Corneal-compensated Intraocular Pressure Research Articles

Changes in biomechanical properties of the ocular fibrous tunic in patients with primary open-angle glaucoma in response to drug-induced stress-relief tests

To determine the effect of drug-induced stress-relief tests on biomechanical properties of the ocular fibrous tunic in eyes with early, moderate, or advanced primary open-angle glaucoma (POAG). A total of 202 eyes of 150 patients with POAG of different severity (early, moderate, or advanced) and 36 eyes of 30 healthy controls were examined. The mean patient age was 62±8.2 years. All groups were standardized by age, sex, and the range of corneal-compensated intraocular pressure (IOP) at baseline (21-30 mmHg). All patients underwent a standard ophthalmic examination, including visometry, biomicroscopy, gonioscopy, ophthalmoscopy, and Humphrey visual field assessment. Corneal hysteresis (CH), corneal resistance factor (CRF), CH-CRF difference, corneal-compensated IOP (IOPcc), and Goldmann-related IOP (IOPg) were measured with Ocular Response Analyzer (ORA, Reichert, USA). The axial eye length was measured on an ultrasonic A-scan (Ocuscan RxP, Alcon, USA) in the 10 MHz mode. CH and CRF variability analysis was conducted to assess changes in biomechanical properties of the fibrous tunic due to an IOP decrease and a tendency toward compensation. For the first time, the ratio between CH and CRF changes (ΔCH/ΔCRF) was used to evaluate biomechanical properties of the fibrous tunic. This ratio provides understanding of the significance of CH and CRF changes after reduction of IOP. In early glaucoma patients, it differed inconsiderably from the control group (p>0.05) and averaged 1.62±0.9. In moderate glaucoma, CH changes were more pronounced than those of CRF: ΔCH/ΔCRF - 2.03±2.41 (under conservative treatment) and 2.12±1.07 (without treatment). In advanced glaucoma an opposite pattern was observed: the CH/CRF ratio got closer to 1.0 largely due to CRF changes, while CH changes became much less pronounced (or even negative, in some cases): ΔCH/ΔCRF - 0.27±0.32 (under conservative treatment), 0.16±1.29 (without treatment). While the IOP decreased as a result of drug-induced stress-relief tests, CH and CRF changes differed between the groups depending on the stage of POAG. In early and moderate glaucoma, CH undergoes greater changes than CRF. In advanced glaucoma, CRF changes are more pronounced, and, hence, the ΔCH/ΔCRF ratio shifts reliably as glaucoma progresses. The ratio has also been shown to depend on the duration of the disease and on whether or not eye drops were prescribed.

Measuring Intraocular Pressure in Patients With Keratoconus With and Without Intrastromal Corneal Ring Segments.

To compare intraocular pressure (IOP) measurements made using 5 tonometers in keratoconic eyes with and without intrastromal corneal ring segments. This was an observational case series study. A total of 147 eyes of 147 patients with keratoconus, 74 of which had undergone corneal ring segment placement, were prospectively evaluated. IOP was measured using the tonometers Tonopen XL, Pascal dynamic contour tonometer, iCare Pro, ocular response analyzer (ORA), and Goldmann applanation (GAT) in random order. The Bland-Altman method was used to examine interinstrument agreement. Effects on readings of central corneal thickness, corneal curvature, and corneal astigmatism were assessed by multivariate regression analysis. Smallest mean IOP differences with GAT measurements in eyes without and with ring segments, respectively, were detected for iCare Pro [0.2 (2.9) mm Hg and 0.4 (3.0) mm Hg, P=0.914] and greatest differences for ORA Goldmann-correlated IOP [5.8 (3.3) mm Hg and 6.0 (3.1) mm Hg, P=0.363]. Best agreement with GAT was shown by iCare Pro (ICC=0.829; 95% CI, 0.721-0.896) and worse agreement by ORA corneal-compensated IOP (ICC=-0.145; 95% CI, -0.826 to 0.283). All but the dynamic contour tonometer readings were influenced by central corneal thickness, yet these measurements were affected by the presence of ring segments (P=0.017) and corneal astigmatism (P=0.030). Corneal curvature only affected ORA Goldmann-correlated IOP (P=0.029). All 5 tonometers provided reliable IOP readings in the keratoconic eyes regardless of the presence of corneal ring segments. iCare Pro readings were most consistent with GAT, whereas ORA readings were least consistent with this reference standard.

