular Response Analyser. The central corneal thickness (CCT) was measured using a hand-held ultrasonic pachymeter in the mid-pupillary axis. RESULTS: The mean ocular hysteresis at 8 am was 12.7 +/- 2.3 mmHg, at 11 am was 12.2 +/- 2.0 mmHg, at 2 PM was 12.7 +/- 2.1 mmHg and at 5 PM was 12.7 +/- 1.7 mmHg; the difference between the values at any time of measurement was not statistically significant (P > 0.9, repeated measures). IOP as measured by non-contact tonometry was 18.4 +/- 2.8 mmHg, 17.9 +/- 3.3 mmHg, 16.9 +/- 3.1 mmHg and 16.8 +/- 3.2 mmHg, respectively, for the same time period; the difference between the values in the morning and afternoon was statistically significant (P < 0.0001, repeated measures). The CCT was 548.8 +/- 29.5 microm, 547.0 +/- 31.4 microm, 548.2 +/- 29.6 microm and 548.6 +/- 29.4 microm, respectively; the difference between the values was not statistically significant at any time points. Multiple regression analysis showed the relationship between IOP and hysteresis was not statistically significant (P = 0.9). CONCLUSION: The ocular hysteresis reading was almost constant throughout the day, whereas the IOP readings showed highest values in the morning with a reducing trend being lowest in the afternoon. The CCT values were almost stable throughout the day. IOP appears to vary independently of a variation in hysteresis or CCT.     

Central corneal thickness in Latinos

PURPOSE: To characterize central corneal thickness (CCT) in Latinos aged 40 or more years. METHODS: A population-based cohort of Latinos from two census tracts in La Puente, California, underwent measurements of CCT and intraocular pressure (IOP). CCT was measured with an ultrasonic pachymeter, and IOP was measured by applanation tonometry. One eye of each of 1699 participants was included in the analyses. RESULTS: The mean (+/-SD) CCT was 546.9 +/- 33.5 micro m. Older participants (>or=70 years) had significantly thinner CCs compared with participants 40 to 49 years of age (P < 0.05). Eyes with ocular hypertension had thicker CCs than did normal and glaucomatous eyes (P < 0.05). Multivariate adaptive regression spline analyses and analysis of variance contrasting IOP subgroups revealed that eyes with thinner CCs had lower IOP than did eyes with thicker CCs (P < 0.001). The absolute range of interocular differences in CCT in the same subject was as high as 24 micro m. CONCLUSIONS: On average, CCT in Latinos was less than that previously reported in whites but greater than that reported in African Americans and Asians. Older Latinos had thinner corneas compared with younger Latinos. Asymmetry in CCT of 25 micro m or more should be evaluated for potential corneal disease. Spline analyses suggest that although the relationship between IOP and CCT is best explained by a nonlinear equation, when measuring IOP with the Goldmann tonometer, it is likely that IOP is underestimated in eyes with thinner CCs and overestimated in eyes with thicker CCs.     

The relationship among race, iris color, central corneal thickness, and intraocular pressure.

PURPOSE: Central corneal thickness (CCT) influences applanation intraocular pressure (IOP) measurement. The present study sought to determine whether iris color might represent a qualitative surrogate for CCT or race, and therefore differential risk for elevated IOP and, consequently, developing glaucoma. METHODS: Eligible patients included those with best-corrected visual acuity (BCVA) better than 20/40 and who had not worn contact lenses within 24 hours. Exclusion criteria were prior ophthalmic surgery, topical ocular or systemic medication that would influence IOP, previous ocular inflammatory conditions, or current treatment for ophthalmic treatment. Data collection included demographic (name, date of birth, race), BCVA, and iris color. Iris color was judged according to a purpose-developed chart (white: blue, green, brown or black: brown) and patients were assigned to one of four groups. Goldmann applanation tonometry and pachymetry measurements were performed consecutively. To attain a power of 90% to find a difference of 40 microm with alpha < 0.05, we examined at least 14 subjects (28 eyes) for each group. RESULTS: Comparing pachymetry measurements among iris colors revealed no statistically significant difference among the three groups of whites: blue (552 microm), green (552 microm), and brown (562 microm). The same held true when comparing IOP and CCT-adjusted IOP with iris color: blue-15.2, 15.1, green-15.4, 15.2, and brown-14.7, 14.0. When comparing CCT between whites and blacks, CCT was significantly thinner in blacks (533 microm), whether evaluating all whites (555 microm, p = 0.03) or comparing only the brown-iris white group with the black group (562 microm vs. 533 microm, p = 0.03). Mean CCT-adjusted IOP was barely significantly different between whites (14.8) and blacks (16.7) (p = 0.04). CONCLUSION: These results suggest that iris color is not associated with CCT and apparently iris color does not influence measured IOP. We were able to establish a relationship between race and IOP when adjusting IOP for CCT. Our data show a significantly higher CCT-adjusted IOP for blacks than whites demonstrating a racial difference in CCT-corrected IOP.     

