Distribution of central corneal thickness and its association with ocular parameters in a large central European cohort: the Gutenberg health study

Change of Intraocular Pressure Over 5 Years and its Relationship to Cardiovascular Parameters: Results From the Gutenberg Health Study

Purpose

To investigate the longitudinal change in intraocular pressure (IOP) over 5 years and its relationship with cardiovascular parameters in a population-based sample in Germany.

Methods

The Gutenberg Health Study is a prospective, observational, single-center cohort study. The sample was equally stratified for sex, residence, and age decade. IOP was measured with noncontact tonometry at baseline and at 5-year follow-up. Cardiovascular parameters, including body mass index (BMI), systolic blood pressure, and diabetes status, were assessed. Participants without IOP measurement at one time point, who were taking IOP-lowering medications, or who had ophthalmic surgery during the 5-year follow-up interval were excluded, as well as those with glaucoma diagnosis. Univariable and multivariable linear regression analyses were conducted.

Results

This analysis included 9633 participants (48.9% female). The mean IOP increased from 14.04 ± 2.78 mmHg at baseline to 14.77 ± 2.92 mmHg at 5-year follow-up (P < 0.001). In multivariable linear regression analyses, an increase in BMI was associated with an increase in IOP over time (P < 0.001), whereas a higher baseline BMI was associated with a lower IOP change (P < 0.001). Higher age and male sex were associated with higher IOP change (P < 0.001). A change in systolic blood pressure was associated with IOP change, whereas baseline systolic blood pressure and diabetes status were not associated.

Conclusions

This population-based study found a relationship between IOP change over 5 years and BMI and systolic blood pressure change, respectively. These findings suggest the importance of monitoring cardiovascular risk factors in IOP management.

Metabolic syndrome as an independent risk factor for glaucoma: a nationally representative study

BACKGROUND

Central insulin resistance contributes to glaucoma development. Given the close association between metabolic syndrome MetS and insulin resistance, this study aimed to determine whether MetS is associated with glaucoma risk.

METHODS

We analyzed data from 11,499 adults aged ≥ 19 years in the 2019-2021 Korean National Health and Nutrition Examination Survey and applied sampling weights to represent the general Korean population. Participants were classified into groups with or without MetS. Ocular hypertension (HTN) was defined as intraocular pressure > 21 mmHg. Primary open-angle glaucoma (POAG) was diagnosed based on the results of a visual field test and optical coherence tomography using the criteria published by the International Society for Geographic and Epidemiological Ophthalmology. We further divided POAG into normal tension (NTG) and POAG with ocular HTN. A spline curve was drawn to determine the dose-response relationship between the number of MetS components and risk of POAG. Odds ratios (ORs) with 95% confidence interval (CI) for POAG according to MetS status were estimated using weighted logistic regression analyses.

RESULTS

The prevalence of POAG was 5.7% and 3.5%, respectively, in groups with and without MetS. We identified a dose-response relationship between the number of MetS components and risk of POAG. Unadjusted ORs (95% CI) for POAG in the group with MetS was 1.85 (1.52-2.25), compared with those without MetS. The trends persisted in adjusted models. The fully-adjusted OR (95% CI) for POAG was 1.47 (1.04-2.09) in the group with MetS. Subgroup analysis revealed that a significant relationship remained only in the NTG group (fully adjusted OR, 1.50; 95% CI 1.05-2.15).

CONCLUSIONS

A comprehensive ophthalmological assessment should be considered for persons with MetS who are at increased risk of POAG, particularly NTG.

Ocular Dominance and Its Association With Central Corneal Thickness: An Observational Study in Central India

Background The aim of this study is to determine ocular dominance and its association with central corneal thickness (CCT). These two parameters are of great significance in clinical practice; identifying the dominant eye helps in planning cataract surgeries, treatment of presbyopia, monovision correction, etc., and assessing the CCT helps in early diagnosis and management of keratoconus, glaucoma, contact lens-related complications, and dry eye. Methods A cross-sectional study that involves patients and volunteers who have come for a checkup to the ophthalmology department of the college hospital. Ninety patients were examined for this study within two months. The hole-in-card test is performed to determine the ocular dominance in people with normal and healthy eyes without any pathologies except refractive errors. Specular microscopy through a non-contact modality will be done to assess the thickness of the central cornea in both eyes. Statistical analysis was done using the paired t-test to compare the patient's eyes and the chi-square test, which helps us associate ocular dominance and CCT.  Results Right eye dominance was seen in the majority of the participants (72.91%), whereas left eye dominance was seen in comparatively fewer participants (27.08%). The CCT of the dominant eye is found to be 520.40 ± 29.83 μm and that of the non-dominant eye is 524.40 ± 29.37 μm. A lower CCT in the dominant eye was seen in 83.33% of the subjects; 14.58% of them had a higher CCT in the dominant eye and 2.08% had the same CCT in both eyes. Conclusion From the observational study that has been made, the majority of the population shows right eye dominance. The CCT is relatively thinner in the dominant eye. About 80-85% of the examined people showed a thinner cornea in the dominant eye. But we cannot generalize that the eye with a lesser corneal thickness will be the dominant eye in all the cases, as a few cases have shown dominance in the eye with a thicker cornea.

Repeatability of corneal pachymetry and epithelial thickness measurements with spectral-domain optical coherence tomography (SD-OCT) and correlation to ocular surface parameters

PURPOSE

To assess the repeatability of corneal pachymetry and epithelial thickness measurements with spectral-domain optical coherence tomography (SD-OCT) and identify correlations between epithelial thickness and ocular surface parameters.

METHODS

Adults who happened to have prolonged computer use were recruited, excluding those with conditions interfering with corneal measurements or tear production. All subjects filled in the ocular surface disease index (OSDI) questionnaire. Three consecutive measurements of central and peripheral corneal and epithelial thickness were performed with SD-OCT (RTVue XR). Schirmer test I and tear film break-up time (TBUT) were performed. Repeatability was evaluated with intraclass correlation coefficient (ICC), coefficient of variation and repeatability limit. Spearman correlation was used for non-parametric variables.

RESULTS

113 eyes of 63 subjects were included in the study. ICC was ≥ 0.989 for all corneal and ≥ 0.944 for all epithelial pachymetry segments. The best repeatability was found centrally and the worst superiorly both for corneal and epithelial measurements. Central epithelial thickness was weakly correlated with Schirmer test I (rho = 0.21), TBUT (rho = 0.02), OSDI symptoms and OSDI score (rho <|0.32|). OSDI symptoms and OSDI score were weakly correlated with Schirmer test I (rho <|0.3|) and TBUT (rho <|0.34|).

CONCLUSION

RTVue XR measurements of corneal and epithelial thickness are highly repeatable in all segments. The lack of correlation between epithelial thickness and ocular surface parameters could suggest the assessment of epithelial integrity with reliable methods such as SD-OCT.

A lower birth weight percentile is associated with central corneal thickness thinning: Results from the Gutenberg Prematurity Eye Study (GPES)

PURPOSE

Prematurity, prenatal growth restriction, and retinopathy of prematurity (ROP) are associated with altered ocular geometry, such as a steeper corneal shape in childhood, but it is unclear whether perinatal history affects corneal thickness development, so this study investigated whether corneal thickness in adulthood is affected by perinatal history.

MARTERIALS AND METHODS

The Gutenberg Prematurity Eye Study (GPES) is a retrospective cohort study with a prospective ophthalmologic examination in Germany. The corneal thickness was measured by Scheimpflug imaging (Pentacam HR, Oculus Optikgeräte GmbH, Wetzlar, Germany), and the relationship between perinatal parameters respective birth weight percentile and corneal thickness at different locations was assessed using uni- and multivariable linear regression models. Covariates included age, sex, mean corneal radius, white-to-white distance, gestational age, birth weight percentile, ROP occurrence, and treatment. The main outcome measures were corneal thickness at the apex, the pupil center, and the corneal periphery.