Comparison between corneal biomechanics and HbA1c levels in healthy individuals and type 2 diabetic patients

Objectives The aim of this study was to evaluate the corneal biomechanical properties using the ocular response analyzer (ORA) in type 2 diabetic patients. Background The ORA is a device developed in recent years and reveals the biomechanical properties of the cornea. It reflects certain biomechanical properties of the cornea, such as corneal hysteresis and corneal resistance factor. Patients and methods A total of 150 eyes of 75 patients were enrolled in a cross-sectional prospective comparative study from May 2015 to May 2016. Patients were divided into three equal groups. ORA and HbA1c evaluation were carried out for all patients. Results The corneal hysteresis of the study groups ranged from 5.5 to 9.8 mmHg for the control group (group A), and it ranged from 6.00 to 11.4 mmHg for the diabetic group (group B), whereas it ranged from 9.5 to 15.20 in the diabetic group (group C). The corneal resistance factor of the study groups ranged from 5.8 to 10.00 mmHg for the control group (group A), from 6.2 to 12.00 mmHg for the diabetic group (group B), and from 8.90 to 16.10 mmHg for the diabetic group (group C). The Goldmann-correlated intraocular pressure of our study groups ranged from 10 to 30 mmHg for the control group (group A), from 10 to 22 mmHg for the diabetic group (group B), and from 10.5 to 26.00 mmHg for the diabetic group (group C). The corneal-compensated intraocular pressure of the study groups ranged from 10.8 to 25 mmHg for the control group (group A), from 11.2 to 30 mmHg for the diabetic group (group B), and from 10.00 to 28.00 mmHg for the diabetic group (group C). Conclusion The corneal biomechanics in diabetic groups are significantly higher than those in the control group.

Refinement of Intraocular Pressure Measurements made by Ocular Response Analyzer following Laser in Situ Keratomileusis using M2 90 Moria Microkeratome for Egyptian Myopic and Astigmatic Patients.

IntroductionThe Goldmann applanation tonometer readings were noted to be markedly reduced after Lasik surgery using a thin flap technique which is widely used nowadays, to correct a wide range of myopia and astigmatism. The Ocular Response Analyzer (ORA) is considered one of the important tools for refinement of Intraocular Pressure (IOP) measurements. The aim of this study is to evaluate and refine ORA measurements for IOP changes post- M2 90 Moria microkeratome Lasik procedure for Egyptian myopic and astigmatic patients trying to aid in glaucoma diagnosis and management.MethodsThirty-five eyes of nineteen Egyptian patients with myopia or myopic astigmatism who had undergone Lasik procedure using M2 90 Moria microkeratome were included in this consecutive case series study. All cases were subjected to full ophthalmological examination including uncorrected and best corrected visual acuity, refraction, slit lamp examination, Scheimpflug imaging and ORA (Reichert Ophthalmic Instruments, Inc., Buffalo, NY, USA). The refractive errors were measured using an auto refractometer and were confirmed by trial. For the ocular response analyzer, the Goldmann-correlated IOP measurement (IOPg) which simulates IOP measured by Goldmann tonometer and the Corneal-Compensated Intraocular Pressure (IOPcc) that takes corneal biomechanical properties into consideration were reported as well as the Corneal Hysteresis (CH) and the Corneal Resistance Factor (CRF). Cases were examined preoperatively and again about one month after Lasik, after stabilization of eye condition. The collected data were tabulated and analysed with the suitable statistical methods. The mean values and standard deviation were calculated for quantitative data. Comparison tests (t-test) and correlation tests (Pearson) were also performed.ResultsIn our study, involving M2 90 Moria microkeratome Lasik procedure, a highly significant post-Lasik reduction in IOPg (t-test = 8.62 (p<0.01), and a statistically significant reduction in IOPcc (t-test = 3.37 (p<0.05) by ocular response analyzer. The average post-Lasik reduction in IOP in mmHg was 4.84±2.82 for IOPg and 2.23±3.51for IOPcc. A statistically significant correlation (p<0.05) existed between post-Lasik reduction of IOPg and ablation depth as well as preoperative spherical equivalent. A non-significant correlation existed between post-Lasik reduction of IOPcc and both of ablation depth and preoperative spherical equivalent.ConclusionsFollowing Lasik procedure using M2 90 Moria microkeratome, the IOPcc values by ORA were closer to the preoperative values than the IOPg values and the reduction of IOPcc values was not affected by ablation depth (i.e. preoperative spherical equivalent). Therefore, it is advisable to use the IOPcc values by ORA when evaluating post-Lasik patients for glaucoma diagnosis and management, but with the addition of the average value for post-Lasik reduction which in the study was 2.23±3.51mmHg.

