Research Jos Rozema

Abstract

During the first years of life the eye grows tremendously, while simultaneously reducing the mean ocular refraction by carefully adjusting the growth speed of the eye globe, cornea, and crystalline lens. This process is called emmetropization and takes place during the first 2–3 years of life. Next, homeostasis occurs, during which eye growth continues while maintain the near-emmetropic refractive error through a combination of scaled growth and active feedback mechanisms. Failure of homeostasis will lead to excessive axial growth and myopia, which causes the retinal image to be out of focus. Animal experiments demonstrated that eye growth involves a delicate interaction between optical and sensory components to provide retinal image clarity throughout life. So, emmetropization is the active, visually guided mechanism whereby the axial length and the combined optical powers of the cornea and lens precisely match with each other to eliminate neonatal refractive errors. Many reports on ocular growth have been published, these are often for a limited age range. Our group recently published a complete overview of normal ocular growth before birth until 18 years of age. Similarly, there are descriptive models for eye growth in the literature, but a quantitative model for the mechanisms of eye growth is currently lacking. This project aims to model the changes of the ocular components involved in visually guided eye growth using differential equations, consisting of two exponential terms representing the scaled growth before birth and the growth with active feedback after birth. Besides, we work on estimating the influence of variations in optical parameters on variations in refractive error using the error propagation method. Moreover, we explore how the parameters of bi-exponential functions can be adjusted to simulate various known refractive development courses described in the literature, such as instant emmetropization, persistent hypermetropia, myopia, and so on. Additionally, it is known from the literature that myopia development is affected by both retinal defocus and the spectral composition of the ambient light. Both factors are known to affect contrast sensitivity function (CSF). It is becoming increasingly clear that CSF may play a large role in refractive development. We measure the CSF of both emmetropes and myopes to investigate the combined effect of defocus and color band on the CSF. Finally, we aim to modulate the exponential function of eye growth (ODE model) and look for the retina response function by considering some important factors such as the CSF of the human eye, the luminance, and the surrounding illumination. Objectives: 1. Propose an active model of normal and abnormal refractive development. 2. Estimate the influence of variations in biometric parameters on variations in refractive error. 3. Propose bi-exponential description for different forms of refractive development. 4. Measure the CSF within the red, green, and blue color bands across different levels of defocus. 5. Develop a modulated ODE model by considering retina function.

Researcher(s)

• Promoter: Rozema Jos
• Fellow: Farzanfar Arezoo

Research team(s)

• Translational Neurosciences (TNW)

Project type(s)

• Research Project

Abstract

Ophthalmic research has made significant progress, evolving from basic ocular refractive models to the sophisticated SyntEyes model. The latter model provides synthetic biometric datasets that reflect real eye statistics for improved optical calculations without additional measurements. However, to date its focus remained limited to optical characteristics, leaving out ocular biomechanics. To address this gap, the SyntEyes OBM (Synthetic Opto-Biomechanical Eye Model) is proposed as a comprehensive platform that integrates both optical and biomechanical properties of the eye to perform detailed analyses under different conditions. This advancement involved the development of a 3D geometric eye model including the cornea, limbus, sclera, lens, iris, ciliary body, and zonular fibres. The model uses Zernike coefficients to define the anterior and posterior surfaces of the cornea, extending their diameters to allow for realistic dimensions. The lens shape was derived from SyntEyes data using aspheric surfaces for accuracy. The sclera was modelled as a spherical shell of constant thickness connecting the corneal limbus to the retinal fovea, while the ciliary body and zonular fibres were customised based on previous research to ensure individual representation. The SyntEyes OBM model offers adaptability to multiple biometric variations, enhancing the original SyntEyes by incorporating biomechanical insights and allowing simultaneous and accurate evaluation of the optical and biomechanical aspects of the eye. This model will significantly enhance optical and clinical simulations, providing a more thorough and accurate tool for ophthalmic research and practice, and marking a notable advancement in the field.

