Influence of age and gender on corneal biomechanical properties in a healthy Italian population

Corneal Biomechanical Changes in Patients with Inherited Retinal Diseases

Purpose

Inherited retinal diseases (IRDs) are a group of degenerative disorders of the retina, that can be potentially associated with changes in the anterior segment, but their prevalence and impact are not known. Exploring these concomitant ophthalmologic changes with biomechanical assessment may help identify other non-retina causes of vision loss in these patients, such as corneal ectasia or susceptibility to glaucoma. This study aimed to measure and compare corneal biomechanics in patients with and without IRDs.

Methods

A total of 77 patients (154 eyes) with IRD were recruited as the study group. The control group consisted of 77 healthy adults (154 eyes) with matched age and sphere equivalents. All participants underwent a comprehensive assessment including corneal tomography (Pentacam®) and biomechanical assessment (Corvis ST®). A total of 4 second-generation biomechanical parameters and 3 indexes were collected: Ambrosio Relational Thickness (ARTh), Deflection Amplitude Ratio Max (DARM), Integrated Radius (IR) and Stiffness Parameter at Applanation (SP-A1), the final deviation value D of the Belin/Ambrosio Enhanced Ectasia Display (BAD-D), Corvis Biomechanical Index (CBI) and Tomographic Biomechanical Index (TBI).

Results

For IRD patients, there was a higher DARM (p < 0.001), lower ARTh (p < 0.001), higher CBI (p < 0.001), higher TBI (p<0.001), and higher BAD-D (p < 0.001) compared to the control group. Regarding discrimination of healthy subjects and IRD patients, ARTh was the most sensitive parameter.

Conclusion

The results showed that IRD patients tend to have softer corneal behaviour, compared to eyes without pathology, which may predispose patients to corneal ectasia or glaucoma development. ARTh could be used to screen IRD patients if a non-retina cause of vision loss is suspected.

Corneal Biomechanical Parameters after 60-Year-Old

Purpose

To determine the distribution of corneal biomechanical parameters in an elderly population.

Methods

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).

Results

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).

Conclusion

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.

Sex-based differences in conjunctival goblet cell responses to pro-inflammatory and pro-resolving mediators

Many conjunctival inflammatory diseases differ between the sexes and altered conjunctival goblet cells (CGCs) response is often involved. Inflammation is initiated by the release of pro-inflammatory mediators and terminated by the biosynthesis of specialized pro-resolution mediators (SPMs). Herein, we determined the sex-based difference in the responses of CGCs to inflammatory stimuli or pro-resolving lipid SPMs and their interaction with sex hormones. GCs were cultured from pieces of human conjunctiva in RPMI media. CGCs were transferred 24 h before the start of experiments to phenol red-free and FBS-free media to minimize exogenous hormones. RT-PCR, immunofluorescence microscopy (IF), and Western Blot (WB) were performed to determine the presence of sex hormone receptors. Cellular response to pro-inflammatory stimuli or SPMs was studied by measuring the increase in intracellular [Ca²⁺] ([Ca²⁺]_i) using fura 2/AM microscopy. Use of RT-PCR demonstrated estrogen receptor (ER) α in 4/5 males and 3/3 females; ERβ in 2/4 males and 2/3 females; and androgen receptors (AR) in 3/3 male and 3/3 female CGCs. Positive immunoreactivity by IF and protein expression by WB was detected using antibodies for the ERα and ERβ in 3/3 males and 3/3 females, while AR were only present in males. Significantly different Ca²⁺ responses between sexes were found with carbachol only at 10^–3 M, but not with histamine or leukotriene (LT) B₄ at any concentration used. Incubation with dihydrotestosterone (DHT), estrone (E1), or estradiol (E2) at 10^–7 M for 30 min significantly inhibited the LTB₄-stimulated [Ca²⁺]_i increase in male and female CGCs. Incubation with DHT, E1, and E2 overnight significantly inhibited the LTB₄ response in females, while DHT and E2 significantly inhibited the LTB₄ response in males. The SPM lipoxin A₄ (LXA₄) (10^–9–10⁻⁸ M), but not the resolvins D1 or D2, induced an [Ca²⁺]_i increase that was significantly higher in males compared to females. We conclude that male and female CGCs showed differences in the expression of sex hormone receptors. Treatment with sex hormones altered pro-inflammatory mediator LTB₄-induced response. Males compared to females have a higher response to the ω-6-fatty acid derived SPM LXA₄, indicating males may terminate inflammation in conjunctival goblet cells faster than females.