RESULTS

The corneal thickness was measured in 390 participants (754 eyes, mean age 29.7+/-8.7 years, 224 females). In multivariable analyses, a lower birth weight percentile was associated with a lower corneal thickness at the apex (B = 0.20, p = 0.003) and the pupil (B = 0.19, p = 0.007). These effects diminished towards the corneal periphery and were not observed beyond the 4-mm diameter circle around the thinnest corneal position. Neither gestational age, ROP occurrence, or ROP treatment affected the corneal thickness.

CONCLUSION

A lower birth weight percentile in subjects born preterm as a proxy for restricted fetal growth is associated with corneal thickness thinning in adults aged 18 to 52 years, indicating that corneal thickness development, particularly in the corneal center, may originate in the fetal stage.

Normal Corneal Thickness and Endothelial Cell Density in Rhesus Macaques (Macaca mulatta)

Purpose

To define the normal range of central corneal thickness (CCT) and corneal endothelial cell density (ECD) in rhesus macaques (Macaca mulatta) and the effects of age, body weight, sex, and intraocular pressure (IOP) on these parameters.

Methods

Ophthalmic examinations were performed on 144 rhesus macaques without anterior segment pathology. The CCT was measured via ultrasound pachymetry (USP) and specular microscopy, and the ECD was semiautomatically and manually counted using specular microscopy. Rebound tonometry was used to measure IOP. Linear regression and mixed-effects linear regression models were used to evaluate the effects of age, body weight, sex, and IOP on CCT and ECD.

Results

We included 98 females and 46 males with an age range of 0.2 to 29.4 years. The mean CCT by USP and specular microscopy were 483 ± 39 and 463 ± 33 µm, respectively, and were statistically different (P < 0.001). The ECDs were 2717 ± 423 and 2747 ± 438 cells/mm2 by semiautomated and manual analysis, respectively. Corneal endothelial degeneration was identified in one aged rhesus macaque.

Conclusions

The mean USP and specular microscopy CCT values differed significantly, whereas the semiautomatic and manual ECD did not. The CCT was associated with the IOP and sex, whereas the ECD was associated with body weight and age (P < 0.05). As in humans, corneal disease in rhesus macaques is uncommon.

Translational Relevance

Establishing reference values is fundamental to use rhesus macaques as a model for corneal disease or to identify toxicity in studies of ocular drugs or devices.

Swept-source OCT for corneal graft quantitative evaluation in the eye bank and the correlation of the measurements to pre-excision values

Quantitative evaluation of the human corneal grafts stored in the tissue banks is usually limited to endothelial cell density and central thickness. Swept-source OCT (SS-OCT) is capable of measuring the central curvatures of the corneal tissue prepared for transplantation without loss of sterileness, providing insights on its refractive state. The aim of the paper is to compare in vitro SS-OCT measurements with pre-excision values. Hand-held keratometry and ultrasound pachymetry was performed on 22 corneas before excision of corneoscleral button and insertion in the vial with Eusol-C solution (AlchimiaS.r.l, Nicolò, Italy). After 12 to 36 h of hypothermic storage the corneas were examined within the vials with custom built SS-OCT system maintaining a sterile environment. The anterior and posterior central curvatures, and central corneal thickness (CCT) were measured. Rotation of the corneoscleral button was controlled by making a 6-o'clock mark during excision. Mean pre-excision CCT was 626.45 ± 28.71 µm and 468.05 ± 52.96 µm when measured with SS OCT (r = 0.55; p < 0.001). Respective values for average keratometry were 7.74 ± 0.39 mm and 7.92 ± 0.57 mm (r = 0.6; p = 0.22). Although high differences were observed in corneal thickness, keratometric radius of curvature at the flat (r = 0.42; p < 0.001) and steep (r = 0.62; p = 0.014) meridian of the anterior corneal surface, as well as corneal anterior astigmatism (r = 0.3; p < 0.001), showed good correlation with pre-excision values. SS-OCT is capable of providing quantitative evaluation of the human corneal grafts in hypothermic storage. Good correlation between curvature measurements before excision and during banking in the vial indicates its clinical utility.

The genetic basis for adult onset glaucoma: Recent advances and future directions

Glaucoma, a diverse group of eye disorders that results in the degeneration of retinal ganglion cells, is the world's leading cause of irreversible blindness. Apart from age and ancestry, the major risk factor for glaucoma is increased intraocular pressure (IOP). In primary open-angle glaucoma (POAG), the anterior chamber angle is open but there is resistance to aqueous outflow. In primary angle-closure glaucoma (PACG), crowding of the anterior chamber angle due to anatomical alterations impede aqueous drainage through the angle. In exfoliation syndrome and exfoliation glaucoma, deposition of white flaky material throughout the anterior chamber directly interfere with aqueous outflow. Observational studies have established that there is a strong hereditable component for glaucoma onset and progression. Indeed, a succession of genome wide association studies (GWAS) that were centered upon single nucleotide polymorphisms (SNP) have yielded more than a hundred genetic markers associated with glaucoma risk. However, a shortcoming of GWAS studies is the difficulty in identifying the actual effector genes responsible for disease pathogenesis. Building on the foundation laid by GWAS studies, research groups have recently begun to perform whole exome-sequencing to evaluate the contribution of protein-changing, coding sequence genetic variants to glaucoma risk. The adoption of this technology in both large population-based studies as well as family studies are revealing the presence of novel, protein-changing genetic variants that could enrich our understanding of the pathogenesis of glaucoma. This review will cover recent advances in the genetics of primary open-angle glaucoma, primary angle-closure glaucoma and exfoliation glaucoma, which collectively make up the vast majority of all glaucoma cases in the world today. We will discuss how recent advances in research methodology have uncovered new risk genes, and how follow up biological investigations could be undertaken in order to define how the risk encoded by a genetic sequence variant comes into play in patients. We will also hypothesise how data arising from characterising these genetic variants could be utilized to predict glaucoma risk and the manner in which new therapeutic strategies might be informed.

Corneal and corneal epithelial thickness distribution characteristics in healthy North Indian eyes using spectral domain optical coherence tomography

Purpose

To determine the pattern of corneal thickness and epithelial thickness distribution in healthy North Indian eyes by using spectral domain optical coherence tomography (SD-OCT).

Methods

The observational study measured total corneal and epithelial thickness in the central 2 mm zone and eight sectors each in paracentral 2-5 mm (ring 1) and midperipheral 5-7 mm (ring 2) zones on SD-OCT.

Results

The study included 67 eyes of 67 subjects with a male:female ratio of 32:35 and mean age of 25.04 ± 4.54 years. The mean central corneal and epithelial thicknesses were 505.97 ± 30.12 μm and 60.48 ± 8.37 μm, respectively. The epithelium of inferior and infero-nasal sectors in ring 1 and inferior sector in ring 2 was significantly thicker than the radially opposite sectors of the respective rings (P = 0.001; P = 0.01 and P = 0.02, respectively). Sector-wise analysis did not reveal any significant correlation between the total corneal thickness and epithelial thickness (all P > 0.05) except in the outer superior sector where there was a weak positive correlation (r = 0.28, P = 0.02). Central epithelial thickness in males (60.59 ± 9.28 μm) and females (60.37 ± 7.58 μm) was comparable (P = 0.91). Pachymetry was thinnest in the inferior, inferonasal, and inferotemporal sectors in 44.79% of eyes (n = 30), while thinnest epithelium was seen in the superior, superonasal, and superotemporal quadrants in 50.75% of eyes (n = 34).

