Comparation of the new rebound tonometer IOPen and the Goldmann tonometer, and their relationship to corneal properties

Purpose

To compare the intraocular pressures (IOPs) obtained with the IOPen rebound tonometer, Goldmann applanation tonometer (GAT) and the ocular response analyzer (ORA) and investigate the effects of corneal biomechanical properties on IOPen measurements.

Methods

A total of 198 normal eyes were included in this cross-sectional and randomized study. Three measurements were taken using IOPen. Agreement between tonometers was calculated using the Bland and Altman limits of agreement (LoA) analysis.

Results

The median IOPen IOP was 3 mm Hg below the GAT (P<0.001), 3 mm Hg below the ORA IOP similar to Goldmann (IOPg), and 3 mm Hg below the ORA IOP corrected using corneal parameters (IOPcc)(P<0.01). The LoA width between the IOPen and GAT IOPs varied between 13.92 (mean IOPen IOP) and 15.99 mm Hg (third IOPen measurement). The central corneal thickness (CCT) was unrelated to IOPen measurements (P>0.05). Corneal hysteresis (CH) and corneal rigidity factor (CRF) were correlated with IOPen and GAT.

Conclusions

IOPen underestimated the IOP compared with GAT and ORA. The effect of measurement quality or measurement order on IOPen was low. CCT did not affect the IOPen, but the CH and CRF did. The LoA width between the IOPen and GAT IOPs was higher than between the ORA IOPg or ORA IOPcc and GAT IOPs.     

Corneal hysteresis in patients with dry eye

Purpose

To measure corneal hysteresis and intraocular pressure (IOP) in patients with dry eye and to compare with normal subjects.

Methods

This cross-sectional study consists of 70 eyes of 40 patients with dry eye (group 1) and 75 eyes of 40 normal subjects (group 2). Eyes were diagnosed as dry eye or normal according to the clinical symptoms, biomicroscopical evaluation, and Schirmer test. Corneal hysteresis (CH), corneal resistance factor (CRF), and cornea-compensated intraocular pressure (IOPcc) were measured by the Ocular Response Analyser (ORA).

Results

Mean CH values were 10.56±0.25 mm Hg and 10.34±0.26 mm Hg, mean CRF values were 10.75±0.28 mm Hg and 10.70±0.28 mm Hg, mean CCT values were 542±3.20 μm and 543±3.89 μm in group 1 and group 2, respectively. There was no statistically significant difference between the groups for these three parameters. IOPcc values measured with ORA were 15.73±0.36 mm Hg in group 1 and 16.60±0.33 mm Hg in group 2, and there was no statistically significant difference between the two groups.

Conclusions

Corneal biomechanical parameters such as CH and CRF are not influenced in dry eye. Also statistical difference was not found between the two groups according to CCT and IOPcc values.     

Assessment of intraocular pressure measured by Reichert Ocular Response Analyzer, Goldmann Applanation Tonometry, and Dynamic Contour Tonometry in healthy individuals

AIM: To investigate the accuracy of intraocular pressure (IOP) as measured by a Reichert Ocular Response Analyzer (ORA), as well as the relationship between central corneal thickness (CCT) and IOP as measured by ORA, Goldmann applanation tonometry (GAT), and dynamic contour tonometry (DCT). METHODS: A total of 158 healthy individuals (296 eyes) were chosen randomly for measurement of IOP. After CCT was measured using A-ultrasound (A-US), IOP was measured by ORA, GAT, and DCT devices in a randomized order. The IOP values acquired using each of the three tonometries were compared, and the relationship between CCT and IOP values were analyzed separately. Two IOP values, Goldmann-correlated IOP value (IOPg) and corneal-compensated intraocular pressure (IOPcc), were got using ORA. Three groups were defined according to CCT: 1) thin cornea (CCT<520μm); 2) normal-thickness cornea (CCT: 520–580μm); and 3) thick cornea (CCT>580μm) groups. RESULTS: In normal subjects, IOP measurements were 14.95±2.99mmHg with ORA (IOPg), 15.21±2.77mmHg with ORA (IOPcc), 15.22±2.77mmHg with GAT, and 15.49±2.56mmHg with DCT. Mean differences were 0.01±2.29mmHg between IOPcc and GAT (P>0.05) and 0.28±2.20mmHg between IOPcc and DCT (P>0.05). There was a greater correlation between IOPcc and DCT (r=0.946, P=0.000) than that between IOPcc and GAT (r=0.845, P=0.000). DCT had a significant correlation with GAT (r=0.854, P=0.000). GAT was moderately correlated with CCT (r=0.296, P<0.001), while IOPcc showed a weak but significant correlation with CCT (r=?0.155, P=0.007). There was a strong negative correlation between CCT and the difference between IOPcc and GAT(r=-0.803,P=0.000), with every 10μm increase in CCT resulting in an increase in this difference of 0.35mmHg. The thick cornea group (CCT>580μm) showed the least significant correlation between IOPcc and GAT (r=0.859, P=0.000); while the thin cornea group (CCT＜520μm) had the most significant correlation between IOPcc and GAT (r=0.926, P=0.000). The correlated differences between IOPcc and DCT were not significant in any of the three groups (P>0.05). CONCLUSION: Measurement of IOP by ORA has high repeatability and is largely consistent with GAT measurements. Moreover, the ORA measurements are affected only to a small extent by CCT, and are likely to be much closer to the real IOP value than GAT.     

