Harilaos Ginis

Harilaos Ginis
Athens Eye Hospital · Department of Research

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100
Publications
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1,284
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Publications

Publications (100)
Article
Purpose: To evaluate peripheral refraction and contrast detection sensitivity in pseudophakic patients implanted with a new type of inverted meniscus intraocular lens (IOL) (Art25; Voptica SL) that was designed to provide better peripheral optics. Methods: One month after cataract surgery, in 87 eyes implanted with the Art25 IOL, peripheral cont...
Article
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Purpose: To show the importance of measuring the angular distribution of straylight as an in vitro test for intraocular lenses (IOLs). Methods: The optical integration method was implemented to measure the point spread function, up to 5.1°, of IOLs immersed in a wet cell. The straylight parameter was calculated as the product of the point spread...
Article
Full-text available
Purpose: To investigate in vitro the accuracy of dynamic contour tonometry, Goldmann applanation tonometry, and Tono-Pen XL in edematous corneas. Methods: Experimental study included 20 freshly enucleated porcine eyes. Epithelium was debrided, and eyes were divided in four groups. Groups were immersed in 35%, 40%, 50%, and 60% glycerin solutions...
Article
Purpose Straylight refers to an optical phenomenon that takes places in the eye and leads to a deterioration of the retinal image. Past clinical findings suggest an increase of straylight with the eye's axial length, but the aetiology of the phenomenon was unclear. The purpose of this work is to demonstrate, through raytracing, simple geometrical o...
Article
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The purpose of this work was to evaluate peripheral image quality in the pseudophakic eye using computational, physical and psychophysical methods. We designed and constructed a physical model of the pseudophakic human eye with realistic dimensions using a corneal phantom and a board-only camera that was pivoted around an axis that matched the anat...
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Macular pigment is a yellowish pigment of purely dietary origin, which is thought to have a protective role in the retina. Recently, it was linked to age-related macular degeneration and improved visual function. In this work, we present a method and a corresponding optical instrument for the rapid measurement of its optical density. The method is...
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The 9th European Meeting on Visual Physiological Optics (VPO2018) was held August 29–31, 2018, in Athens, Greece. This issue of the Journal of the Optical Society of America A (JOSA A) is a dedicated feature, including numerous articles that span a large range of visual optics related topics, ranging from geometrical optics to visual psychophysics...
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Purpose Eyes that have undergone phacoemulsification with implantation of a multicomponent intraocular lens (MCIOL) may further undergo an enhancement procedure for correction of residual refractive errors. The enhancement procedure is accomplished by exchanging the front lens used in the primary surgery with another lens containing the correct dio...
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Light scattering in the eye affects the quality of vision and its effect increases with aging and related pathologies, such as cataracts. Simulating methods were developed in order to reproduce the effects of this phenomenon. We introduce a statistical model of wavefront perturbations at the pupil plane of the eye that replicates the characteristic...
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Fundus reflectometry is a common in-vivo, noninvasive method to estimate the macular pigment optical density (MPOD). The measured density, however, can be affected by the individual's intraocular scattering. Scattering causes a reduction in the contrast of the fundus image, which in turn leads to an underestimation of the measured density. Intraocu...
Conference Paper
A very common descriptor for the quantitative characterization of the human visual function, is the Visual Acuity (VA). Although it seems to be representative for the assessment of the effect of -at least- the low order aberrations, it falls short to precisely detect effects of another very common reason of visual deterioration, the effects of -Int...
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Purpose: Scattering in the eye occurs mainly at two sites: the eye's optical media and the deeper retinal layers. Although the two phenomena are often treated collectively, their spatial domain of contribution to the double-pass Point Spread Function (PSF) is different: the fundus effect is limited to the narrow and middle part of the PSF whereas...
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Increased intraocular scatter degrades quality of vision, especially in the presence of glare sources. Standard tests, such as visual acuity, are not well suited to capture this condition. There are specific methods to measure intraocular scatter, but require dedicated instruments. In this work, we propose a method to estimate the amount of scatter...