Conclusion

The epithelial thickness distribution in this sample of topographically normal healthy North Indian eyes was nonuniform and independent of the underlying corneal thickness. Epithelium was thinner in the superior cornea, whereas total corneal thickness was minimum in the inferior part.

[Normal Tension Glaucoma]

Normal tension glaucoma (NTG) is a subvariant of primary open angle glaucoma (POAG) or a separate entity. NTG is defined as chronic open angle glaucoma without elevated intraocular pressure or normal intraocular pressure. Normal intraocular pressure is between 10 and 21 mmHg and is defined as two times the standard deviation of the mean intraocular pressure in the normal population. In addition to the absence of elevated intraocular pressure, all the classic symptoms of glaucoma are otherwise present. These include a conspicuous glaucomatous optic disc excavation, nerve fibre bundle defects, and corresponding visual field defects. Papillary rim haemorrhages are frequently found. The visual field defects in NDG are usually more central compared to POAG and are therefore described as more disturbing by the patient. The anterior chamber angle is open and there are no other changes suggestive of secondary glaucoma (pigment dispersion, pseudo-exfoliation). The exact pathophysiology of NDG is not well understood. Pathophysiologically, circulatory disturbances in the sense of arterial hypo- as well as hypertension may play an essential role or at least increase the susceptibility of the optic nerve to intraocular pressure fluctuations as well as blood pressure dips. Therefore, this requires not only a purely ophthalmologic but also interdisciplinary treatment of the patient with confirmed NDG. The primary goal of treatment is the reduction of intraocular pressure, which can stop the disease. This article gives an overview of epidemiology, aetiology, clinical findings and therapies.

Normaldruckglaukome

Das Normaldruckglaukom wird definiert wird als primär chronisches Offenwinkelglaukom, bei dem kein erhöhter Augeninnendruck vorliegt. Trotz normalem Augeninnendruck ist das primäre Ziel der Behandlung die Augeninnendrucksenkung, mit der es gelingen kann, die Erkrankung aufzuhalten. Dieser Artikel soll eine Übersicht über Epidemiologie, Ätiologie, Pathogenese, klinische Befunde sowie Therapien geben.

Intraocular Pressure and Its Relation to Ocular Geometry: Results From the Gutenberg Health Study

Purpose

The purpose of this study was to investigate the association between intraocular pressure (IOP) and ocular geometry.

Methods

The Gutenberg Health Study is a population-based cohort study in Mainz, Germany. Study participants underwent a comprehensive ophthalmologic examination including noncontact tonometry, objective refraction, optical biometry, and Scheimpflug imaging of the anterior segment at the first 5-year follow-up examination (in 2012–2017). Multivariable linear regression analysis was carried out to determine associations of IOP and geometric parameter of the human phakic eye, namely central corneal thickness (CCT), corneal curvature, anterior chamber depth (ACD), lens thickness, and axial length. In addition, the relationship of IOP and the anterior chamber angle (ACA) width was analyzed.

Results

There were 6640 participants with phakia (age 57.3 ± 10.2 years, 49.1% women) that were included in this cross-sectional analysis. Mean IOP was 14.8 ± 2.9 mm Hg in the right eyes and 14.9 ± 2.9 mm Hg in the left eyes. IOP increased with higher CCT, greater posterior segment length, higher age (all P < 0.001), thicker lens (P = 0.003), and female sex (P = 0.05), whereas the ACD was not associated with higher IOP. The IOP increased with a narrower ACA in univariable analysis (P < 0.001), but not in adjusted analysis in subjects with an open angle.

Conclusions

IOP values are related to ocular geometry, as shown in this population-based study on Caucasian subjects. Thus, knowledge of the architecture of the eye is an important factor when measuring IOP. Longitudinal evaluation will analyze whether some of these parameters are also risk factors for the development of glaucoma.

Peripheral corneal thickness and associated factors - results from the population-based German Gutenberg Health Study

PURPOSE

Changes in peripheral corneal thickness are described in various corneal diseases such as corneal ectasia. However, few data exist describing the increase in corneal thickness from central to peripheral and reporting the normal distribution of corneal thickness in rings around the corneal centre. The aim of this study was to report these cornea characteristics and investigate associated factors in a population-based setting.

METHODS

The Gutenberg Health Study is a prospective, population-based study examining participants in a 5-year follow-up (age range 40-80 years) using Scheimpflug imaging. Corneal thickness was assessed in each participant at the apex, as well as in the corneal centre (thinnest corneal thickness) and in rings with 2, 4, 6, 8 and 10 mm diameter around the corneal centre, and the increase in corneal thickness towards the periphery. The relationship between corneal thickness at these locations and possible associated factors was determined using linear regression models. For this purpose, general and ocular parameters were included.

RESULTS

A total of 9729 participants were included in the present analysis (4874 women, age 59.2 ± 10.8 years). Multivariable analysis showed a correlation between the increase in corneal thickness in the circles from 0 to 10 mm (diameter) and the following parameters: age (B = -0.24 µm per year, p < 0.001); body height (B = -0.04 µm, p = 0.005); smoking (B = -0.72 µm, p < 0.001); spherical equivalent (B = -0.70 µm per dioptre, p < 0.001); white-to-white distance (B = -0.75 µm/mm, p < 0.001); mean corneal radius (B = -3.61 µm/mm, p < 0.001); intraocular pressure (B = -0.12 µm/mmHg, p < 0.001); glaucoma (B = -1.94 µm, p < 0.001); and pseudophakia (B = 0.89 µm, p < 0.001).

CONCLUSION

The results of the present study suggest that several general and ocular parameters are associated with peripheral corneal thickness. In the context of diagnosing glaucoma, a smaller increase in corneal thickness towards the periphery might be a new additional marker.

Association of Birth Weight with Central and Peripheral Corneal Thickness in Adulthood-Results from the Population-Based German Gutenberg Health Study

Purpose: Low birth weight (BW) is associated with altered ocular geometry such as a steeper corneal shape in adulthood. However, it is unclear whether low birth weight affects corneal thickness development in the center or periphery in adulthood which may contribute to ocular disease. The purpose of this study was to investigate corneal thickness in former low birth weight individuals in adulthood. Methods: The German Gutenberg Health Study is a prospective, population-based study in which every participant (age range 40–80 years) was measured with Scheimpflug imaging (Pentacam HR, Oculus Optikgeräte GmbH, Wetzlar, Germany). BW was collected by self-reports. The relationship between birth weight and corneal thickness at different locations were assessed. Linear regression models were carried out including uni- and multivariable analyses with adjustment for age, sex, mean corneal radius, and white-to-white distance. Main outcome measures were corneal thickness at the apex, at the pupil center, and at the corneal periphery. Results: Overall, 5657 participants were successfully measured (3019 females, aged 56.0 ± 10.3 years). In multivariable analyses a lower BW was associated with a thinner corneal thickness at the apex (B = 1.71 µm/500 g, p < 0.001) and at the pupil (B = 1.69 µm/500 g, p < 0.001). These effects diminished towards the corneal periphery resulting in no differences in the perilimbal regions. Conclusion: The present study provides evidence that lower birth weight goes along with corneal thickness alterations even into adult ages of 40 to 80 years. Thinner measurements of the cornea were particularly found in the corneal center and diminished in the periphery. This indicates that there may be fetal origins affecting corneal thickness development particularly in the corneal center.

Macular perfusion normative data acquired with optical coherence tomography angiography in healthy four-year-old Caucasian children

BACKGROUND

The purpose of this cross-sectional study involving healthy emmetropic four-year-old Caucasian children was to provide a macular perfusion normative database acquired with optical coherence tomography angiography (OCTA). One eye of each examinee underwent OCTA imaging. The following parameters were analyzed using AngioTool Image J software: vessels area (VA), vessels density (VD), total number of junctions (TNJ), junctions density (JD), total vessel length (TVL), average vessel length (AVL), total number of endpoints (TNEP), lacunarity (L), vessel diameter index (VDI), tortuosity (T) and foveal avascular zone (FAZ). Average central macular thickness (CMT) and average central macular volume (CMV) were measured.