Double safe suture during cataract surgery on post radial keratotomy patients using clear corneal incisions

PURPOSE

the aim of this study is to find a safer surgical approach in cataract surgery on eyes previously treated with radial keratotomy using clear corneal incisions.

SETTING

Department of Biomedical and Dental Sciences and Morphofunctional Imaging, Ophthalmology Clinic, University of Messina, Messina, Italy.

DESIGN

Prospective study.

METHODS

A prospective study was conducted on a group of 20 patients, 21 eyes with 16 RK incisions were evaluated for cataract phacoemulsification. Samples were divided into two groups: Group 1 underwent surgery with pre-operative one corneal stitch along radial keratotomy incisions near the main access site whereas Group 2 underwent modified surgery with two corneal stitches.

RESULTS

After surgery, visual acuity, corneal hysteresis and corneal strength was evaluated. In all cases, an increased visual acuity was observed. Group 1 showed an UCVA of logMAR 0.22 ± 0.14, while group 2 presented a logMAR of 0.1 ± 0.07. Data did not show a statistically significant difference in UCVA after surgery between the two groups (P = 0.133). Instead, a significant difference in corneal hysteresis (CH), respectively with values of 8.65 ± 1.6 mmHg in group 1 and 9.2 ± 1.8 in group 2 (P = 0.031), and a corneal resistance factor (CRF) with values of 7.87 ± 1.4 mmHg in the first group and 8.65 ± 1.6 mmHg in the second one (P = 0.039) was observed.

CONCLUSIONS

Double safe suture technique offers better stabilization of corneal structure during surgery in patients preventively treated with 16 incisions RK.

Corneal-compensated intraocular pressure, Goldmann-correlated intraocular pressure and their associated factors in the geriatric population, a population-based study

PURPOSE

To determine the distribution of corneal-compensated intraocular pressure (IOPcc), Goldmann-correlated intraocular pressure (IOPg) and their associated factors in a geriatric population.

METHODS

The present cross-sectional study was performed in individuals above 60 years of age in Tehran, the capital of Iran. The sampling was performed using multi-stage random cluster sampling method. All participants underwent preliminary ocular examinations, and then imaging by Pentacam HR and IOL master 500. Measurement of IOPg, IOPcc, and corneal biomechanical indices including corneal hysteresis (CH) and corneal resistant factor (CRF) was performed in a random sub-sample using ocular response analyzer (ORA).

RESULTS

The mean IOPg and IOPcc were 16.76 ± 4.71 mmHg and 19.05 ± 4.67 mmHg, respectively. There were no statistically significant differences in both IOPg (p = 0.891) and IOPcc (p = 0.248) between males and females. Based on the multiple linear regression models, both IOPg and IOPcc showed a statistically significant direct relationship with CRF (P < 0.001) and a significant inverse relationship with CH (P < 0.001 for IOPg and IOPcc), anterior chamber angle (ACA) (p = 0.006 for IOPg and p = 0.017 for IOPcc), and spherical equivalent refractive error (p = 0.032 for IOPg and p = 0.046 for IOPcc).

CONCLUSION

Mean IOPg and IOPcc in the present study were higher compared to most previous studies. Corneal biomechanical indices including CH and CRF, refractive error and anterior chamber angle were independent associated factors of IOPg and IOPcc in the present study. There was no significant relationship between ORA-derived IOP values and CCT.

Associated factors and distribution of posterior corneal astigmatism in a middle-aged population

CLINICAL RELEVANCE

Posterior corneal astigmatism has an important role in diagnosis and treatment of astigmatism, but it is usually overlooked.

BACKGROUND

This cross-sectional study aimed to investigate the distribution of posterior corneal astigmatism (PCA) and its associated factors in a middle-aged population that participated in the Shahroud Eye Cohort Study (ShECS) phase II.

METHODS

Anterior corneal astigmatism (ACA) and PCA values were measured using rotating Scheimpflug System (Pentacam HR, Oculus). With-the-rule (WTR) astigmatism was considered when the steepest corneal meridian was aligned within 90° ± 30°, and against-the-rule (ATR) astigmatism when the steepest meridian was 0 ± 30°. All the remaining values were considered as oblique astigmatism. Logistic regression models were used for evaluating the association of PCA magnitudes with other factors.

