Imaging Refractor: Wide Angle Vision Evaluation

Project Information

IRWAVE

Grant agreement ID: 891741

DOI

10.3030/891741

Project closed

EC signature date 9 April 2020

Start date 1 May 2020

End date 30 April 2022

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 153 085,44

EU contribution

€ 153 085,44

Coordinated by

ATHENS EYE CLINIC AE
Greece

Periodic Reporting for period 1 - IRWAVE (Imaging Refractor: Wide Angle Vision Evaluation)

Reporting period: 2020-05-01 to 2022-04-30

Summary of the context and overall objectives of the project

Our visual system offers both high spatial resolution using the fovea and high temporal and high sensitivity using the periphery. Our ability to perform highly complex tasks, such as face recognition or reading, depends mainly in the quality of our foveal (central) vision. Peripheral vision, however, is important for noticing stimuli and moving the eye towards them if more detailed vision is needed, for orientation and for the detection of movement and, generally, for the awareness of our surroundings.
While a decrease of image quality in central vision is immediately noticed, a reduced image quality in the periphery can generally go unnoticed. It has been shown that increased refractive error in the periphery of the visual field can lead to a significant decrease in the detection of a stimulus. This functional limitation of vision can have significant implications in safety and efficiency in daily tasks e.g. while walking (detections of an obstacle such as a stairstep) or driving (awareness of other vehicles and surroundings). Peripheral refraction is also thought to play an important role in the emmetropization process and is a candidate for the mechanism causing myopia. The main hypothesis is that eye growth depends on peripheral defocus: it is believed an emmetropic eye with a hypermetropic periphery will lead to a continuous eye growth, even when foveal vision becomes myopic. Until now, there has not been conclusive evidence to fully establish the relationship between peripheral defocus and astigmatism with myopia. The proposed project concerns the design, construction and testing of an optical instrument and a corresponding method for the in-vivo, quick and accurate measurement of the central and peripheral refraction of the human eye. The instrument will have the potential to become a very valuable tool in ophthalmology, and specifically in the study of children myopia.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The peripheral refractor developed during this project, is an open-view double pass optical system, capable of taking central and peripheral measurements of the eye’s refraction (defocus and astigmatism. The project involved a series of steps towards the successful development and validation of the instrument.
First, in order to study the behaviour of the optical system, evaluate its performance and try different optical components prior to the physical construction, all optical components were inserted in an optical simulation software (Optics Studio/Zemax) and the optical system was modelled. The model showed a diffraction limited performance of the system on-axis and a nearly-diffraction limited performance off-axis, showing that the system is suitable for both central and peripheral measurements with the selected optical components. All optical components used were off-the-self from optical equipment companies (lenses, beam-splitters from Thorlabs Inc, dichroic mirrors from Edmund Optics Inc). Optoelectronic components such as the tunable lens and the camera were also off-the-self products to minimize cost and lead time. The laser power was determined based on ISO 15004-2 for retinal exposure in ophthalmic devices for the given wavelength.
The optical system was then designed in a CAD software (Rhino) to determine its spatial characteristics and it was, then, built on an optical bench. Subsequently, the system was tested on a model eye with the appropriate anatomical and geometrical characteristics, to simulate the real eye. The model eye could turn in order to achieve peripheral measurements.
Following the built of the bench top instrument, the need for a compact system that would spin to the desired eccentricity, allowing the eye to remain fixed, arose. This was essential to make the instrument require minimum subject involvement and, thus make it apt for use outside the laboratory environment. Therefore, the final instrument was a table-top instrument. A user-friendly graphical user interface was developed for the full control of the instrument.
A series of measurements was carried out on a model eye and 5 healthy volunteers. Each measurement consisted of a through focus scan of the retinal spot with a step of 0.1 diopters foveally and then at 30 degrees in the periphery. The objective of this first measurements was to determine if the system was capable to collect enough signal from the fundus with the given laser intensity, check the system’s stability and repeatability over time and its capability to perform measurements at the periphery and the centre of the retina. Furthermore, during these first measurements the comfortability and speed of the measurement was tested, and a preliminary measurement protocol was established. Finally, a large number of images was captured in order to test different algorithms for the assessment of defocus and astigmatism.
The benchtop system and the general method was presented at the Association of Research in Vision and Ophthalmology (ARVO) meeting in 2021 (virtual meeting). The development of the instrument was presented at the KTH Biomedical and X rays physics group in Stockholm, Sweden. The project was also presented by the National Documentation Centre - NDC (in Greek https://www.ekt.gr/el/news/25526) and was also featured in the NDC newsletter. The project and details on the scholarship was also presented at the summer 2020 meeting of the Greek chapter of the Marie Curie Alumni Association (MCAA) and on the NDC day seminar on funding opportunities for young researchers (https://www.ekt.gr/el/events/24706) reaching an audiance of several hundred young researchers. The instrument and the importance of peripheral image quality was also presented at the Athens Eye Hospital to clinical professionals (ophthalmologists and optometrists). A webpage dedicated to the project was created (irwave.eu). Finally, the tabletop instrument and some comparative results from measurements done at the Host and KTH, will be submitted for publication in a journal of the field and will also be presented at The 10th Visual and Physiological Optics meeting (VPO 2022) in Cambridge, UK

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The current state-of-the-art of peripheral image quality instruments involves only complicated bench-top laboratory instruments not suitable for clinical use. The expected outcome of the project is a technology that could potentially reach wide clinical use to assess accurately and fast peripheral image quality. Our technology can spark further research on peripheral image quality and its impact on myopia but also in other everyday tasks.
Myopia has seen an unprecedent rise in the recent decades particularly in east Asia with almost 90% of teenagers being myopic. Therefore, the need of a technology with the potential to reach clinical practice to assist in myopia diagnosis and control is urgent.

Schematic of the bench-top open-view peripheral refractor.

Bench-top version of the instrument measuring an artifical eye.

Table-top version of the instrument measuring a subject.