Changes in intraocular pressure values measured with noncontact tonometer (NCT), ocular response analyzer (ORA) and corvis scheimpflug technology tonometer (CST) in the early phase after small incision lenticule extraction (SMILE).

BackgroundCorneal biomechanical properties are always compromised after corneal refractive surgeries thus leading to underestimated intraocular pressure (IOP) that complicates the management of IOP. We investigated the changes in postoperative baseline of IOP values measured with noncontact tonometer (NCT), ocular response analyzer (ORA) and corvis scheimpflug technology (CST) in the early phase after small incision lenticule extraction (SMILE).MethodsTwenty-two eyes (−6.76 ± 1.39D) of 22 moderate and high myopes, (28.36 ± 7.14 years, 12 male and 10 female) were involved in this prospective study. IOP values were measured using a non-contact tomometer (NCT-IOP), an ocular response analyzer (corneal-compensated IOP, IOPcc and Goldmann-correlated IOP, IOPg) and a Corvis scheimpflug technology tonometer (CST-IOP) preoperatively, at 20 min and 24 h, postoperatively. Repeated measures analysis of variance (RM-ANOVA), Pearson’s correlation analysis and multiple linear regression models (stepwise) were performed. Cut-off P values were 0.05.ResultsExcept for IOPcc, NCT-IOP, IOPg, and CST-IOP values significantly decreased after SMILE procedure (All P values <0.05). ΔCCT, as well as ΔMRSE and ΔKm, did not significantly correlated with ΔNCT-IOP, ΔIOPcc, ΔIOPg or ΔCST-IOP, (all P values >0.05). Multiple linear regression models (stepwise) showed that the practical post-operative IOP value was the main predictor of the theoretical post-operative NCT-IOP, IOPcc and IOPg values (all P values <0.001). The postoperative applanation time 1 (AT1) value (B = 8.079, t = 4.866, P < 0.001), preoperative central corneal thickness (CCT) value (B = 0.035, t = 2.732, P = 0.014) and postoperative peak distance (PD) value (B = 0.515, t = 2.176, P = 0.043) were the main predictors of the theoretical post-operative CST-IOP value.ConclusionsIOP values are underestimated when assessed after SMILE by using NCT-IOP, IOPg and CST-IOP. The practical postoperative IOPcc value and theoretical post-operative CST-IOP value may be more preferable for IOP assessment in the early phase after SMILE.Trial registrationCurrent Controlled Trials ChiCTRONRC13003114. Retrospectively registered 17 March 2013

Can Corneal Biomechanical Properties Give Clues About Elasticity of Optic Nerve Scleral Component in Nonarteritic Anterior Ischemic Optic Neuropathy?

To investigate corneal biomechanical properties among individuals with unilateral nonarteritic anterior ischemic optic neuropathy (NAION) compared to healthy gender- and age-matched subjects. The study subjects were separated into 2 groups: 66 eyes of 33 patients with unilateral NAION (study group) and 33 eyes of 33 healthy individuals (control group). Reichert ocular response analyzer (Reichert Ophthalmic Instruments) was used to assess corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPcc), and Goldmann-correlated intraocular pressure values. Also, central corneal thickness was measured using Scheimpflug camera combined with a Placido disc corneal topographer (Sirius; Costruzioni Strumenti Oftalmici). Mean CH and median CRF values were significantly lower in the affected eyes (8.8 ± 1.8 mm Hg, 9.4 mm Hg, respectively) and contralateral unaffected eyes (9.1 ± 1.6 mm Hg, 9.8 mm Hg, respectively) of NAION patients than those in the control group (9.9 ± 1.3 mm Hg, 10.4 mm Hg, respectively; all P < 0.017). Mean IOPcc was significantly higher in the affected eyes of NAION patients (19.2 ± 3.5 mm Hg) than in the eyes of control group (17.1 ± 3.6 mm Hg; P = 0.002). CH and CRF are significantly reduced in patients with NAION, possibly indirectly reflecting structural weakness in the lamina cribrosa.

