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.     

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)     

超声乳化联合小梁切除术及术中应用5-氟尿嘧啶治疗青光眼合并白内障的长期疗效观察

目的探讨超声乳化联合小梁切除术及术中应用5氟尿嘧啶(5fluorouracil,5Fu)治疗青光眼合并白内障的疗效。方法对1996年1月至1998年12月,在新加坡国立眼科中心行超声乳化联合小梁切除术及术中应用5Fu治疗的71例(71只眼)原发性开角型青光眼(POAG)和原发性闭角型青光眼(PACG)患者的临床资料进行回顾性分析。除外随访时间<6个月的患者。结果术后患者平均眼压和平均用药种数均较术前明显降低,差异有统计学意义(P<001)。术后随访1~5年的患者眼压与术前比较均明显下降,差异有统计学意义(P<001)。手术完全成功率1、3及5年分别为842%、627%及553%。在手术完全成功的条件下,POAG与PACG(P=0281)、同一切口与不同切口(P=0487)手术疗效比较(采用Cox模型进行多因素生存分析),手术成功率差异无统计学意义(P>005)。但POAG与PACG术后平均眼压比较,差异有统计学意义(P=002)。术后较术前平均视力提高差异有统计学意义(P<001)。术后与术前平均视野缺损(MD)值(P=055)和模式标准差(PSD)值(P=064)比较,差异无统计学意义,表明患者术后视野保持稳定。术后4d发生眼内炎1例,术后晚期由于脉络膜渗漏和伤口漏引起低眼压2例。结论超声乳化联合小梁切除术及术中应用5Fu治疗POAG和PACG的成功率高,手术安全,长期观察疗效稳定。POAG与PACG或     

Role of central corneal thickness on baseline parameters and progression of visual fields in open angle glaucoma

PURPOSE: To evaluate the relationship of central corneal thickness (CCT) to baseline visual field parameters and visual field progression in patients with primary open-angle glaucoma (POAG). METHODS: Charts of consecutive patients with POAG were reviewed to obtain visual field data. Visual field was measured by standard threshold static perimetry. Variables analyzed included mean deviation (MD) and pattern standard deviation (PSD). RESULTS: A total of 121 eyes examined over 4 years were evaluated. A significant negative relationship between CCT and PSD (correlation coefficient: -0.02, p<0.05) was found. Analyses comparing CCT to change in PSD and MD (visual field progression) were statistically not significant. CONCLUSIONS: Patients with thinner corneas initially present with a greater visual field defect, indicating that thin corneas may contribute to advanced glaucomatous damage at the time of diagnosis. However, CCT does not seem to be a significant risk factor for progression of the disease.     

Central corneal thickness and corneal hysteresis associated with glaucoma damage

PURPOSE: We sought to measure the impact of central corneal thickness (CCT), a possible risk factor for glaucoma damage, and corneal hysteresis, a proposed measure of corneal resistance to deformation, on various indicators of glaucoma damage. DESIGN: Observational study. METHODS: Adult patients of the Wilmer Glaucoma Service underwent measurement of hysteresis on the Reichert Ocular Response Analyzer and measurement of CCT by ultrasonic pachymetry. Two glaucoma specialists (H.A.Q., N.G.C.) reviewed the chart to determine highest known intraocular pressure (IOP), target IOP, diagnosis, years with glaucoma, cup-to-disk ratio (CDR), mean defect (MD), pattern standard deviation (PSD), glaucoma hemifield test (GHT), and presence or absence of visual field progression. RESULTS: Among 230 subjects, the mean age was 65 +/- 14 years, 127 (55%) were female, 161 (70%) were white, and 194 (85%) had a diagnosis of primary open-angle glaucoma (POAG) or suspected POAG. In multivariate generalized estimating equation models, lower corneal hysteresis value (P = .03), but not CCT, was associated with visual field progression. When axial length was included in the model, hysteresis was not a significant risk factor (P = .09). A thinner CCT (P = .02), but not hysteresis, was associated with a higher CDR at the most recent examination. Neither CCT nor hysteresis was associated with MD, PSD, or GHT "outside normal limits." CONCLUSIONS: Thinner CCT was associated with the state of glaucoma damage as indicated by CDR. Axial length and corneal hysteresis were associated with progressive field worsening.     