Comparison of iCare tonometer and Goldmann applanation tonometry in normal corneas and in eyes with automated lamellar and penetrating keratoplasty

Purpose

To compare intraocular pressure (IOP) measurements with Goldmann applanation tonometry (GAT) and iCare tonometry in normal and post-keratoplasty corneas and to assess the influence of central corneal thickness (CCT), corneal curvature (CC), and corneal astigmatism (CA) on IOP.

Methods

This prospective cross-sectional study included one eye of 101 subjects with normal corneas (58 healthy subjects, 43 glaucoma); and 90 post-keratoplasty patients: 34 penetrating keratoplasties (PK); 20 automated-lamellar-therapeutic keratoplasties (ALTK); 19 Descemet-stripping-automated-endothelial keratoplasties (DSAEK); 17 edematous grafts. All subjects underwent GAT and iCare IOP measurements in random order, and CCT, CC, and CA evaluation. The Bland–Altman method and multivariate regression analysis were used to assess inter-tonometer agreement and the influence of CCT, CC, and CA on IOP.

Results

iCare significantly underestimated IOP in all groups compared with GAT (GAT minus iCare of 3.5±3.5 mm Hg, P<0.001), but overestimated IOP in the edematous grafts (GAT minus iCare of −6.5±1.9 mm Hg, P<0.001). In normal corneas, both tonometer measurements were directly related to CCT values; iCare readings appeared inversely related to CC. There was no significant relationship between IOP and CCT, CC and CA in post-keratoplasty eyes, except between CC and iCare measurements for PK eyes.

Conclusions

The agreement between GAT and iCare was clinically acceptable in control, ALTK and DSAEK groups, and poor in PK and edematous grafts eyes. In normal corneas, GAT was significantly affected by CCT; iCare was influenced by CCT and CC. The iCare appeared less influenced by corneal edema when compared with GAT. High IOP readings taken with both tonometers in grafts should raise suspicion of true elevated IOP.     

The biomechanical properties of the cornea in patients with systemic lupus erythematosus

Pupose:

The purpose of this study was to compare the biomechanical properties of the cornea and intraocular pressure (IOP) between patients with systemic lupus erythematosis (SLE) and age-matched controls.

Patients and Methods:

In this prospective study, 30 healthy individuals (control group) and 30 patients with SLE (study group) underwent Reichert ocular response analyzer (ORA) measurements. In the right eye of each participant, the corneal hysteresis (CH), corneal resistance factor (CRF), and Goldman-related IOP (IOPg) were recorded using the ORA.

Results:

Mean CH, CRF, IOPg were significantly different between groups. Mean CH was 10.2±0.6 mm Hg in the study group and 11.3±1.3 in the control group (P=0.02); mean CRF was 9.7±1.1 mm Hg and 11.9±1.5 mm Hg, respectively (P=0.001). Mean IOP_g was 13.9±2.9 mm Hg in the study group and 16.9±2.6 mm Hg in the control group (P=0.001).

Conclusion:

The biomechanical properties of the cornea are altered in patients with SLE compared with normal controls. These findings should be taken into account when measuring IOP values in patients with SLE as IOP readings may be underestimated in SLE eyes.     

