On repeated corneal applanation with the Goldmann and two non‐contact tonometers

Background: Several authors believe it is necessary to randomise the order in which contact and non‐contact tonometers are used in comparison studies. This study was carried out to investigate the effect of repeated applanation on the measured intraocular pressure. Methods: One set of measurements per session was made on each of three sessions (one session per day) with the Goldmann and two non‐contact tonometers (Topcon CT80 and Keeler Pulsair EasyEye), in a pre‐determined order, on one randomly selected eye of 120 subjects randomised to one of two groups. For session one, only the non‐contact tonometers were used to assess the intraocular pressure of both groups. For session two, either non‐contact or Goldmann tonometry was performed first and this order was reversed for session 3. Average intraocular pressures were compared between sessions to determine the presence or absence of effects on the intraocular pressure caused by prior repeated applanation with the Goldmann or either one (or both) of the non‐contact tonometers. Results: Prior applanation with a non‐contact tonometer did not cause a significant (p > 0.05) reduction of the mean pressure measured with either non‐contact tonometer. The mean pressure was slightly but significantly (p < 0.05) reduced (for both non‐contact tonometers in both subject groups) when non‐contact tonometry was performed after Goldmann tonometry. There was no significant difference (p > 0.05) between the pressures measured with the Goldmann tonometer prior to and subsequent to non‐contact tonometry, in both subject groups. Conclusion: A small but statistically significant reduction in the intraocular pressure was found following applanation with the Goldmann tonometer but not with either one of two non‐contact tonometers.     

The effect of contact lens-induced corneal edema on Goldmann applanation tonometry and dynamic contour tonometry

Purpose  To evaluate the effect of contact lens-induced corneal edema on intraocular pressure (IOP) measurements using Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT) in Asian subjects. Participants  The study included 40 eyes of 20 normal volunteers with no evidence of ocular disease. Methods  Forty eyes of 20 healthy volunteers were required to wear soft contact lenses for 2 hours to induce corneal swelling. Central corneal thickness (CCT) and IOP were measured before and immediately after contact lens wear using specular microscope, GAT, and DCT. The IOP measurements by GAT and DCT were compared. The changes in the CCT and the IOP measurements after wearing contact lenses were assessed. Results  The mean CCT of the 40 eyes evaluated was 532.6 ± 31.6 μm. The mean IOP was 11.78 ± 2.04 mmHg for the GAT and 14.46 ± 1.89 mmHg for the DCT, and the difference was statistically significant (P < 0.001). After wearing contact lenses, the mean CCT was 553.2 ± 34.3 μm, which was 20.6 ± 12.9 μm greater than before wearing them (P < 0.001). The mean IOP measurements of the GAT and DCT were decreased after wearing the contact lenses. The mean decrease of the GAT values was 0.43 ± 1.95 mmHg, which was not statistically significant (P = 0.175). However, the mean decrease of the DCT readings, which was 0.75 ± 1.74 mm Hg, was statistically significant (P = 0.010). Conclusion  The IOP measurements with DCT were significantly higher than those with GAT in healthy Asian eyes. Although the mean IOP measurements of both the GAT and the DCT were decreased in the edematous cornea, IOP measurements of the DCT were more affected by corneal edema than were the GAT. The authors have no proprietary, commercial, or financial interests in any of the products described in this study.     

Effect of corneal thickness on intraocular pressure measurements with the Pascal dynamic contour,Canon TX‐10 non‐contact and Goldmann applanation tonometers in healthy subjects

Purpose: To investigate the effects of central corneal thickness (CCT) on intraocular pressure (IOP) measurements of the Pascal dynamic contour tonometry (DCT), Canon TX‐10 non‐contact tonometry (NCT) and Goldmann applanation tonometry measurements (GAT) in healthy subjects. Methods: IOP values of 135 eyes with normal corneas of 135 healthy volunteers were determined by DCT, NCT and by GAT. The CCT was measured using an ultrasonic pachymeter after all IOP determinations had been made. Results: When DCT measurements were compared (IOP = 17.52 ± 2.0 mmHg) with NCT measurements (IOP = 16.54 ± 2.77 mmHg) and GAT measurements (IOP = 15.07 ± 2.35 mmHg), DCT measurements were significantly higher than NCT and GAT (p < 0.001). There was a significant correlation between CCT with both NCT (r = 0.260, p = 0.003) and GAT measurements (r = 0.257, p = 0.005). There was a weak correlation that was not statistically significant between CCT and DCT (r = 0.160, p = 0.079). Conclusion: The IOP measurements with DCT seem to be less dependent on CCT. NCT appears to be more affected by variation in CCT than GAT.     