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.     

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.     

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     

原发性开角型青光眼非对称性视野损害的影响因素

目的：探讨原发性开角型青光眼（POAG）非对称性视野损害的相关因素，并了解非对称性视野损害者双眼间眼部参数的差异。方法：横断面研究。收集2014年1月至2018年12月温州青光眼进展研究 （WGPS）中确诊的POAG患者，分析双眼眼部参数，包括眼压、眼轴长度（AL）、中央角膜厚度（CCT）、 前房深度（ACD）、晶状体厚度（LT）、视野平均偏差（MD）、视网膜神经纤维层厚度（RNFLT）、盘沿 面积、视盘面积、杯盘比、视杯容积。非对称性视野损害定义为双眼视野MD的绝对差值≥5 dB， 根据此标准将受检者分为对称组和非对称组，分析2组眼部参数与非对称性视野损害的关系。非对称组进一步行双眼间眼部参数的比较。采用独立样本t检验、Mann-Whitney U检验、配对t检验、 Wilcoxon检验、Logistic回归分析对数据进行分析。结果：共纳入POAG患者142例（284眼），对称组 92例（64.8%），男39例（42.4%），年龄（65.3±1.0）岁；非对称组50例（35.2%），男32例（64.0%），年 龄（67.6±9.1）岁。男性[OR=4.52，95%可信区间（CI）：1.90～10.73，P=0.001]、较差眼的CCT较薄 （OR=0.97，95%CI：0.95～0.99，P=0.003）、双眼平均RNFLT差值增大（OR=1.10，95%CI：1.04～1.15， P<0.001）为非对称性视野损害的危险因素。非对称组中，视野损害较重眼相比对侧眼，其平均 RNFLT较薄（Z=-7.80，P<0.001），盘沿较窄（t=-4.97，P<0.001），视盘面积较大（t=2.38，P=0.02）， 平均杯盘比（Z=-4.51，P<0.001）和垂直杯盘比（Z=5.16，P<0.001）均较大，视杯容积较大（Z=-3.31， P<0.001），但双眼间眼压、等效球镜度（SE）、AL、CCT、LT和ACD的差异均无统计学意义。结论：男性、CCT较薄、双眼平均RNFLT差值增大为POAG非对称性视野损害的独立危险因素，而非对称性视野损害者其双眼中的较大视盘眼，更容易发生视神经损害。     

Intraocular pressure and visual field loss in primary angle closure and primary open angle glaucomas

AIM: To compare the correlation between visual field loss and the pretreatment intraocular pressure (IOP) in primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG). METHODS: In a cross sectional observational study of 74 patients (43 PACG, 31 POAG), pretreatment IOP was measured at presentation, before treatment was initiated. The severity of visual field loss was assessed by AGIS score, mean deviation (MD), pattern standard deviation (PSD), and corrected pattern standard deviation (CPSD). Glaucomatous optic neuropathy was assessed from simultaneous stereo disc photographs. RESULTS: There was a stronger correlation between pretreatment IOP and the extent of visual field loss in PACG subjects than in those with POAG for both MD (PACG: Pearson correlation coefficient (r) = 0.43, p = 0.002; r(2) = 0.19), (POAG: r = 0.21, p = 0.13; r(2) = 0.04) and AGIS score (PACG: r = 0.41, p = 0.003; r(2) = 0.17), (POAG: r = 0.23, p = 0.19; r(2) = 0.05 respectively). No such associations were seen for pattern standard deviation (PSD) or corrected pattern standard deviation (CPSD) in either group (p> 0.29). Both horizontal and vertical cup-disc ratio were well correlated with severity of field loss but not with presenting IOP for either diagnosis. CONCLUSIONS: This is consistent with the hypothesis of a greater IOP dependence for optic nerve damage in PACG than POAG and, conversely, a greater importance of other, less pressure dependent mechanisms in POAG compared to PACG.     

