Distribution of central corneal thickness and intraocular pressure in emmetropic eyes of healthy children of Palestine: a representative cross-sectional study

AIM: To determine the distributions of central corneal thickness (CCT) and intraocular pressure (IOP) in emmetropic eyes of healthy children of Palestine. METHODS: This representative cross sectional study included a total of 1156 eyes from 578 healthy school children aged 7-15y. Inclusion criteria included emmetropia, no previous history of ocular or systemic diseases, no previous history of contact lens use, and the availability of both eyes. CCT and IOP were measured using ultrasound pachymeter and Goldmann applanation tonometer, respectively. The relationship of the results with age and gender was investigated. RESULTS: The mean age of school children was 11.13±2.8y. Mean CCT was 542.2±37.4 and 544.3±39.2 μm for right and left eyes, respectively. Mean IOP was 12.5±2.2 and 12.3±2.2 mm Hg for right and left eyes, respectively. A positive correlation was observed between CCT and IOP of the right eye (P<0.001, R=0.358) and CCT and IOP of the left eye (P<0.001, R=0.324). No significant differences were observed in CCT and IOP due to age or gender (P>0.05). There were significant differences in mean CCT and IOP between right and left eyes (P=0.004, P=0.001, respectively). CONCLUSION: A population profile of CCT and IOP is established in Palestinian children for the first time. Mean CCT is comparable to some studies but differ from others. Mean IOP is considerably lower than that of majority children of other ethnic groups. Intereye difference of more than 36 μm in CCT, and 5 mm Hg in IOP should prompt evaluation for potential ocular disorders.     

两种非接触眼压计临床应用效果及其关联因素的临床研究

目的探讨两种非接触眼压计测量的眼压(IOP)值之间的关联性及一致性，及其与中央角膜厚度(CCT)、陡峭角膜曲率(Ks)和平坦角膜曲率(Kf)的关联性。 方法横断面研究。收集2018年3月至2018年4月在首都医科大学附属北京同仁医院眼科屈光中心招募的71例(142只眼)健康志愿者的眼科资料，依次使用CanonTX20型非接触气动眼压计测量IOP，VX120型多参数测量系统测量IOP、校正IOP及CCT，角膜地形图测量Ks、Kf。采用Wilcoxon秩和检验分析两种非接触眼压计测量的IOP值之间的关联性及一致性。应用Spearman相关分析分析非接触眼压计测量的IOP值与CCT、Ks和Kf的相关性；应用Bland-Altman以及95%的一致性界限(LoA)分析两种非接触眼压测量计的一致性。 结果CanonTX20、VX120测量的IOP和校正后的VX120测量的IOP分别为(15.7±2.5)mmHg(1 mmHg＝0.133 kPa)、(16.7±3.4)mmHg、(16.8±3.3)mmHg，其不同性别间的差异无统计学意义(Z＝0.295，0.366，0.131；P>0.05)。VX120测量的IOP值比CanonTX20测量的IOP值高(1.007±2.651)mmHg，两者之间差异有统计学意义(t＝-4.527，P<0.05)。CanonTX20、VX120测量的IOP分别与VX120、Lenstar LS900测量的CCT有相关性(r＝0.177，0.167，0.221，0.178；P<0.05)。校正后的VX120测量的IOP和VX120、Lenstar LS900测量的CCT无相关性(r＝0.026，-0.001，0.026；P>0.05)。三种方式测量的IOP与Ks及Kf的相关性均无统计学意义(r＝0.158，0.158；P>0.05)。通过Bland-Altman以及95%LoA分析显示两者的95%LoA为±5.2 mmHg。年龄和IOP之间无明显的线性趋势。 结论CanonTX20测量的IOP值和VX120测量的IOP值一致性较差，说明不可相互替代；CCT与CanonTX20及VX120测量的IOP值均存在相关性，但CCT与校正后的VX120测量的IOP值无相关性；Ks和Kf与IOP值均无相关性。     

非接触眼压计对青光眼患者筛查的临床意义

目的应用Topcon CT-80A非接触眼压计在临床应用中筛查高眼压患者,并对其进行进一步的检查诊断及治疗,探讨非接触眼压计对于青光眼患者筛查的临床意义。方法用非接触眼压计测量602例（1204眼）眼压,对于单眼眼压〉21mmHg或双眼眼压差〉8mmHg的患者,于随后两天同一时间连续测量3次,并进行房角、视野、眼底等其他眼科相关检查。结果测量的602例（1204眼）中发现高眼压患者83人（137眼）,复诊有21人（33眼）被确诊青光眼患者,并对其进行治疗及随访。结论非接触眼压计对青光眼患者的筛查具有重要的临床意义。     

Comparaison des signaux radial et carotidien mesurés par deux appareils tonométriques