Intraocular Pressure Changes and Relationship With Corneal Biomechanics After SMILE and FS-LASIK.

The purpose of this article was to evaluate intraocular pressure (IOP) changes and investigate the relationship with corneal biomechanics after small-incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). A total of 193 eyes of 193 patients who underwent SMILE and FS-LASIK procedures were included in this retrospective study. Data were collected preoperatively and postoperatively, including Goldmann-correlated IOP (IOPg), corneal-compensated IOP (IOPcc), corneal hysteresis (CH), and corneal resistance factor (CRF) by ocular response analyzer, noncontact intraocular pressure (IOPNCT) by noncontact tonometer, and Ehlers, Shah, Dresden, Kohlhaas, Orssengo/Pye by the Pentacam corrected system. Changes in both groups and differences between groups were evaluated. Multiple linear regression models were constructed to explore factors influencing IOP changes. In SMILE, the IOPg, IOPcc, IOPNCT, and Kohlhaas decreased significantly at 1 month postoperatively (P < 0.01), whereas with the Ehlers formula they significantly increased (P < 0.01). IOPs decreased at 3 and 6 months compared with all preoperative values except Ehlers values (P < 0.01), but there was no significant difference between 3 and 6 months (P > 0.05). In FS-LASIK, the IOPg, IOPcc, and IOPNCT decreased significantly at 1 month (P < 0.01), whereas in the Ehlers and Shah formulas they significantly increased (P < 0.01). Compared with preoperative values, the IOPs decreased at 3 and 6 months except in the Ehlers and Shah formulas (P < 0.01). Only IOPg and IOPcc differed between 3 and 6 months (P < 0.05). The Ehlers and Shah formulas were closer to the preoperative IOP for both groups, with variation approximately 1 mm Hg at 6 months postoperatively. Preoperative IOP, postoperative corneal resistance factor, corneal hysteresis, and flat keratometry were enrolled into the regression equations. IOP underestimation after SMILE or FS-LASIK was related to corneal biomechanics as well as preoperative IOP and flat keratometry. IOP after SMILE seem to remain more stable. Accordingly, the Ehlers and Shah formulas were closer to the preoperative IOP. It may be useful to estimate future IOP with the best-fit models after surgery.

Evaluation of biomechanical properties of the cornea in patients with primary hyperparathyroidism.

The purpose of this study is to compare the corneal biomechanical properties in primary hyperparathyroid patients and healthy control subjects. The study consisted of 31 patients with primary hyperparathyroidism (study group) and 31 healthy subjects (control group). Corneal biomechanical properties, including corneal hysteresis (CH), corneal resistance factor (CRF), and intraocular pressure (IOP) were measured with an ocular response analyzer (ORA). IOP was also measured using Goldmann applanation tonometry (GAT), and central corneal thickness (CCT) was measured with an ultrasonic pachymeter. The differences in ORA parameters and CCT between study and control group participants were analyzed. The mean CH in study and control groups was 8.7±1.9mmHg (5.3-13.7mmHg) and 9.8±1.5mmHg (7.7-14.3mmHg), respectively (p=0.018). The mean CRF was 9.5±1.8 (5.5-13.7) in the study group compared with 9.8±1.5 (6.2-12.8) in the control group. The difference for CRF was not statistically significant (p=0.41). In study and control group, corneal-compensated IOP (IOPcc) values were 18.2±4.2and 16.9±2.7mmHg, respectively (p=0.12). Mean IOP measurement values with GAT were 16.3±3.4mmHg for study group and 16.5±2.7mmHg for control group (p=0.71). The mean differences of IOPcc and IOPGAT in the study group eyes were higher than that of control group eyes (1.9 vs. 0.4mmHg). CCT was 536.5±25.4µm (490-593µm) in study group eyes compared with 534.2±31.4µm (472-602µm) in control eyes (p=0.75). Hyperparathyroidism could be associated with a decrease of CH. The differences between IOPcc and IOPGAT in these patients were higher than normal subjects. Underestimation of IOP readings with GAT may be a consequence of the lower CH in patients with hyperparathyroididsm.

Effect of biometric characteristics on biomechanical properties of the cornea in cataract patient.