RESULTS

The current study consisted of 3871 eyes with available Pentacam data. Mean age of participants was 55.4 ± 6.1 years and 1557 (40.2%) subjects were male. Means of ACA and PCA were 0.77 ± 0.67 and -0.24 ± 0.15 D, respectively. The majority of PCA consisted of WTR astigmatism (82.43%), while ACA mostly showed ATR astigmatism (55.46%). PCA > 0.3 D was associated with male sex (OR = 1.16, P-value = 0.028) and spherical equivalent (OR = 0.93, P-value = 0.011) in the adjusted model, while PCA > 0.5 dioptre was strongly associated with myopia (OR = 4.6, P-value < 0.001).

CONCLUSION

The most common forms of ACA and PCA in middle-aged Iranian adults were ATR and WTR, respectively. While the shape of posterior corneal surface remained mostly unchanged across ages of 45 to 69 years, ACA was associated with a decrease in ATR proportion. Moreover, the most significant factors associated with higher magnitudes of PCA were male sex and myopia.

Corneal Biomechanical Parameters and Central Corneal Thickness in Glaucoma Patients, Glaucoma Suspects, and a Healthy Population

PURPOSE

To evaluate and compare corneal hysteresis (CH), corneal resistance factor (CRF), and central corneal thickness (CCT), measurements were taken between a healthy population (controls), patients diagnosed with glaucoma (DG), and glaucoma suspect patients due to ocular hypertension (OHT), family history of glaucoma (FHG), or glaucoma-like optic discs (GLD). Additionally, Goldmann-correlated intraocular pressure (IOPg) and corneal-compensated IOP (IOPcc) were compared between the different groups of patients.

METHODS

In this prospective analytical-observational study, a total of 1065 patients (one eye of each) were recruited to undergo Ocular Response Analyzer (ORA) testing, ultrasound pachymetry, and clinical examination. Corneal biomechanical parameters (CH, CRF), CCT, IOPg, and IOPcc were measured in the control group (n = 574) and the other groups: DG (n = 147), FHG (n = 78), GLD (n = 90), and OHT (n = 176). We performed a variance analysis (ANOVA) for all the dependent variables according to the different diagnostic categories with multiple comparisons to identify the differences between the diagnostic categories, deeming p < 0.05 as statistically significant.

RESULTS

The mean CH in the DG group (9.69 mmHg) was significantly lower compared to controls (10.75 mmHg; mean difference 1.05, p < 0.001), FHG (10.70 mmHg; mean difference 1.00, p < 0.05), GLD (10.63 mmHg; mean difference 0.93, p < 0.05) and OHT (10.54 mmHg; mean difference 0.84, p < 0.05). No glaucoma suspects (FHG, GLD, OHT groups) presented significant differences between themselves and the control group (p = 1.00). No statistically significant differences were found in the mean CRF between DG (11.18 mmHg) and the control group (10.75 mmHg; mean difference 0.42, p = 0.40). The FHG and OHT groups showed significantly higher mean CRF values (12.32 and 12.41 mmHg, respectively) than the DG group (11.18 mmHg), with mean differences of 1.13 (p < 0.05) and 1.22 (p < 0.001), respectively. No statistically significant differences were found in CCT in the analysis between DG (562 μ) and the other groups (control = 556 μ, FHG = 576 μ, GLD = 569 μ, OHT = 570 μ). The means of IOPg and IOPcc values were higher in the DG patient and suspect groups than in the control group, with statistically significant differences in all groups (p < 0.001).

CONCLUSION

This study presents corneal biomechanical values (CH, CRF), CCT, IOPg, and IOPcc for diagnosed glaucoma patients, three suspected glaucoma groups, and a healthy population, using the ORA. Mean CH values were markedly lower in the DG group (diagnosed with glaucoma damage) compared to the other groups. No significant difference was found in CCT between the DG and control groups. Unexpectedly, CRF showed higher values in all groups than in the control group, but the difference was only statistically significant in the suspect groups (FHG, GLD, and OHT), not in the DG group.