Asymmetries and visual field summaries as predictors of glaucoma in the ocular hypertension treatment study

PURPOSE: To evaluate whether baseline visual field data and asymmetries between eyes predict the onset of primary open-angle glaucoma (POAG) in Ocular Hypertension Treatment Study (OHTS) participants. METHODS: A new index, mean prognosis (MP), was designed for optimal combination of visual field thresholds, to discriminate between eyes that developed POAG from eyes that did not. Baseline intraocular pressure (IOP) in fellow eyes was used to construct measures of IOP asymmetry. Age-adjusted baseline thresholds were used to develop indicators of visual field asymmetry and summary measures of visual field defects. Marginal multivariate failure time models were constructed that relate the new index MP, IOP asymmetry, and visual field asymmetry to POAG onset for OHTS participants. RESULTS: The marginal multivariate failure time analysis showed that the MP index is significantly related to POAG onset (P < 0.0001) and appears to be a more highly significant predictor of POAG onset than either mean deviation (MD; P = 0.17) or pattern standard deviation (PSD; P = 0.046). A 1-mm Hg increase in IOP asymmetry between fellow eyes is associated with a 17% increase in risk for development of POAG. When threshold asymmetry between eyes existed, the eye with lower thresholds was at a 37% greater risk of development of POAG, and this feature was more predictive of POAG onset than the visual field index MD, though not as strong a predictor as PSD. CONCLUSIONS: The MP index, IOP asymmetry, and binocular test point asymmetry can assist in clinical evaluation of eyes at risk of development of POAG.     

Central corneal thickness and intraocular pressure relationship in eyes with and without previous LASIK: comparison of Goldmann applanation tonometer with pneumatonometer

PURPOSE: To investigate central corneal thickness (CCT) and intraocular pressure (IOP) relationship in eyes with and without previous corneal laser refractive surgery and to compare the estimates of two different tonometers-Goldmann applanation and pneumatonometer. METHODS: The study population included 234 glaucoma suspects who were referred to the glaucoma clinic with cup/disc ratios greater than 0.4, asymmetric cupping, and/or IOP greater than 22 mmHg during routine eye examination. Of those, 84 had previous myopic laser-assisted in situ keratomileusis (LASIK) (Group 1) while 150 of them did not (Group 2). CCT was measured by using optical coherence tomography (OCT) and IOP with both Goldmann applanation tonometer (GAT) and pneumatonometer (PT). In both groups, the difference between IOP estimates of two different tonometers and the relationship between CCT and IOP were analyzed. RESULTS: In eyes with previous LASIK, GAT measured IOP significantly lower than PT (mean difference of 3.8+/-1.9 mmHg, p<0.0001). In eyes with virgin corneas, IOP estimates of GAT or PT were not different from each other (19.9+/-2.8 versus 19.9+/-2.2 mmHg, respectively, p=0.81). In both groups, there was a significant positive correlation between CCT and IOP estimates of GAT(R=0.29, p=0.007 in eyes with LASIK and R=0.38, p<0.0001 in those without), while no similar relationship was present between CCT with those of PT (R=0.03, p=0.76 in eyes with LASIK and R=0.03, p=0.69 in those without). CONCLUSIONS: In eyes with previous LASIK, GAT measured IOP significantly lower than PT. Because IOP estimates of PT were found to be independent from CCT in all of the study eyes, this device was considered to be a more reliable method of IOP estimation than GAT in eyes with and without previous LASIK.     

Should Orbscan pachometry be performed before or after Goldmann applanation tonometry?

