角膜中央厚度与眼压读数

目的　探讨角膜中央厚度与眼压读数的关系。方法　对44例88眼屈光角膜手术前的患者,分别用压平眼压计和超声角膜测厚仪进行角膜中央厚度和眼压的测量,并对二者之间的关系进行统计分析。结果　Ⅰ组角膜中央厚度≥580μm,眼压为21.50～27.00mmHg(23.70mmHg±1.36mmHg)(1kPa=7.5mmHg),屈光度-2.00～-12.00D。Ⅱ组角膜中央厚度＜520μm,眼压为11.00～20.00mmHg(15.66mmHg±1.71mmHg),屈光度-1.25～-11.25D。Ⅰ组眼压高于Ⅱ组（P＜0.001）。结论　角膜厚度与眼压有明显的相关性,即角膜厚度增加眼压相应增高,当眼压读数高于正常时,应考虑到是角膜中央厚度的改变。     

中央角膜厚度对3种眼压计眼压测量值的影响

目的比较分析不同中央角膜厚度(central corneal thickness,CCT)下Icare回弹式眼压计、Goldmann压平式眼压计(Goldmann applanation tonometer,GAT)和动态轮廓眼压计(dynamic contour tonometry,DCT)的眼压测量结果,探讨CCT对3种眼压计测量值的影响。方法 对78例患者152眼分别用Icare、GAT、DCT3种眼压计进行眼压测量,并进行CCT的测量,对比不同CCT下3种眼压计的测量结果,分析眼压测量值与CCT的关系。结果 在全部受测者中Icare、GAT、DCT测得的眼压均值分别为(19.16±5.03)mmHg(1 kPa=7.5 mmHg)、(18.41±4.52)mmHg和(17.23±3.69)mmHg,三者之间有显著差异(F=7.256,P=0.001)。Icare和GAT的眼压测量值均与CCT显著相关(r=0.341,P<0.001;r=0.333,P<0.001),CCT每改变10μm,Icare的眼压值改变0.47 mmHg,GAT的眼压值改变0.41 mmHg;而DCT的眼压测量值与CCT无显著相关(r=0.032,P=0.699)。结论 Icare、GAT的眼压测量值均明显受CCT的影响,而Icare受CCT影响的程度较GAT的稍大,DCT的眼压测量值基本不受CCT的影响。     

Effects of corneal thickness on intraocular pressure measured with three different tonometers

Purpose: To compare intraocular pressure (IOP) measured by a Goldmann applanation tonometer (GAT), a noncontact tonometer (NCT), and a portable noncontact tonometer (PNCT) in eyes of healthy volunteers, and to determine if a significant correlation exists between the IOP and the central corneal thickness (CCT). Methods: A total of 144 healthy participants were randomly assigned to one of two groups; in the first group, IOP was measured first with the NCT and then with the GAT. In the second group, IOP was measured first with the PNCT and then with the GAT. Subsequently, the CCT of all subjects was measured with an ultrasonic pachymeter. Results: The IOPs determined by the GAT and NCT and were strongly correlated, as were those determined by the GAT and PNCT, in both groups. However, a Bland-Altman plot showed that the correlations between the GAT and NCT and between the GAT and the PNCT measurements were not significant. With all three instruments, the IOP readings varied with the CCT. The mean IOPs obtained with the GAT increased by 0.23 mmHg with each 10-μm increase in CCT (0.23 mmHg/10 μm). The comparable value for the NCT was 0.29 mmHg/10 μm, and that for the PNCT was 0.31 mmHg/10 μm. Conclusions: For measurements of IOP in normal eyes, the GAT is the tonometer least affected by the CCT, compared with the PNCT and NCT. A PNCT is more likely to be affected by variations in CCT than the GAT.     

婴儿先天性白内障摘出术后早期中央角膜厚度变化与眼压的相关性研究

目的　测量并观察生后１２个月以内行先天性白内障摘出术患儿术后术眼中央角膜厚度（ｃｅｎｔｒａｌｃｏｒｎｅａｌｔｈｉｃｋｎｅｓｓ,ＣＣＴ）及眼压（ｉｎｔｒａｌｏｃｕｌａｒｐｒｅｓｓｕｒｅ,ＩＯＰ）的变化。方法　选取２６例（４９眼）生后１２个月内行白内障摘出术的先天性白内障患儿为观察组,按行手术时月龄分为三组:１组:月龄≤３个月,２组:３个月＜月龄≤６个月;３组:６个月＜月龄≤１２个月。分别在术前、术后１个月、３个月、６个月时测量术眼ＣＣＴ与ＩＯＰ。另选取与各观察组最后一次随访时的患儿年龄与性别相匹配的相对正常眼婴幼儿作为对照组。结果　观察组术后１个月、３个月、６个月的ＣＣＴ为（５７８．３９±４７．７９）μｍ、（５８１．３４±５１．５４）μｍ、（５８８．２９±４９．９０）μｍ,均显著大于术前（５６３．５６±３７．１４）μｍ及对照组（５３４．９６±４０．３４）μｍ（均为Ｐ＜０．０５）。观察组术前、术后１个月、３个月、６个月ＩＯＰ测量值间差异无统计学意义（Ｐ＞０．０５）,观察组术后６个月ＩＯＰ测量值大于对照组（Ｐ＜０．０５）。观察组术后６个月ＣＣＴ与ＩＯＰ线性相关（ｒ＝０．５３８,Ｐ＝０．００４）。结论　婴儿先天性白内障摘出术后早期的ＣＣＴ显著大于正常同龄婴儿,且与ＩＯＰ线性相关。     

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.     