Central corneal thickness and visual field progression in patients with chronic primary angle-closure glaucoma with low intraocular pressure

PURPOSE: To determine the association of central corneal thickness (CCT) and visual field progression in patients with chronic primary angle-closure glaucoma (CPACG) with low intraocular pressure (IOP). DESIGN: Retrospective, comparative case series. METHODS: A total of 163 eyes with CPACG and sustained IOP <18 mm Hg were included. Initial and three-year after mean deviation (MD) on Humphrey field analyzer and CCT with ultrasonic pachymetry were recorded. On the basis of the CCT value, the sample was split in two groups (group 1 <540 microm; group 2 > or =540 microm). RESULTS: Mean CCT was 525.8 +/- 11.6 microm in group 1 and 574.4 +/- 24.0 microm in group 2. There was no significant difference for initial MD (P = .979), but a significant difference was found between two groups for follow-up MD (P = .023). CONCLUSIONS: Patients with CPACG with a thinner cornea are at greater risk for visual field progression even if they maintain a low IOP after treatment.     

Central corneal thickness in children: stability over time

PURPOSE: To evaluate central corneal thickness (CCT) in children over time. DESIGN: Prospective observational case series. METHODS: CCT was measured by ultrasonic pachymetry in 69 eyes of 38 subjects age 3 to 14 years recruited from the Duke University Eye Center. Subjects included patients with and without glaucoma. RESULTS: For eyes on no glaucoma medication, the mean change in CCT was -1.9 +/- 14 microm (n = 30; mean time between CCT measurements, 567 days). For eyes on stable glaucoma medication, the mean change in CCT was +8.1 +/- 26 microm (n = 27; mean time between CCT measurements, 580 days). For eyes with a change in medical therapy between visits, the mean change in CCT was -3.8 +/- 24 microm (n = 8, mean number of days between visits 723). Four eyes underwent trabeculectomy between measurements and experienced a mean change in CCT of -9.0 +/- 6 microm with a mean of 1257 days between measurements. These CCT changes were not statistically significant. CONCLUSIONS: CCT of children ages 3 to 14 years appears stable over a one- to two-year interval.     

Pachymetry of donor corneas: effect of ethnicity and gender on central corneal thickness

PURPOSE: To examine demographic differences associated with the central corneal thickness (CCT) of donor corneas and to investigate whether these differences confirmed previous clinical studies. METHODS: CCT was prospectively measured using noncontact pachymetry among 704 eye bank corneas. The effects of gender, ethnicity, age, cause of death, times until preservation and evaluation, and endothelial cell density and morphometry on CCT were examined. RESULTS: The CCT of black women was significantly thinner (P = 0.05) than that of other corneal donors. The average CCT +/- SD of black women was 530 +/- 35.9 microm, whereas those of white and Hispanic women were 554 +/- 59.1 microm and 556 +/- 51.2 microm, respectively. Average values for black, white, and Hispanic men were 553 +/- 44.7 microm, 551 +/- 53.4 microm, and 543 +/- 50.4 microm, respectively. Age and cause of death did not significantly affect CCT. CONCLUSION: Gender may modify racial differences of CCT. Measurements using donated corneal tissues support pachymetric differences by ethnic origin, although this finding was limited to female donors only.     

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.     

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.     