To determine the impact of biometric characteristics on the biomechanical properties of the human cornea using the ocular response analyzer (ORA) and standard comprehensive ophthalmic examinations before and after standard phacoemulsification. This study comprised 54 eyes with cataract with significant lens opacification in stages I or II that underwent phacoemulsification (2.8 mm incision). Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated intraocular pressure (IOPcc) were measured by ORA preoperatively and at 1mo postoperatively. Biometric characteristics were derived from corneal topography [TMS-5, anterior equivalent (EQTMS) and cylindric (CYLTMS) power], corneal tomography [Casia, anterior and posterior equivalent (EQaCASIC, EQpCASIA) and cylindric (CYLaCASIA, CYLpCASIA) power], keratometry [IOLMaster, anterior equivalent (EQIOL) and cylindric (CYLIOL) power] and autorefractor [anterior equivalent (EQAR)]. Results from ORA were analyzed and correlated with those from all other examinations taken at the same time point. Preoperatively, CH correlated with EQpCASIA and CYLpCASIA only (P=0.001, P=0.002). Postoperatively, IOPg and IOPcc correlated with all equivalent powers (EQTMS, EQIOL, EQAR, EQaCASIA and EQpCASIA) (P=0.001, P=0.007, P=0.001, P=0.015, P=0.03 for IOPg and P<0.001, P=0.003, P<0.001, P=0.009, P=0.014 for IOPcc). CH correlated postoperatively with EQaCASIA and EQpCASIC only (P=0.021, P=0.022). Biometric characteristics may significantly affect biomechanical properties of the cornea in terms of CH, IOPcc and IOPg before, but even more after cataract surgery.

Age-related variations in corneal biomechanical properties

PurposeTo determine age-related changes in corneal viscoelastic properties in healthy individuals. MethodsThis observational cross-sectional study was performed at the Department of Ophthalmology, Imam Khomeini Hospital, Ahvaz, Iran and included 302 healthy individuals in 6 age decades (range: 10–69 years). After complete ocular examination, corneal viscoelastic properties were measured by ocular response analyzer and central corneal thickness (CCT) by an ultrasonic pachymeter. Our main outcome measures were corneal viscoelastic properties in different age groups. ResultsCorneal hysteresis (CH) and corneal resistance factor (CRF) showed a significant negative correlation with age (P < 0.001 for both, r = −0.353 and r = −0.246, respectively). Female gender had significantly higher CH (P = 0.017) and CRF (P = 0.019). CH and CRF were significantly correlated (P < 0.001, r = 0.821). CCT showed a biphasic pattern with significantly higher thicknesses before 20 and after 50 years of age. CH and CRF were significantly correlated with CCT (P < 0.001 for both, r = 0.21 and r = 0.26, respectively) and intraocular pressure (IOP) (P < 0.001 for both, r = −0.474 and r = 0.598, respectively). Corneal-compensated IOP (IOPcc) was significantly higher after age 40 compared to age group <20 (p < 0.045). Goldmann-correlated IOP (IOPg) was significantly correlated with CCT (P = 0.001, r = 0.193), while IOPcc showed no correlation with CCT (P = 0.265, r = 0.062). CH was significantly higher in hyperopic eyes compared to emmetropic eyes (P = 0.009) and myopic eye (P < 0.001). ConclusionsIn this study, there was a decrease in CH and CRF with an increase in age. Hyperopia and female gender are associated with higher CH and CRF. CCT is higher toward the extremes of life and is significantly correlated with CH and CRF.

Corneal biomechanics in normal Saudi individuals

PurposeThe aim of this study was to determine and relate corneal biomechanical metrics with demographic, tomographic and refractive data in healthy Saudi people. DesignProspective, cross-sectional, observational study. ParticipantsThe study included 215 normal Saudi adult individuals. MethodsCorneal hysteresis (CH) and corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg) and corneal-compensated intraocular pressure (IOPcc) were measured by ocular response analyzer. The central keratometry (CK), central corneal thickness (CCT), and anterior chamber depth (ACD) were measured using Pentacam system. The spherical equivalent of refraction (SER) was obtained by an Auto-refractometer. ResultsThe mean CH was 11.16±2.11, CRF was 11.07±2.31 and IOP was 15.12±3.5. Mean CK, ACD, CH and CRF were distinct among gender with the significant P values of 0.05, 0.006, 0.020, and 0.047 respectively. CRF was negatively correlated with ACD (r=−0.146, P=0.032). A positive correlation was found between CRF and SER (r=0.176, P=0.010), CCT (r=0.447, p=0.000) and CH (r=0.878 and p=0.000). CH was negatively correlated with IOPcc (−0.433, p=0.000). A positive correlation was found between CH and ACD (r=−0.14, p=0.044), SER (r=0.617, p=0.014), CCT (r=0.412, p=0.000) and IOPg (r=0.183, p=0.007). ConclusionThis study demonstrated a distinct difference among gender values of corneal hysteresis and corneal resistance factor being higher in female Saudi subjects. CH and CRF values were higher in Saudi subjects than values in other populations. This may suggest the presence of ethnic differences in ocular parameters and support the importance of establishing population norms for corneal biomechanical parameters.