Article
PURPOSE: To measure straylight in a cohort of patients with cataract using a novel optical instrument and to correlate optical straylight values with clinical grade of cataracts and psychophysical straylight values. METHODS: Measurements were performed on 53 eyes of 44 patients with cataract admitted to the ophthalmol- ogy service of the university...
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Purpose: The aim of this study is to demonstrate the functionality of a new design of a thick endocapsular open ring for prevention of anterior capsule opacification (ACO) and posterior capsule opacification (PCO). Setting: The Institute of Vision and Optics, University of Crete and University Hospital of Heraklion, Crete, Greece. Design: Pros...
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Intraocular scattering affects fundus imaging in a similar way that affects vision; it causes a decrease in contrast which depends on both the intrinsic scattering of the eye but also on the dynamic range of the image. Consequently, in cases where the absolute intensity in the fundus image is important, scattering can lead to a wrong estimation. In...
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Purpose: To study the relative impact of genetic and environmental factors on the variability of intraocular scattering within a classical twin study. Methods: A total of 64 twin pairs, 32 monozygotic (MZ) (mean age: 54.9 ± 6.3 years) and 32 dizygotic (DZ) (mean age: 56.4 ± 7.0 years), were measured after a complete ophthalmologic exam had been...
Conference Paper
A novel mathematical and physical method of generating complete ocular wavefronts, based on the parametrization and numerical optimization of the discrete cosine spectrum of the phase maps.
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We investigated the spatial characteristics of the diffuse light in the eye at two different wavelengths and the extent to which this may affect red-green relative spectral sensitivity. The fundus reflectance of six subjects was measured for different field sizes ranging from a 0.18° to 7.28° radius and for two different wavelengths, 560 and 650 nm...
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A variety of anti-glaucomatous shunt designs have been proposed so far. This study evaluates the feasibility of a novel shunt design, the intra-scleral parathalamus implant (IPI), in a rabbit eye model. Ten healthy albino rabbits were included. Measurements of the IOP, using TonoPenXL, as well as ocular rigidity (OR) and aqueous outflow facility (A...
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Purpose: To compare ocular rigidity (OR) and outflow facility (C) in patients with nonproliferative diabetic retinopathy (NPDR) and control subjects. Methods: Twenty-four patients with NPDR (NPDR group) and 24 controls (control group) undergoing cataract surgery were enrolled. NPDR group was further divided into patients with mild NPDR (NPDR1-gr...
Conference Paper
Light scattering in the human eye can deteriorate image quality and limit visual performance especially at the presence of a glare source. Optical measurement of straylight in the human eye is a challenging task where issues related to various inherent artifacts must be addressed. We report on a novel instrument based on the principle of double-pas...
Article
PurposeThe intraocular pressure (IOP) is determined by a dynamic equilibrium between the production and outflow of the aqueous humour. The relationship between IOP and the outflow rate through the conventional and unconventional pathway is quantified by the outflow facility coefficient (C). The purpose of this study is to employ a direct (manometri...
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Full-text available
Optical measurement of straylight in the human eye is a challenging task. Issues such as illumination geometry, detector sensitivity and dynamic range as well as various inherent artifacts must be addressed. We developed a novel instrument based on the principle of double-pass optical integration adapted for fast measurements in a clinical setting....
Conference Paper
Purpose To quantify intraocular forward scattering (straylight) by using three different methods in a group of normal subjects.Methods Intraocular straylight was measured in the dominant eye of 10 emmetropic subjects without any known ocular pathology (30±5 years).Two different, commercially available, scatter filters (Black Pro-Mist ¼ and Black Pr...
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Introduction: A previous study has employed shear-wave ultrasound elastographic imaging to assess corneal rigidity in an ex-vivo porcine eye model. This study employs the same modality in vivo in a rabbit eye model in order to assess lens, ciliary body and total ocular rigidity changes following the instillation of atropine and pilocarpine. Metho...
