Normal Human Eyes Research Articles

Expression Profile of the Matricellular Protein Osteopontin in Primary Open-Angle Glaucoma and the Normal Human Eye

PURPOSE. To characterize the role of osteopontin (OPN) in primary open-angle glaucoma (POAG) and normal eyes. METHODS. OPN quantification was performed by enzyme-linked immunosorbent assay in aqueous humor (AH) obtained from human donor eyes (POAG and normal) and surgical samples (POAG and elective cataract removal). OPN expression and localization in whole eye tissue sections and primary normal human trabecular meshwork (NTM) cells were studied by Western blot and immunohistochemistry. Latanoprost-free acid (LFA)-treated NTM cells were analyzed for OPN gene and protein expression. Intraocular pressure was measured by tonometry, and central corneal thickness was measured by optical coherence tomography in young OPN(-/-) and wild-type mice. RESULTS. OPN levels were significantly reduced in donor POAG AH compared with normal AH (0.54 ± 0.18 ng/μg [n = 8] vs. 0.77 ± 0.23 ng/μg [n = 9]; P = 0.039). A similar trend was observed in surgical AH (1.05 ± 0.31 ng/μg [n = 20] vs. 1.43 ± 0.88 ng/μg [n = 20]; P = 0.083). OPN was present in the trabecular meshwork, corneal epithelium and endothelium, iris, ciliary body, retina, vitreous humor, and optic nerve. LFA increased OPN gene expression, but minimal change in OPN protein expression was observed. No difference in intraocular pressure (17.5 ± 2.0 mm Hg [n = 56] vs. 17.3 ± 1.9 mm Hg [n = 68]) but thinner central corneal thickness (91.7 ± 3.6 μm [n = 50] vs. 99.2 ± 5.5 μm [n = 70]) was noted between OPN(-/-) and wild-type mice. CONCLUSIONS. OPN is widely distributed in the human eye and was found in lower concentrations in POAG AH. Reduction of OPN in young mice does not affect IOP.

Reproducibility of Measuring Lamina Cribrosa Pore Geometry in Human and Nonhuman Primates with In Vivo Adaptive Optics Imaging

The ability to consistently resolve lamina cribrosa pores in vivo has applications in the study of optic nerve head and retinal disease mechanisms. Repeatability was assessed in imaging laminar pores in normal living eyes with a confocal adaptive optics scanning laser ophthalmoscope (AOSLO). Reflectance images (840 nm) of the anterior lamina cribrosa were acquired using the AOSLO in four or more different sessions in two normal rhesus monkey eyes and three normal human eyes. Laminar pore areas, elongations (ratio of major to minor axes of the best-fit ellipse) and nearest neighbor distances were calculated for each session. Measurement repeatability was assessed across sessions. Pore areas ranged from 90 to 4365 μm(2) in monkeys and 154 to 6637 μm(2) in humans. Mean variabilities in measuring pore area and elongation (i.e., mean of the standard deviation of measurements made across sessions for the same pores) were 50 μm(2) (6.1%) and 0.13 (6.7%), respectively, in monkeys and 113 μm(2) (8.3%) and 0.17 (7.7%), respectively, in humans. Mean variabilities in measuring nearest neighbor distances were 1.93 μm (5.2%) in monkeys and 2.79 μm (4.1%) in humans. There were no statistically significant differences in any pore parameters across sessions (ANOVA, P > 0.05). The anterior lamina cribrosa was consistently imaged in vivo in normal monkey and human eyes. The small intersession variability in normal pore geometry suggests that AOSLO imaging could be used to measure and track changes in laminar pores in vivo during glaucomatous progression.

Determinants of Perimacular Inner Retinal Layer Thickness in Normal Eyes Measured by Fourier-Domain Optical Coherence Tomography

To determine the effects of age, sex, spherical equivalent, axial length, anterior chamber depth, optic disc area, and central corneal thickness on perimacular inner retinal layer thickness in the normal human eye as measured by Fourier-domain optical coherence tomography (FD-OCT). In this cross-sectional observational study, 182 Korean healthy subjects aged from 22 to 84 years were included. To obtain the inner retinal layer thickness, perimacular ganglion cell complex thickness, which extends from the internal limiting membrane to the inner nuclear layer, was measured by FD-OCT on one randomly selected eye of each subject. Linear regression analyses of the effects of demographic and clinical variables, including age, sex, spherical equivalent, axial length, anterior chamber depth, optic disc area, and central corneal thickness, on perimacular inner retinal layer thickness were performed. The mean inner retinal layer thickness for the entire population was 93.87 μm. Thinner inner retinal layer measurements were associated with older age (P = 0.010) and greater axial length (P = 0.021). Mean inner retinal layer thickness decreased by approximately 1.59 μm for every decade of age and by approximately 1.56 μm for every 1-mm greater axial length. There was no relationship between inner retinal layer thickness and sex, anterior chamber depth, optic disc area, or central corneal thickness. Inner retinal layer thickness, as measured by FD-OCT, varies significantly with age and axial length. The effect is small but clinically relevant in the interpretation of inner retinal layer thickness measurements.

