VICAT : Vision Improvement through CATaracts funded by the European Commision (HORIZON EUROPE Marie Sklodowska-Curie Actions (897300))

Motivation of the Project

Cataracts is a common ocular pathology affecting approximately 70% of people aged over 65, which accounts to approximately 700 million worldwide, and due to longer life expectancy, this numbers are expected to grow. If not treated in time, it can cause blindness, being so far responsible for 51% of the cases of blindness all over the world, according to the World Health Organization. So far, the only solution available is cataract surgery, an invasive procedure that can cause different side effects as corneal edemas or retinal detachment among others. In addition, this solution is not suitable for every patient, for example if they have other eye conditions or in the case of infants born with cataracts. For these reasons, a non-invasive alternative to surgery is highly desirable, even it can be the preferred option for many people, if they had the opportunity to wear correcting glasses, as most people do for myopia correction for instance, instead of laser surgery.

In this project we studied the feasibility of a non-invasive correction of cataracts, which could benefit many people around the world, not only people that cannot undergo surgery for a medical condition, but also all those that prefer not to undergo surgery if only a non-invasive solution (in the form of wearable glasses) was possible. The goal of this project was to optimize the wavefront shaping technique capable of reverting the effect of cataract’s light scattering and combine it with the optical memory effect of cataracts, for the full optical characterization of cataracts and to improve retinal image formation by shaping and optimizing the incident wavefront, for future wearable devices based on these principles. In addition, we explored the feasibility of miniaturizing this system for wearability.

Progress during the Project

The results of the action have fulfilled very well the originally proposed objectives, demonstrating for the first time the double-pass (or non-invasive) correction of a cataractous PSF in a cataract’s eye model [Paniagua-Díaz, A. M. et al. (2021). Opt. Express, 29(25), 42208-42214]. Here we demonstrated the possibility of an all-optical correction of cataractous vision. We also simulated the potential of the optimized PSF in improving retinal images, however in reality this depends on the scattering properties of cataracts and their Optical Memory Effect. These results were presented at professional conferences focused on Industry and Medicine (Adaptive Optics for Industry and Medicine 2019) and Optics (OSA’s Imaging and Applied Optics congress in 2020 and 2021).

We fully characterized the scattering properties of cataracts of different grades, measuring their objective straylight parameter (a value that can be measured in vivo in patients), the contrast of the formed images with those lenses and the Optical Memory Effect, finding linear correlations between them, producing a peer-reviewed publication [Paniagua-Diaz, A.M. et al. (2023) Biomed. Opt. Express 14 (2), 693-650]. These results are of great importance when diagnosing cataracts in patients and determining the optimal approach for the PSF optimization leading to the optimal retinal image improvement. This work has been presented in two conferences in Optics (OPTICA Imaging and Sensing Congress 2022, XXXVIII Reunión Bienal de la Real Sociedad Española de Física 2022) and in the largest conference in Vision and Ophthalmology (ARVO 2022). We are currently studying the strategies for image projection after wavefront manipulation based on the Optical Memory Effect, with some preliminary excellent results presented in SPIE Photonics West 2023 [Paniagua-Diaz, A.M. et al. (2023) Ophthalmic Technologies XXXIII, 12360-35, SPIE].

In parallel we also investigated how to improve fundus imaging in a non-invasive manner, avoiding the scattering of cataracts by amplitude modulation. In collaboration with a group at University Nicholaus Copernicus in Poland we explored the manipulation of the wavefront using amplitude masks, demonstrating its potential for improved fundus imaging as well as for improving visual performance [Panezai, S. et al. (2022) Biomed. Opt. Express, 13(4), 2174-2185], that we are pushing forward with a collaboration with the University Jaume I in Castellon (Spain), where we are adding the non-invasive and inexpensive detection of non-homogeneous scattering areas with Spatial Frequency Domain Imaging (SFDI) techniques [Ipus, E. et al. Imaging and Applied Optics Congress 2022 (3D, AOA, COSI, ISA, pcAOP), CM3A.6]. This work will allow the implementation of a non-invasive system for the optical imaging of the eye’s fundus through cataracts in a low-cost approach, which will be very useful for retinal diseases diagnosis before cataract surgery and determining which patients might not be suitable for surgery where only a non-invasive solution could be applicable. A peer-review publication is under preparation for this last piece of work.