PURPOSE: To compare the Orbscan central corneal thickness (CCT) values before and after intraocular pressure (IOP) measurement with Goldmann applanation tonometry in young normal adults. MATERIALS AND METHODS: Fifty-three eyes of 53 subjects who were free from any ocular problems were studied. The measurements included optical pachometry by the Orbscan II system, followed by Goldmann applanation tonometry, and finally Orbscan optical pachometry again. Standard Goldmann technique was adopted with the application of one drop of 0.4% benoxinate and fluorescein sodium prior to the measurement. The same operator was involved in the Orbscan pachometry before and after Goldmann tonometry. Another investigator was responsible for Goldmann tonometry. Three readings were obtained in each case, and the means were used for analysis. RESULTS: The mean IOP of the sample was 14.6 +/- 2.6 mmHg. There was no significant difference (paired t-test: p = 0.50) in the mean CCT values before and after the Goldmann tonometry (551 +/- 32 and 552 +/- 35 microm respectively). CONCLUSION: Standard Goldmann applanation tonometry does not affect the Orbscan CCT values. Measurement of CCT for the adjustment of true IOP can be carried out either before or after Goldmann tonometry.     

Comparative evaluation of diode laser trabeculoplasty vs frequency doubled Nd : YAG laser trabeculoplasty in primary open angle glaucoma

AIMS: To evaluate the efficacy of diode laser trabeculoplasty (DLT) and frequency doubled Nd : YAG laser trabeculoplasty (YLT) in primary open angle glaucoma (POAG). METHODS: A total of 52 eyes of 35 patients with POAG were included. In all, 25 eyes underwent DLT (Group I) and 27 eyes underwent YLT (Group II). IOP, gonioscopy and visual fields were evaluated before and 3, 6, and 9 months and 1 year after the laser. An IOP<21 mmHg without medications or a decrease in the number of glaucoma medications with no progression of disc and field changes was considered a success. RESULTS: The mean age of patients in Group I was 57.72+/-8.1 years and the patients in Group II had a mean age of 59.85+/-7.76 years. The mean prelaser IOP was 24.93+/-1.49 mmHg and 25.36+/-1.57 mmHg. The mean IOP after DLT at 12 months follow-up was 18.0+/-0.93 mmHg and after YLT was 18.6+/-1.52 mmHg. The reduction of IOP was statistically significant in both the groups at 3, 6, 9, and 12 months (P<0.001), however there was no significant difference between the two groups. Success rates in both groups were similar, 92% in Group I and 92.6% in Group II. CONCLUSIONS: DLT and Fd YLT are equally effective in controlling IOP in eyes with POAG.     

Relationship between visual field sensitivity and retinal nerve fiber layer thickness as measured by optical coherence tomography

PURPOSE: To evaluate the strength and pattern of the relationship between visual field (VF) sensitivity and retinal nerve fiber layer (RNFL) thickness as measured by StratusOCT (Carl Zeiss Meditec, Inc., Dublin, CA). METHODS: Three hundred eleven subjects--45 normal, 102 with preperimetric glaucoma (PPG), and 164 with primary open-angle glaucoma (POAG)--were enrolled in this cross-sectional study. The relationship between RNFL thickness and VF sensitivity, expressed as mean deviation (MD) and mean sensitivity (MS), were evaluated with linear and nonlinear regression models, and the coefficient of determination (R(2)) was calculated. The association between RNFL/VF was described by bivariate Pearson correlation coefficients. RESULTS: The correlation of RNFL and the VF parameters MS and MD in normal and PPG eyes was not significant. In POAG eyes, RNFL and both MS (r = 0.733) and MD (r = 0.718) correlated significantly. Linear regression plots of MS or MD against RNFL thickness demonstrated a negligible degree of determination in normal (R(2) = 0.0378 and 0.0121, respectively) and PPG groups (R(2) = 0.0215 and 0.0151, respectively), whereas their relationship fit a curvilinear regression model (R(2) = 0.6947 and 0.723) in the POAG group. Receiver operating characteristic (ROC) curves describing the VF parameters and average RNFL thickness (AVG) were evaluated to differentiate PPG from POAG eyes. Repeated analysis with the best-performing test parameter, pattern standard deviation (PSD) (AUROC = 0.937) with a cutoff of 1.9 dB, showed that regression profiles in the POAG group with PSD >1.9 dB maintained a strong curvilinear RNFL/VF relationship, whereas those with PSD <1.9 dB exhibited a relationship almost indistinguishable from the PPG group. CONCLUSIONS: Evaluation of the structure-function relationship in normal subjects and those with PPG or POAG showed strong curvilinear regression in POAG eyes with PSD >1.9 dB and RNFL AVG thickness below 70 microm, whereas no correlation was detectable above these values.     