Changes in SIRT1 Expression and Its Downstream Pathways in Age-Related Cataract in Humans

Purpose: SIRT1, the most well-known sirtuin family (class III histone deacetylases) member, is involved in many age-related diseases. However, no study has demonstrated its relationship with age-related cataract (ARC). This study was to investigate the expression of SIRT1 in human lens epithelial cells, and to observe the changes in SIRT1 expression and its downstream P53 and forkhead box class O (FOXO) proteins at the onset of ARC.Methods: The anterior lens capsule specimens from 360 normal human donor eyes (age 19–91 years) were divided into three groups: group A of young lens (younger than age 49 without cataract), group B of old but normal lens (older than age 50 without cataract), and group C of ARC lens (older than age 50 with ARC). Real-time quantitative reverse transcription of SIRT1 mRNA; Western blot analysis by anti-SIRT1, anti-p53, anti-p53 (acetyl K379), anti-FOXO3a, anti-FOXO4, anti-p27kip1, anti-p130, and anti-Bim; immunofluorescence of SIRT1; and TUNEL assay were performed in each group.Results: SIRT1 expression was significantly decreased in group B compared with group A, but increased in group C compared with group B. P53 expression increased with age and topped in group C; however, there was a decrease in active acetyl-P53 expression in group C compared with group B. The expression of both FOXO3a and FOXO4 decreased with age, but in group C, their expression level is equivalent to group A. Accordingly, the downstream p27kip1 and p130 showed the similar changes among three groups. In contrast, the expression of Bim was lowest in the ARC lens, and TUNEL assay showed significantly increased apoptosis incidence in group C.Conclusions: The expression of SIRT1 increased in ARC in humans. Its downstream p53 was inhibited, and FOXO pathway was activated, indicating that SIRT1 may play a protective role in ARC formation.

Comparison of factors that influence the measurement of corneal hysteresis in vivo and in vitro

The purpose of this study was to compare measurements of corneal hysteresis (CH) obtained in vivo, with similar measurements from excised human eyes and from excised human corneas mounted in an artificial anterior chamber. Corneal hysteresis was measured using an ocular response analyser (Reichert Ophthalmic Instruments) from three groups: 53 healthy normal corneas of fifty-three patients, six excised eyes and 17 excised corneas. In vivo, it was found that CH was independent of gender, age and mean spherical equivalent, but has a significant inverse relationship with intraocular pressure (IOP(cc)) (r = 0.53; p < 0.0001). However, there was no correlation between CH and IOP(G) (r = 0.10; p = 461). The same inverse relationship with IOP(cc) was recorded in intact, excised eyes (r = 0.74; p < 0.0001), with no significant differences between the behaviour each individual eye. Excised corneas also showed an inverse relationship between CH and trans-corneal pressure (r = 0.72; p < 0.0001), but the measured values of CH were lower than those recorded in vivo and from intact globes. In both excised eyes and excised corneas, we found a significant correlation between CH and central corneal thickness [r = 0.86; p < 0.0001 and r = 0.611; p < 0.0005 (respectively)]. The in vitro results indicate that every normal human eye at physiological hydration shows an identical dependence of CH on IOP(cc) , the same dependence as is observed in vivo. This therefore would appear to be an intrinsic response of the tissue to a change in IOP. However, it is possible that the lower values of CH recorded from excised corneas reflect the influence of the artificial chamber replacing the eye globe, so in vivo values of CH may be influenced to some extent by the presence of the other components of the eye.