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.     

Diurnal fluctuation of higher order ocular aberrations: correlation with intraocular pressure and corneal thickness

PURPOSE: Optimal wavefront-guided refractive corneal laser surgery requires sufficiently exact data of optical higher order aberrations. We investigated whether these aberrations had a systematic during-the-day variation, studied the range of variation, and changes in intraocular pressure and central corneal thickness. METHODS: In 22 eyes of 22 young volunteers the optical aberrations of higher order were measured by means of a Tscherning-type ocular aberrometer three times during one day (7 AM, 12 noon, 4 PM). In addition, in 12 of these eyes the intraocular pressure and central corneal thickness were measured. The intraocular wavefront aberration was computed using Zernike polynomials up to the sixth order, and Zernike coefficients of third and fourth order were analyzed. RESULTS: Only the coefficient Z 2/4 (C13) showed a significant increase during the day by a mean 0.016 microm. A significant regression could be detected between changes of coefficients Z3/3, Z-2/4, Z0/4, Z4/4, and changes of intraocular pressure or central corneal thickness during the day. CONCLUSIONS: Due to the small values, the measured during-the-day changes of higher order aberrations had no direct practical consequences for the aberrometry-guided corneal laser surgery. Alterations of some Zernike coefficients during the day may be explained by the biomechanical behavior of the cornea.     

Central corneal thickness and intraocular tension in patients with acromegaly

In 27 patients with pituitary adenomas the central corneal thickness and the intraocular tension were measured. Thirteen of the patients were suffering from acromegaly, and in this group the central corneal thickness was 0.561 mm +/- 0.35 (mean +/- SD). In the 14 patients with pituitary adenomas but no acromegaly the central corneal thickness was 0.526 mm +/- 0.030 (mean +/- SD). This difference is statistically significant 0.01 greater than P greater than 0.001. In the 13 patients with acromegaly the intraocular tension measured by applanation was 16.9 mmHg +/- 2.3 (mean +/- SD) and in the control group 14.7 mmHg +/- 2.4 (mean +/- SD). This difference is statistically significant (0.05 greater than P greater than 0.02). When the applanation reading is corrected for the difference in the central corneal thickness, the patients suffering from acromegaly have an intraocular tension of 14.1 mmHg, which is of the same magnitude as the tension in the patients without acromegaly.     

Central corneal thickness and measured IOP: a clinical study.

PURPOSE: We have attempted to document that the pachometer used in primary eye care practices will show the same corneal thickness relationship with measured intraocular pressure (mIOP) as the research studies. A second purpose of the study is to determine what role, if any, corneal thickness has on the increase in mIOP with age. METHODS: Sonogage Corneo-Gage Plus ultrasound central corneal thickness (CCT) measurements were taken on 101 white ocular hypertensive (OHT) patients with mIOP at or above 21 mmHg, as measured by Goldmann tonometry, and compared with age-matched controls with mIOP of 16 mmHg or less. To evaluate the impact of CCT on mIOP with age, a subset of patients was selected from the subjects and controls who had had a Goldmann tonometry reading recorded more than 10 years before the collection of the study data. RESULTS: The mean age of the (OHT) patients was 65.3 years +/- 12.3. The average CCT of the OHT patients was 595 pm +/- 36 microm, and for the control patients the average CCT was 554 microm +/- 34 microm. This difference was statistically significant (P < 0.0001). Evaluation of the age subset revealed that patients with thick corneas showed a 1.22 mmHg increase in mIOP per decade, whereas the patients with thin corneas showed a 0.69 mmHg decrease in mIOP per decade. This difference was statistically significant (P = 0.0001). This study demonstrates the same relationship between corneal thickness and mIOP in clinical practice as has been reported from research settings. This finding suggests that knowledge of corneal thickness is necessary to adjust the mIOP to better monitor and evaluate patients for glaucoma risk in the primary eye care practice. Of more significance is the finding that mIOP increases in the thick cornea patients over time. This suggests an age-related change in corneal resistance to applanation that impacts on mIOP measurements. More study is needed pertaining to the role of CCT on mIOP.     

准分子激光原位角膜磨镶术后眼压与角膜厚度及角膜屈光力的相关性

目的 :研究准分子激光原位角膜磨镶术后非接触式眼压计 (NCT)测量值的改变情况 ,以及其与术中角膜切削厚度及术后角膜屈光力改变值之间的相关性。方法 :随机选择接受LASIK手术的近视患者 1 77例 337眼 ,对术前、术后 1个月NCT测量值及角膜屈光力分别作配对t检验 ,并对术后眼压改变值与术中角膜切削厚度及术后角膜屈光力改变值分别作相关性分析 ,计算回归方程。结果 :①术后 1个月NCT测量值、角膜屈光力明显低于术前 ,差异有显著性 (P <0 .0 0 0 1 )。②术后眼压下降值 (Y)与术中角膜切削厚度 (X_1)呈正相关 (r =0 .2 4 1 ,P <0 .0 0 0 1 ,Y =2 .571 + 0 .0 2 5×X1)。③术后眼压下降值 (Y)与角膜屈光力下降值 (X2 )呈正相关(r =0 .2 6 1 ,P <0 .0 0 0 1 ,Y =2 .94 7+ 0 .2 85×X2 )。结论 :LASIK术后NCT测量值低于实际值 ,眼压下降与角膜厚度变薄及角膜屈光力下降有关。为避免LASIK术后青光眼的漏诊 ,应对NCT测量值进行矫正。     

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.