Predictors of Myopic Regression for Laser-assisted Subepithelial Keratomileusis and Laser-assisted in Situ Keratomileusis Flap Creation with Mechanical Microkeratome and Femtosecond Laser in Low and Moderate Myopia

Purpose: To determine the predictive factors of postoperative myopic regression in subjects who have undergone laser-assisted subepithelial keratomileusis (LASEK), laser-assisted in situ keratomileusis (LASIK) with flaps created using a mechanical microkeratome (MM) or LASIK with flaps created using a femtosecond (FS) laser for -0.50 D to -6.0 D myopia.Materials and Methods: This study was designed as a retrospective comparison. We included 236 eyes in the LASEK group, 1,178 eyes in the MM-LASIK group and 1,333 eyes in the FS-LASIK group. Refractive outcomes were recorded at one day; one week; and one, three, six and 12 months postoperatively. Predictors affecting myopic regression and other covariates were estimated using a Cox proportional hazards model for the three methods of surgery.Results: At 12 months, the survival rates (no myopic regression) were 63.36%, 74% and 77% in the MM-LASIK, LASEK, and FS-LASIK groups, respectively. Risk factors for myopic regression were indicated for patients with greater preoperative central corneal thicknesses (CCT) (P = .02), female patients (P < .01), patients with aspherical ablations (P = .01) and those with larger transitional zones (TZ) (P < .01). Among the three surgeries, MM-LASIK had a significantly higher probability of postoperative myopic regression (P < .01). Longer durations of myopia (P = .03), steeper corneal curvatures (K_max) (P < .01) and larger optical zones (OZ) (P < .01) were protective factors.Conclusion: MM-LASIK had the highest risk for myopic regression. OZ, TZ, aspherical ablations, preoperative corneal curvatures and being a female patient had significant influence on myopic regression in -0.50 D to -6.0 D myopia.

The Mechanical Interpretation of Ocular Response Analyzer Parameters

Purpose

Ocular Response Analyzer (ORA) is one of the most widely used devices in clinic, while the mechanical interpretations of parameters obtained from ORA have not been understood completely. The aim of this research is to explore the mechanical interpretation of ORA parameters.

Methods

Rabbits aged 3-24 months were measured with ORA in vivo and corneal strips uniaxial tensile tests to get ORA parameters and corneal biomechanical parameters (corneal elastic modulus, relaxation time, and relaxation limit). The mechanical interpretation of ORA parameters was cognized preliminarily by analyzing the correlation between ORA parameters and corneal biomechanical parameters. On the other hand, finite element method was applied to simulate ORA measurements with different corneal biomechanical parameters to obtain quantitative relationship between ORA parameters and corneal biomechanical parameters further.

Results

Biomechanical experimental results showed that Corneal Resistance Factor (CRF) was correlated with corneal elastic modulus and relaxation limit significantly, while the significant correlations between Corneal Hysteresis (CH) and corneal biomechanical parameters were not observed. Results of finite element analysis showed that both CH and CRF were correlated with corneal elastic modulus, relaxation limit, and relaxation time significantly. Besides, corneal elastic modulus was positively correlated with upslop1 and upslop2 and negatively correlated with w2.

Conclusions

For all ORA parameters, CH, CRF, the upslope, and the width of the peaks are parameters which may reflect corneal elastic properties. It is viable to cognize mechanical interpretation of ORA parameters by the comparisons of the data from ORA and biomechanical tests of rabbits with different ages and the simulations of ORA based on finite element methods. Further studies are needed to confirm the mechanical interpretation.

Corneal and Anterior Chamber Morphology in Human Immunodeficiency Virus-1-Infected Patients Without Opportunistic Infections

OBJECTIVES

To evaluate corneal and anterior chamber morphology as measured by Pentacam HR in human immunodeficiency virus (HIV)-infected patients without opportunistic infections and to search for signs of accelerated aging.

METHODS

This prospective study included 41 eyes of 41 HIV-1-infected patients (study group) and 50 eyes of 50 healthy subjects (control group). Specular microscope and Pentacam HR were used for corneal and anterior chamber morphology evaluation. Corneal endothelial cell density (CECD), hexagonal cell ratio, coefficient of variation, corneal thickness, density and volume, maximum keratometry, anterior chamber volume (ACV), and anterior chamber depth (ACD) measurements were recorded for analysis.

