Mean Corneal Hysteresis Research Articles

Corneal Hysteresis in Adult Indian Population

Purpose: To evaluate corneal hysteresis (CH) and to study its inter-ocular variability along with its association with gender and age using Ocular Response Analyzer (ORA) among healthy adult Indian population. Methods: This prospective, cross-sectional, observational study was conducted at a tertiary eye care centre in a medical university in India between July and December 2020. 300 healthy participants in age group between 18 to 60 years were recruited from amongst the residents, staff and patients coming for routine examination in Ophthalmology department. Participants with history of systemic/ocular disease, ocular surgery, pregnancy or spherical equivalent refraction >±1D were excluded from study. CH and corneal compensated intra-ocular pressure (IOP-cc) was assessed using ORA. Statistical analysis was done to calculate mean CH in study population. Inter-ocular and gender-wise variability in mean CH was analysed using independent-t test. Pearson correlation coefficient was calculated to study correlation of CH between eyes and with age, gender, IOP-cc and central corneal thickness (CCT). Results: 162 males and 134 females were recruited. The mean age was 37.5±11 years and mean CH in overall study population, males and females were 10.57±1.12, 10.25±0.90, 10.96±1.22 mm Hg. No significant difference in CH, IOP-cc and CCT was observed between eyes. A strong positive correlation was observed in CH between eyes (r=0.75, p<0.001). Conclusions: Mean CH among healthy Indian adult is 10.57±1.12 mm Hg. CH values are higher among females compared to males. CH values between the two eyes in normal individuals are coherent and positively correlated.

Surgical outcomes of trabeculectomy augmented with sub-Tenon injected mitomycin C.

Recently, trabeculectomy with mitomycin C (MMC) where MMC is applied by injection into the Tenon layer has attracted close attention. However, the data on efficacy and safety of this technique is still limited and more clinical studies are needed. Therefore, the work is aimed at comprehensive evaluation of the effectiveness of trabeculectomy using MMC applied by intra-Tenon injection. A set of 50 eyes in 50 patients underwent trabeculectomy using MMC at concentration of 0.4 mg/ml in a total volume of 0.05 ml. The primary end point was to control intraocular pressure (IOP) on postoperative days 1, 8, 30 and 90 and subsequently at 6 and 12 months after surgery. The secondary end point was to evaluate the changes in various corneal parameters prior to and 90 days after surgical procedure. The mean preoperative IOP was 32.34 ± 9.45 mmHg. After surgery, the mean IOP significantly decreased to 17.52 ± 4.58 mmHg at the 90-day follow-up, and to 18.14 ± 3.74 and 19.30 ± 3.82 mmHg at 6 and 12 months after the procedure, respectively. The mean BCVA values remained unchanged compared to baseline (0.77 ± 0.23) to the 90-day follow-up (0.80 ± 0.23). The mean number of anti-glaucoma medications significantly reduced from 3.50 ± 0.74 to 0.58 ± 1.03 postoperatively. Similarly, the mean corneal hysteresis and ACD of the eye as well as CECD were significantly changed postoperatively. Trabeculectomy using MMC applied by injection is a safe and effective surgical method for the treatment of primary and secondary forms of open-angle glaucoma. It has a significant hypotonising effect and allows a complete discontinuation of antiglaucoma drugs (Tab. 3, Fig. 3, Ref. 58).

Evaluation of the corneal biomechanical properties and corneal thickness in patients with Graves' orbitopathy.

To evaluate the corneal biomechanical properties and central corneal thickness in patients with Graves' orbitopathy (GO). A total of 132 eyes of 66 patients with GO and 108 eyes of 54 healthy subjects were enrolled. Eyes with GO were classified as high score clinical activity score (CAS, ≥ 3) (Group 1, n = 64) and low CAS score (< 3) (Group 2, n = 68). Corneal biomechanical parameters [corneal hysteresis (CH), corneal resistance factor (CRF)], Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) levels were measured with Ocular Response Analyzer (ORA, Reichert Ophthalmic Instruments, Buffalo, NY) and compared between the groups. The mean CH values were found as 9.6 ± 1mmHg in Group 1, 10.2 ± 0.9mmHg in Group 2, and 11.4 ± 1.7mmHg in the Control Group (p < 0.001). In post hoc analysis the mean CH was significantly lower in Group 1 than Group 2 and Control Group (Group 1-Group 2, p < 0.001; Group 1-Control Group, p < 0.001). The mean CRF was found as 10.5 ± 2.1 in Group 1, 10.4 ± 2.2 in Group 2, and 10.43 ± 2.0 in the Control group. There was no statistically significant difference between the groups in CRF measurements (p = 0.959). The mean IOPcc values were found as 17.1 ± 3.6mmHg in Group 1, 15.8 ± 4.0mmHg in Group 2 and 15.2 ± 4.1mmHg in the Control Group. The IOPcc and IOPg measurements between all groups were statistically significant (p = 0.009, p = 0.027, respectively). Corneal biomechanical measurements were different in the GO patients with varying CAS scores compared to healthy individuals.