The impact of chronic use of prostaglandin analogues on the biomechanical properties of the cornea in patients with primary open-angle glaucoma

AimsTo determine the influence of prostaglandin analogues (PGAs) on corneal biomechanical properties in patients undergoing chronic treatment for primary open-angle glaucoma (POAG).MethodsProspective, interventional case–control study. 70 eyes from 35 patients...

Does severity of dermatochalasis in aging affect corneal biomechanical properties?

PurposeThe aim of this study was to investigate the possibility of a relationship between corneal biomechanical properties and different grades of dermatochalasis.Patients and methodsPatients were assigned to four groups according to the severity of their dermatochalasis: normal (Group 1), mild (Group 2), moderate (Group 3), and severe (Group 4). An Ocular Response Analyzer device was used to measure corneal hysteresis (CH), corneal resistance factor (CRF), and corneal-compensated intraocular pressure (IOPcc).ResultsWe found no significant differences in the mean values of the CH, CRF, and IOPcc of all groups (P=0.75, P=0.93, and P=0.11, respectively). However, CH and IOPcc were negatively correlated in Group 1, Group 2, and Group 3 patients (P=0.013, r=−0.49; P=0.015, r=−0.52; and P=0.011, r=−0.47, respectively), but this correlation was not apparent in the Group 4 patients (P=0.57, r=0.12). CRF and IOPcc were correlated, but only in Group 4 (P=0.001, r=0.66).ConclusionSevere dermatochalasis was associated with altered corneal biomechanical properties. Some of the important visual consequences of dermatochalasis and related diseases (such as floppy eyelid syndrome) can be understood by considering corneal biomechanical alterations.

Corneal biomechanics in asymmetrical normal-tension glaucoma.

PurposeWe aimed to assess corneal biomechanics using the ocular response analyzer in patients with normal-tension glaucoma (NTG), and to evaluate the relationship between corneal biomechanics and visual field loss.MethodsThis was a prospective observational case series including patients with bilateral asymmetric NTG. For all patients, corneal hysteresis (CH), corneal resistance factor (CRF), CH − CRF difference, and central corneal thickness values were matched against the mean deviation (MD) of the visual field and the cup/disc ratio. For paired-eye comparison in each patient, both eyes were categorized into a better-eyes group and a worse-eyes group according to lower and higher corneal-compensated intraocular pressure readings, respectively. Statistical analysis was carried out with the independent-samples Student’s t-test, and the level of statistical significance was set at 0.05. Correlation was assessed using Pearson’s correlation coefficient.ResultsThe study included 240 eyes of 120 patients. CH was inversely proportional to the MD in the visual field (P=0.01). CRF in both eyes was inversely proportional to the MD of the visual field (P=0.01). CH − CRF difference was directly proportional to the MD of the visual field (P=0.01). For paired-eye comparison, lower corneal-compensated intraocular pressure was associated with higher CH, higher CRF, smaller cup/disc ratio, and less deterioration of MD of visual field.ConclusionCH, CRF, and CH − CRF are more powerful predictors of NTG progression than central corneal thickness.

ANATOMO-TOPOGRAPHIC AND HYDRODYNAMIC PARAMETERS OF THE EYE AFTER CATARACT PHACOEMULSIFICATION

Актуальность. Удаление нативного хрусталикавызывает изменение взаимного расположения структур переднего отдела глазного яблока, что влечет за собой колебания внутриглазного давления. Контроль внутриглазного давления важен для предотвращения осложнений в раннем послеоперационном периоде.

Corneal biomechanical properties changes after coaxial 2.2-mm microincision and standard 3.0-mm phacoemulsification.