The effect of contact lens induced corneal edema on Goldmann applanation tonometry measurements

AIM: To determine the effect of small increases in corneal hydration on the accuracy of Goldmann applanation tonometry estimates of intraocular pressure (IOP). MATERIALS AND METHODS: Twenty-five young healthy subjects presented on 3 separate days approximately 1 week apart. On 2 visits, subjects were required to wear a hydrogel contact lens with either a center thickness of 0.3 and 0.7 mm (HEMA 38% water content, parallel surface curve) in 1 eye only under closed-eye conditions for 2 hours to induce corneal swelling. The third visit acted as a control. IOP, corneal thickness, and corneal curvature were measured in both eyes before and after contact lens wear on all visits. RESULTS: There was a statistically significant increase in corneal thickness of 40.2+/-14.4 microm (P<0.001) and 41.9+/-16.4 microm (P<0.001) after wearing the 0.3 and 0.7 mm thick contact lenses, respectively (2-tailed paired t test). There was an increase in IOP of 2.8+/-2.2 mm Hg (P<0.001) after wearing the 0.3 mm thick contact lens, and a statistically insignificant difference of 1.3+/-3.0 mm Hg (P=0.058) after wearing the 0.7 mm thick contact lens (2-tailed paired t test). There was a statistically significant Pearson correlation between the change in corneal thickness and the change in IOP after lens wear (r=0.500, P<0.001, 0.3 mm lens and r=0.399, P<0.001, 0.7 mm lens). The corneal hydration-induced measurement error was 0.46 mm Hg per 10 microm change in corneal thickness (0.3 mm lens) and 0.35 mm Hg per 10 microm change in corneal thickness (0.7 mm lens). CONCLUSION: A small increase in corneal hydration and thickness may cause a clinically significant overestimation of IOP when measured using Goldmann applanation tonometry.     

LASIK与LASEK手术对脉络膜血流影响对比研究

目的:通过对LASIK和LASEK两种手术前后眼脉动振幅(ocular pulse amplitude,OPA)值的对比分析,探讨两种手术对脉络膜血流的影响。方法:对行LASIK或LASEK手术的患者各20例39眼于术前和术后1mo常规检查验光后用Pentacam系统检查中央角膜厚度(CCT)和角膜曲率(CCV),用动态轮廓眼压计进行眼压(IOP)和OPA值测量,将测量结果进行统计学分析。结果:LASIK和LASEK两组病例术前和术后1mo各自的OPA值比较差异无统计学意义(P>0.05),两组病例之间术前和术后1mo的OPA值差异亦无统计学意义(P>0.05)。结论:LASIK和LASEK手术对脉络膜血流未产生明显影响。     

非接触式眼压计与Goldmann压平眼压计测量眼压的比较

目的 :比较非接触式眼压计 ( NCT)和 Goldm ann压平眼压计测量眼压的差异。方法 :对 112例 ( 2 2 0眼 )志愿者分别进行 NCT和 Goldmann压平眼压计眼压测量及中央角膜厚度测量 ,并对其中 16 8眼进行自动验光检查。结果 :NCT和 Goldmann眼压计眼压测量值分别为 1.98± 0 .6 9k Pa和 2 .34± 0 .77k Pa。 NCT眼压测量值较 Goldmann眼压测量值偏低 0 .36± 0 .37k Pa( P<0 .0 5 )。眼压在 1.33～ 2 .6 7k Pa内 ,二种眼压计测量眼压值偏差最小。角膜厚度和眼球屈光度与 NCT眼压测量值分别呈明显正相关和负相关。结论 :NCT眼压测量值较Goldmann眼压测量值偏低 ,NCT眼压值为临界眼压时 ,应应用 Goldm ann压平眼压计校正     