Corneal Biomechanical Parameters after 60-Year-Old.

To determine the distribution of corneal biomechanical parameters in an elderly population. This cross-sectional study was conducted in subjects above 60 years living in Tehran. The participants were selected using multi-stage cluster sampling. Corneal biomechanical parameters were measured in a randomly selected subsample of this population using the Reichert Ocular Response Analyzer (Reichert Ophthalmic Instruments, Inc., Buffalo, NY, USA). Of 470 subjects, the data of 420 participants aged over 60 years were analyzed (mean age: 69.3 ± 6.5 years and range: 61-88 years), 363 (86.4%) of whom were male. The mean and standard deviation of corneal hysteresis (CH) and corneal resistance factor (CRF) were 8.37 ± 1.55 mmHg (95% confidence interval [CI]: 8.02-8.72) and 9.06 ± 1.70 mmHg (95% CI: 8.69-9.44), respectively. The mean CH was 8.27 ± 1.54 mmHg in men and 9.25 ± 1.28 mmHg in women, and the mean CRF was 9.00 ± 1.71 mmHg in men and 9.63 ± 1.37 mmHg in women. According to the results of multiple linear logistic regression analysis, CH had a significant association with younger age (β = -0.05, P = 0.032), female sex (β = 1.83, P < 0.001), reduced maximum keratometry (β = -0.22, P = 0.06), and increased anterior chamber volume (β = 0.01, P = 0.007). CRF had a significant correlation with a younger age (β = -0.06, P = 0.02), female sex (β = 1.01, P = 0.05), central corneal thickness (β = 0.02, P < 0.001), and reduced maximum keratometry (β = -0.39, P = 0.010). The mean CH and CRF values were low in this sample of the Iranian population aged over 60 years indicating the weaker elasticity of the corneal connective tissue.

The Effects of Anti-glaucoma Eyedrops on Corneal Hysteresis in Patients with Open-angle Glaucoma and Glaucoma-suspect

Purpose: We explored the effects of topical anti-glaucoma medications on the corneal biochemical properties of patients with open-angle glaucoma (OAG) and glaucoma suspect (GS patients).Methods: We retrospectively reviewed data on 115 OAG and 98 GS patients (225 and 128 eyes respectively). Corneal hysteresis (CH) was measured using an ocular response analyzer. Factors influencing CH were determined using a generalized estimation equation.Results: The mean CH was lower in OAG than GS patients (p &lt; 0.001). A lower cornea-compensated intraocular pressure, concomitant use of a beta-adrenergic blocker and an alpha2-adrenergic agonist, a higher visual field mean deviation, and a larger central corneal thickness were associated with a higher CH in the OAG group.Conclusions: Concomitant use of a topical beta-adrenergic blocker and an alpha2-adrenergic agonist was associated with a higher CH.