RESULTS

The mean CD4 count was 428.3±231.9 (36-950) cells/mL, and the time since diagnosis was 27.5±34.1 months in the study group. The difference in anterior segment parameters was not significantly different between the study and the control groups (P>0.05). Age significantly correlated with CECD (r=-0.436, P=0.004), ACV (r=-0.570, P<0.001), ACD (r=-0.471, P=0.002), and corneal density (r=0.424, P=0.006) in the study group, whereas it did not show a significant correlation with any ocular parameters in the control group (Pearson correlation).

CONCLUSION

Corneal density, CECD, ACV, and ACD showed significant correlation with age in HIV-1-infected patients. Further studies are needed to show whether ocular parameters may serve as useful tools to monitor HIV-related accelerated aging.

Corneal Biomechanical Properties of Keratoconic Eyes Following Penetrating Keratoplasty

Objectives

To investigate the corneal biomechanical properties of keratoconic eyes following penetrating keratoplasty (PKP).

Materials and Methods

Thirty-five patients (70 eyes) were enrolled to this prospective study. Operated and contralateral keratoconic eyes were defined as Group 1 and 2, respectively. All patients underwent ophthalmological examination and measurements of corneal biomechanical properties by Ocular Response Analyzer (ORA), intraocular pressure (IOP) by Goldmann applanation tonometry, and central corneal thickness (CCT) by Pentacam. Shapiro-Wilk W test was performed to test normality of the data. The statistical significance was evaluated with the paired t-test and Wilcoxon signed ranks test. Pearson correlation and Spearman rho tests were used for correlation analysis.

Results

The average age and male/female ratio were 31.34±11.65 (15-60) years and 21/14, respectively. The mean values of the data obtained from Group 1 and 2 respectively were: corneal hysteresis (CH): 9.35±1.66, 8.18±1.84 mmHg (p=0.013), corneal resistance factor (CRF): 9.48±1.96, 7.14±2.05 mmHg (p<0.001), IOPcc: 16.90±4.32, 14.26±3.69 mmHg (p=0.004), IOPg: 15.45±4.61, 10.91±3.97 mmHg (p<0.001), IOPapl: 14.26±3.11, 13.09±2.54 mmHg (p=0.046), and central corneal thickness (CCT): 545.64±60.82, 442.60±68.14 μM (p<0.001). The positive correlation between CH and CRF was moderate (r=0.444) in Group 1 and strong (r=0.770) in Group 2. There was a moderate negative correlation between CH and IOPcc in both groups (r=-0.426, r=-0.423), but CH was not correlated with IOPg or IOPapl in either group. There were weak to strong positive correlations between CRF and all IOP values in both groups. There was no correlation between CRF and CCT in Group 1 (r=0.075) and a very weak correlation in Group 2 (r=0.237). Only IOPcc and IOPg were strongly correlated in both groups.

Conclusion

Better understanding of corneal biomechanical properties is essential for elucidating the pathophysiology and diagnosis of several corneal pathologies such as keratoconus. The biomechanical properties of keratoconic eyes seem to be closer to normal values after PKP.

Corneal hysteresis and anterior segment optical coherence tomography anatomical parameters in primary angle closure suspects

IMPORTANCE

Corneal hysteresis (CH) is a dynamic marker of structural and functional changes in the cornea associated with intraocular pressure (IOP) and central corneal thickness, but its utility in assessing primary angle closure suspects (PACS) has not been fully elucidated.

BACKGROUND

This study assesses if anterior segment measurements correlate with CH in PACS patients.

DESIGN

IRB-approved retrospective review of imaging and records at a university practice.

PARTICIPANTS

Sixty-three eyes from 37 patients diagnosed as PACS, without other ocular pathology.

METHODS

Every eye underwent measurements including: ocular response analyzer (ORA), anterior segment optical coherence tomography (OCT) and a clinical evaluation. ORA measurements were correlated with other anatomic parameters using a mixed effects multivariable linear regression framework.