We also tested phase correction in subjects, however, due to the current limitation we found in fixing subjects in the bench-based system we decided to correct high-order aberrations as a first step, with phase sections larger than those of cataracts, and therefore more resilient to small head movements. We also added an extra feature that was the use of inexpensive phase modulators, which can allow the final development of an inexpensive wearable device for this correction. We succeeded at this, demonstrating how we could successfully correct high-order aberrations in voluntary subjects, whilst measuring their visual acuity and contrast sensitivity [Paniagua-Diaz, A. M. et al. (2022) Optical Engineering, 61(12), 121806]. During the secondment at Voptica S.L. we also moved the first steps towards a miniaturization of this system based on a double pass through an inexpensive phase modulator, integrating a bench-based system occupying an approximate space of 1000x500x100mm to 100x50x20mm using commercial elements, still with a large potential for further miniaturization. These works have been presented both in Physics (OSA’s Imaging and Applied Optics congress & Optical Sensors and Sensing Congress 2022, XXXVIII Reunión Bienal de la Real Sociedad Española de Física 2022, SPIE Photonics West 2023) and Engineering conferences (SPIE AR VR MR (Optical Architectures for Displays and Sensing in Augmented, Virtual, and Mixed Reality (AR, VR, MR) 2022).

In summary, during this period I have demonstrated the non-invasive correction of cataractous vision in a cataract’s model for the first time, opening new possibilities for an all-optical correction of cataracts, potentially the only alternative to cataract’s surgery. We performed a full scattering characterization of cataract’s scattering, measuring the Optical Memory Effect for the first time, building bridges between different disciplines, as ophthalmology and physics (optics in particular). I also explored different approaches for the non-invasive and inexpensive characterization of the eye’s fundus, for the detection of potential diseases usually hidden behind cataracts, some of them being a contraindication for cataract surgery and only discovered after cataract removal during surgery. Lastly I also made important advances in the development of a compact and low-cost device for in-vivo cataract correction, successfully testing its capabilities by correcting high-order aberrations in healthy volunteers.

Progress beyond the state of the art and expected socio-economic impact

Wavefront shaping through cataracts had been previously suggested by doing it through simulated cataracts in a single pass through the cataratous lens [Arias, A. et al. (2020) Optica, 7(1), 22-27]. We advanced the state of the art by demonstrating the correction of the cataract effect over the PSF by using wavefront shaping techniques in a completely non-invasive manner or double-pass through the lens with a real artificial eye [Paniagua-Díaz, A. M. et al. (2021). Opt. Express, 29(25), 42208-42214]. We are now demonstrating the capability of doing it through real cataractous crystalline lenses [Paniagua-Diaz, A.M. et al. Ophthalmic Technologies XXXIII,12360-35, SPIE].

We also characterized for the first time the objective scattering of cataractous lenses, together with the intrinsic correlations that will allow us to determine the optimal image formation with wavefront shaping, the optical memory effect. In this way by measuring in vivo the straylight parameter on real subjects, we can estimate the optical memory effect of their lenses and so determine the optimal approach for their cataract’s correction. This multidisciplinary characterization build bridges between ophthalmology and optics, two fields that can benefit from each other a lot. Having the scattering of cataracts characterized can help transferring other techniques existing in the field of light in scattering media, advancing the multidisciplinarity and collaboration between fields.

We also demonstrated that we can use VA-LCoS for phase modulation, which are very economic and compact, which will enable the use of this technology for future affordable wearable devices based on phase modulation, enabling wavefront shaping at a low cost for the first time, helping spreading the use of this technique in the scientific community as to medical devices companies.

In addition to it we miniaturized the phase modulation optical system, enabling the first wearable device for ocular phase modulation, which not only advances the state of the art in this case, where such devices have been traditionally bench-based due to the high prices and large dimensions of the SLMs. It also paves the way for the use of phase modulation in wearable devices in the future.

The expected socio-economic impact of this project can be high, since it opens new ways to the development of an all-optical correction of cataracts in a non-invasive manner, in the form of a wearable and potentially low-cost device. Since cataracts is a problem affecting approximately 700.000 million people worldwide where only an invasive solution is available, being the only alternative to it, presents a great advantage of a potentially high impact in the lives of many people. In addition, being a wearable technology, it could help preventing cataract’s induced blindness in remote areas where surgery is not possible, as well as for all those patients where surgery is contraindicated.