Factors associated with topographic changes of the optic nerve head induced by acute intraocular pressure reduction in glaucoma patients

Purpose

To investigate factors associated with changes in optic nerve head (ONH) topography after acute intraocular pressure (IOP) reduction in patients with primary open-angle glaucoma (POAG).

Methods

Untreated POAG patients (IOP >21 mm Hg) were prospectively enrolled. Systemic and ocular information were collected, including central corneal thickness (CCT) and corneal hysteresis (CH). All patients underwent confocal scanning laser ophthalmoscopy and tonometry (Goldmann) before and 1 h after pharmacological IOP reduction. The mean of three measurements was considered for analysis. Changes in each ONH topographic parameter were assessed (one eye was randomly selected), and those that changed significantly were correlated with patient''s systemic and ocular characteristics.

Results

A total of 42 patients were included (mean age, 66.7±11.8 years). After a mean IOP reduction of 47.3±11.9%, significant changes were observed in cup area and volume, and in rim area and volume (P<0.01), but not in mean cup depth (P=0.80). Multiple regression analysis (controlling for baseline IOP and magnitude of IOP reduction) showed that CH (r²=0.17, P<0.01) and diabetes diagnosis (r²⩾0.21, P<0.01) were negatively correlated with the magnitude of changes in ONH parameters, whereas the cup-to-disc ratio was positively correlated (r²=0.30, P<0.01). Age, race, disc area, and CCT were not significant (P⩾0.12). Including all significant factors in a multivariable model, only the presence of diabetes remained significantly associated with all ONH parameters evaluated (P<0.01).

Conclusions

Different systemic and ocular factors, such as diabetes, CH, and the relative size of the cup, seem to be associated with the magnitude of changes in ONH topography after acute IOP reduction in POAG patients. These associations partially explain the ONH changes observed in these patients and suggest that other factors are possibly implicated in an individual susceptibility to IOP.     

Repeatability and agreement of CCT measurement in myopia using entacam and ultrasound pachymetry

AIM: To evaluate the repeatability of central corneal thickness (CCT) measurement by entacam, and agreement of CCT measured by Pentacam and ultrasound pachymetry (USP) in Chinese myopia. Thereby investigate the possibility of Pentacam as a substitute for USP in CCT measurement before refractive surgery. The effects of corneal curvature measured by Pentacam on CCT were also evaluated. METHODS: One hundred and forty-eight right eyes of 148 individual with myopia were included in this study. Three successive Pentacam CCT measurements followed by 10 successive ultrasound pachymetry were carried out in the 148 eyes. Mean of CCT taken by each device was calculated for comparison. According to the CCT measured by USP, all the 148 eyes were divided into 3 groups: <520μm, 520-560μm, >560μm. For all eyes and each group the CCT obtained by Pentacam and USP were compared. Anterior corneal curvature of the 148 eyes was also adopted for correlation analysis with CCT obtained by ultrasound pachymetry. In addition, CCT measurement using 60 random selected Scheimpflug images was performed by 3 skilled investigators at different time, and this was repeated for 3 times by a forth investigator to assess repeatability of Pentacam CCT measurement using Scheimpflug images. RESULTS: Intraclass correlation coefficient (ICC) analysis revealed high intraobserver repeatability (ICC=0.994, F=158.60, P<0.001) for CCT measurement by Pentacam. The interobserver (ICC=0.998, F=494.73, P<0.001) and intraobserver (ICC=0.997, F=383.98, P<0.001) repeatability for Pentacam CCT measurements using Scheimpflug images were also excellent. There was high positive correlation between the CCT values measured by Pentacam and ultrasound pachymetry (r=0.963, P<0.001). Bland-altman plots showed that the Pentacam underestimate the CCT by 8.02μm compared with ultrasouond pachymetry. The differences between Pentacam and USP increased as the CCT readings by USP increased (Pentacam vs USP: slope=-0.04, P<0.05). The 95% upper and lower limits of agreement between CCT values obtained from the two devices were +9.33μm and -25.37μm. No significant association could be found between CCT and anterior corneal curvature. CONCLUSION: Inter- and intraobserver variability for CCT measurements by Pentacam was considerably below clinically significant levels. CCT of myopia obtained by Scheimpflug camera, Pentacam, were highly correlated to that by ultrasound pachymetry. However, the values obtained are not directly interchangeable between Pentacam and ultrasound pachymetry as the 95% limits of agreement are relatively wide. Pentacam can be a useful instrument for measuring CCT in candidates to refractive surgery in clinic.     