中央角膜厚度及屈光度对压平眼压计测量值的影响

目的 探讨中央角膜厚度(CCT)以及屈光状态对Goldmann压平眼压计(GAT)测量值的影响.方法 应用OCT3测量正常人121例(199只眼)与近视患者81例(159只眼)的CCT,用Goldmann压平眼压计测量眼压,比较两组之间CCT和眼压测量值的差异,分析CCT与眼压测量值的关系.结果 正视组平均CCT值为(525.05±32.83)μm,眼压的均值为(12.91±2.26)mmHg;近视组平均CCT值为(524.85±29.76)μm,眼压的均值为(14.23±2.54)mmHg;两组的CCT值比较差异无显著性(t=-0.600,P=0.952),两组的眼压值比较差异有显著性(t=-5.139,P＜0.001).高度近视眼CCT偏薄,眼压随屈光度数较少而增加,近视组眼压与屈光度相关(r=-0.296,P＜0.001),屈光度数每增加-4.05D,眼内压升高1 mmHg.正视组(r=0.317,P＜0.001)和近视组(r=0.341,P＜0.001)的眼压与CCT相关,眼压校正公式分别为1 mmHg/45.45 μm、1 mmHg/34.48 μm.结论 CCT可以影响Goldmann压平眼压计测量值,屈光状态也可以影响眼压值,高度近视眼的眼压建议用从近视人群中获得的眼压校正公式校正.     

PRK对压平眼压测量的影响

目的：通过前瞻性研究方案探讨ＰＲＫ手术对压平眼压测量的影响。方法：使用手持ＰＥＲＫＩＮＳ压平眼压计、超声角膜测量仪及角膜曲率测量仪测量ＰＲＫ术前及术后１个月眼压、中央角膜厚度及角膜曲率。结果：ＰＲＫ术后压平眼压、中央角膜厚度及角膜曲率。结果：ＰＲＫ术后压平眼压、中央角膜厚度及角膜曲率均较术前明显降低,眼压的变化与中央角膜厚度的变化直接相关,中央角膜厚度每减少１０βｍ,压平眼压测量值降低１ｍｍＨｇ,     

The effect of contact lens induced oedema on the accuracy of Goldmann tonometry in a mature population

Aim

To determine the effect of contact lens induced oedema on the accuracy of Goldmann tonometry measurements of intraocular pressure (IOP) in mature subjects.

Methods

22 healthy subjects aged between 50 and 60 years were recruited. Corneal curvature, IOP, and central corneal thickness (CCT) were measured before and after two hours of monocular closed eye wear of a thick hydroxyethyl methacrylate (HEMA) contact lens. Measurements were then repeated at 20 minute intervals for one hour after lens removal.

Results

Both CCT (+54.1 μm) and IOP (+2.7 mm Hg) increased significantly after lens wear (p<0.001, paired t test with Bonferroni correction). For the hour following lens removal, the measured IOP was correlated to the increase in CCT (r = 0.84, p<0.001), at a rate of 1.0 mm Hg/10 μm (95% confidence interval, 0.8 to 1.2 mm Hg/10 μm, linear mixed model analysis).

Conclusions

A relatively small increase in CCT from contact lens induced corneal oedema caused an overestimation error in Goldmann tonometry measurements of IOP in healthy mature subjects.     

LASIK前后角膜厚度对眼压测量的影响

目的:研究LASIK手术前后角膜厚度改变与眼压值的关系。方法:我们从4086眼随机选择872眼在LASIK术前术后用非接触眼压计测量,应用华西医科大学PEMS统计软件包进行U 检验分析。结果:LASIK术前术后经统计分析有非常显著性差异,P <0.001,说明术后角膜厚度变薄,眼压较术前显著降低。结论:LASIK手术使膜基质层变薄,对外界压力所产生的抵抗力相应减弱,使一定的气体脉冲力压平变薄了的中央角膜所需的时间明显减少,眼压测量值就偏低。但临床医生需注意应用矫正眼压的公式计算和分析眼压时考虑角膜厚度对眼压测量值的影响以免对青光眼诊断的误诊。     

The effect of lateral decubitus position on intraocular pressure in healthy young subjects