Comparisons between Pascal dynamic contour tonometry, the TonoPen, and Goldmann applanation tonometry in patients with glaucoma

PURPOSE: To compare intraocular pressure (IOP) measurements taken with Pascal dynamic contour tonometry (DCT), the TonoPen and the Goldmann applanation tonometry (GAT). The influence of central corneal thickness (CCT) on IOP measurements taken with Pascal DCT and the TonoPen was evaluated. METHODS: One eye in each of 101 consecutive patients with primary open-angle glaucoma (POAG) underwent ultrasonic CCT measurement and IOP evaluation with GAT, Pascal DCT and the TonoPen in random order. The agreement between results from Pascal DCT and the TonoPen and those of GAT was assessed using the Bland-Altman method. The deviation of Pascal DCT and TonoPen readings from GAT values, corrected for CCT, was calculated and correlated to CCT using a linear regression model. RESULTS: The mean of the differences in IOP measurements was 3.2 +/- 2.4 mmHg for Pascal DCT minus GAT readings and 0.5 +/- 4.5 mmHg for TonoPen minus GAT readings. The 95% confidence interval of differences in IOP measurements was higher between TonoPen and GAT readings (- 6 to 7 mmHg) than between Pascal and GAT readings (0.1-6.8 mmHg). Pascal DCT significantly overestimated IOP compared with GAT, especially for higher IOP readings. Bland-Altman scatterplots showed reasonable inter-method agreement between Pascal DCT and GAT measurements, and poor agreement between TonoPen and GAT measurements. The deviations of Pascal DCT and TonoPen readings from the corrected GAT values were both highly correlated with CCT values (linear regression analysis, p < 0.0001). The mean change in measured IOP for a 10-microm increase in CCT was 0.48 mmHg for Pascal DCT and 0.74 mmHg for the TonoPen. CONCLUSIONS: Agreement with GAT measurements was higher for Pascal DCT than for TonoPen readings; however, Pascal DCT significantly overestimated IOP values compared with GAT. Measurements of IOP obtained with both Pascal DCT and the TonoPen appeared to be influenced by CCT, and this influence appeared to be greater for the latter.     

Comparison of dynamic contour tonometry with goldman applanation tonometry over a wide range of central corneal thickness

PURPOSE: To compare dynamic contour tonometry with Goldmann applanation tonometry in structurally normal corneas over a wide range of central corneal thickness (CCT). PATIENTS AND METHODS: Twenty-five patients each with normal CCT (group A), thin corneas (group B), and thick corneas (group C) had IOP measured with the Goldmann (GAT) and dynamic contour tonometer (DCT). RESULTS: In group A (mean CCT = 552 +/- 16 microm) the mean GAT was 15.9 +/- 3.1 mm Hg and mean DCT was 16 +/- 3.3 mm Hg (P = 0.91). In group B (mean CCT = 491 +/- 19 microm) the mean GAT was 13.2 +/- 3.5 mm Hg and the mean DCT was 15.9 +/- 3.5 mm Hg (P = 0.009). For group C (mean CCT = 615 +/- 22 microm), the mean GAT was 17.4 +/- 3.8 mm Hg and the mean DCT was 17.4 +/- 3.5 mm Hg (P = 0.95). The 95% agreement limits for DCT were -3.1 mm Hg to 2.9 mm Hg. The mean GAT-DCT difference was -2.6 mm Hg in thin corneas and -0.06 mm Hg in thick corneas. Below 520 microm reduction of 10 microm in CCT appears to result in a significant underestimation of the GAT IOP by 0.7 mm Hg (P < .001) and above 580 microm a non-significant overestimation of 0.2 mm Hg per 10 microm increase in CCT (P = 0.27). CONCLUSION: Dynamic contour tonometer agrees well on average with GAT but the agreement limits are wide. In structurally normal thin corneas DCT may give a more accurate assessment of the true IOP but it does not appear to have any benefit over GAT in thick corneas.     