RESULT

Sixty-two eyes of 62 children of average age 50.4 ± 3.8 months were examined. VA, VD, and T increased from the inner towards the outer layers of the retina. The intermediate capillary plexus had the highest JD and TNEP and narrowest FAZ. Retinal sexual differentiation was supported with higher values of the retinal VA, VDI and TNEP, and chorioretinal VA, VDI and L in males. The choriocapillaris presented with the highest VD, AVL, and T and the lowest L and TNEP.

CONCLUSION

The study provides the first detailed normative database of the macular vascular network in the youngest uniform cohort of emmetropic four-year-old children.

Interocular Symmetry and Repeatability of Central Corneal Thickness and Corneal Endothelial Cell Morphology and Density in Healthy Eyes of Congolese

PURPOSE

To determine the limits of normal interocular symmetry and the repeatability of central corneal thickness (CCT) and endothelial cell morphology and density.

METHODS

Two hundred and seventy-eight subjects (age: 10.9-80.7 years) with healthy eyes were studied. CCT as well as endothelial cell morphology and density were measured by non-contact specular microscopy. Three measurements were obtained per eye per participant. Upper and lower tolerance limits of normal interocular symmetry were defined as the 2.5th and 97.5th percentiles of the interocular differences in CCT, endothelial cell density (CECD), coefficient of variation (CoV), hexagonality, and cell size. Repeatability was determined using the intraclass coefficient correlation (ICC), the coefficient of variation (CV), and the test-retest variability standard deviation (TRTSD).

RESULTS

The mean interocular differences were -1.05 ± 17.5 µm (p = .32) for CCT and 0.5 ± 90.8 cells/mm² (p = .76) for CECD. The 2.5th and 97.5th percentiles of the interocular differences were -13.9 and 15.4 µm for CCT and -177.4 cells/mm² to 182.0 cells/mm² for CECD. Only interocular difference in CoV correlated weakly with age (r = -0.22, P < .001). ICCs were 0.93 (95% CI: 0.89-0.96, P < .001) for CCT and 0.95 (0.94-0.96, P < .001) for CECD. CV and TRTSD were 1.2% ± 5.3% and 4.4 ± 3.4 µm for CCT and 2.4% ± 3.9% and 17.7 ± 7.7 cells/mm² for CECD, respectively.

CONCLUSIONS

CCT and CECD showed good repeatability and interocular symmetry in normal Congolese subjects. Absolute interocular differences in CCT and CECD exceeding 15.5 µm and 182 cells/mm², respectively, should be considered suspicious and investigated. When comparing two intrasession measurements from the same eye, a difference of approximately 4.5 µm in CCT and 18 cells/mm² or greater may be considered statistically significant.

Update and Review of Diagnosis and Management of Post-Refractive Surgery Ectasia

ABSTRACT

Post-Refractive Surgery Ectasia is a serious, sight-threatening, and highly - avoided complication seen after the following procedures: Laser in situ Keratomileusis, Photorefractive Keratectomy, Small Incision Lenticule Extraction, Radial and/or Arcuate Keratotomy. Specific risk factors may include age, corneal thickness, degree of refractive error, corneal topographic changes including irregular astigmatism, percent tissue ablation, and residual stromal bed. Biomarkers may be a new option to help indicate who is at greatest risk for ectasia. Visual aids including glasses or contacts lenses are often required to achieve optimal vision. Collagen crosslinking is the only treatment thought to stop progression of ectasia and prevent keratoplasty. Other surgical options may include topography-guided phototherapeutic keratectomy and intrastromal corneal ring segments. Ultimately an "ounce of prevention is a pound of cure" so careful preoperative screening and ultimately offering the safest and most effective treatments for patients is arguably the most important job of the refractive surgeon.

Comparison of central corneal thickness using non-contact tono-pachymeter (Tonopachy) with ultrasound pachymetry in normal children and in children with refractive error

Purpose

To compare the central corneal thickness (CCT) measured by non-contact tono-pachymeter [Tonopachy (TP)] with the gold standard ultrasound pachymetry (UP) in normal children and in children with refractive error.

Methods

This cross-sectional study involved 95 normal children (190 eyes) and 123 children with refractive error (246 eyes), a total of 218 children (436 eyes) aged 7-15 years. After refraction and complete ophthalmic evaluation, axial length was measured with IOLMaster 700, CCT was measured with TP followed by UP. The correlation between the CCT measurements obtained with the two methods was analysed by Intraclass correlation coefficient (ICC) and the limits of agreement were assessed with Bland-Altman analysis plot.

Results

Mean CCT measured with TP was 537.46 ± 36.41 μm and by UP was 537.17 ± 39.80 μm in normal children (P = 0.79) and in refractive error group, the mean CCT was 533.50 ± 34.91 μm by TP and 531.60 ± 36.30 μm by UP (P = 0.04). The 95% limits of agreement between TP and UP ranged from -19.2 to + 21.6 μm (mean = 1.20) for total children, -20.8 to + 21.4 μm (mean = 0.29) for normal group and -18.0 to + 21.8 μm (mean = 1.90) for refractive error group. ICC for CCT measurement between TP and UP was 0.980 for total children and refractive error group and 0.981 for normal group.

Conclusion

The CCT measurement obtained by TP showed an excellent agreement with UP. Hence non-contact TP can be used to assess CCT in children above seven years of age.

Profile of central corneal thickness and corneal endothelial cell morpho-density of in healthy Congolese eyes

Purpose

To determine the pachymetric and corneal endothelial cell morphometric features and their relationship to ocular and systemic factors in healthy Congolese subjects.

Methods

Non-contact specular microscopy was used in 278 healthy eyes (278 subjects) to measure central corneal thickness (CCT), corneal endothelial cell density (CECD) along with cell size, coefficient of variation (CV) in cell size, and hexagonality (HEX). The lower and upper reference limits and average values for each parameter were determined. Correlation and association of average values with anthropo-demographic and clinical variables were assessed.

Results

The mean age was 38.9 ± 17.2 years (10.9–80.7 years). Average values were 504.2 ± 30.7 μm (CCT), 2907.1 ± 290.9 cells/mm² (CECD), 348.5 ± 38.4 μm² (cell size), 32.9 ± 3.6% (CV), and 51.8 ± 7.2% (HEX). CCT was 504.9 ± 33.6 μm in men and 503.6 ± 28.3 μm in women (p = .73); values for CECD were 2917.1 ± 253.5 cells/mm² and 2899.2 ± 317.8 cells/mm² (p = 0.61), respectively. Lower and upper reference limits were 449.6 μm and 566.0 μm for CCT, and 2165.3 cells/mm² and 3414.4 cells/mm² for CECD, respectively. CCT correlated with body mass index (BMI), (r = − 0.12, P = 0.04). CECD decreased with age (r = − 0.49, P < 0.001), BMI (r = − 0.20, P = 0.001), intraocular pressure (r = − 0.13, P = 0.029) and ocular perfusion pressure (r = − 0.28, P = 0.028). CECD decayed by 8.3 cells/mm² or 0.30% per year of age and CCT decreased by 0.72 μm per kg/m².

Conclusions

Mean central cornea was thinner, CECD higher, and references limits lower than reported in other African populations. The CCT and CECD normative values reported herein will be useful for both clinical and research purposes in this population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-01947-x.

Abnormal corneal properties in osteogenesis imperfecta and glaucoma: a case series

Objective

We aimed to carry out ocular examination and genetic studies in a family in which some members are affected with osteogenesis imperfecta (OI) and primary open-angle glaucoma (POAG). We compared the corneal properties of affected and unaffected members (ie, cases and controls).