Corneal biomechanical parameters after 60 years old

AbstractPurposeTo determine the distribution of corneal biomechanical parameters in an elderly population and their correlation with some demographic and ocular variables.MethodsThis cross‐sectional study was conducted in subjects above 60 years living in Tehran, Iran. The participants were selected using multi‐stage cluster sampling. All of the subjects underwent optometric and ophthalmic examinations as well as imaging using the Pentacam and IOL Master. Corneal biomechanical parameters were measured in a subsample of this population randomly selected from subjects using the Reichert Ocular Response Analyzer.ResultsOf 470 subjects, the data of 420 participants aged over 60 years were analyzed (mean age = 69.3 ± 6.5 years). The mean corneal hysteresis (CH) and corneal resistance factor (CRF) was 8.37 mmHg (95% CI: 8.02–8.72) and 9.06 mmHg (95% CI: 8.69–9.44), respectively. The mean CH was 8.27 mmHg (95% CI: 7.92–8.62) in men and 9.25 mmHg (95% CI: 8.56–9.93) in women, and the mean CRF was 9.00 mmHg (95% CI: 8.60–9.40) in men and 9.63 mmHg (95% CI: 8.86–9.98) in women. According to the results of multiple linear logistic regression analysis, CH had a significant correlation with younger age (Coefficien = −0.05, p = 0.032), female sex (Coefficien = 1.83, p &lt; 0.001), reduced maximum keratometry (Coefficien = −0.22, p = 0.060), and increased anterior chamber volume (Coefficien = 0.01, p = 0.007). The results also showed that CRF was significantly correlated with a younger age (Coefficien = −0.06, p = 0.022), female sex (Coefficien = 1.01, p = 0.053), central corneal thickness (Coefficien = 0.02, p &lt; 0.001), and reduced maximum keratometry (Coefficien = −0.39, p = 0.010).ConclusionsThe mean CH and CRF were low in the Iranian population aged over 60 years indicating the weaker elasticity of the corneal connective tissue. Advanced age and male sex were associated with a decrease in corneal biomechanical parameters. Due to the relationship between CRF and maximum keratometry, it seems that this parameter can be used to predict keratoconus in the elderly.

Corneal Hysteresis in Thais and Variation of Corneal Hysteresis in Glaucoma.

PurposeTo collect the normal value data of corneal hysteresis in Thais and study the variation of corneal hysteresis in glaucomatous eyes.MethodsRetrospective cross-sectional study of corneal hysteresis (CH) in healthy non-glaucomatous and glaucomatous eyes. Demographic data, type and staging of glaucoma, Goldmann applanation tonometry (GAT) and ocular response analyzer parameters; CH, corneal-compensated intraocular pressure (IOPcc) and Goldmann-correlated intraocular pressure (IOPg) were collected.ResultsData from one eye of 465 normal participants were included for the normal value data of CH. Mean CH, IOPcc and IOPg were 10.18 ± 1.48, 15.01 ± 3.04 and 14.16 ± 3.06 mmHg, respectively. Average age was 57.21 ± 14.4 years. CH at the fifth percentile was 8.0 mmHg. Women had significantly higher CH than men (10.29 ± 1.46 vs 9.90 ± 1.49 mmHg, p=0.009). Moderate negative correlation was found between age and CH, r = −0.338, p<0.001. There were 695 glaucomatous eyes from 429 patients including primary-open angle glaucoma (POAG), primary close-angle glaucoma (PACG), normal tension glaucoma (NTG) and ocular hypertension (OHT). CH in each glaucoma type and severity stage (early, moderate and severe) were as follows: POAG: 8.74 ± 1.52 mmHg (9.22 ± 1.47, 8.74 ± 1.23 and 7.92 ± 1.40 mmHg, p<0.001), PACG: 9.09 ± 1.72 mmHg (9.85 ± 1.45, 9.04 ± 1.68 and 8.45 ± 1.74 mmHg, p= 0.004), NTG: 9.55 ± 1.67 mmHg (9.47 ± 1.38, 9.75 ± 2.42 and 9.77 ± 1.34 mmHg, p 0.525) and OHT: 10.10 ± 1.40 mmHg.ConclusionCompared with normal value data of corneal hysteresis, CH in glaucomatous eyes was lower. The more advanced glaucoma stage was associated with lower CH. Arising from normal value data, a low percentile of CH could be applied as the deviation value from normal and this dynamic property of CH could represent a glaucoma predictor in an effort to improve glaucoma care.

Effects of Corneal Biomechanical Properties on Rebound Tonometry (Icare200) and Applanation Tonometry (Perkins) Readings in Patients With Primary Congenital Glaucoma.