To compare the changes in corneal biomechanics measured by ocular response analyzer (ORA) after 2.2-mm microincision cataract surgery and 3.0-mm standard coaxial phacoemulsification. The prospective nonrandomized study comprised eyes with cataract that had 2.2-mm coaxial microincision or 3.0-mm standard incision phacoemulsification. The corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPcc) and Goldmann-correlated intraocular pressure (IOPg) were measured by ORA preoperatively and at 1d, 1-, 2-, 3- and 4-week postoperatively. Results were analyzed and compared between groups. In both groups, CH decreased in the immediate postoperative period (P<0.05), returned to the preoperative level at one week (P=0.249) in the 2.2-mm group, and at two weeks in the 3.0-mm group (P=0.264); there was no significant change in CRF values. In 2.2-mm group, mean IOPcc and IOPg increased at 1d postoperatively (both P<0.05), and returned to preoperative level at one week (P=0.491 and P=0.923, respectively). In 3.0-mm group, mean IOPcc and IOPg increased at 1d and 1wk postoperatively (P=0.005 and P=0.029, respectively), and returned to preoperative level at 2wk (P=0.347 and P=0.887, respectively). Significant differences between preoperative and postoperative corneal biomechanical values were found for CH, IOPcc and IOPg. But the recovery time courses were different between the two groups. The 2.2-mm coaxial microincision cataract surgery group seemed recovery faster compared to the 3.0-mm standard coaxial phacoemulsification group.

Associations with Intraocular Pressure in a Large Cohort: Results from the UK Biobank

PurposeTo describe the associations of physical and demographic factors with Goldmann-correlated intraocular pressure (IOPg) and corneal-compensated intraocular pressure (IOPcc) in a British cohort.DesignCross-sectional study within the UK Biobank, a large-scale multisite cohort study in the United Kingdom.ParticipantsWe included 110 573 participants from the UK Biobank with intraocular pressure (IOP) measurements available. Their mean age was 57 years (range, 40–69 years); 54% were women, and 90% were white.MethodsParticipants had 1 IOP measurement made on each eye using the Ocular Response Analyzer noncontact tonometer. Linear regression models were used to assess the associations of IOP with physical and demographic factors.Main Outcome MeasuresThe IOPg and IOPcc.ResultsThe mean IOPg was 15.72 mmHg (95% confidence interval [CI], 15.70–15.74 mmHg), and the mean IOPcc was 15.95 mmHg (15.92–15.97 mmHg). After adjusting for covariates, IOPg and IOPcc were both significantly associated with older age, male sex, higher systolic blood pressure (SBP), faster heart rate, greater myopia, self-reported glaucoma, and colder season (all P < 0.001). The strongest determinants of both IOPg and IOPcc were SBP (partial R2: IOPg 2.30%, IOPcc 2.26%), followed by refractive error (IOPg 0.60%, IOPcc 1.04%). The following variables had different directions of association with IOPg and IOPcc: height (−0.77 mmHg/m IOPg; 1.03 mmHg/m IOPcc), smoking (0.19 mmHg IOPg, −0.35 mmHg IOPcc), self-reported diabetes (0.41 mmHg IOPg, −0.05 mmHg IOPcc), and black ethnicity (−0.80 mmHg IOPg, 0.77 mmHg IOPcc). This suggests that height, smoking, diabetes, and ethnicity are related to corneal biomechanical properties. The increase in both IOPg and IOPcc with age was greatest among those of mixed ethnicities, followed by blacks and whites. The same set of covariates explained 7.4% of the variability of IOPcc but only 5.3% of the variability of IOPg.ConclusionsThis analysis of associations with IOP in a large cohort demonstrated that some variables clearly have different associations with IOPg and IOPcc, and that these 2 measurements may reflect different biological characteristics.

A Comparison of Three Techniques for Measurement of Intraocular Pressure in Normal Eyes