Methods

Eight family members from two generations, both affected and unaffected, were examined. Corneal hysteresis (CH), intraocular pressure (IOP) measured with Goldmann applanation tonometer, central corneal thickness (CCT) and cornea-corrected IOP (IOPcc) were recorded. Blood samples were obtained from seven family members, both affected and unaffected, and tested for a panel of genes associated with OI.

Results

Family members affected with OI (n=6) had a heterozygous splice site mutation in intron 26 of the COL1A1 gene. The family members affected with OI had reduced CCT (476.5±24.6 µm) and CH (7.9 ±1.4 mmHg) compared with the unaffected controls (CCT, 575.8±10.8 µm; CH, 12.3±0.8 mmHg). Two of the six patients affected with OI had a glaucoma diagnosis and were on topical therapy and under regular clinical review.

Conclusions

Patients affected with OI have a significant risk of developing POAG due to the effects of abnormal collagen on various ocular structures. Two of these effects which place them at risk are reduced CCT and CH. They should be screened and monitored for glaucoma from a young age, and the examination should include corneal biomechanical measurements and CCT to identify those most at risk. IOPcc may be a more accurate way to monitor IOP in the presence of abnormal corneal properties.

Reference Values of the Central Corneal Thickness with Different Refractive Errors for the Adult Egyptian Population

AIM

To generate reference values of the central corneal thickness (CCT) with different refractive errors for the adult eastern Egyptian population.

SUBJECTS AND METHODS

This study was a retrospective, observational, and cross-sectional study. It included 1166 eyes (1166 subjects) scheduled for LASIK, who came to private refractive eye centre, Ismailia, Egypt. The study period was from January 2018 to January 2020. The subjects were divided into a broad range of myopia with spherical equivalent (SE) ≤-0.5D and hyperopia (SE) ≥+0.5D. Then, the myopic eyes divided into low (SE>-3.0D), moderate (SE-3.0D to >-6.0D), and high (SE≤-6.0D). Similarly, the hyperopic eyes were divided into low (SE<+3.0D) and moderate (SE+3.0D to <+6.0D) and high ≥+6.0D. The refractive error was measured by an auto-refractometer, and CCT was measured using ultrasonic pachymetry.

RESULTS

The data of 556 myopic eyes in 556 subjects (31.1% males and 68.9% females) and 610 hyperopic subjects (34.4% males and 65.6% females) were included in this study. The mean±SD of CCT for the total myopic subjects was 532.8±32.6μm, range (470 to 627μm). The mean±SD of SE was -4.06±2.50D, range (-0.50 to -14.00D). The mean±SD of CCT for the total hyperopic subjects was 530.8±37.2μm, range (471 to 616μm). The mean±SD of SE was +3.57±1.98D, range (+0.50 to +8.50D). About 16.2% of the myopic eyes and 12.7% of the hyperopic eyes have CCT less than 500μm.

CONCLUSION

The mean of the central corneal thickness of the eastern Egyptian population was 532.8μm for myopic and 530.8μm for hyperopic subjects, respectively. The myopic and hyperopic subjects show a reduction in CCT with age. Females have a thinner cornea than males, 16.2% of the myopic eyes and 12.7% of the hyperopic eyes have CCT less than 500μm.

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

PURPOSE

To describe the distribution of corneal hysteresis (CH) in a large cohort and explore its associated factors and possible clinical applications.

DESIGN

Cross-sectional study within the UK Biobank, a large cohort study in the United Kingdom.

PARTICIPANTS

We analyzed CH data from 93 345 eligible participants in the UK Biobank cohort, aged 40 to 69 years.

METHODS

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.

MAIN OUTCOME MEASURES

Corneal hysteresis (mmHg).

RESULTS

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.

CONCLUSIONS

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.

Sequence variation at ANAPC1 accounts for 24% of the variability in corneal endothelial cell density

The corneal endothelium is vital for transparency and proper hydration of the cornea. Here, we conduct a genome-wide association study of corneal endothelial cell density (cells/mm2), coefficient of cell size variation (CV), percentage of hexagonal cells (HEX) and central corneal thickness (CCT) in 6,125 Icelanders and find associations at 10 loci, including 7 novel. We assess the effects of these variants on various ocular biomechanics such as corneal hysteresis (CH), as well as eye diseases such as glaucoma and corneal dystrophies. Most notably, an intergenic variant close to ANAPC1 (rs78658973[A], frequency = 28.3%) strongly associates with decreased cell density and accounts for 24% of the population variance in cell density (β = -0.77 SD, P = 1.8 × 10-314) and associates with increased CH (β = 0.19 SD, P = 2.6 × 10-19) without affecting risk of corneal diseases and glaucoma. Our findings indicate that despite correlations between cell density and eye diseases, low cell density does not increase the risk of disease.

The Prevalence of Glaucoma in Young People

BACKGROUND

Earlier information on the prevalence of glaucoma among children in Germany was based solely on estimates. Reported values for congenital glaucoma range from 1 in 10 000 to 1 in 68 000 depending on ethnic origin. The estimate for juvenile glaucoma is 1 in 44 000.

METHODS

The Gutenberg Health Study is a populationbased, prospective, monocentric cohort study with 15 010 participants aged 35 to 74. To determine the history-based prevalence of childhood glaucoma, participants were asked about the diagnosis of glaucoma, any operations for glaucoma that were performed, regular use of drugs for glaucoma, and the age of onset of glaucoma. The affected individuals were classified in four groups based on the age of onset: congenital (<2 years), juvenile (2 to <18 years), late juvenile (18 to <40 years), and early adult (40 to <45 years). In the identified glaucoma patients, the visual acuity, intraocular pressure, corneal thickness, visual fields, and optic discs were evaluated.

RESULTS

352 persons were identified from their medical history as having glaucoma. The weighted prevalences in the four groups were 0% in the congenital group, 0.01% (95% confidence interval [0, 0.03]) in the juvenile group, 0.16 % ([0.09; 0.23]) in the late juvenile group, and 0.17% ([0.15; 0.19]) in the early adult group. For participants over age 45, the weighted prevalence of glaucoma was 1.98% [1.7; 2.2].

CONCLUSION

In our cohort, the history-based prevalence of juvenile glaucoma was 0.01% (2 patients). The prevalence was an order of magnitude higher (0.16%) between the ages of 18 and 40, and two orders of magnitude higher at later ages (1.98%). The burden of disease seems to be markedly higher than previously assumed.

Reproducibility of Central Corneal Thickness Measurements in Normal Eyes Using the Zeiss Cirrus 5000 HD-OCT and Pentacam HR

Objectives:

To determine the repeatability and reproducibility of Central Corneal Thickness (CCT) measurements using two different anterior segment imaging modalities, including those obtained with the new anterior segment lens attachments for the Cirrus 5000 HD-OCT.

Methods:

A total of 32 eyes from 16 normal volunteers (8 male, 8 female) were enrolled in this prospective study. CCT was measured by the same examiner using the Cirrus 5000 HD-OCT and Pentacam HR. The results of CCT obtained by each method were averaged and compared using t-test analysis. The agreement between the measurement methods was evaluated. Coefficient of Repeatability (CoR) and Intra-Class Correlation Coefficient (ICC) were computed.