The aim was to assess the influence of corneal biomechanics on intraocular pressure (IOP) measurements made with the Icare200 (IC200) rebound tonometer and the Perkins handheld applanation tonometer in patients with primary congenital glaucoma (PCG). A total of 40 PCG patients and 40 healthy controls, age, and sex-matched, were recruited. IOP was measured with the Ocular Response Analyzer (IOPc, IOPg), IC200 and Perkins. The variables age, IOP, corneal hysteresis (CH), corneal resistance factor (CRF), central corneal thickness (CCT), best-corrected visual acuity, spherical equivalent, medications, and glaucoma surgeries were recorded for each subject. Univariate and multivariate analysis were used to detect effects of variables on IOP measurements. Mean CCT was 545.65±71.88 μm in PCG versus 558.78±27.58 μm in controls (P=0.284). CH and CRF were significantly lower in PCG group than in control group: mean CH 8.11±1.69 versus 11.15±1.63 mm Hg (P<0.001), and mean CRF 9.27±2.35 versus 10.71±1.75 mm Hg (P=0.002). Mean differences between IOP IC200-Perkins were 0.79±0.53 mm Hg in PCG versus 0.80±0.23 mm Hg in controls (P<0.001) and mean differences IC200-IOPc were -0.89±5.15 mm Hg in PCG (P<0.001) versus 1.60±3.03 mm Hg in controls (all P<0.009). Through multivariate analysis, CRF showed positive association and CH negative association with IOP measured with Perkins or IC200 in both subject groups. No association was detected for CCT, age, or sex. CH and CRF were identified as the main factors interfering with IOP measurements made with both tonometers in patients with PCG and healthy controls.

Five-year results of non-penetrating deep sclerectomy with demineralized cancellous bone xenogenically derived collagen glaucoma implant.

To investigate the long-term effectiveness of non-penetrating deep sclerectomy (NPDS) with xenogenically derived cancellous bone collagen glaucoma implant (XCB-CGI) implantation in patients with primary open-angle glaucoma (POAG). Retrospective chart review of patients with POAG stages 2 and 3 was treated with NPDS and XCB-CGI. Follow-up was at 6months, 1, 2, 3, 4 and 5years after surgery. Main outcomes were intraocular pressure (IOP) and medication burden. Secondary outcomes were visual acuity, corneal hysteresis (CH), visual field (VF) and optical coherence tomography (OCT) parameter analysis. Among 71 patients (71 eyes), the mean age was 72.7 ± 9.8. Average initial IOP was 27.7 ± 7.9 and average initial med load was 2.36 ± 0.99. At 6months, 1, 2, 3, 4 and 5years, the average IOP was 14.9 ± 3.3mm Hg (46.2% reduction), 15.3 ± 4.0mm Hg (44.7% reduction), 14.2 ± 3.8mm Hg (48.7% reduction), 15.2 ± 3.3mm Hg (45.0% reduction), 15.5 ± 3.3mm Hg (44.0% reduction) and 14.2 ± 2.8mm Hg (48.7% reduction), respectively. In 5years, the success rate was 34% and 67%, without, and with medications (1.8 ± 0.8 meds required), respectively. Visual acuity was not significantly different (P > .05) at all follow-up visits from baseline. Mean CH increased by 2.1 ± 0.8 (P = .05). No glaucomatous deterioration of the VF and OCT parameters was detected in 56 eyes at the 5-year follow-up. NPDS with XCB-CGI implantation is an effective procedure to normalize the level of IOP, stabilize glaucomatous changes and decrease the number of meds needed for glaucoma control.

Corneal biomechanics in connective tissue disorders

Purpose: The purpose of this study is to determine the corneal biomechanical properties in patients with connective tissue disorders (CTDs) and compare them with age-matched healthy control. Materials and Methods: In this cross-sectional study, 62 patients (study group) with CTDs and 44 healthy patients (control) were analyzed by Ocular Response Analyzer (Reichert Inc., Depew, N. Y., USA) and Corneal Pachymetry (SP-2000, Tomey, Nagoya, Japan). The right eye of all patients was assessed for corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPc), and Goldmann-correlated intraocular pressure (IOPg), and central corneal thickness (CCT). Results: Mean CH (9.54 ± 1.66 mm Hg [study group] and 10.62 ± 1.21 mm Hg [control]; P = 0.013) and mean CRF (9.95 ± 1.47 mm Hg [study group] and 10.76 ± 1.25 mm Hg [control]; P = 0.040) were significantly different between groups. Mean IOPc, IOPg, and CCT were not significantly different between groups. In the subgroup analysis of study cases (oral steroid versus nonsteroid therapy) of CTDs, CRF which was significantly lower in steroid (9.25 mm Hg) compared nonsteroid therapy (10.20 mm Hg) (P = 0.045), whereas, other parameters such as CCT, CH, IOPc, and IOPg were comparable between the two groups (P ≥ 0.05). Conclusion: CH is altered in CTDs which may be an independent risk factor for glaucoma and might underestimate intraocular pressure so CH is an important consideration in patients with CTDs.s

Corneal biomechanical properties in patients with kidney transplant.