Article
The spatial organization of stromal collagen of ex-vivo corneas has been quantified in adaptive-optics second harmonic generation (SHG) images by means of an optimized Fourier transform (FT) based analysis. At a particular depth location, adjacent lamellae often present similar orientations and run parallel to the corneal surface. However this patt...
Article
Purpose: To compare ocular rigidity (OR) and outflow facility (C) coefficients in medically treated open-angle glaucoma (OAG) patients and controls, and to investigate differences in ocular pulse amplitude (OPA) and pulsatile ocular blood flow (POBF) between the two groups. Methods: Twenty-one OAG patients and 21 controls undergoing cataract sur...
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Purpose: Ocular straylight is the combined effect of light scattering in the optical media and the diffuse reflectance from the various fundus layers. The aim of this work was to employ an optical technique to measure straylight at different wavelengths and to identify the optimal conditions for visually relevant optical measurements of straylight...
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Purpose: Previous studies have shown a negative correlation between axial length (AL) and pulsatile ocular blood flow (POBF). This relation has been questioned because of the possible confounding effect of ocular volume on ocular rigidity (OR). The purpose of this study was to investigate the relation between AL, as a surrogate parameter for ocula...
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Corneal biomechanical properties are usually measured by strip extensiometry or inflation methods. We developed a two-dimensional (2D) flap extensiometry technique, combining the advantages of both methods, and applied it to measure the effect of UV-Riboflavin cross-linking (CXL). Corneal flaps (13 pig/8 rabbit) from the de-epithelialized anterior...
Article
Background: The purpose of this study is to evaluate in-vitro the immediate effect of corneal collagen cross-linking (CXL) on corneal hydration and stiffness. Methods: Forty-two corneal buttons from freshly enucleated porcine eyes were immersed in riboflavin 0.1% in dextran 20% dilution for 3 h in order for their hydration to reach equilibrium....
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The point spread function (PSF) of the human eye spans over a wide angular distribution where the central part is associated mostly to optical aberrations while the peripheral zones are associated to light scattering. There is a plethora of optical methods for the direct and indirect measurements of the central part of the PSF as a result of monoch...
Article
Purpose The intraocular pressure (IOP) is determined by a dynamic equilibrium between the production and the outflow of the aqueous humor. The dependence of outflow facility on IOP may be related to the biomechanical properties of the eye. This study examines the relationship between the outflow facility and IOP for the living human eye using an in...
Article
Purpose To compare ocular rigidity in patients with age-related macular degeneration (AMD) and control subjects.Methods The ocular rigidity coefficient was measured in 32 patients with AMD (16 with neovascular and 16 with nonneovascular AMD) and 44 age-matched control patients (control group) who underwent cataract surgery. The measurement procedur...
Article
Purpose Several instruments and methods are applied for the non invasive measurement of intraocular pressure, ocular rigidity and pulsatily blood flow. Most of this instruments and methods are based on the deformation force-area principle. The purpose of this study was to present a novel device for the measurement of intraocular pressure, ocular ri...
Article
Purpose The design of advanced (such as multifocal) intraocular lenses (IOLs) is based on the exact alignment of the optical element with the center of the pupil and its optical axis with the line of sight of the eye. It is the purpose of this study to evaluate the impact of multifocal IOL decentration and tilt on retinal image quality.Methods A se...
Conference Paper
Purpose A photo-polymerisable hydrophilic material (PEG/Irg) has been previously evaluated in terms of biocompatibility and toxicity in a series of laboratory animals. It was the purpose of this study to evaluate the bio-mechanical effect of lamellar implants created from PEG/Irg in porcine cadaver eyes.Methods Twenty porcine corneas where removed...
Article
Purpose To develop and demonstrate a new optical technique for the measurement of light scatter in the human eye based on extended source imaging in a double pass configuration.Methods The experimental setup is based on a double-pass (DP) configuration. Series of disks of uniform radiance having angular dimensions ranging from 0 to 9.1 degrees (rad...