Results:

The mean measurements taken with the Cirrus OCT anterior chamber lens (CCT_AC), HD cornea lens (CCT_HDC) and pachymetry scans (CCT_Pach) were 545.35 ± 31.02, 537.87 ± 26.82, and 532.04 ± 29.82 µm, respectively. The mean CCT obtained with the Pentacam (CCT_Pent) was 545.51 ± 30.71 µm. CCT_Pent were significantly higher than CCT_HDC and CCT_Pach (p< 0.0001). In contrast, the CCT_Pent and CCT_AC were similar (p=0.87). CCT, as evaluated by the two different instruments, showed excellent correlation (r > 0.98, p< 0.0001) with an ICC > 0.99 (95% CI, 0.97 – 0.99). CoR was the highest for CCT_Pach (3.7 ± 1.4, 95% CI (3.0- 4.6)).

Conclusion:

CCT measurements from the Cirrus OCT using the new anterior segment lens attachments and the Pentacam HR are highly correlated. This should allow the use of a standardized correction factor if necessary to inter-relate the measurements between the two devices.

Longitudinal Change in Central Corneal Thickness in the Tema Eye Survey

PURPOSE

To determine the change and rate of change in central corneal thickness (CCT) and their determinants.

DESIGN

Longitudinal observational population-based study.

METHODS

A total of 758 normal and 58 glaucomatous subjects underwent complete eye examination, with CCT measurements at 2 separate visits. Change and rate of change in CCT were determined. Univariate and multivariate linear regression analyses were performed to determine the factors associated with change and rate of change.

RESULTS

The mean follow-up duration was 8.4 ± 0.7 years. The overall change was -8.9 ± 16.7 μm in OD and -9.8 ± 16.2 μm in OS, both P < .0001. Changes in glaucomatous and normal subjects were -14.1 ± 2.2 μm vs -8.6 ± 0.6 μm in OD (P = .02) and -14.5 ± 2.2 μm vs -9.5 ± 0.6 μm in OS (P = .03), respectively. The overall rate of thinning was -1.1 μm/year (OD) and -1.2 μm/year (OS). Rates in glaucomatous and normal eyes were -1.7 ± 0.3 μm/year vs -1.0 ± 0.1 μm/year in OD (P = .02) and -1.7 ± 0.3 μm/year vs -1.1 ± 0.1 μm/year in OS (P = .03), respectively. Change and rate of change were associated with baseline CCT (ß = -0.1 to -0.09 and -0.011, respectively, all P < .001) and glaucoma (ß = -6.8 to -5.6, P ≤ .009, and -0.75 to -0.69, P ≤ .007, respectively).

CONCLUSION

CCT decreased significantly over time. The change and rate of change were greater in glaucomatous than normal eyes, and were greater than described in cross-sectional studies.

Distribution of corneal thickness and its determinants in 6-12-year-old children in an Iranian general population

Purpose

To determine the central corneal thickness (CCT), apex, and paracentral thicknesses and their determinants in children aged 6-12 years.

Methods

The present study was part of the phase 1 of Shahroud School Children Eye Cohort Study in 2015. Cluster sampling was done in urban areas while all children were invited to participate in the study in rural areas. The Pentacam HR was used for measurements. CCT was measured within the central 3 mm zone of the cornea, and corneal thickness 3 mm further from the center was considered paracentral thickness.

Results

Of 6624 students who were selected, 5620 (84.8%) participated in the study. Among 4956 students, studied in this report, 52.2% were boys, and the mean age of the study participants was 9.75 ± 1.71 years (6-12). The mean CCT and apical thickness was 556.29 ± 34.04 and 557.43 ± 34.03 μm, respectively. The mean paracentral thickness was 657.62 ± 39.11 μm in the superior, 632.65 ± 37.63 μm in the inferior, 648.64 ± 38.75 μm in the nasal, and 617.36 ± 37.19 μm in the temporal region. A multiple regression model showed that CCT decreased by 4.70 μm with every 1 diopter increase in the mean keratometry and increased by 20.06 μm with every 1 mm increase in the anterior chamber depth (ACD) (Both P-Value < 0.001). Age, sex, ethnicity and residence place were also found to be associated with CCT.

Conclusions

This study is the first to describe the distribution of corneal thickness in Iranian children with a large sample size. This study showed that corneal thickness was significantly correlated with younger age, female gender, urban residence, and a number of biometric variables.

Steeper Iris Conicity Is Related to a Shallower Anterior Chamber: The Gutenberg Health Study

PURPOSE

To report the distribution of iris conicity (steepness of the iris cone), investigate associated factors, and test whether pseudophakia allows the iris to sink back.

METHODS

A population-based cross-sectional study was carried out. Ophthalmological examination including objective refraction, biometry, noncontact tonometry, and Scheimpflug imaging (Pentacam®, Oculus) was performed including automated measurement of iris conicity. 3708 phakic subjects, 144 subjects with bilateral and 39 subjects with unilateral pseudophakia were included. Multivariable analyses were carried out to determine independently associated systemic and ocular factors for iris conicity in phakic eyes.

RESULTS

Mean iris conicity was 8.28° ± 3.29° (right eyes). Statistical analysis revealed associations between steeper iris conicity and shallower anterior chamber depth, thicker human lens and higher corneal power in multivariable analysis, while older age was related to a flatter iris conicity. Refraction, axial length, central corneal thickness, pupil diameter, and intraocular pressure were not associated with iris conicity. Pseudophakia resulted in a 5.82° flatter iris conicity than in the fellow phakic eyes.

CONCLUSIONS

Associations indicate a correlation between iris conicity with risk factors for angle-closure, namely, shallower anterior chamber depth and thicker human lens. In pseudophakic eyes, iris conicity is significantly lower, indicating that cataract surgery flattens the iris.

Effect of age, sex, and refractive errors on central corneal thickness measured by Oculus Pentacam®

BACKGROUND

Central corneal thickness (CCT) can be used to assess the corneal physiological condition as well as the pathological changes associated with ocular diseases. It has an influence on the measurement of intraocular pressure and is being used as a screening tool for refractive surgery candidates. The aim of this study was to determine the median CCT among normal Pakistani population and to correlate CCT with age, sex, and refractive errors.

METHODS

We conducted a retrospective analysis of 5,171 healthy eyes in 2,598 patients who came to Hashmanis Hospital, Karachi, Pakistan. The age of the patients ranged from 6 to 70 years. The refractive error was gauged by an auto-refractometer, and CCT was measured using Oculus Pentacam^®.

RESULTS

The median CCT of our study was 541.0 μm with an interquartile range (IQR) of 44.0 μm. The median age was 26.0 years (IQR: 8.0). Median spherical equivalent (SE) of the patients was -4.3 D (IQR: 3.3) with the median sphere value as -4.0 D (IQR: 3.8). Lastly, the median cylinder was -1.0 D (IQR: 1.3). Age has a weak negative correlation with CCT (r=-0.058) and shows statistical significance (P<0.001). Additionally, males had thinner CCT readings than females (P=0.001). The cylinder values, on the other hand, had a significant (P=0.004) and positive correlation (r=0.154). Three values showed no significant correlation: sphere (P=0.100), SE (P=0.782), and the left or right eye (P=0.151).

CONCLUSION

Among the Pakistani population, CCT was significantly affected by three variables: sex, age, and cylinder. No relationship of CCT was observed with the left or right eye, sphere, and SE.

Influence of eye biometrics and corneal micro-structure on noncontact tonometry

Purpose

Tonometry is widely used as the main screening tool supporting glaucoma diagnosis. Still, its accuracy could be improved if full knowledge about the variation of the corneal biomechanical properties was available. In this study, Optical Coherence Tomography (OCT) speckle statistics are used to infer the organisation of the corneal micro-structure and hence, to analyse its influence on intraocular pressure (IOP) measurements.

Methods

Fifty-six subjects were recruited for this prospective study. Macro and micro-structural corneal parameters as well as subject age were considered. Macro-structural analysis included the parameters that are associated with the ocular anatomy, such as central corneal thickness (CCT), corneal radius, axial length, anterior chamber depth and white-to-white corneal diameter. Micro-structural parameters which included OCT speckle statistics were related to the internal organisation of the corneal tissue and its physiological changes during lifetime. The corneal speckle obtained from OCT was modelled with the Generalised Gamma (GG) distribution that is characterised with a scale parameter and two shape parameters.