Evaluation of corneal biomechanical properties following penetrating keratoplasty using ocular response analyzer

Purpose:

To evaluate corneal biomechanical properties in eyes that has undergone penetrating keratoplasty (PK).

Materials and Methods:

Retrospective observational study in a tertiary care centre. Data recorded included ocular response analyzer (ORA) values of normal and post-keratoplasty eyes [corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and cornea-compensated intraocular pressure (IOPcc)], corneal topography, and central corneal thickness (CCT). Wilcoxon signed rank test was used to analyze the difference in ORA parameter between post-PK eyes and normal eyes. Correlation between parameters was evaluated with Spearman''s rho correlation.

Results:

The ORA study of 100 eyes of 50 normal subjects and 54 post-keratoplasty eyes of 51 patients showed CH of 8.340 ± 1.85 and 9.923 ± 1.558, CRF of 8.846 ± 2.39 and 9.577 ± 1.631 in post-PK eyes and normal eyes, respectively. CH and CRF did not correlate with post-keratoplasty astigmatism (P =0.311 and 0.276, respectively) while a significant correlation was observed with IOPg (P =0.004) and IOPcc (P < 0.001).

Conclusion:

Biomechanical profiles were significantly decreased in post-keratoplasty eyes with significant correlation with higher IOP as compared with that in normal eyes.     

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.     

近视人群中角膜生物力学特性的分布

目的：分析伊朗近视眼及散光人群中角膜生物力学参数的分布特征。

方法：对接受激光矫正手术的近视眼及散光患者180眼进行前后节、显然验光等效球镜度、Orbscan II和Zywave全面的术前检查。用眼反应分析仪测量角膜滞后量,角膜阻力因子,模拟Goldmann眼压值及角膜补偿后眼压值。分析所有角膜生物力学的分布特性及其与显然验光等效球镜度、性别和年龄的相关性。数据采用SPSS 17软件进行统计学分析,以P<0.05为有显著性差异。

结果：平均年龄为28.20±6.78岁。平均显然验光等效球镜为-4.21±1.19D。平均角膜滞后量,角膜阻力因子,模拟Goldmann眼压值和角膜补偿后眼压值分别为10.00±1.28mmHg,10.17±1.45mmHg,15.71±2.67mmHg和 16.68±2.41mmHg。近视人群中,28.4%角膜滞后量约为10mmHg,71%从9mmHg增长到11mmHg。25.9%的近视人群的角膜阻力因子为10mmHg,48.7%为9mmHg增长到11mmHg。显然验光等效球镜与角膜滞后量(Rs=0.001,P=0.71)和显然验光等效球镜与角膜阻力因子(Rs=0.01,P=0.18)之间正相关性不明显。

结论：研究显示了伊朗近视眼人群中角膜生物力学的分布特征(角膜滞后量,角膜阻力因子,模拟Goldmann眼压值及角膜补偿后眼压值),并证实了角膜生物力学特性参数和显然验光等效球镜,年龄及性别之间没有统计学相关性。     

Combining corneal hysteresis with central corneal thickness and intraocular pressure for glaucoma risk assessment

Purpose

To determine whether adjusting corneal hysteresis (CH) values for central corneal thickness (CCT) and intraocular pressure (IOP) improves its capability to differentiate primary open-angle glaucoma (POAG) from ocular hypertension (OH).

Methods

This prospective, observational, cross-sectional study included 169 eyes of 169 subjects with a diagnosis of POAG (n=81) or OH (n=88). We utilized the Ocular Response Analyzer (ORA), Pascal Dynamic Contour Tonometer (DCT), Goldmann applanation tonometer (GAT), and ORA ultrasound pachymeter to obtain CH, IOP, and CCT values. Correlational, regression, and t-test analyses were conducted before and after the sample was divided into low, intermediate, and thick CCT subgroups.

Results

In the full sample, CH and CCT were moderately correlated (r=0.44, P<0.001). Although both were related to diagnosis in univariate regression analysis, only CH was independently related to glaucoma diagnosis in multivariate analysis. After the sample was divided into CCT tertiles, CH was significantly lower in POAG vs OH eyes within all three CCT subgroups, and CH was the only multivariate variable that differentiated POAG from OH in each CCT subgroup. Moreover, the relationship between CH and diagnosis was more robust within the CCT subgroups compared with the full sample, suggesting that integrating CCT into CH interpretation is beneficial. Adjusting CH for IOP did not aid diagnostic precision in this study.