PURPOSE:The purpose of the study was to evaluate the corneal biomechanical properties in patients post kidney transplant and to compare them with healthy age-matched control.MATERIALS AND METHODS:In this cross-sectional study, 68 patients with kidney transplant (study group) and 68 healthy individuals (control group) were analyzed with ocular response analyzer measurements. Only the right eye of each participant was assessed for corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPcc), and Goldmann-correlated intraocular pressure (IOPg).RESULTS:The mean CH in the study group was 9.70 ± 1.62 mmHg which was significantly lower than the control group with the mean CH of 10.60 ± 1.49 mmHg (P = 0.001). The mean IOPcc was 18.17 ± 4.00 mmHg and 16.00 ± 3.94 mmHg in the study and control groups, respectively (P = 0.002). CRF and IOPg were not significantly different between groups.CONCLUSION:CH and IOPccare altered in kidney transplant patients.

Evaluation of corneal biomechanical properties on ocular response analyzer and their correlation with the clinical profile of the patients with thyroid-associated ophthalmopathy

ABSTRACT Purpose: The study evaluates the corneal biomechanical properties on Ocular Response Analyzer (ORA) and aims to establish their correlation with the clinical profile of patients with TAO. Methods: A tertiary care centre-based cross-sectional observational study was conducted. Eighty patients with stage I and II TAO (EUGOGO classification), categorized as group A, were age and sex matched with 85 controls constituting group B. The disease activity was assessed using clinical activity score (CAS). The thyroid hormonal profile of within one-week duration was recorded for each patient of group A. Mean IOP-GAT (IOP using Goldmann applanation tonometer), IOPg (Goldmann-correlated IOP value), IOPcc (cornea-compensated IOP value), CRF (corneal resistance factor), and mean corneal hysteresis (CH) of group A and B were compared. The variation of CH with disease severity, activity, and thyroid status in group A was evaluated. Results: Mean GAT, IOPg, and IOPcc of group A were significantly higher than that of group B (p < .001). Mean CH of group A i.e the visco-elastic dampening ability of cornea was significantly lower than that of group B (p < .001). In group A, mean CH of patients with stage 1 disease severity and CAS<3 was significantly higher than that of patients with stage 2 severity and CAS≥3 (p < .001). CH of hyperthyroid patients was significantly lower than CH of hypothyroid patients (p < .01). Conclusion: TAO affects the biomechanical properties of the globe as reflected by the corneal biomechanics on ORA. The disease severity, activity, and hyperthyroid status are negatively correlated with the CH.

Corneal Biomechanical Properties in Childhood Obesity.

To investigate corneal biomechanical properties in patients with childhood obesity. The study included 47 patients with childhood obesity (study group) and 39 healthy patients (control group). Corneal hysteresis, corneal resistance factor, corneal compensated intraocular pressure (IOPcc), and Goldmann-correlated IOP (IOPg) were measured with the Ocular Response Analyzer (Reichert, Ophthalmic Instruments, Buffalo, NY) in each eye. Central corneal thickness (CCT), anterior chamber angle (ACA), anterior chamber volume (ACV), and anterior chamber depth (ACD) measurements were obtained by the Pentacam rotating Scheimpflug camera (Oculus Optikgeräte GmBh, Wetzlar, Germany). The mean corneal hysteresis was 10.56 ± 1.52 mm Hg in the study group and 11.16 ± 1.92 mm Hg in the control group (P = .022). The mean IOP was 14.9 ± 2.0 mm Hg in the study group and 14.1 ± 1.3 mm Hg in the control group (P = .003). Corneal hysteresis showed a significant, positive correlation with corneal resistance factor (P < .001, r = 0.851), IOPg (P = .044, r = 0.213), CCT (P < .001, r = 0.477), and IOP (P = .005, r = 0.295). Corneal hysteresis showed a significant, negative correlation with IOPcc (P = .001, r = -0.355), ACA (P = .005, r = -0.294), ACV (P = .019, r = -0.246), and ACD (P = .046, r = -0.211). Patients with childhood obesity have lower corneal hysteresis and higher IOPcc measurements when compared with healthy patients. Corneal tissue changes may occur in early life in childhood obesity, which could lead to ocular disease in the future. [J Pediatr Ophthalmol Strabismus. 2020;57(2):103-107.].