Purpose: To investigate the effect of change of body posture from supine to lateral decubitus position (LDP) on intraocular pressure (IOP) in healthy young subjects. Methods: We evaluated 38 eyes of 19 healthy young Korean subjects. IOP was measured using Tonopen XL^® in both eyes in the sitting and supine position, 5 and 30 min after right LDP and 5 min after returning to the supine position. A week later, IOP was measured in the same sequence except that the subjects assumed the left LDP. The eye on the lower side in the LDP was termed as a dependent eye. Results: The mean IOP of the dependent eyes increased significantly at 5 min after changing from supine to right (16.26 ± 2.73 mmHg versus 18.54 ± 2.95 mmHg, p < 0.01) or left LDP (15.53 ± 2.41 mmHg versus 17.53 ± 3.37 mmHg, p < 0.01); this IOP increase in the dependent eyes persisted at 30 min after changing to right (18.47 ± 2.97 mmHg, p < 0.01) or left LDP (17.79 ± 2.20 mmHg, p < 0.01). Upon returning to the supine position, IOP of the dependent eyes decreased significantly (16.83 ± 2.67 mmHg, p < 0.01 for right LDP and 16.47 ± 2.32 mmHg, p < 0.01 for left). However, this effect of the positional change was not found in the non‐dependent eyes (all, p > 0.05). Mean IOP in the dependent eye was significantly higher than that in the non‐dependent eye at 30 min after changing to the right (+0.89 ± 1.52 mmHg) or left LDP (+1.84 ± 2.03 mmHg). Conclusion: The postural change from supine to LDP significantly increased IOP of the dependent eyes.     

视物距离对知觉性优势眼的影响

目的研究基于Gabor识别的知觉性优势眼（OSD）是否会因视物距离的改变而发生变化。方法实验研究。OSD定量通过计算机辅助的心理物理学方法完成。经分视系统为60例健康受检者的两眼分别呈现Mordrian噪声和Gabor信号。在Mordrian噪声持续减弱而Gabor信号不断增强的过程中,受检者探测到Gabor信号的阈值被记录为眼知觉指数（OSI）。两眼各测试50次OSI。两眼间差异经标准化即为该受检者的眼优势指数（ODI）。ODI绝对值>2,则该受检者优势眼明确,OSI取值较小的眼别即优势眼别;否则无明确优势眼。分别在6 m的远距和60 cm的近距各进行一次测试。采用配对t检验测试ODI的变化是否显著。结果在距离对知觉性优势眼类型的影响的分析中,31例（52%）受检者的知觉性优势眼在远距和近距的检测中保持一致,26例（43%）受检者在不同距离下出现了有显著优势眼和无显著优势眼之间的转换,另有3例（5%）受检者出现了优势眼眼别的互换。在距离对知觉性优势眼影响的量化分析中,受检者的平均ODI由远距的－1.88±2.71变为近距的－0.72±2.95,表明在近距时知觉优势向平衡方向偏移（P＜0.01）。同时,45例（75%）受检者在远距某一眼相对优势的情况下,会在近距离检测中表现为优势向对侧眼（即原优势较弱眼）偏移的现象,另有15例（25%）受检者情况相反。向原优势较弱眼偏移的平均偏移量（2.66±0.32）明显大于向原优势较强眼的偏移量（1.04±0.25）,差异有统计学意义（P＜0.01）。结论视物距离对知觉性优势眼存在影响。远距某一眼的知觉优势会在距离变近时向对侧眼发生偏移。近距视物时,双眼的知觉优势较远距更趋向平衡。     

Quantifying the effect of intraocular pressure reduction on the occurrence of glaucoma

Purpose: To estimate the effect of reducing intraocular pressure (IOP) on: (i) the incidence of primary open‐angle glaucoma (POAG) in patients with ocular hypertension (OH), and (ii) the progression of glaucoma. Methods: A meta‐analysis of relevant randomized controlled trials was conducted. A literature search was performed to identify trials with: a randomized comparison of IOP‐lowering intervention versus placebo or no treatment; visual field loss or optic disc changes as outcome; and follow‐up >6 months. A pooled relative risk (RR) was calculated by a random effects model. Risk reduction of glaucoma conversion per mmHg of IOP reduction was quantified in a meta‐regression model. Results: We identified nine OH and one POAG trials. A meta‐analysis of OH trials gives a pooled RR of 0.61 [95% confidence interval (CI) 0.45–0.83]. A meta‐regression shows a decrease of the RR of glaucoma conversion by 14% with each mmHg extra IOP reduction (P = 0.045). No meta‐analysis of POAG trials was performed because only one study has been identified. Conclusion: There is sufficient evidence that OH therapy reduces the risk of conversion to glaucoma. This risk reduction increases with greater IOP reduction.     