Background and aimPulse wave analysis is a pivotal instrument to estimate central hemodynamic parameters. Applanation tonometry on radial and/or carotid arteries is usually used to detect pressure waveforms. Available commercial devices have been validated against invasive catheterism, showing a good agreement of harmonics pattern. In a previous investigation, we observed differences on radial second systolic peak (rSPB2) between two commonly used devices: SphygmoCor (AtCor, Australia) and PulsePen (Diatecne, Italy). The aim of our study was to further quantify differences on radial and carotid signals from the two devices.MethodsWe measured radial and carotid pressure waveforms in 38 patients where systolic, diastolic blood pressure and heart rate presented minimal changes between measurements. Waveforms were digitally extracted for off-line analysis.ResultsRadial rSBP2, mean arterial pressure, form factor and augmentation index were different with SphygmoCor providing lower values. Carotid augmentation index and form factor were similar. However, carotid systolic pressure (cSBP) from PulsePen was higher that cSBP from SphygmoCor (2.7 ± 4.4 mmHg, P < 0.001).ConclusionPulsePen and SphygmoCor sensors are not equivalent and provide different wave shapes. These differences on wave shape have important consequences on parameters computed from these waveforms with more discrepancy on radial derived parameters such as rSBP2 and mean arterial pressure than on carotid derived parameters. Further studies are required to compare invasive pressure parameters to indices derived from these two devices.     

Effect of Pneumatic Tourniquet on Muscle Oxygen Tension

Recent investigations suggest that circulation in a limb can be reduced with a tourniquet to less than 1 per cent of the control limb, or even completely occluded. The development of tissue oxygen tonometry with implanted silastic tubes has provided new possibilities for assessing muscle tissue oxygen tension. In the present work, this method was employed to register the effect of tourniquet blockade on the lower limb muscle PO₂, in rabbits. The duration of the tourniquet blockade was 60, 120 and 180 minutes. The baseline muscle PO₂, in the tibialis anterior muscle was 22.6 ± 0.6 mmHg. During the tourniquet blockade the oxygen tension dropped to minimal values between 9.2 ± 0.5 and 10.7 ± 0.6 mmHg in these experimental groups, but the tissue microclimate never reached fully anoxic conditions. The rapid response of muscle PO₂ to oxygen breathing after release of the blockade suggests that limb microcirculation tolerates tourniquet occlusion well.     

Goldmann tonometry versus the Tono-Pen XL for intraocular pressure measurement: an evaluation of the potential impact on clinical decision making in glaucoma

Aim:  To assess the validity of the Tono-Pen XL as an alternative to the Goldmann applanation tonometer (GAT) for the measurement of intraocular pressure (IOP) in patients with ocular hypertension (OHT) and glaucoma.
Methods:  Over a 3 month period, patients with OHT or glaucoma attending a general clinic had IOP measurements taken using the Tono-Pen XL and the GAT. Tono-Pen measurements were taken by suitably trained nursing staff, while Goldmann tonometry was performed by the examining ophthalmologist.
Results:  There were 124 eyes of 62 patients in this study. Overall, mean IOP was 18.3 ± 4.8 mmHg using GAT and 18.8 ± 5.5 mmHg using the Tono-Pen. Using the Bland–Altman method, the upper and lower limits of agreement between the two devices were +10.6mmHg and −9.6 mmHg, respectively. Significant over- and under-estimates of IOP were noted in 10 (16%) patients.
Conclusion:  Our findings suggest that the Tono-Pen XL cannot be used as a substitute for GAT in the management of patients with glaucoma or OHT.     

Effect of 0.5 mm larger donor corneal size on intraocular pressure following penetrating keratoplasty

Background

Glaucoma can develop after penetrating keratoplasty resulting in irreversible loss of vision. The incidence of post-penetrating keratoplasty glaucoma varies from 31% in the early postoperative period to 29% after three months. Various factors are responsible for the rise of intraocular pressure (IOP). This study was carried out to evaluate the effect of 0.5 mm larger donor corneal size on IOP following penetrating keratoplasty.

Methods

Patients were divided into two groups: group I was phakic and group II consisted of aphakic and pseudophakic patients. The same surgical technique was used for obtaining and suturing the donor graft. The viscoelastics and the postoperative regime also remained the same in all cases. IOP was measured by the rebound tonometer.

Results

The incidence of postoperative raised IOP in the first seven days in the phakic group was found to range from 16 mmHg to 25 mmHg and IOP in the aphakic/pseudophakic group ranged from 16 mmHg to 42 mmHg. The IOP in the phakic group after three weeks of surgery was around 12.3 mmHg and that in the pseudophakic/aphakic group was 14.8 mmHg-16.2 mmHg. In aphakic patients, IOP was controlled in the first six months with eyedrops Timolol 0.5% and tablet acetazolamide which was given only for short periods. IOP settled to <12 mmHg with timolol 0.5% after six months. In the pseudophakic patients, IOP became normal by six months. These were inclusive of patients who had undergone anterior reconstruction and/or vitrectomy.

Conclusion

The study proves that keeping the donor corneal size 0.5 mm larger does not affect IOP and that aphakia itself is a factor responsible for rise of IOP due to anterior chamber angle compression.     