Study on change in corneal biomechanics and effect of percent tissue altered in myopic laser-assisted in situ keratomileusis.

Purpose:To evaluate corneal biomechanical changes and their correlation with the percentage of tissue altered (PTA) in myopic femtosecond (FS)-flap LASIK.Methods:Prospective longitudinal observational study of 80 eyes of FS LASIK. Demographic details, LASIK parameters, preoperative and postoperative (day 1, month 1, 3, and 6), UCVA, BCVA, refraction, corneal topography, corneal hysteresis (CH), and a corneal resistance factor (CRF) were noted. Change in CH and CRF and its correlation with PTA were analyzed. Data were analyzed in three subgroups [subgroup 1: PTA 23 to <27%; subgroup 2: 27 to <33%; subgroup 3: 33 to <40%].Results:FS LASIK for MRSE - 3.5D ± 1.6D with mean PTA of 31.6 ± 4.4% (range 23.8–39.8%), showed statistically significant decrease in CH and CRF. Mean CH decreased from a preoperative value of 10.4 ± 1.9 to 8.1 ± 1.1; mean CRF from 10.5 ± 1.6 to 7.5 ± 1.3 at 6-months postoperative period, respectively. Mean preoperative CH decreased by 25%, 24%, 23%, and 21% and mean preoperative CRF decreased by 34%, 28%, 28%, and 28% at postoperative day 1, month 1, 3, and 6 follow-ups. Mean CH and CRF showed a significant negative correlation with PTA (CH: r = - 0.33 [P = <0.0001], CRF: r = - 0.34 [P = <0.001]. Subgroup analysis noted greater decrease in CRF and CH in eyes with higher PTA (subgroup 3).Conclusion:Myopic FS LASIK causes a decrease in corneal biomechanics with a significant negative correlation with PTA indicating a greater decrease in corneal biomechanics with higher PTA.

Effects of vitamin D deficiency on intraocular pressure values obtained by ocular response analyzer

AbstarctTo compare corneal biomechanical properties measured with ocular response analyzer (ORA) and intraocular pressure (IOP) measurements in patients with vitamin D deficiency and in healthy cases.One hundred twenty eyes of 120 subjects (between the ages of 19–78) who applied to university outpatient clinic between June 2015 and August 2018 were included in this study, 41 lack of vitamin D (Group 1), 39 insufficient vitamin D (Group 2) and 40 controls (Group 3). The eyes included in the study were randomly chosen. Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann correlated intraocular pressure (IOPg) and corneal compensated intraocular pressure (IOPcc) of patients were measured by ORA. The study protocol had the approval of the university’s ethics committee and complied with the guidelines set forth in the Declaration of Helsinki.The mean ages were 48.9 ± 12.1, 52.8 ± 13.6 and 52.1 ± 13.9 in Group 1, 2 and 3, respectively (p = 0.370). 22 (53.7%) were female, 19 (46.3%) were male in Group 1, 20 (51.3%) were female, 19 (48.7%) were male in Group 2 and 20 (50.0%) were female, 20 (50.0%) were male in Group 3 (p = 0.946). Mean IOPcc values were 16.5 ± 3.6 (8.1–27.3), 16.7 ± 2.7 (12.0–22.7) and 16.3 ± 3.3 (10.8–27.4) mmHg (p = 0.889); mean IOPg values were 16.8 ± 5.0 (6.5–39.5), 16.3 ± 2.9 (10.3–23.0) and 15.9 ± 3.2 (10.0–26.0) mmHg (p = 0.539); mean CH values were 10.8 ± 1.9 (8.3–19.0), 11.4 ± 1.6 (6.9–14.0) and 11.2 ± 1.5 (7.5–13.2; p = 0.257); mean CRF values were 10.5 ± 2.7 (7.4–25.0), 11.1 ± 1.5 (6.8–13.5) and 10.5 ± 1.2 (7.7–12.8; p = 0.282) in Groups 1, 2 and 3, respectively. There was no statistical difference between the groups in terms of IOPcc, IOPg CH and CRF. However, mean CH values were found less in the lack of vitamin D group.In our study, we found that the CH values were lower and the IOPg values were higher in cases of vitamin D deficiency. Corneal biomechanical differences in patients with lack of vitamin D were not statistically significant.