MAIN OUTCOME MEASURES

ORA measurements included: CH, corneal resistance factor, Goldmann IOP (IOP_g ) and corneal compensated IOP (IOP_cc ). Anterior segment OCT measurements included: central corneal thickness (CCT_OCT ), nasal and temporal peripheral corneal thicknesses (PCT1 and PCT2), anterior chamber depth (ACD), nasal angle to temporal angle distance (ATA) and temporal and nasal angle measurements. Clinical measurements included: central corneal thickness via pachymetry, IOP measured by Goldmann applanation, axial length by A-scan ultrasound and spherical equivalent.

RESULTS

CH was negatively correlated with IOP_cc, and ACD CH was positively correlated with CCT_OCT , CCT_p , CRF, PCT1 and PCT2. Females were found to have lower CH. In multivariable regression controlling for gender, CCT, PCT, IOP and ACD, no correlation was seen between CH and anatomic measurements.

CONCLUSIONS AND RELEVANCE

CH values in PACS do not correlate with anterior segment anatomy.

Age-related change in corneal biomechanical parameters in a healthy Caucasian population

PURPOSE

To determine the effect of aging on corneal biomechanical parameters measured via ocular response analyzer in a homogenous healthy Caucasian population.

METHODS

A total of 2039 Caucasian adults were consecutively recruited and divided into seven groups according to decades of age. The difference in mean corneal hysteresis (CH), mean corneal resistance factor (CRF), mean Goldmann-correlated intraocular pressure (IOPg), and mean corneal-compensated IOP (IOPcc) between decades of age were investigated. The strength of the correlations between corneal biomechanical parameters, and between each biomechanical parameter and age were evaluated. The effect of age on each corneal biomechanical parameter was analyzed.

RESULTS

Mean age of the participants (1173 female and 866 male) was 43.30 ± 14.64 years. Mean CH, CRF, IOPcc, and IOPg were 11.49 ± 1.89 mmHg, 11.40 ± 2.30 mmHg, 15.01 ± 3.11 mmHg, and 15.72 ± 3.80 mmHg, respectively. There were significant differences in mean CH, CRF, IOPcc, and IOPg between groups (p < 0.001 for all parameters). There was a significant negative correlation between age and CH (r = -0.067 and p = 0.003), and a significant negative correlation between age and CRF (r = -0.053 and p = 0.017). There was a significant positive correlation between age and IOPg (r = 0.25 and p < 0.001), and between age and IOPcc (r = 0.20 and p < 0.001). Linear regression analysis showed that for every 1-year increase CH decreased 0.011 mmHg, CRF decreased 0.004 mmHg, IOPcc increased 0.053 mmHg, and IOPg increased 0.047 mmHg.

CONCLUSIONS

Aging can cause significant changes in corneal biomechanical parameters. Corneal biomechanical parameters were correlated with each other, and each was correlated with aging.

Age-Related Variations of Rabbit Corneal Geometrical and Clinical Biomechanical Parameters

Purpose

To study the variations in corneal clinical biomechanical parameters (CCBP) and corneal geometrical parameters of rabbit in relation to age.

Methods

Rabbits aged 3, 7, 12, 18, and 24 months were enrolled. Each eye of the rabbits was tested with Ocular Response Analyzer (ORA), Optical Coherence Tomography (OCT), and Pachymeter to obtain the intraocular pressure (IOP): Goldmann-correlated IOP (IOPg) and Corneal Compensated Intraocular Pressure (IOPcc); CCBP: Corneal Hysteresis (CH) and Corneal Resistance Factor (CRF); corneal geometric parameters: corneal curvature radius (CCR) and central corneal thickness (CCT).

Results

The IOP of the rabbits changes slightly from 3 to 7 months of age, while it significantly decreases from 7 to 18 months of age and increases from 18 to 24 months of age; CH and CRF decrease with the increase of age; CCT increases from 7 to 18 months and decreases from 3 to 7 months of age and from 18 to 24 months of age; CCR presents an upward trend from 3 to 18 months and a significant decrease between 18 and 24 months of age.

Conclusion

CH and CRF are negatively correlated with age. CCT and CCR are positively correlated with age.