Article
Purpose The wavelength dependence of the light scattering is related with the characteristics of the inhomogeneities in the ocular media, and therefore, an objective assessment could be used to the early detection of underlying ocular pathologies. We developed a new optical instrument for measuring light scattered in the human eye at different wave...
Conference Paper
Purpose It is known that corneal edema is associated to increased light scatter. It was the purpose of this study to calculate the intensity and angular distribution of scattered light in a series of corneal samples at different hydration, using a sensitive optical technique.Methods Sixteen fresh porcine eyes were obtained from a local abattoir. To...
Article
Purpose Besides refractive aberrations, ocular light scattering is a major parameter affecting image quality on the retina in healthy eyes. Several pathologies in the anterior segment such as corneal scarring and cataract cause significant increase of straylight in the eye. In this study, we link morphologic changes addressed to corneal scarring to...
Article
Purpose To evaluate the primary effect of corneal collagen crosslinking on corneal hydration.Methods Twenty corneal buttons from freshly enucleated porcine eyes where immersed in riboflavin 0.1% in dextran 20% dilution for three hours in order for their hydration to reach an equilibrium. Corneal buttons where divided in two groups; the first group...
Article
Purpose Straylight in the human eye is associated with low light intensities scattered at angles large compared to the part of the Point Spread Function that is governed by refractive error and aberrations. It is the purpose of this talk to summarise existing methods for the measurement of straylight in the human eye and to discuss new developments...
Conference Paper
Purpose To study the acute mechanical effect of corneal cross-linking in vitro.Methods Twenty porcine eyes were harvested from a local abattoire. The epithelium was removed using a rotating brush and corneal buttons having diameter of 8 mm were excised using a Barron’s PKP trephine. The buttons were left immersed for four hours in Dextran solution...
Article
Purpose To record the spectrum emitted during excimer laser-cornea interaction at fluences intensities resulting to ablation and investigate the relation between its spectroscopic features and corneal hydration.Methods Porcine corneas from eyes obtained from a local abattoir were used for the experiments. The corneal samples were de-epithelialized...
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Full-text available
Ocular rigidity is a macroscopic parameter characterizing the relationship between pressure and volume changes in the human eye. Ocular rigidity depends on the architecture and material properties of the globe. Measurements of ocular rigidity have mainly been performed by means of invasive manometric devices or paired Schiotz tonometry. These measu...
Article
Purpose: Seven existing and three new image quality metrics were evaluated in terms of their effectiveness in predicting subjective cycloplegic refraction. Methods: Monochromatic wavefront aberrations (WA) were measured in 70 eyes using a Shack-Hartmann based device (Complete Ophthalmic Analysis System; Wavefront Sciences). Subjective cycloplegi...
Article
We studied the effect on the intraocular pressure (IOP) and the ciliary body (CB) morphology after four consecutive contact transcleral photodynamic treatments of the ciliary body (CB-PDT) with verteporfin in pigmented rabbits. Twenty-two pigmented rabbits underwent CB-PDT (study group), performed once (six rabbits) or repeated for up to four times...
Article
In order to quantitatively evaluate testicular consistency, we designed a device for measurement of testis rigidity, which reflects the resistance caused by testicular pressure and elasticity. The device was tested in experimental models of cryptorchidism and torsion. The Testis Rigidity Tester (TRT) prototype consists of a system of weights and le...
Article
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...
Article
Purpose The change of outflow facility is determined by the value of intraocular pressure (IOP) possibly due to changes in the angle of the anterior chamber, the trabecular meshwork and the Schlemm’s canal. The purpose of this study was to determine the relationship between outflow facility and IOP (especially for elevated values of IOPs) in living...
Article
Purpose However corneal scattering is clinically often quantified as haze (backscattered light), the visual function is affected by the forward light scattering in the anterior ocular media. The angular light distribution of the scattered light is inherent to the interaction between the light and the scattering media. The purpose of this study is t...