Associations with Corneal Hysteresis in a Population Cohort: Results from 96 010 UK Biobank Participants

To describe the distribution of corneal hysteresis (CH) in a large cohort and explore its associated factors and possible clinical applications. Cross-sectional study within the UK Biobank, a large cohort study in the United Kingdom. We analyzed CH data from 93 345 eligible participants in the UK Biobank cohort, aged 40 to 69 years. All analyses were performed using left eye data. Linear regression models were used to evaluate associations between CH and demographic, lifestyle, ocular, and systemic variables. Piecewise logistic regression models were used to explore the relationship between self-reported glaucoma and CH. Corneal hysteresis (mmHg). The mean CH was 10.6 mmHg (10.4 mmHg in male and 10.8 mmHg in female participants). After adjusting for covariables, CH was significantly negatively associated with male sex, age, black ethnicity, self-reported glaucoma, diastolic blood pressure, and height. Corneal hysteresis was significantly positively associated with smoking, hyperopia, diabetes, systemic lupus erythematosus (SLE), greater deprivation (Townsend index), and Goldmann-correlated intraocular pressure (IOPg). Self-reported glaucoma and CH were significantly associated when CH was less than 10.1 mmHg (odds ratio, 0.86; 95% confidence interval, 0.79-0.94 per mmHg CH increase) after adjusting for covariables. When CH exceeded 10.1 mmHg, there was no significant association between CH and self-reported glaucoma. In our analyses, CH was significantly associated with factors including age, sex, and ethnicity, which should be taken into account when interpreting CH values. In our cohort, lower CH was significantly associated with a higher prevalence of self-reported glaucoma when CH was less than 10.1 mmHg. Corneal hysteresis may serve as a biomarker aiding glaucoma case detection.

Comparative analysis of biomechanical parameters of the corneas following Descemet membrane endothelial keratoplasty and contralateral healthy corneas.

To compare the biomechanical properties of the unilateral operated corneas in patients who had undergone Descemet membrane endothelial keratoplasty (DMEK) for pseudophakic bullous keratopathy (PBK) with those of the contralateral normal corneas. This was a retrospective cohort study conducted at university hospitals (Department of Ophthalmology, Rabin Medical Center, Petach Tikva, Israel, and S. Fyodorov Eye Microsurgery State Institution, Moscow, Russia). Forty eyes of 20 patients who underwent DMEK for unilateral PBK 3.5 to 36months ago and with normal fellow eyes were included in the study. An ocular response analyzer was used to measure the corneal biomechanical properties in the operated and normal fellow eyes. The main outcome measures were corneal hysteresis (CH) and corneal resistance factor (CRF). The mean CH (8.4 ± 1.5mmHg vs. 8.2 ± 1.5mmHg, P = 0.707) and the mean CRF (8.7 ± 1.6mmHg vs. 8.3 ± 1.6mmHg, P = 0.419) values did not show any statistically significant difference between the operated and the normal fellow eyes. In our study, the corneas that underwent DMEK for PBK showed normal values for biomechanical parameters. These findings support the previous studies that have reported near complete visual, functional, and ultra-structural rehabilitation of the corneas following DMEK.

Corneal Biomechanics in Patients with Glaucoma: The Effect of Pupillary Dilatation

\n Aim: In this study, we aimed to evaluate the effect of pupillary dilatation on intraocular pressure values and corneal biomechanical properties using Ocular response analyzer in eyes with primer open angle glaucoma.\n\n Patients and Methods: Goldmann correlated intraocular pressure, corneal corrected intraocular pressure, corneal hysteresis and corneal resistance factor were all respectively evaluated in 28 eyes of 15 patients with primary open angle glaucoma before and 30 minutes after tropicamide 0.5% instillation.\n\n Results: Their mean age was 57.7±13.2 years (range 45–65 years). The mean corneal hysteresis, corneal resistance factor, Goldmann correlated intraocular pressure and corneal corrected intraocular pressure measurements of the eyes were 9.5±2.2 mmHg, 10.1±2.1 mmHg, 16.2±2.8 mmHg, 17.2±3.6 mmHg before tropicamide instillation, and 9.7±2.2 mmHg, 10.1±2.0 mmHg, 16.9±3.5 mmHg, 18.2±4.0 mmHg after tropicamide instillation, respectively. There was statistically significant difference between pre- and post-tropicamide instillation for Goldmann correlated intraocular pressure and corneal corrected intraocular pressure (p=0.043, p=0.015, respectively; paired t-test) while no statistically significant difference was found for corneal hysteresis and corneal resistance factor (p=0.057 p=0.702, respectively; paired t-test ). \n\n Conclusion: Pupillary dilatation with 0.5% tropicamide seems to have a decreasing effect on on intraocular pressure while no effect was noted for corneal biomechanical properties in primer open angle glaucoma patients.\n\n \n\n \n