The effects of changed biomechanical parameters on measurements of intraocular pressure in keratoconus patients

Background: Keratoconus is associated with changes in the corneal structure, such as defects of Bowman's layer, a decrease of corneal thickness etc. They result in alterations of some of the biomechanical parameters of the cornea, namely, rigidity and elasticity. The present study was performed to examine how impression tonometry and applanation tonometry for determination of intraocular pressure (IOP) are affected by the changed biomechanical parameters associated with keratoconus. Patients and methods: We examined 20 normal subjects (40 eyes) and 17 keratoconus patients (25 eyes). The corneal thickness was measured by ultrasound pachymetry in the corneal center. In the keratoconus patients, an additional measurement was made at the conus peak. The corneal curvature was determined using the TMS keratoscope. The IOP measurements were made with the Schi?tz tonometer (10 g). For comparison, additional IOP measurements in the corneal center and, in the keratoconus group, on the conus peak were made with the applanation tonometer. Results: The normal subjects had a central corneal thickness of 548 ± 30 μm, compared to 505 ± 42 μm in the corneal center and 425 ± 41 μm on the conus peak in keratoconus patients. The average corneal curvature was 43.3 ± 1.8 D in the normal subjects and 47.8 ± 4.1 D in keratoconus patients. Applanation tonometry produced results on 11.33 ± 1.43 mm Hg in the normal group (corneal center) compared to values of 12.00 ± 2.55 mm Hg (corneal center) and 7.30 ± 1.95 mm Hg (conus peak) in the keratoconus cohort. The coefficient of rigidity was 0.0236 ± 0.0026 μl⁻¹ in the normal subjects, compared to 0.0173 ± 0.0050 μl⁻¹ in the keratoconus patients. Conclusion: The morphological changes associated with keratoconus may cause tonometry errors.      

The effect of corynanthine on intraocular pressure in clinical trials

A single drop, dose-response, double-masked study of the effect corynanthine, a selective alpha 1 adrenergic antagonist, on intraocular pressure (IOP) was carried out in 10 symmetrically ocular hypertensive patients. Corynanthine 1% had no significant pressure lowering effect. Topical application of a 2% solution significantly (P less than 0.05) reduced IOP for at least eight hours; at five hours, mean IOP (+/- SEM) was 20.6 +/- 2.0 mmHg and 26.0 +/- 4.9 mmHg, comparing treated and control eyes, respectively. The 5% solution caused a significant (P less than 0.05) bilateral reduction in IOP, comparing treated and control eyes to baseline IOP respectively. Two percent corynanthine applied topically two or three times daily for one, two, or three weeks to seven patients with symmetrical ocular hypertension did not reduce IOP. Alpha adrenergic antagonists may have a role in the treatment of glaucoma.     

下斜肌后徙转位术对眼球运动的影响

目的观察下斜肌后徙转位术对眼球运动的影响。方法顺序选择手术后系统观察≥3年的下斜肌后徙转位和后徙手术两组病例,比较眼球运动状况,并观察前者原在位眼位。结果（1）下斜肌后徙转位组原在位均未出现下斜视,14例单眼手术病例有上转受限,以颞上方为著,6例双眼手术病例无明显上转受限。（2）下斜肌后徙转位组手术后远期（≥3年）下斜肌运动程度、眼球上转程度均明显低于下斜肌后徙组,P〈0.001。（3）下斜肌后徙转位组术后远期下斜肌运动程度、眼球上转程度均低于近期（1周～1个月）,P〈0.05,而术后中期（3～6个月）与远期下斜肌运动程度、眼球上转程度之间无明显差异,P〉0.05。结论下斜肌后徙转位术导致术后眼球运动出现非共同性变化,主要是上转受限,对侧眼上转亢进。     

川芎嗪对兔高眼压视神经轴突损伤保护作用的研究

目的 探讨川芎嗪对兔持续性高眼压视神经轴突损伤的保护作用。方法 对３６只新西兰白兔眼前房注人α－糜蛋白酶,制作成持续性刘眼压模型后,随机等分为高眼压对照组和川芎嗪治疗组,治疗组于高眼压持续７ｄ始肌注川芎嗪,观察不同时间两组动物球结膜微循环变化及视神经轴突光、电镜结构改变。结果 与高眼压对照组相比,川芎嗪组结膜微循环障碍明显减轻（ｐ〈０．０１）,视神经轴突数目多、直径小,占视神经面积百分比高（Ｐ〈０