Article
Purpose Laser correction of ametropias is achieved by changing the radius of curvature of a central portion of the cornea. Although current refractive laser technology allows relative uniform correction across an optical zone larger than the scotopic pupil it must be kept in mind that centration of the ablation pattern pertains only to objects on t...
Article
Purpose The cone mosaic is characterised by a quasi-periodic hexagonal organization. The purpose of this work was to develop a mathematical model of cone mosaic including irregularities and to employ this model to evaluate its effectiveness in sampling simple patterns including optotypes (letters) of different sizes and gratings.Methods Cone mosaic...
Conference Paper
Purpose In terms of excimer laser ablation, the cornea is water bound on an organic matrix. Corneal hydration might affect the excimer laser ablation rate, which could affect the accuracy of correction. It was the purpose of the study to investigate the use of Dextran solutions of varying concentrations to control corneal hydration in rabbit cornea...
Article
Purpose Measurement of scattered light in biological media and particularly the optical media of the human eye is associated with two main challenges: The extremely low intensity of the scattered light and artefacts associated to tissue handling and preparation.Methods Our strategies in reducing the errors associated with the above mentioned challe...
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Full-text available
The purpose of this study was to characterize the pressure-volume relation in the living human eye, measure the ocular pulse amplitude (OPA), and calculate the corresponding pulsatile ocular blood flow (POBF) in a range of clinically relevant IOP levels. Fifty patients with cataract (50 eyes) were enrolled in the study. After cannulation of the ant...
Article
Corneal haze following excimer laser ablation is an adverse after-effect of photorefractive keratectomy (PRK) and is associated with the development of subepithelial opacities. The present work pertains to the measurement of light scattering in rabbit corneas following excimer laser treatment; to the microscopic analysis of the light-scattering cor...
Article
Corneal haze is a well-known pathology associated with decreased corneal transparency and increased ocular scattering. Clinically, haze is typically estimated as the amount of backscattered light observed in a slit lamp examination while the small angle forward scattering cannot be directly observed. It was the purpose of this study to demonstrate...
Article
Purpose The purpose of this study is to demonstrate proof of principle of a new rigidity based invasive technique to assess pulsatile ocular blood flow in a wide range of clinically relevant IOP levels.Methods An invasive manometric dynamic measurement procedure is employed, using a computer controlled device, comprising a pressure transducer and a...
Article
Purpose The intraocular pressure (IOP) is the primary mechanical load to several ocular structures. It fluctuates over time as a result of a dynamic equilibrium between the systems of aqueous and blood flow. The purpose of this study is to characterize the eye’s pressure volume relationship and quantify hydro and haemodynamic parameters in the livi...
Article
Purpose The purpose of the present study is to demonstrate pilot measurements of ocular rigidity and intraocular pressure (IOP) with a minimally invasive opto-mechanical device.Methods The device consists of a glass lens that is used to contact and deform the corneal surface, while the force required for this deformation is measured by means of a l...
Article
Purpose To measure the pressure-volume relationship (ocular rigidity) and outflow facility in the living human eye using a manometric device.Methods Fourty cataract patients (aged 63 (13)) were enrolled in the study. An invasive manometric intraoperative dynamic measurement procedure was employed, using a computer controlled device, comprising a pr...
Article
Purpose The ablation rate of corneal tissue depends primarily on the fluence of the laser and corneal hydration. It was the purpose of the study to compare the dependence of the ablation rate on corneal hydration for two different laser wavelengths (193 and 213-nm).Methods ArF Excimer laser (Allegretto, Wavelight) with a wavelength of 193nm and Nd:...
Article
Purpose The present work pertains to the measurement of light scatter in rabbit corneas after Excimer laser treatment, to the microscopic characterisation of the corneal irregularities and to the development of a mathematical model of light propagation through the post-laser treatment cornea, based on the statistical properties of the scattering st...