Changes in ocular wavefront aberrations and retinal image quality with objective accommodation

To evaluate changes in ocular wavefront aberrations and retinal image quality with objective accommodation in normal human eyes. Department of Ophthalmology and Visual Science, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea. Cohort study. Healthy emmetropic eyes were measured with an iTrace wavefront aberrometer while the subjects fixated at far (6.0 m) and near (40 cm). Wavefront data were analyzed with 3.0 mm and 5.0 mm pupil diameters. The influence of higher-order aberrations (HOAs) on retinal image quality was simulated by computing the modulation transfer function (MTF) from the wavefront aberrations. Eighty-two eyes of 42 subjects were evaluated. The root mean square values of total HOAs before and after accommodation with 5.0 mm pupils were statistically significantly different (P=.021). In particular, total spherical aberrations became more negative with accommodation, and the difference was statistically significant with 3.0 mm and 5.0 mm pupils (both P<.001). The MTF curves were significantly different before and after accommodation at 5 cycles per degree (cpd) and 10 cpd with 5.0 mm pupils (P=.031 and P=.045, respectively). Ocular wavefront aberrations and retinal image quality changed with accommodation in normal human eyes. Total spherical aberration changed more than other HOAs with accommodation.

Morphometric Characteristics of Central Retinal Artery and Vein Endothelium in the Normal Human Optic Nerve Head

This study documents the morphometric features of arterial and venous endothelia in the different laminar regions of the normal human optic nerve head and speculates on the hemodynamic characteristics of the central retinal artery (CRA) and central retinal vein (CRV). Twenty normal human eyes were used. Microcannulation techniques were used to label the cytoskeleton and nuclei of endothelial cells in the CRA and CRV, after which images were captured using confocal microscopy. Length, width, length-to-width ratio, and area measurements were obtained from endothelium and its nuclei. Nucleus position with respect to cell apex and direction of blood flow was also quantified. Comparisons were made between prelaminar, anterior lamina cribrosa, posterior lamina cribrosa, and retrolaminar regions. Venous and arterial endothelial cell morphology was also compared. There was significant variation in venous endothelial morphology across the different laminar regions; however, no differences were found in arterial endothelial characteristics (all P > 0.1065). Significant differences were found between arterial and venous endothelium in all laminar regions apart from the posterior lamina cribrosa, where only nuclear area (P = 0.0001) and nucleus position (P = 0.0088) were found to be different. Arterial-like appearance of venous endothelium in the posterior lamina cribrosa, where pressure gradient forces are predicted to be greatest and CRV luminal diameter is known to be narrowest, implicates this as a site of altered hemodynamic stress. Heterogeneity of venous endothelium may have relevance for understanding ocular vascular diseases such as central retinal vein occlusion.

Test–Retest Repeatability of the Pupil Light Response to Blue and Red Light Stimuli in Normal Human Eyes Using a Novel Pupillometer

In this study, we evaluated the repeatability of pupil responses to colored light stimuli in healthy subjects using a prototype chromatic pupillometer. One eye of 10 healthy subjects was tested twice in the same day using monochromatic light exposure at two selected wavelengths (660 and 470 nm, intensity 300 cd/m2) presented continuously for 20 s. Pupil responses were recorded in real-time before, during, and after light exposure. Maximal contraction amplitude and sustained contraction amplitude were calculated. In addition, we quantified the summed pupil response during continuous light stimulation as the total area between a reference line representing baseline pupil size and the line representing actual pupil size over 20 s (area under the curve). There was no significant difference in the repeated measure compared to the first test for any of the pupil response parameters. In conclusion, we have developed a novel prototype of color pupillometer which demonstrates good repeatability in evoking and recording the pupillary response to a bright blue and red light stimulus.

Imaging the aqueous humor outflow pathway in human eyes by three-dimensional micro-computed tomography (3D micro-CT)

The site of outflow resistance leading to elevated intraocular pressure in primary open-angle glaucoma is believed to be located in the region of Schlemm’s canal inner wall endothelium, its basement membrane and the adjacent juxtacanalicular tissue. Evidence also suggests collector channels and intrascleral vessels may have a role in intraocular pressure in both normal and glaucoma eyes. Traditional imaging modalities limit the ability to view both proximal and distal portions of the trabecular outflow pathway as a single unit. In this study, we examined the effectiveness of three-dimensional micro-computed tomography (3D micro-CT) as a potential method to view the trabecular outflow pathway. Two normal human eyes were used: one immersion fixed in 4% paraformaldehyde and one with anterior chamber perfusion at 10 mmHg followed by perfusion fixation in 4% paraformaldehyde/2% glutaraldehyde. Both eyes were postfixed in 1% osmium tetroxide and scanned with 3D micro-CT at 2 μm or 5 μm voxel resolution. In the immersion fixed eye, 24 collector channels were identified with an average orifice size of 27.5 ± 5 μm. In comparison, the perfusion fixed eye had 29 collector channels with a mean orifice size of 40.5 ± 13 μm. Collector channels were not evenly dispersed around the circumference of the eye. There was no significant difference in the length of Schlemm’s canal in the immersed versus the perfused eye (33.2 versus 35.1 mm). Structures, locations and size measurements identified by 3D micro-CT were confirmed by correlative light microscopy. These findings confirm 3D micro-CT can be used effectively for the non-invasive examination of the trabecular meshwork, Schlemm’s canal, collector channels and intrascleral vasculature that comprise the distal outflow pathway. This imaging modality will be useful for non-invasive study of the role of the trabecular outflow pathway as a whole unit.