Conclusion

Our findings suggest that combining CH and CCT for glaucoma risk assessment improves diagnostic capability compared to using either factor alone. Conversely, adjusting CH for IOP provided no clear clinical benefit in this study.     

Comparison of intraocular pressure measurements with different contact tonometers in young healthy persons

AIM: To analyze the correlation of Goldmann applanation tonometer (GAT), I-Care tonometer and Tono-Pen tonometer results in young healthy persons, and to investigate the influence of central corneal thickness (CCT) on intraocular pressure (IOP) measurements recorded with these tonometers. METHODS: We conducted a pilot clinical study in 78 eyes of 78 subjects aged 22-28 years old (44 women and 34 men; mean age 23.8±1.19y). IOP was measured using GAT, I-Care and Tono-Pen tonometers, followed by measurements of CCT. Statistical analysis was performed using SPSS 20.0. RESULTS: The mean IOPs and standard deviation (±SD) for GAT, I-Care and Tono-Pen were 15.62±2.281 mm Hg, 16.29±2.726 mm Hg and 16.32±2.393 mm Hg, respectively. The mean CCT was 555.15±29.648 μm. Clear positive correlations between GAT and I-Care, GAT and Tono-Pen, and I-Care and Tono-Pen tonometers were found (r=0.867, P<0.001; r=0.861, P<0.001; r=0.915, P<0.001, respectively). In comparison between devices, Bland–Altman analysis showed a significant mean difference (MD) in the measurements by GAT and I-Care of ?0.679 mm Hg and by GAT and Tono-Pen of ?0.705 mm Hg ( P<0.001), but there was no significant difference between I-Care and Tono-Pen ( P>0.05). Both non-gold standard tonometers were affected by CCT; that is, both I-Care and Tono-Pen tonometer values were significantly higher with higher CCT means (>555 μm; MD=?1.282, P<0.001; MD=?0.949, P<0.001, respectively) compared with GAT. CONCLUSION: Both I-Care and Tono-Pen tonometers overestimated IOP compared with the GAT values. Either the I-Care or Tono-Pen tonometer could be used instead of GAT because there was no significant difference between their results. Higher CCT values (>555 μm) were associated with overestimated IOP values.     

The effect of orbital decompression surgery on refraction and intraocular pressure in patients with thyroid orbitopathy

Purpose

To investigate the effect of orbital decompression surgery in thyroid orbitopathy (TO) on both refractive status and intraocular pressure (IOP).

Patients and methods

A prospective, multicentre, consecutive audit of patients undergoing thyroid decompression surgery. Indications for surgery included cosmetically unacceptable proptosis or corneal exposure. Exclusion criteria included the following: previous orbital surgery, glaucoma, corneal disease, steroid use in the preceding 12 months, or an acute optic neuropathy. Automated refraction, keratometry, pachymetry, Hertel exophthalmometry, and IOP were recorded at 1 month pre- and 3 months postoperatively. IOP using the Tono-Pen (mean of three readings) was measured in the primary, upgaze, and downgaze positions.

Results

Data were collected from 52 orbits of 33 patients (East Grinstead, New York, and Adelaide). There was no significant difference between pre- and postoperative data for sphere, cylinder, or central corneal thickness (CCT). The mean spherical equivalent was −0.43±1.49 D pre-operatively and −0.28±1.52 D postoperatively. The steepest meridian of corneal curvature was 93.1 degrees pre- and 94.2 degrees postoperatively, with no significant difference. Mean IOP significantly decreased when measuring by Goldmann applanation tonometry (GAT) (2.28 mm Hg, ^* P=0.001) and Tono-Pen (3.06 mm Hg, ^* P=<0.0001). IOP measured in upgaze was significantly greater than that in the primary position. Regression analysis between change in IOP and either Hertel exophthalmometry or the number of orbital walls decompressed was non-significant (^*Student''s t-test).

Conclusion

Patients with TO undergoing orbital decompression had, on average, with-the-rule astigmatism not affected by orbital decompression surgery. IOP was significantly reduced by decompression surgery although no relationship between IOP and the degree of decompression was observed.     