TFOS DEWS II Sex, Gender, and Hormones Report

One of the most compelling features of dry eye disease (DED) is that it occurs more frequently in women than men. In fact, the female sex is a significant risk factor for the development of DED. This sex-related difference in DED prevalence is attributed in large part to the effects of sex steroids (e.g. androgens, estrogens), hypothalamic-pituitary hormones, glucocorticoids, insulin, insulin-like growth factor 1 and thyroid hormones, as well as to the sex chromosome complement, sex-specific autosomal factors and epigenetics (e.g. microRNAs). In addition to sex, gender also appears to be a risk factor for DED. "Gender" and "sex" are words that are often used interchangeably, but they have distinct meanings. "Gender" refers to a person's self-representation as a man or woman, whereas "sex" distinguishes males and females based on their biological characteristics. Both gender and sex affect DED risk, presentation of the disease, immune responses, pain, care-seeking behaviors, service utilization, and myriad other facets of eye health. Overall, sex, gender and hormones play a major role in the regulation of ocular surface and adnexal tissues, and in the difference in DED prevalence between women and men. The purpose of this Subcommittee report is to review and critique the nature of this role, as well as to recommend areas for future research to advance our understanding of the interrelationships between sex, gender, hormones and DED.

Cataract surgery on post radial keratotomy patients

This study aims to evaluate and to compare three different approaches of cataract surgery to patients with previous radial keratotomy (RK), and to analyze the mechanical properties of the cornea after cataract surgery. Three groups of patients, each one including 8 eyes of patients with 16 RK incisions. The first group includes eyes with the first cataract incision superiorly, the second group in the temporal area, the third group in temporal area and a precautionary stabilizing suture across the RK incision adjacent to the main tunnel. In the first group intraoperative dehiscence occurred in three eyes (37.5%): it required immediate application of a suture. In the second group dehiscence occurred intraoperatively in two radial scars (20%): it required immediate application of a suture. In the third group, no intraoperative dehiscences were observed. The stabilizing suture of the RK incision works safer, with a lower risk of dehiscences and less post-operative astigmatism.

Agreement among Goldmann applanation tonometer, iCare, and Icare PRO rebound tonometers; non-contact tonometer; and Tonopen XL in healthy elderly subjects

PURPOSE

To evaluate the inter-device agreement among the Goldmann applanation tonometer (GAT), iCare and Icare PRO rebound tonometers, non-contact tonometer (NCT), and Tonopen XL tonometer.

METHODS

Sixty healthy elderly subjects were enrolled. The intraocular pressure (IOP) in each subject's right eye was measured thrice using each of the five tonometers. Intra-device agreement was evaluated by calculating intraclass correlation coefficients (ICCs). Inter-device agreement was evaluated by ICC and Bland-Altman analyses.

RESULTS

ICCs for intra-device agreement for each tonometer were >0.8. IOP as measured by iCare (mean ± SD, 11.6 ± 2.5 mmHg) was significantly lower (p < 0.05) than that measured by GAT (14.0 ± 2.8 mmHg), NCT (13.6 ± 2.5 mmHg), Tonopen XL (13.7 ± 4.1 mmHg), and Icare PRO (12.6 ± 2.2 mmHg; Bonferroni test). There was no significant difference in mean IOP among GAT, NCT, and Tonopen XL. Regarding inter-device agreement, ICC was lower between Tonopen XL and other tonometers (all ICCs < 0.4). However, ICCs of GAT, iCare, Icare PRO, and NCT showed good agreement (0.576-0.700). The Bland-Altman analysis revealed that the width of the 95% limits of agreement was larger between the Tonopen XL and the other tonometers ranged from 14.94 to 16.47 mmHg. Among the other tonometers, however, the widths of 95% limits of agreement ranged from 7.91 to 9.24 mmHg.

CONCLUSION

There was good inter-device agreement among GAT, rebound tonometers, and NCT. Tonopen XL shows the worst agreement with the other tonometers; therefore, we should pay attention to its' respective IOP.

CLINICAL TRIAL REGISTRATION

Japan Clinical Trials Register; number: UMIN000011544.

Distribution of the anterior, posterior, and total corneal astigmatism in healthy eyes

PURPOSE

To evaluate the magnitude and axis orientation of the anterior, posterior, and total corneal astigmatism in normal healthy eyes of an Iranian population.

METHODS

In a prospective cross-sectional study, ophthalmic and anterior segment parameters of 153 healthy eyes of 153 subjects were evaluated by Galilei dual Scheimpflug analyzer. The magnitude and axis orientation [with-the-rule (WTR), against-the-rule (ATR), and oblique] of the anterior, posterior, and total corneal astigmatism measurements (ACA, PCA, and TCA) were compared according to the age, sex, and other ophthalmic parameters.