Repeatability of central aortic blood pressures measured non-invasively using radial artery applanation tonometry and peripheral pulse wave analysis

Objective. To estimate the repeatability of radial pulse wave analysis (PWA) in measuring central systolic and diastolic blood pressures (cSBP/cDBP), pulse pressure (cPP), augmentation pressure (cAP) and pulse pressure amplification (PPA). Methods. After 15 min supine rest, 20 ambulant patients (aged 27-82 years; four female) underwent four SphygmoCor PWA measurements on a single occasion. Two nurses independently undertook two measurements in alternate order, blind to their colleague's measurements. Analysis was by Bland-Altman limits of agreement (LOA). Results. Heart rate and brachial blood pressure (BP) were stable during assessment. Based on the average of two PWA measurements between-observer differences (LOA, mean difference±2SD) were small (cSBP 1.5±10.9 mmHg; cDBP 0.4±5.2 mmHg; cAP 0.5±4.5 mmHg; cPP 1.1±10.5 mmHg; PPA -0.5%±5.6%). Between-observer differences were much greater for single/initial PWA measurement (cSBP 3.6±15.9 mmHg; cDBP 2.8±8.8 mmHg; cAP 0.7±5.8 mmHg; cPP 0.8±13.6 mmHg; PPA -1.2±9.4%). Within-observer LOA were very similar for both nurse A (cSBP -4.2±14.1 mmHg; cDBP -4.6±13.1 mmHg; cAP -0.4±4.4 mmHg; cPP 0.5±11.0 mmHg; PPA 0.7%±9.0%) and nurse B (cSBP 0.0±12.1 mmHg; cDBP 0.2±8.5 mmHg; cAP -0.1±4.4 mmHg; cPP -0.2±11.9 mmHg; PPA -0.7%±10.6%). Conclusion. Non-invasive assessment of central aortic pressures using PWA on a single occasion is highly repeatable in ambulant patients even when used by relatively inexperienced staff.     

Evaluation of some factors affecting the agreement between the Proview Eye Pressure Monitor and the Goldmann applanation tonometer measurements

Background: Our aim was to examine whether training level and ocular factors could account for part of the difference in intraocular pressure (IOP) measured using the Goldmann applanation tonometer (GAT) and Proview Eye Pressure Monitor (PPT). Methods: One hundred and nineteen individuals (238 eyes) were enrolled in the study. The mean age was 35.8 years (range 21 to 79). All study participants obtained IOP measurements using the PPT after hearing instructions on how to perform PPT. Glaucoma patients obtained additional IOP measurements using PPT after viewing an instructional video and after 30 days of home use. IOP was also measured using the GAT at each experimental session. Results: The difference in IOP measured by the GAT and the PPT was 0.55 ± 3.38 mmHg, 0.17 ± 3.79 mmHg and ‐1.30 ± 3.79 mmHg for myopic, emmetropic and hypermetropic groups, respectively, which were statistically significant (ANCOVA; p = 0.014). The difference in IOP between GAT and PPT was not significantly different for measurements obtained after verbal instructions, instructional video or after 30 days of home use (Repeated‐ANCOVA; p = 0.30). The overall agreement between the GAT and the PPT was poor. Intra‐class correlation coefficient was 0.575, and the 95% confidence interval (CI) of agreement was ‐6.93 to +6.73 mmHg. Conclusion: There was a small systematic difference in IOP measured by the GAT and PPT when comparing the different refraction groups; however, this level of difference between the groups is unlikely to be of clinical significance. The level of training in using the PPT did not influence its measurements. The limits of agreement between the PPT and the GAT were wide and long‐term use of PPT did not improve its agreement.     

Comparison of intraocular pressure measurement between rebound, non-contact and Goldmann applanation tonometry in treated glaucoma patients

Background: To compare the intraocular pressure readings obtained with the iCare rebound tonometer and the 7CR non‐contact tonometer with those measured by Goldmann applanation tonometry in treated glaucoma patients. Design: A prospective, cross‐sectional study was conducted in a private tertiary glaucoma clinic. Participants or Samples: One hundred nine (54 males : 55 females) patients including only eyes under medical treatment for glaucoma. Methods: Measurement by Goldmann applanation tonometry, iCare rebound tonometry and 7CR non‐contact tonometry. Main Outcome Measures: Intraocular pressure. Results: There were strong correlations between the intraocular pressure measurements obtained with Goldmann and both the rebound and non‐contact tonometers (Spearman r‐values ≥ 0.79, P < 0.001). However, there were small, statistically significant differences between the average readings for each tonometer. For the rebound tonometer, the mean intraocular pressure was slightly higher compared with the Goldmann applanation tonometer in the right eyes (P = 0.02), and similar in the left eyes (P = 0.93); however, these differences did not reach statistical significance. The Goldmann correlated measurements from the non‐contact tonometer were lower than the average Goldmann reading for both right (P < 0.001) and left (P > 0.01) eyes. The corneal compensated measurements from the non‐contact tonometer were significantly higher compared with the other tonometers (P ≤ 0.001). Conclusions: The iCare rebound tonometer and the 7CR non‐contact tonometer measure intraocular pressure in fundamentally different ways to the Goldmann applanation tonometer. The resulting intraocular pressure values vary between the instruments and will need to be considered when comparing clinical versus home acquired measurements.