Evaluation of Corneal Biomechanical Properties Following Penetrating Keratoplasty Using the Ocular Response Analyzer

Purpose

To evaluate corneal biomechanical properties in eyes that had previously undergone penetrating keratoplasty (PK) using the ocular response analyzer (ORA).

Methods

We recruited 26 patients who had received unilateral PK. Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and cornea-compensated intraocular pressure (IOPcc) were measured with the ORA and were compared to the measurements from the contralateral eyes that did not undergo PK.

Results

The CH was 8.95±2.59 mmHg in eyes that underwent PK and 9.78±1.45 mmHg in the contralateral eyes that did not undergo PK (p=0.077). The CRF was 10.26±2.64 mmHg in post-PK eyes and 9.75±1.45 mmHg in the contralateral eyes (p=0.509), and the CH-CRF was significantly smaller in post-PK eyes (-1.31±2.32 mmHg in post-PK eyes vs. 0.03±0.88 mmHg in fellow eyes, p=0.016). The IOPg and IOPcc were significantly higher in the PK group than they were in the control group. The IOPcc''s were 20.81±7.81 mmHg and 16.27±2.49 mmHg in post-PK and control eyes, respectively (p=0.011); and the IOPg''s were 19.22±7.34 mmHg and 15.07±3.03 mmHg in post-PK and control eyes, respectively (p=0.019). The IOPcc-g''s were 1.59±2.81 mmHg and 1.21±1.30 mmHg in post-PK and control eyes, respectively (p=0.412), and the central corneal thickness (CCT)''s were 489.11±90.60 µm and 556.24±42.84 µm in post-PK and control eyes, respectively (p=0.068).

Conclusions

Following PK, CH tended to decrease while CRF tended to increase, significantly decreasing CH-CRF. A significantly higher intraocular pressure and a thinner CCT following PK may have contributed to the observed changes in these corneal biomechanical parameters.     

Are There Any Changes in Corneal Biomechanics and Central Corneal Thickness in Fuchs’ Uveitis?

Purpose: To compare corneal biomechanics, intraocular pressure (IOP) and central corneal thickness (CCT) of 38 patients with unilateral Fuchs’ uveitis (FU) with 42 healthy controls.

Methods: Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated and corneal-compensated IOP (IOPg and IOPcc, respectively) and CCT were measured.

Results: The mean CH, CRF, and IOPg of the involved FU eyes were significantly lower (9.5?±?1.6, 9.0?±?1.9 and 13.1?±?4.3?mmHg) than contralateral eyes (10.1?±?1.7, 9.9?±?1.7 and 14.6?±?3.4?mmHg), and controls (10.5?±?1.5, 10.3?±?1.5 and 14.8?±?2.5?mmHg), respectively. There was no significant difference for mean IOPcc between involved FU or contralateral eyes and controls (14.8?±?4.1, 15.5?±?3.4 and 15.0?±?2.7?mmHg). The CCT values correlated with CH and CRF in the involved and contralateral eyes.

Conclusions: Involved FU eyes had lower CH, CRF, and IOPg than contralateral eyes and controls, with no difference regarding IOPcc.     

The impact of off the visual axis retinoscopy on objective central refractive measurement in adult clinical practice: a prospective, randomized clinical study

Purpose

The objective of this study was to examine the effect of the off axis retinoscopy on objective central refractive measurement in adult clinical practice.

Methods

In all, 40 subjects underwent undilated retinoscopy in a randomly selected eye both on and off the visual axis by a single masked examiner. Off axis retinoscopy was defined as retinoscopy performed with the testing eye of the examiner aligned with the contralateral (non-test) eye of the subject resulting in an off axis deviation in the nasal horizontal visual field. Retinoscopy was performed in negative cylinder only and spherocylindrical measurements were converted to power vectors for analysis. Paired t-test was used to assess differences in M, J₀ and J₄₅ power vectors including differences between mean aided and unaided LogMar acuities.

Results

In all, 14 subjects were myopic (SE≤−0.5 D), 13 subjects were emmetropic (SE between −0.49 and 1.0 D) and 13 subjects were hyperopic (SE >1.0 D). Mean angle of deviation was 5.58° in the nasal horizontal visual field. J₀ showed a significant negative shift in those with myopia (P<0.001) and emmetropia (P=0.049) following off axis retinoscopy. No significant differences in M, J₀ and J₄₅ were found in the hyperopes. Mean aided LogMar acuities after on and off axis retinoscopy were both significantly better than mean unaided LogMar VA (P<0.001 in both cases).