Researcher(s)

• Promoter: Rozema Jos
• Fellow: Ghaderi Hosna

Research team(s)

• Translational Neurosciences (TNW)

Project type(s)

• Research Project

Abstract

In the coming years the VOLANTIS research group, plans to conduct several studies related to visual optics and ocular biomechanics. Overall, these studies may be grouped into three topics. The first is refractive development and eye modelling, which studies how the eye grows and how this can be described as a mathematical model. Such models will look at e.g. how during eye growth the different components of ocular biometry interact with each other to first bring the eye in focus ('emmetropia') and then maintain this condition as the eye continues to grow. Other studies look at what happens if such a balance is disrupted or how it is accomplished in pathological eyes (e.g. premature infants or infants operated for cataract). Within the European OBERON project, we will also develop a new type of model that combines the biomechanics of the eye with its optical function as a platform for testing new treatments in virtual clinical trials. This 'opto-biomechanical' model will need close interactions with our European partners. The next study topic is keratoconus, a disease that gradually deforms the cornea, leading to a considerable loss in visual quality. Early detection of the disease and its possible progression is very important in its management as it allows the patients to preserve a higher visual quality through timely treatment. To this end, we are working on machine learning systems that can tell ophthalmologists whether an eye has keratoconus and, if so, if it is in a progressive state. Another project looks at improving the popular 'crosslinking' treatment that increases corneal elasticity and stops the progression. To do this, we need to develop corneal elasticity maps that can inform ophthalmologists what areas of the cornea need treatment. Although the current methods to develop such maps are very computationally intensive, we will use new methods that have not yet been tried to speed up this process from several hours to minutes, making it clinically useful. Finally, we will study straylight and dark adaptation, which refers to being blinded by bright lights ('glare') and the time needed to recover afterwards. These phenomena can play a major role in traffic safety as drivers may be blinded by the headlights of oncoming cars. Since it is not yet understood at what level of glare the safety risks for safe driving become too high, we will organize a study to test the effect of a bright light source on performance in a driving simulator in a darkened room. The outcomes of these experiments will later be formulated as advice to legislative authorities to improve traffic safety.

Researcher(s)

• Promoter: Rozema Jos
• Fellow: Rozema Jos

Research team(s)

• Translational Neurosciences (TNW)

Project type(s)

• Research Project

Abstract

Keratoconus is an eye disease in which the cornea gradually deforms, which causes the patients to experience a rapidly deteriorating visual quality. Early detection and follow-up of this disease is therefore very import as it allows for a quick therapeutical intervention. Recently, the Visual Optics Lab Antwerp (VOLANTIS) has developed new computational methods to monitor the structural changes in the cornea and to provide the best possible optical correction. The goal of this project is to expand on these methods, as well as to apply them to a large amount of previously collected patient data. This way we want to improve the prospects of patients by allowing to retain the highest possible quality of life.

Researcher(s)

• Promoter: Rozema Jos
• Fellow: Francis Sharon

Research team(s)

• Translational Neurosciences (TNW)

Project type(s)

• Research Project

Abstract

The eye is a biological tissue with optical and biomedical properties that govern the way the eye refracts light, focuses that light onto the retina and can dynamically alter that focus over a range of distances. This impressive flexibility results from the delicate way in which the mechanical properties of the eye very precisely affect its optics. These properties vary considerably between individuals and can alter over time in response to visual demands, as well as with eye growth, ageing and pathology. The origins of these biomechanical changes over time are very poorly understood, however, and point at a need for answers, given the increase in life expectancy and in societal demands for high quality vision. To address these issues, we present the first European collaboration that brings together a group of scientists that work on the optics and biomechanics of the eye, cover a broad range of disciplines and skills. This highly interdisciplinary consortium will also create a training network to give young researchers the opportunity to learn from renowned experts on ocular opto-mechanics, share their learning experiences and take advantage of placements in Universities, hospitals and industry. This will give them a wide and novel skill set to translate their research to scientific, industrial, or clinical applications, such as a new generation intraocular implants for cataract surgery, biologically relevant eye models that mimic the eye at any age, and novel treatment therapies that can control, reduce or ultimately prevent refractive error from occurring. These anticipated innovations will lead to wide-reaching and pioneering advances to enhance our understanding of the interrelationship between ocular optics and biomechanics. From this, the young researchers will emerge with multi-disciplinary, versatile skills, be highly employable, able to address skills shortages, be leaders in vision science and pioneer new industries in optical design and modelling.

Researcher(s)

• Promoter: Koppen Carina
• Co-promoter: Rozema Jos

Research team(s)

• Translational Neurosciences (TNW)

Project website

Project type(s)

• Research Project

Abstract

The principles of phase contrast microscopy are used to map the aberrations of the human eye's optical system. There are reasons to belief this will result in a very fast and accurate method to determine eye aberrations.

Researcher(s)

• Promoter: Van Dyck Dirk
• Co-promoter: Rozema Jos

Research team(s)

Project type(s)

• Research Project

Abstract

Researcher(s)

• Promoter: Rozema Jos

Research team(s)

Project type(s)

• Research Project