RESULTS

The mean ± SD age of the study population was 30 ± 5.9 years. The mean magnitude was 1.09 ± 0.76 diopters (D) for ACA, 0.30 ± 0.13 D for PCA, and 1.08 ± 0.77 D for TCA. Males had a significantly higher magnitude of PCA than females (p = 0.041). Most eyes had a WTR anterior astigmatism and an ATR posterior astigmatism. The WTR astigmatism had a higher mean magnitude compared to the ATR and oblique astigmatism in all the astigmatism groups, with a significant difference in the ACA and TCA groups (p < 0.05). PCA magnitude exceeded 0.50 D in only 7.8% of the subjects. ACA, PCA, and TCA were significantly correlated with each other and also had a significant correlation with the anterior and posterior maximum corneal elevation measurements (p < 0.001).

CONCLUSION

The results of this study although are limited due to the small number of participants and confined to our demographics, provided information regarding a population that was not described before and may be helpful in obtaining optimum results in astigmatism correction in refractive surgery or designing new intraocular lenses.

Differences in Corneal Biomechanics in Nonpenetrating Deep Sclerectomy and Deep Sclerectomy Reconverted into Trabeculectomy

PURPOSE

To evaluate the differences in intraocular pressure (IOP) and in corneal biomechanics in eyes with uneventful nonpenetrating deep sclerectomy (NPDS) in 1 eye and with intended deep sclerectomy reconverted into trabeculectomy (RIT) in the fellow eye of the same patient.

PARTICIPANTS

Forty eyes of 20 patients with both types of glaucoma surgery and more than 6 months of follow-up, and 31 eyes of 50 controls.

METHODS

IOP was assessed with Goldmann applanation tonometry (GAT), ocular response analizer (ORA), and dynamic contour tonometer (DCT). Student t test for independent samples and a univariate generalized estimating equations model were used to analyze the results.

MAIN OUTCOME MEASURES

Overall, no significant differences were found between IOP of NPDS and RIT eyes when measured with 3 tonometers.

RESULTS

Although NPDS showed lower values of IOP measured with GAT and ORA, RIT presented lower IOP if DCT is the chosen tonometry. Biomechanically, NPDS eyes had higher corneal hysteresis (CH) and corneal resistance factor (CRF). When compared with control patients, eyes that underwent glaucoma surgery had lower IOP using GAT, DCT and ORA (P<0.001, 0.315, and 0.260, respectively), and lower CRF (P<0.001).

CONCLUSIONS

Eyes with NPDS tended to have higher values of CH and CRF and lower IOP than RIT eyes, as measured with 3 of 4 tonometry methods; these differences did not reach statistical significance.

Corneal Biomechanics Determination in Healthy Myopic Subjects

Purpose. To determine the corneal biomechanical properties by using the Ocular Response Analyzer™ and to investigate potential factors associated with the corneal biomechanics in healthy myopic subjects. Methods. 135 eyes from 135 healthy myopic subjects were included in this cross-sectional observational study. Cornea hysteresis (CH), corneal resistance factor (CRF), cornea-compensated intraocular pressure (IOPcc), and Goldmann-correlated intraocular pressure (IOPg) were determined with the Reichert Ocular Response Analyzer (ORA). Univariate and multivariate regression analyses were performed to investigate factors associated with corneal biomechanics. Results. The mean CH and CRF were 9.82 ± 1.34 mmHg and 9.64 ± 1.57 mmHg, respectively. In univariate regression analysis, CH was significantly correlated with axial length, refraction, central corneal thickness (CCT), and IOPg (r = −0.27, 0.23, 0.45, and 0.21, resp.; all with p ≤ 0.015), but not with corneal curvature or age; CRF was significantly correlated with CCT and IOPg (r = 0.52 and 0.70, resp.; all with p < 0.001), but not with axial length/refraction, corneal curvature, or age. In multivariate regression analysis, axial length, IOPcc, and CCT were found to be independently associated with CH, while CCT and IOPg were associated with CRF. Conclusions. Both CH and CRF were positively correlated with CCT. Lower CH but not CRF was associated with increasing degree of myopia. Evaluation of corneal biomechanical properties should take CCT and myopic status into consideration.