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.     

Effects of central corneal thickness and corneal curvature on the intraocular pressure measurement by Goldmann applanation tonometer and ocular blood flow pneumatonometer

PURPOSE: To assess the effects of central corneal thickness (CCT) and corneal curvature (CC) on the measurements of intraocular pressure (IOP) using Goldmann applanation tonometer (GAT) and the ocular blood flow pneumatonometer (OBFT). METHODS: 104 patients were recruited from a glaucoma clinic. The CCT was measured using ultrasound pachymetry and the mean radius of CC using a keratometer. The IOP of each eye was measured using both GAT and the OBFT in a random order. Right eyes only were analysed for statistical purposes. RESULTS: The mean (+/-SD) IOP by GAT and OBFT was 18.2 mmHg (+/-4.4) and 18.2 mmHg (+/-4.0), respectively, with no statistically significant difference. IOP measurement with both instruments varied with CCT and CC. GAT showed an IOP increase of 0.40 mmHg per 10 microm increase of CCT and OBFT showed an increase of 0.38 mmHg in IOP per 10 microm increase of CCT. Multiple regression analysis showed that the effect of CCT was statistically significant (P<0.001) on IOP recorded by both the GAT and OBFT but CC did not have a statistically significant effect on IOP recordings performed by either technique. CONCLUSION: IOP measurements by GAT and OBFT are positively correlated with CCT with both tonometers being similarly affected. There was no significant correlation between CC and IOP measured by either tonometer.     

Baseline thickness of macular ganglion cell complex predicts progression of visual field loss

Background

Previous studies reported that the thickness of the macular ganglion cell complex (mGCC) showed good diagnostic ability for detecting glaucoma. However, its impact on the progression of visual field loss in primary open angle glaucoma (POAG) is unknown. The purpose of this study was to assess whether baseline mGCC thickness is associated with the progression of visual field loss in POAG.

Methods

Fifty-six patients with POAG were included in the study. All patients were followed for more than 2 years after baseline optical coherence tomography (OCT) measurements. They had at least five reliable Humphrey visual field tests with 30–2 Swedish Interactive Threshold Algorithm standard tests during the follow-up period. The subjects were divided into two groups according to the slope of the mean deviation (MD): the fast progression group (MD slope < ?0.4 dB/y) and the slow progression group (MD slope ≥ ?0.4 dB/y). Factors compared between the groups were as follows: age, baseline intraocular pressure (IOP), mean IOP during the follow-up, refraction, baseline MD, pattern standard deviation (PSD), and baseline OCT measurements.

Results

There were no significant differences between the two groups in age, baseline IOP, mean IOP during the follow-up, refraction, baseline MD or PSD, average thickness of retinal nerve fiber layer (RNFL), or disc parameters. However, the baseline mGCC thickness (average and inferior hemifield) was significantly thinner in the fast progression group than in the slow progression group (74.0?±?7.2 μm vs. 80.3?±?8.6 μm; 68.0?±?6.6 μm vs. 78.2?±?11.6 μm, respectively). Moreover, global loss volume and focal loss volume, which are parameters of mGCC, showed significantly higher rates in the fast progression group than in the slow progression group. In multivariate analysis, only mGCC thickness of the inferior hemifield was associated with disease progression (P?=?0.007).

Conclusions

Baseline mGCC thickness can be predictive of progressive visual field loss in patients with POAG.