Results

In macro-structure analysis, only CCT showed a statistically significant correlation with IOP (R² = 0.25, p<0.001). The scale parameter and the ratio of the shape parameters of GG distribution showed statistically significant correlation with IOP (R² = 0.19, p<0.001 and R² = 0.17, p<0.001, respectively). For the studied group, a weak, although significant correlation was found between age and IOP (R² = 0.053, p = 0.04). Forward stepwise regression showed that CCT and the scale parameter of the Generalised Gamma distribution can be combined in a regression model (R² = 0.39, p<0.001) to study the role of the corneal structure on IOP.

Conclusions

We show, for the first time, that corneal micro-structure influences the IOP measurements obtained from noncontact tonometry. OCT speckle statistics can be employed to learn about the corneal micro-structure and hence, to further calibrate the IOP measurements.

Correlation between central corneal thickness and visual field defects, cup to disc ratio and retinal nerve fiber layer thickness in primary open angle glaucoma patients

Objective:

To evaluate the correlation between Central Corneal Thickness (CCT) and Visual Field (VF) defect parameters like Mean Deviation (MD) and Pattern Standard Deviation (PSD), Cup-to-Disc Ratio (CDR) and Retinal Nerve Fibre Layer Thickness (RNFL-T) in Primary Open-Angle Glaucoma (POAG) patients.

Methods:

This cross sectional study was conducted at Armed Forces Institute of Ophthalmology (AFIO), Rawalpindi from September 2015 to September 2016. Sixty eyes of 30 patients with diagnosed POAG were analysed. Correlation of CCT with other variables was studied.

Results:

Mean age of study population was 43.13±7.54 years. Out of 30 patients, 19 (63.33%) were males and 11 (36.67%) were females. Mean CCT, MD, PSD, CDR and RNFL-T of study population was 528.57±25.47µm, -9.11±3.07, 6.93±2.73, 0.63±0.13 and 77.79±10.44µm respectively. There was significant correlation of CCT with MD, PSD and CDR (r=-0.52, p<0.001; r=-0.59, p<0.001;r=-0.41, p=0.001 respectively). The correlation of CCT with RNFL-T was not statistically significant (r=-0.14, p=0.284).

Conclusion:

Central corneal thickness had significant correlation with visual field parameters like mean deviation and pattern standard deviation, as well as with cup-to-disc ratio. However, central corneal thickness had no significant relationship with retinal nerve fibre layer thickness.

Corneal Thickness in Highlanders

Patyal, Sagarika, Amit Arora, Arun Yadav, and Vijay K. Sharma. Corneal thickness in highlanders. High Alt Med Biol. 18:56-60, 2017.

BACKGROUND

Corneal thickness is an important parameter with diagnostic and therapeutic implications. Various studies have highlighted increase in corneal thickness in lowlanders on ascending to high altitude. However, there are no studies in the published literature pertaining to corneal thickness of the highlanders who are inhabitants of such altitudes. Hence, study was carried out with objective to determine the corneal thickness of highlanders living at heights of more than 11,000 feet and compare it with corneal thickness of lowlanders.

MATERIALS AND METHODS

The highlander participants of the study consisted of inhabitants of Ladakh region of India at an altitude of 11,000 feet or more and lowlander participants consisted of inhabitants at an altitude of 1500 feet. A total of 254 highlanders and 212 lowlanders participated. A mean of 25 measurements of central corneal thickness (CCT) of every participant was obtained for each eye using ultrasonic pachymeter.

RESULTS

The mean age of the participants was 41.8 (15.9) and 47.7 (17.7) years among lowlanders and highlanders, respectively. The highlanders had 11.95 μm lower mean CCT reading compared to lowlanders after adjusting for age and sex (p value <0.001). There was no statistically significant difference in mean CCT readings of right eye and left eye in either lowlanders or highlanders. Age also had a significant effect after adjustment for location and gender (p = 0.001). CCT decreased by 0.31 μm with every year increase in the age. Gender had no statistically significant effect.

CONCLUSION

This study found statistically significant difference in CCT measurements between highlanders and lowlanders. The thinner corneas of highlanders may have a bearing on diagnosis and treatment of glaucoma, refractive surgery, contact lens fitting implantation of Intacs, and astigmatic keratectomy done on such patients. The study also opens the scope of further research in the area.

Central Corneal Thickness in Spectral-Domain OCT and Associations with Ocular and Systemic Parameters

Background. Optical coherence tomography (OCT) allows quantitative analysis of the anterior segment of the eye with a noncontact examination. The aim of this study is to analyze associations of central corneal thickness (CCT) as measured by OCT with ocular and systemic cardiovascular parameters. Methods. A cross-sectional study of 734 persons was performed in a working age population. Only healthy eyes were included. A comprehensive ophthalmological examination including refraction, noncontact tonometry, and imaging of the anterior segment by SD-OCT was performed. In parallel, a broad range of systemic cardiovascular parameters were measured. Associations were analyzed using a generalized estimating equations' model. Results. CCT measurements showed a significant association with corneal curvature and intraocular pressure: a thinner CCT was associated with a flatter cornea and with lower intraocular pressure (p < 0.001). Age was positively associated with CCT (p < 0.001); all other cardiovascular parameters were not associated. Conclusion. A thinner cornea is associated with a flatter surface and with lower intraocular pressure readings, while there are no independent associations with refraction and systemic cardiovascular parameters. Our findings highlight the value of SD-OCT CCT measurements as a standard tool in anterior segment analysis.

Effect of supine body position on central corneal thickness

BACKGROUND

To evaluate the effect of supine body position on central corneal thickness (CCT) in open-angle glaucoma patients and in healthy subjects.

DESIGN

A cross-sectional study at a university eye clinic.

PARTICIPANTS

Twenty-three subjects were recruited in each group, for a total of 46 patients.

METHODS

CCT was measured using an ultrasound pachymeter in each subject. Three consecutive measurements in each eye were first taken in the sitting position, and repeated after 10 min and 30 min in a supine position. Results were analyzed using mixed model repeated measures, which adjusted for age, gender and laterality of eyes.

MAIN OUTCOME MEASURES

CCT RESULTS: In healthy subjects, CCT decreased with supine positioning at 10 min (mean = -5.2 µm, P = 0.0043) and at 30 min (mean = -6.5 µm, P < 0.0001). In the glaucoma group, CCT decreased with supine positioning at 10 min (mean = -6.7 µm, P = 0.0043) and at 30 min (mean = -10.2 µm, P < 0.0001). There was no statistically significant difference between the CCT at 10 min supine and at 30 min supine in the healthy subjects (P = 0.37) and glaucoma patients (P = 0.14). CCT was shown to decrease linearly over time (P < 0.0001), and the slopes were not statistically different between groups (P = 0.40).

CONCLUSIONS

CCT is a dynamic measurement that can be influenced by body position. It decreases linearly in the first 30 min of supine positioning at a similar rate in both open angle glaucoma patients and in healthy subjects.

Intra-Ocular Pressure Measurement in a Patient with a Thin, Thick or Abnormal Cornea

Accurate measurement of intra-ocular pressure is a fundamental component of the ocular examination. The most common method of measuring IOP is by Goldmann applanation tonometry, the accuracy of which is influenced by the thickness and biomechanical properties of the cornea. Algorithms devised to correct for corneal thickness to estimate IOP oversimplify the effects of corneal biomechanics. The viscous and elastic properties of the cornea influence IOP measurements in unpredictable ways, a finding borne out in studies of patients with inherently abnormal and surgically altered corneal biomechanics. Dynamic contour tonometry, rebound tonometry and the ocular response analyzer provide useful alternatives to GAT in patients with abnormal corneas, such as those who have undergone laser vision correction or keratoplasty. This article reviews the various methods of intra-ocular pressure measurement available to the clinician and the ways in which their utility is influenced by variations in corneal thickness and biomechanics.