3D web-splines solution to human eye heat distribution using bioheat equation

A bioheat transfer model of the human eye is constructed using weighted extended b-splines as shape functions for the finite element method. This newly developed computational approach is employed to calculate the steady-state temperature distribution in a normal human eye. Firstly, the human eye is evaluated in two dimensions. The simulation results which are verified using the values reported in the literature, point out to better efficiency in terms of the accuracy level. Consequently, to give a more precise representation of the actual human eye, three dimensional modeling is simulated using these new finite elements in conjunction with linear, quadratic and cubic b-splines. Grid convergence number estimates are derived for both sets of simulations. It is shown in this paper that 3D cubic web-spline model is 0.03 °C closer to the mean value of the previous studies including the experimental studies as compared with 0.17 °C improvement obtained with the standard finite element method. Our findings indicate that weighted extended b-spline solutions improve the computational methods for health care.

Mass spectrometry provides accurate and sensitive quantitation of A2E

Orange autofluorescence from lipofuscin in the lysosomes of the retinal pigment epithelium (RPE) is a hallmark of aging in the eye. One of the major components of lipofuscin is A2E, the levels of which increase with age and in pathologic conditions, such as Stargardt disease or age-related macular degeneration. In vitro studies have suggested that A2E is highly phototoxic and, more specifically, that A2E and its oxidized derivatives contribute to RPE damage and subsequent photoreceptor cell death. To date, absorption spectroscopy has been the primary method to identify and quantitate A2E. Here, a new mass spectrometric method was developed for the specific detection of low levels of A2E and compared to a traditional method of analysis. The new mass spectrometric method allows the detection and quantitation of approximately 10,000-fold less A2E than absorption spectroscopy and the detection and quantitation of low levels of oxidized A2E, with localization of the oxidation sites. This study suggests that identification and quantitation of A2E from tissue extracts by chromatographic absorption spectroscopy overestimates the amount of A2E. This mass spectrometric approach makes it possible to detect low levels of A2E and its oxidized metabolites with greater accuracy than traditional methods, thereby facilitating a more exact analysis of bis-retinoids in animal models of inherited retinal degeneration as well as in normal and diseased human eyes.

Ocular Biomarkers for Early Detection of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia and is clinically characterized by a progressive decline in memory, learning, and executive functions, and neuropathologically characterized by the presence of cerebral amyloid deposits. Despite a century of research, there is still no cure or conclusive premortem diagnosis for the disease. A number of symptom-modifying drugs for AD have been developed, but their efficacy is minimal and short-lived. AD cognitive symptoms arise only after significant, irreversible neural deterioration has occurred; hence there is an urgent need to detect AD early, before the onset of cognitive symptoms. An accurate, early diagnostic test for AD would enable current and future treatments to be more effective, as well as contribute to the development of new treatments. While most AD related pathology occurs in the brain, the disease has also been reported to affect the eye, which is more accessible for imaging than the brain. AD-related proteins exist in the normal human eye and may produce ocular pathology in AD. There is some homology between the retinal and cerebral vasculatures and the retina also contains nerve cells and fibers that form a sensory extension of the brain. The eye is the only place in the body where vasculature or neural tissue is available for non-invasive optical imaging. This article presents a review of current literature on ocular morphology in AD and discusses the potential for an ocular-based screening test for AD.