Conclusion

Small degrees of off axis retinoscopy encountered in everyday clinical practice can induce errors in objective central refractive measurement.     

Corneal biomechanical properties in normal‐tension glaucoma

Purpose: To investigate the intraocular pressure (IOP) and corneal biomechanical properties of normal and normal‐tension glaucoma (NTG) eyes. Methods: This study included 83 normal and 83 NTG eyes. We measured corneal‐compensated IOP (IOPcc), Goldmann‐correlated IOP (IOPg), corneal resistance factor (CRF), corneal hysteresis (CH) and central corneal thickness (CCT) three times each for normal and NTG eyes using an Ocular Response Analyzer (ORA). Results: No significant difference in CCT was seen between normal eyes (541.4 ± 26.8 μm) and NTG eyes (535.4 ± 24.9 μm; p = 0.16). IOPcc was significantly higher in NTG eyes (16.1 ± 2.6 mmHg) than in normal eyes (15.1 ± 2.9 mmHg; p = 0.01), while IOPg was significantly lower in NTG eyes (14.1 ± 2.7 mmHg) than in normal eyes (15.1 ± 3.0 mmHg; p = 0.04). CRF and CH were significantly lower in NTG eyes (CRF, 8.9 ± 1.5 mmHg; CH, 9.2 ± 1.3 mmHg) than in normal eyes (CRF, 10.6 ± 1.4 mmHg; CH, 10.8 ± 1.3 mmHg; p < 0.0001 each). Conclusion: IOPcc was significantly higher in NTG eyes than in normal eyes. The ORA may be useful for distinguishing between the IOPcc of NTG eyes with normal IOP and that of normal eyes. In addition, the ORA enables CRF and CH to be measured in vivo, and weakness of the lamina cribrosa may be clinically inferred from the fact that CRF and CH were reduced in NTG eyes in our study. Low CRF and CH may be clues to the pathology of NTG.     

同轴微切口超声乳化白内障吸出术后角膜生物力学变化

目的　比较同轴微切口超声乳化白内障吸出术（ｐｈａｃｏｅｍｕｌｓｉｆｉｃａｔｉｏｎ,Ｐｈａｃｏ）及标准切口Ｐｈａｃｏ术后角膜生物力学的变化。方法　年龄相关性白内障患者３１２例（３１２眼）随机分成两组。其中研究组（２．２ｍｍ同轴微切口组）１５９例,对照组（３．０ｍｍ标准切口组）１５３例。记录两组术前数据,包括年龄、性别、裸眼视力（ｕｎｃｏｒｒｅｃｔｅｄｖｉｓｕａｌａｃｕｉｔｙ,ＵＣ-ＶＡ）、最佳矫正视力（ｂｅｓｔｃｏｒｒｅｃｔｅｄｖｉｓｕａｌａｃｕｉｔｙ,ＢＣＶＡ）、角膜滞后性（ｃｏｒｎｅａｌｈｙｓｔｅｒｅｔｉｅ,ＣＨ）、角膜阻力因数（ｃｏｒｎｅａｌｒｅｓｉｓｔａｎｃｅｆａｃｔｏｒ,ＣＲＦ）、Ｇｏｌｄｍａｎｎ相关眼压（ｇｏｌｄｍａｎｎｃｏｒｒｅｌａｔｅｄｉｎｔｒａｏｃｕｌａｒｐｒｅｓｓｕｒｅ,ＩＯＰｇ）、角膜补偿眼压（ｃｏｒｎｅａｌｃｏｍｐｅｎｓａｔｅｄＩＯＰ,ＩＯＰｃｃ）、中央角膜厚度（ｃｅｎｔｒａｌｃｏｒｎｅａｌｔｈｉｃｋｎｅｓｓ,ＣＣＴ）、角膜内皮细胞计数（ｅｎｄｏｔｈｅｌｉａｌｃｅｌｌｃｏｕｎｔ,ＥＣＣ）;术中数据包括累积能量复合参数（ｃｕｍｕｌａｔｉｖｅｄｉｓｓｉｐａｔｅｄｅｎｅｒｇｙ,ＣＤＥ）、手术时间。术后１ｄ、１周、２周、１个月复查,比较两组ＵＣＶＡ、ＢＣＶＡ、ＥＣＣ、ＣＣＴ、ＣＨ、ＩＯＰｇ、ＣＲＦ和ＩＯＰｃｃ。结果　术后１ｄ两组ＣＨ、ＣＲＦ均较术前明显降低,差异均有统计学意义（均为Ｐ＜０．０５）。术后１周,研究组ＣＨ、ＣＲＦ与术前差异均无统计学意义（均为Ｐ＞０．０５）;对照组ＣＨ、ＣＲＦ较术前降低,差异均有统计学意义（均为Ｐ＜０．０５）。术后２周,两组ＣＨ、ＣＲＦ均恢复至术前水平（均为Ｐ＞０．０５）;两组ＩＯＰｇ、ＩＯＰｃｃ仍高于术前（均为Ｐ＜０．０５）,而低于术后１周（均为Ｐ＜０．０５）;两组ＣＣＴ恢复至术前水平（均为Ｐ＞０．０５）。术后４周,两组ＣＨ、ＣＲＦ、ＩＯＰｇ、ＩＯＰｃｃ、ＣＣＴ均恢复至术前水平（均为Ｐ＞０．０５）。术前,两组ＣＨ、ＣＲＦ与ＣＣＴ存在正相关性（研究组:ｒ１＝０．４３,ｒ２＝０．５２,对照组:ｒ１＝０．５６,ｒ２＝０．５３;均为Ｐ＜０．０５）。术后１ｄ,两组ＣＨ与ＣＣＴ均无相关性（ｒ１＝０．１３,ｒ２＝０．１０,均为Ｐ＞０．０５）。两组的ＣＲＦ值与ＣＣＴ在不同时相始终存在相关性（均为Ｐ＜０．０５）。两组间不同时相的ＣＨ与ＣＲＦ均存在正相关性（均为Ｐ＜０．０５）。结论　同轴微切口Ｐｈａｃｏ和标准切口Ｐｈａｃｏ均会改变角膜生物力学特征。同轴微切口Ｐｈａｃｏ比标准切口Ｐｈａｃｏ术后角膜生物力学特征恢复更快。     