Corneal Thickness Profile and Associations in Chinese Children Aged 7 to 15 Years Old

Corneal thickness (CT) maps of the central (2-mm diameter), para-central (2 to 5-mm diameter), peripheral (5 to 6-mm diameter), and minimum (5-mm diameter) cornea were measured in normal Chinese school children aged 7 to 15 years old using Fourier-domain optical coherence tomography. Multiple regression analyses were performed to explore the effect of associated factors [age, gender, refraction, axial length and corneal curvature radius (CCR)] on CT and the relationship between central corneal thickness (CCT) and intraocular pressure (IOP). A total of 1228 eyes from 614 children were analyzed. The average CCT was 532.96 ± 28.33 μm for right eyes and 532.70 ±28.45 μm for left eyes. With a 10 μm increase in CCT, the IOP was elevated by 0.37 mm Hg, as measured by noncontact tonometry. The CT increased gradually from the center to the periphery. The superior and superior nasal regions had the thickest CTs, while the thinnest points were primarily located in the inferior temporal cornea. The CCT was associated with CCR (p = 0.008) but not with gender (p = 0.075), age (p = 0.286), axial length (p = 0.405), or refraction (p = 0.985). In the para-central region and the peripheral cornea, increased CT was associated with younger age, male gender, and a flatter cornea.

Prevalence and risk factors of retinal vein occlusion: the Gutenberg Health Study

OBJECTIVE

To determine the age- and sex-specific prevalence and determinants of retinal vein occlusions (RVOs) in a large population-based German cohort.

METHODS

The investigation included 15,010 participants (aged 35-74 years) from the Gutenberg Health Study. We determined the prevalence of RVO (central retinal vein occlusion [CRVO] and branch retinal vein occlusion [BRVO]) for the local population by assessing fundus photographs of 12 954 (86.3%; 49.8% women and 50.2% men) participants. Further, we analyzed the associations of RVO with cardiovascular, anthropometric, and ophthalmic parameters.

RESULTS

The weighted prevalences of RVO, CRVO, and BRVO were 0.40%, 0.08%, and 0.32%, respectively. Men were 1.7 times more frequently affected by RVO than were women. Prevalence of RVO was 0.2% in participants aged 35-44 and 45-54 years, respectively, 0.48% in those aged 55-64 years, and 0.92% in those aged 65-74 years. Of persons with RVO, 91.5% had one or more cardiovascular risk factor or disease vs. 75.9% of persons without RVO. BRVO was associated with arterial hypertension (odds ratio 2.69, 95% confidence interval 1.27-5.70) and atrial fibrillation (3.37, 1.24-9.12) and CRVO with higher age (7.02, 1.63-30.19) and a family history of stroke (4.64, 1.18-18.25). Median visual acuity (base 10 logarithm of minimum angle of resolution) was 0.2 in persons with RVO vs. 0.05 in those without.

CONCLUSION

The prevalence of RVO in this German population was 0.4%, and men were 1.7 times more frequently affected than women. CRVO was associated with higher age and a family history of stroke, and BRVO was associated with arterial hypertension and atrial fibrillation.

Prevalence and Cardiovascular Associations of Diabetic Retinopathy and Maculopathy: Results from the Gutenberg Health Study

Objective

Diabetic retinopathy (DR) is the leading cause of blindness in people of working age. The purpose of this paper is to report the prevalence and cardiovascular associations of diabetic retinopathy and maculopathy (DMac) in Germany.

Research Design and Methods

The Gutenberg Health Study (GHS) is a population-based study with 15,010 participants aged between 35 at 74 years from the city of Mainz and the district of Mainz-Bingen. We determined the weighted prevalence of DR and DMac by assessing fundus photographs of persons with diabetes from the GHS data base. Diabetes was defined as HbA1c ≥ 6.5%, known diagnosis diabetes mellitus or known diabetes medication. Furthermore, we analysed the association between DR and cardiovascular risk factors and diseases.

Results

Overall, 7.5% (1,124/15,010) of the GHS cohort had diabetes. Of these, 27.7% were unaware of their disease and thus were newly diagnosed by their participation in the GHS. The prevalence of DR and DMac was 21.7% and 2.3%, respectively among patients with diabetes. Vision-threatening disease was present in 5% of the diabetic cohort. In the multivariable analysis DR (all types) was associated with age (Odds Ratio [95% confidence interval]: 0.97 [0.955–0.992]; p = 0.006) arterial hypertension (1.90 [1.190–3.044]; p = 0.0072) and vision-threatening DR with obesity (3.29 [1.504–7.206]; p = 0.0029). DR (all stages) and vision-threatening DR were associated with duration of diabetes (1.09 [1.068–1.114]; p<0.0001 and 1.18 [1.137–1.222]; p<0.0001, respectively).

Conclusions

Our calculations suggest that more than a quarter-million persons have vision-threatening diabetic retinal disease in Germany. Prevalence of DR was lower in the GHS compared to East-Asian studies. Associations were found with age, arterial hypertension, obesity, and duration of diabetes mellitus.

Ocular surface displacement with and without contact lenses during non-contact tonometry

PURPOSE

To evaluate the displacement of the central ocular surface during non-contact tonometry with and without soft contact lenses and determine the factors associated with the displacement of the central ocular surface and intraocular pressure (IOP) reading changes caused by wearing soft contact lenses (CLs).

METHODS

One eye each in 21 subjects was studied. The cornea was photographed using a high-speed camera at 5,000 frames/sec during non-contact tonometry without contact lenses (NCL), with -5.0 diopters (D), -0.5 D and +5.0 D CL. The displacement of the ocular surface and the factors affecting displacement at the IOP reading and maximum displacement time were investigated.

RESULTS

The IOP readings while wearing +5 D CL were significantly higher than those obtained while wearing -5 D CL. The ocular surface displacement between +5 D CL and other groups were significantly different. A significant positive correlation was found between the ocular surface displacement of subjects at the IOP reading time and the IOP obtained with the non-contact tonometer. A significant negative correlation was found between the ocular surface curvature and the IOP obtained using the non-contact tonometer. The radius of curvature of the ocular surface affected the displacement during the IOP reading and maximum displacement time.

CONCLUSIONS

Our results indicate that soft contact lens use changes the ocular surface behavior and IOP readings during non-contact tonometry. The radius of curvature of the eye affects the ocular surface displacement and IOP readings in this situation.

One Year of Glaucoma Research in Review: 2012 to 2013

PURPOSE

The objective of this study was to provide the practicing clinical ophthalmologist with an update of pertinent glaucoma literature published from 2012 to 2013.

DESIGN

Literature review.

METHODS

The authors conducted a 1-year (July 1, 2012, to September 30, 2013) English-language glaucoma literature search on PubMed using the following terms: glaucoma, automated perimetry, optic nerve imaging, optical coherence tomography, glaucoma structure and function, intraocular pressure, central corneal thickness, glaucoma medical therapy, neuroprotection, glaucoma laser treatment, secondary glaucoma, glaucoma surgery, and miscellaneous topics in glaucoma.

RESULTS

Of 2659 articles on glaucoma published during our time frame, this review selected original and review articles that reflect novel aspects and updates in the field of glaucoma, while excluding letters to the editor, unpublished works, and abstracts. Preference was given to human research.

CONCLUSIONS

This review focuses on literature that is applicable to ophthalmologists in practice and also highlights studies that may enhance the diagnosis and management of glaucoma.