Infiltrating macrophages in extratumoural tissues after brachytherapy of uveal melanoma

To compare distribution of macrophages in extratumoural ocular tissues in enucleated eyes with irradiated and nonirradiated uveal melanomas to find out how irradiation affects distribution of macrophages so as to gain insight into their potential routes of migration and changes in local inflammatory responses. Thirty-four matched pairs of primarily enucleated nonirradiated and secondarily enucleated irradiated eyes with choroidal and ciliary body melanoma were stained with mAb PG-M1, and the extratumoural immunopositive elements were counted under the microscope. Main outcome variables were the number of macrophages in the sclera underlying the tumour, in the choroid adjacent to the tumour, and in the ciliary body. The number of macrophage aggregates in the anterior ipsi- and contralateral episclera adjacent to the limbus was also counted. Macrophages were more numerous within the sclera under the tumour in irradiated eyes when compared to primarily enucleated eyes (median 1514 versus 619/mm², p = 0.0001), and more aggregates of episcleral macrophages adjacent to the limbus were found after irradiation (ipsilateral side, median 132 versus 0, p = 0.0034; contralateral side, median 79 versus 0, p = 0.014). In primarily enucleated eyes, increasing numbers of tumour-infiltrating macrophages were associated with presence of higher numbers of macrophages in the ciliary body (p = 0.003) and the adjacent choroid (p = 0.044), whereas in the irradiated eyes, increasing numbers of tumour-infiltrating macrophages (p = 0.010) and increasing extent of necrosis (p < 0.001) were associated with higher numbers of intrascleral macrophages underlying the tumour. Resident macrophages are present in extratumoural tissues in eyes with uveal melanoma. Brachytherapy may alter their route of migration and increase the number of macrophages in the sclera and episclera. Histopathologically detectable episcleral aggregates of macrophages adjacent to the limbus are detected predominantly after irradiation, a population of which is clinically visible as episcleral deposits after irradiation.

A correction algorithm to simultaneously control dual deformable mirrors in a woofer-tweeter adaptive optics system

We present a direct slope-based correction algorithm to simultaneously control two deformable mirrors (DMs) in a woofer-tweeter adaptive optics system. A global response matrix was derived from the response matrices of each deformable mirror and the voltages for both deformable mirrors were calculated simultaneously. This control algorithm was tested and compared with a 2-step sequential control method in five normal human eyes using an adaptive optics scanning laser ophthalmoscope. The mean residual total root-mean-square (RMS) wavefront errors across subjects after adaptive optics (AO) correction were 0.128 ± 0.025 μm and 0.107 ± 0.033 μm for simultaneous and 2-step control, respectively (7.75-mm pupil). The mean intensity of reflectance images acquired after AO convergence was slightly higher for 2-step control. Radially-averaged power spectra calculated from registered reflectance images were nearly identical for all subjects using simultaneous or 2-step control. The correction performance of our new simultaneous dual DM control algorithm is comparable to 2-step control, but is more efficient. This method can be applied to any woofer-tweeter AO system.

Eye shape and peripheral visual field recording in high myopia at approximately 54 years of age, as based on ultrasonography and Goldmann kinetic perimetry

This study describes the posterior pole contour and visual field (VF) findings in an unselected series of adults (aged approximately 54 years) with high myopia. In 1962, 39 14-year-old teenagers with myopia of >or=6 D, in one or both eyes, were identified in a 1948 Copenhagen birth cohort (n=9243). At a follow-up in 2002, 61 eyes (52 with high myopia and nine fellow eyes; n=31 subjects) were examined by ultrasound B-scan, to allow: (a) measurement of the axial vitreous length supplementary to the customary axial A-scan, and (b) assessment of the posterior pole contour of the eye. Further, the large-object (V, 4e) kinetic Goldmann perimetry isoptre was recorded to outline the ambulatory VF. An irregular posterior pole contour was observed in 15 eyes, unilaterally in 11 eyes and bilaterally in four (two subjects). Nasal fundus ectasia was suggested in six and other deviations from the sphere in seven subjects. Kinetic Goldmann perimetry showed marginal restriction in 14 eyes (12 subjects). Larger defects were found in four eyes (three subjects); the corresponding axial lengths exceeded 32 mm in the two subjects with unilateral defects, and symmetrical inferior binasal defects, probably unrelated to the myopia, were found in the bilateral subject. Unselected adult-age high myopia mainly presented with a regular eye shape that was close to spherical. An irregular shape suggesting posterior staphyloma was seen in 13 of the 32 subjects under study, mainly unilaterally. No subjects were restricted in everyday activities by VF defects. Marginal Goldmann perimetry restrictions were described in 12 and significant defects in three subjects. Generally, longer eyes more often tended to show irregular posterior eye contours and/or VF defects.