角膜补偿眼压与前房穿刺测量眼内压的比较

目的 比较角膜补偿眼压(IOPcc)与前房穿刺测量眼压(direct intracameral IOP,IOPintra),探讨角膜生物特性对眼压测量的影响.方法 双肓前瞻性研究.拟行超声乳化手术患者73例(73只眼),随机选择1只眼.超声测厚仪测量中央角膜厚度(CCT),ORA测量IOPcc和角膜生物属性:角膜滞后性(cornealhysteresis,CH).角膜阻力因子(corneal resistance factor,CRF).应用IOD眼压测量装置行前房穿刺测量IOPintra.结果 IOPintra为(15.48±4.64)mmHg,IOPcc为(16.63±3.68)mmHg;IOPcc高出IOPintra(1.15±4.12)mmHg(P=0.019);IOPcc和IOPintra与CH、CRF相关,IOPcc,IOPintra及两者的差异与CCT不相关;IOPcc与IOPintra的差异与cH相关(r=-0.283 P=0.015).结论 IOPcc读数比IOPintra高1.15mmHg,其差异受CH影响.角膜生物属性对眼压测量的影响需慎重考虑.     

Evaluation of Anterior Segment Parameters in Obesity

Purpose

To investigate anterior segment parameters in obese patients in comparison to healthy individuals.

Methods

Thirty-four obese subjects and 34 age-sex-matched healthy subjects were enrolled in this prospective cross-sectional study. Ophthalmological examinations including intraocular pressure (IOP), central corneal thickness (CCT), anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), and axial length (AL) measurements were performed on each subject. Height and weight of all subjects were recorded and body mass index (BMI) was calculated.

Results

IOP was significantly higher in the obese group (p = 0.003). The mean ACD in obese subjects was significantly lower than that in control subjects (p = 0.036). AL, ACV, ACA and CCT were not significantly different between the groups. There was a positive correlation between BMI and IOP (r = 0.404, p < 0.001). ACD and ACA were negatively correlated with BMI.

Conclusions

IOP was significantly higher and ACD was significantly lower in obese subjects. AL, ACV, ACA and CCT were not significantly different between the groups. The impact of obesity on anterior chamber parameters should be further investigated.