Comparison of anterior segment optical coherence tomography and ultrasound biomicroscopy for assessment of the anterior segment

PURPOSE: To compare anterior segment parameters using quantitative imaging by anterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM). SETTING: Tertiary-care glaucoma research center. METHODS: Sixty-three eyes of 63 subjects had anterior segment evaluation by AS-OCT (Visante-Zeiss) and UBM (Paradigm). Central corneal thickness (CCT), anterior chamber depth (ACD) (measured from the central corneal endothelium to the anterior lens capsule), and the peripheral iridocorneal angles (temporal and nasal) were assessed and compared. RESULTS: There was an excellent correlation between AS-OCT and UBM measurements for the nasal angle (r = 0.84; P<.0001), temporal angle (r = 0.86; P<.0001), ACD (r = 0.97; P<.0001), and CCT (r = 0.91; P<.0001). There was no significant difference (paired t test) between the mean ACD, CCT, and angle parameters measured by AS-OCT or UBM. The mean values of the parameters measured by AS-OCT and UBM were, respectively, as follows: nasal angle, 26.25 degrees +/- 11.0 (SD) and 28.27 +/- 11.3 degrees (P = .3); temporal angle, 25.1 +/- 11.4 degrees and 28.3 +/- 13.5 degrees (P = .15); ACD, 2.85 +/- 0.5 mm and 2.78 +/- 0.5 mm (P = .2); and CCT, 512 +/- 46 microm and 502 +/- 46 microm (P = .25). The AS-OCT images showed sharper definition of the scleral spur than the UBM images. CONCLUSION: Anterior segment optical coherence tomography and UBM can both be used for anterior segment measurements and yielded comparable results.     

Central corneal thickness in individuals with intellectual disabilities

PURPOSE: To assess central corneal thickness (CCT) values in individuals with intellectual disabilities (ID). METHODS: The study group was made up of 25 participants with ID (mean age, 36.9 +/- 8.7 years). The control group was made up of 25 healthy individuals (mean age, 37.1 +/- 10.1 years) with normal intellectual capacity and without any systemic or intraocular pathology. CCT value was measured by ultrasound pachymetry. Ten consecutive measurements were made at the center of the cornea of each eye. RESULTS: In the ID group, mean CCT value was 554.0 +/- 39.7 microm in the right eye and 556.8 +/- 38.7 microm in the left eye. In the control group, mean CCT value was 535.7 +/- 24.2 microm in the right eye and 536.5 +/- 24.8 microm in the left eye. CCT value in the ID group was significantly greater than in the control group for both right (P < 0.05) and left eyes (P < 0.02). CONCLUSIONS: CCT should be kept in mind during measurements of intraocular pressure (IOP) in individuals with ID because their CCTs may be greater than those in the general population.     

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   

Corneal thickness in children

OBJECTIVE: To determine normal central and paracentral corneal thickness measurements in the pediatric population and to determine if these measurements are consistent across different pediatric age groups and different racial groups. DESIGN: Prospective observational case series. METHODS: Pachymetry measurements were performed on 198 eyes of 108 children. The measurements were taken centrally as well as at four paracentral sites 3 mm from the corneal center at the 3, 6, 9, and 12 o'clock positions. The two-tailed t test was used for comparison of the continuous means for values of corneal thickness. Analysis of variance (ANOVA) was performed to determine differences among age and ethnic groups RESULTS: The mean central corneal thickness (CCT) was 549 +/- 46 microm. Paracentral corneal thickness mean values, as measured 3 mm from the corneal center, were as follows: superior, 575 +/- 52 microm; nasal, 568 +/- 50 microm; inferior, 568 +/- 51 microm; and temporal, 574 +/- 47 microm. The mean CCT values were significantly thinner than at each of the mean paracentral points (P < .05 for each comparison, paired t test). Paracentral corneal thickness measurements demonstrated no significant differences between locations (P > .05, variance analysis). The mean CCT +/- SD for each age group was as follows: 6 to 23 months, 538 +/- 40 microm; 2 to 4 years, 546 +/- 41 microm; 5 to 9 years, 566 +/- 48 microm; and 10 to 18 years, 554 +/- 35 microm (ANOVA P = .012). ANOVA performed on central pachymetry values demonstrated no significant differences among racial subgroups. CONCLUSIONS: Pediatric central and paracentral corneal thicknesses increase slowly over time and reach adult thicknesses at 5 to 9 years of age.     

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.