Vision improvement when correcting monochromatic higher-order aberrations with phase plates in normal and abnormal human eyes

Vision improvement when correcting monochromatic higher-order aberrations with phase plates in normal and abnormal human eyes

Bruch's membrane and choroidal macrophages in early and advanced age-related macular degeneration

AimTo determine the sub-macular Bruch's membrane (BrM) macrophage count and the choroidal and BrM macrophage immunophenotype in normal eyes and in eyes with early and advanced age-related macular degeneration (AMD).MethodsBrM...

Cyclooxygenase-2 expression in the normal human eye and its expression pattern in selected eye tumours

Cyclooxygenase-2 (COX-2) is an enzyme involved in neoplastic processes. The purpose of the present study is to investigate COX-2 expression in the normal human eye and the expression pattern in selected eye tumours involving COX-2 expressing cells. Immunohistochemical staining using antibodies against COX-2 was performed on paraffin sections of normal human eyes and selected eye tumours arising from cells expressing COX-2. Cyclooxygenase-2 expression was found in various structures of the normal eye. Abundant expression was seen in the cornea, iris, ciliary body and retina. The COX-2 expression was less in tumours deriving from the ciliary epithelium and also in retinoblastoma. Cyclooxygenase-2 is constitutively expressed in normal human eyes. The expression of COX-2 is much lower in selected eye tumours involving COX-2 expressing cells.

Active HIF-1 in the Normal Human Retina

A unique feature of the retina is the presence of photoreceptors, which require an enormous amount of oxygen for the conversion of light to an electrical signal. Hypoxia-inducible factor-1 alpha (HIF-1alpha) is a transcription factor that is the master regulator of cellular adaptation to low oxygen tension. Only in hypoxic conditions is HIF-1alpha protein stabilized and translocated to the nucleus, where it induces transcription of target genes involved in oxygen delivery and energy metabolism. We hypothesized that HIF-1alpha is constitutively stabilized and active in the normal human retina. We investigated the cellular distribution of HIF-1alpha and the expression of its downstream targets, vascular endothelial growth factor (VEGF), glucose transporter 1 (GLUT-1), and carbonic anhydrase IX (CAIX), by immunohistochemistry and immunoblotting in the retina of normal rats and human donor eyes. Both human and rat retinas displayed prominent staining of HIF-1alpha in nuclei of most cell types in inner and outer nuclear layers and the ganglion cell layer, a cellular distribution pattern which was confirmed in human retina by immunoblotting of nuclear extracts. A negative correlation was found between HIF-1alpha protein levels and postmortem times. In human retina, staining of VEGF, GLUT-1, and CAIX was found. Our observations indicate that active HIF-1 signaling occurs constitutively in the normal human and rat retina, suggesting that HIF-1 has a physiological role in the retina.

Factors affecting ocular rigidity in normal human eyes

Abstract Purpose To measure the ocular rigidity coefficient and evaluate its relation with axial length (AL), age and mean systemic blood pressure (SBP). Methods Sixty three patients (63 eyes) undergoing cataract surgery, with different refractive errors and no ocular or systemic pathology were enrolled in this study. An invasive, computer controlled device comprising a microdosimetric pump and a pressure sensor, is connected to the anterior chamber under topical anaesthesia with drops. The system is used to raise the intraocular pressure (IOP) from 15 to 40mmHg, by infusing the eye with a saline solution. After each 4 ul infusion step, the IOP is continuously recorded for 2 seconds. From an initial level of 40mmHg an IOP decay curve of 1 minute is obtained. SBP and pulse rate are measured during the procedure. The rigidity coefficient is calculated by an exponential fit to the pressure volume data after correction for outflow. The study was approved by the Institutional Board and performed under the patient’s informed consent. Results Mean AL was 24.8 (range 21.2‐32.5). Mean age and SBP was 59 (12) years and 93.7 (10.5) mmHg respectively. The mean ocular rigidity coefficient was 0.021 (0.005) ul‐1. Increasing axial length is associated with a decrease in the rigidity coefficient (r=‐0.61, p&lt;0.01). A positive correlation between the rigidity coefficient and age of the patients is found (r=0.31, p=0.01), whereas similar findings were not observed for SBP (p&gt;0.05). Conclusion This manonetric approach of measuring ocular rigidity provides a normative database of this parameter in living human eyes. Axial length and age influence ocular rigidity. These results may have implications on tonography and ocular pulse studies.