Intraocular Pressure Based on Dynamic Bidirectional Applanation and Air-puff Tonometry: A Comparative Study.

ABSTRACTAimThe aim of this study is to compare intraocular pressure (IOP) in healthy eyes measured via dynamic bidirectional applanation and air-puff tonometry, and to evaluate the effect of age, gender, the spherical equivalent (SE), mean keratometry (Kmean), corneal hysteresis (CH), and the corneal resistance factor (CRF) on IOP measurements.Materials and methodsIOP measured in 956 healthy eyes using the ocular response analyzer (ORA) and air-puff tonometer was compared in this cross-sectional retrospective study. Correlations between IOP, and age, gender, SE, Kmean, CH, and CRF were investigated using univariate and multivariate analyses. Bland–Altman plots were used to determine the level of agreement between the IOP values obtained with the two devices: IOP via air-puff tonometer (IOP-air-puff) and corneal-compensated IOP (IOPcc) using ORA (ORA-IOPcc). Linear mixed modeling was used to evaluate the effects of the study parameters on IOP. Intermethod reliability was established by calculating intraclass correlation coefficients (r).ResultsThe mean age of the patients was 39.56 ± 14.44 years. The mean IOPair-puff and ORA-IOPcc were 16.72 ± 2.37 mm Hg and 13.75 ± 3.12 mm Hg, respectively (p < 0.001). The mean CH and CRF were 11.14 ± 1.61 mm Hg and 10.53 ± 1.65 mm Hg, respectively. Multivariate analysis showed that both CH and CRF were significantly correlated with IOP-air-puff and ORA-IOPcc (p < 0.001). The 95% limit of agreement for IOP-air-puff and IOPcc was −2.843 to 8.784. There was a significant correlation between IOP-air-puff and ORA-IOPcc (r = 0.443, p < 0.001); the R2 value was 0.196.ConclusionA low degree of agreement was noted between IOP-air-puff and ORA-IOPcc. The present findings show that air-puff tonometry overestimates IOP, as compared to ORA.Clinical significanceIOP based on air-puff tonometry must be interpreted in conjunction with other ophthalmologic findings and the same IOP measuring device should be used for follow-up evaluations.How to cite this articleBahadir Kilavuzoglu AE, Cosar CB, et al. Intraocular Pressure Based on Dynamic Bidirectional Applanation and Air-puff Tonometry: A Comparative Study. J Curr Glaucoma Pract 2019;13(2):68–73.

Evaluation of the Effect of Diabetes Mellitus on Corneal Biomechanics

Background: the cornea exhibits viscoelastic properties, which give it the quality of hysteresis. Corneal hysteresis is an important indicator of the biomechanical properties of the cornea. Aim: to compare the biomechanical properties of the cornea in patients having diabetes mellitus and age matched normal individuals as regards to corneal hysteresis (CH), corneal resistance factor (CRF), Corneal compensated IOP (IOPcc) and Goldman- correlated IOP (IOPg). Patients and Methods: A total of 200 eyes of 100 patients were enrolled in our study. Patients were selected from Ophthalmology outpatient clinics in Minia Health Insurance Hospital – Ophthalmology department. The type of our study is a case-control one. Patients were divided into two equal groups: Group A: included 50 patients (100 eyes) of age matched normal individuals. Group B: included 50 patients (100 eyes) having type 2 diabetes mellitus. Results: mean CH in control group was 9.8±1.3 mm Hg in comparison to mean CH in diabetic group which was 11.9±1.4 mm Hg, which was statistically significantly higher in diabetic patients when compared to control group, (P value = 0.<001). Conclusion: the corneal biomechanics in diabetic group are significantly higher compared with those of the control group.