Objectives: To compare the precision of intraocular pressure (IOP) measurements acquired using an ocular response analyser (ORA), Auto Kerato-Refracto-Tonometer (TRK-1P), and Goldmann applanation tonometer (GAT) in healthy eyes. Methods: In this prospective study, one eye of each of 57 normal subjects was randomly selected for analysis. Measurements of the IOP were performed using ORA, TRK-1P, and GAT, and measurements of corneal hysteresis (CH), corneal resistance factor (CRF), and central corneal thickness (CCT) were performed using ORA. Repeatability was assessed by the coefficient of variation (CV) and interclass correlation coefficients (ICCs). Agreement among tonometers was assessed by Bland–Altman plots and one-way ANOVA. Results: The average IOPs measured using Goldmann-correlated IOP (IOPg), corneal-compensated IOP (IOPcc), TRK-1P, and GAT (± SDs) were 15.13 ± 2.76, 14.39 ± 2.59, 16.54 ± 2.93, and 15.21 ± 2.54 mmHg, respectively. Intra-observer agreement across all tonometers was strong and slightly higher for GAT and IOPg than for TRK-1P. The intra-observer CVs for GAT IOPg, and TRK-1P, were 4.22 (ICC=0.94), 4.99 (ICC=0.93), and 6.69 (ICC=0.86), respectively. Inter-observer agreement between various measurement methods was evaluated with Bland-Altman plots with multiple measurements per subject and ICCs. Results indicated fairly poor agreement across measurement methods, as supported by large limits of agreement and ICCs. Conclusion: GAT, ORA, and TRK-1P are highly reliable methods for measurement of the IOP; however, the instruments cannot be used interchangeably.

Intraocular pressure and biomechanical corneal properties measure by ocular response analyser in patients with primary congenital glaucoma.

To measure the differences in corneal hysteresis (CH) and corneal resistance factor (CRF) in primary congenital glaucoma (PCG) and in control subjects using ocular response analyser (ORA) and also to compare intraocular pressure (IOP) measurements given by ORA against IOP given by Perkins tonometer, a handheld version of Goldman applanation tonometer (GAT), to determine correlation. One hundred and eighteen eyes of 78 patients with PCG (group I) and 103 eyes of 53 controls (group II) were evaluated using ORA. In all participants, IOP was measured using the Perkins tonometer. The ORA device uses applanation pressure peaks to generate the corneal-compensated IOP (IOPcc), which is reportedly independent of corneal thickness, and the measurement of Goldman-correlated IOP (IOPg), which is influenced by corneal thickness. The measures in group I were as follows: IOPcc 20.92±5.33; IOPg 18.87±6.67; CH 8.51±2.25; CRF 9.85±3.03; and IOP measured by Goldman 18.32±5.13. The measures in group II were as follows: IOPcc 14.33±2.91; IOPg 14.77±3.00; CH 11.37±1.61; CRF 11.02±1.74; and IOP measured by Goldman 13.74±2.42. The differences of all parameters compared between both groups were statistically significant (p<0.001 for CH and for all IOP measures and p=0.001 for CRF). The values of IOPcc, IOPg and IOP measured with Goldman were higher in group I than the values in group II. However, CH and CRF values were lower in group I. A decrease in CH and CRF has been observed in patients with PCG compared to controls. Future research should assess how these parameters are modified in PCG and whether they could provide more information about progression.

Evaluation of sex differences in corneal hysteresis.

To study sex differences in corneal biomechanical parameters in Egypt as regards to corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated intraocular pressure (IOPcc). This is a cross-sectional observational study that includes 350 eyes of 350 normal subjects (175 men and 175 women) who were evaluated using the Reichert ocular response analyzer (ORA) to measure CH, CRF, IOPg, and IOPcc. The mean CH in men was 9.69 ± 2.05 mm Hg (range 5.7-14.6 mm Hg) and in women 10.41 ± 1.65 mm Hg (range 7-14.4 mm Hg) with a p value of 0.00038. The mean CRF in men was 9.54 ± 2.16 mm Hg (range 4.9-14.4 mm Hg) and in women was 10.37 ± 1.71 mm Hg (range 7.3-15.5 mm Hg) with a p value of 0.00008. The mean IOPg in men was 14.78 ± 4.15 mm Hg (range 7.2-26.5 mm Hg) and in women was 15.44 ± 3.3 mm Hg (range 8.6-23.7 mm Hg) with a p value of 0.09. The mean IOPcc in men was 16.2 ± 4.08 mm Hg (range 10.9-28.9 mm Hg) and in women was 15.86 ± 3.41 (range 9.7-24.2 mm Hg) with a p value of 0.4. There was a statistically significant difference between men and women in CH and CRF while IOPg and IOPcc showed no statistically significant difference (p&gt;0.05). There is a statistically significant difference between men and women in CH and CRF, where women show higher values, while no statistically significant difference exists between the groups in IOPg or IOPcc.